A method for smelting a high scrap ratio low nitrogen molten steel

Abstract

This invention provides a method for smelting high-scrap-ratio, low-nitrogen molten steel, belonging to the field of converter steelmaking. The method increases the scrap ratio to 35%–75% and includes: smelting molten iron and a first type of scrap steel in a first converter to obtain a first semi-molten steel; increasing the carbon content of the first semi-molten steel to obtain a second semi-molten steel; and smelting the second semi-molten steel and a second type of scrap steel in a second converter, using CO2 as a carrier gas to inject pulverized coal to reduce the nitrogen content of the molten steel, resulting in converter molten steel. By employing a dual-converter process to smelt steel, the scrap ratio is increased, and the smelting cycle can be controlled. Bottom injection of pulverized coal increases carbon content and provides additional heat, enhancing the heat output and denitrification effect. Using CO2 as a carrier gas generates twice the volume of CO, strengthening agitation and achieving better denitrification. Furthermore, the kinetic conditions are improved, resulting in lower O content at the converter endpoint and reduced T and Fe content in the slag.

Description

Technical Field

[0001] This application relates to the field of converter steelmaking technology, and in particular to a method for smelting molten steel with a high scrap ratio and low nitrogen content. Background Technology

[0002] In the traditional long-process steelmaking process of "blast furnace + converter," over 80% of carbon emissions originate from the ironmaking stages. Therefore, increasing the scrap steel ratio and reducing the iron-to-steam ratio in steelmaking will be one of the main measures to reduce carbon emissions in the near future.

[0003] Currently, measures to increase the scrap ratio mainly include improving efficiency and reducing temperature drop, increasing the molten iron inlet temperature, and adding supplemental heating agents to the converter. However, increasing the scrap ratio in the converter leads to a significant increase in nitrogen content, which fluctuates considerably. This is primarily due to the following reasons: a lower molten iron ratio reduces the total amount of carbon-oxygen reaction in the converter, resulting in fewer carbon-oxygen reaction bubbles and making denitrification more difficult; the scrap itself has a high nitrogen content, increasing the total amount of nitrogen introduced; and the diverse sources and types of scrap make quality control difficult, leading to large fluctuations in nitrogen levels. Therefore, reducing the nitrogen content in molten steel while maintaining a high scrap ratio during smelting is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application provides a smelting method for high scrap ratio, low nitrogen molten steel, to solve the technical problem in the prior art that it is difficult to reduce the nitrogen content of molten steel while ensuring a high scrap ratio during smelting.

[0005] This application provides a method for smelting high scrap ratio, low nitrogen molten steel, the method comprising:

[0006] The molten iron and the first scrap steel are smelted in the first converter to obtain the first semi-steel molten steel.

[0007] The first semi-steel molten steel is carbonized to obtain a second semi-steel molten steel; and,

[0008] The second semi-steel molten steel and the second scrap steel are smelted in a second converter, and CO2 is used as the carrier gas to inject pulverized coal to reduce the nitrogen content of the molten steel, thus obtaining converter molten steel.

[0009] Optionally, the amount of the first scrap steel added is 250 kg / t steel to 450 kg / t steel.

[0010] Optionally, the amount of the second scrap steel added is 100 kg / t steel to 300 kg / t steel.

[0011] Optionally, the smelting time in the first converter is t1, where t1 is 10 min to 15 min; wherein,

[0012] When the smelting time in the first converter is less than 5 minutes, pure CO2 is blown from the bottom of the converter.

[0013] When the smelting time of the first converter is 5 min to t1, CO2 is used as the carrier gas for injecting pulverized coal at the bottom of the converter.

[0014] Optionally, the CO2 flow rate is 2500 Nm³ relative to a 300 t converter. 3 / h~4500Nm 3 The flow rate of the pulverized coal is 200 kg / min to 400 kg / min.

[0015] Optionally, the smelting time in the second converter is t2, which is 13 min to 20 min; wherein,

[0016] When the smelting time in the second converter is less than 12 minutes, CO2 is used as the carrier gas for injecting pulverized coal at the bottom of the converter.

[0017] When the smelting time in the second converter is 12 min to t2, pure argon gas is blown into the bottom of the converter.

[0018] Optionally, the CO2 flow rate relative to a 300t converter is (3500 + t² × 500) Nm³. 3 The flow rate of the pulverized coal is (300 + t² × 50) kg / min, and the flow rate of the argon gas is 1000 Nm³. 3 / h~3000Nm 3 / h.

[0019] Optionally, the mass fraction of C in the second semi-steel molten steel is 1.5% to 2.5%; the tapping temperature of the second semi-steel molten steel is 1350℃ to 1450℃.

[0020] Optionally, in the molten steel from the converter, the mass fraction of C is 0.02% to 0.06%, the mass fraction of N is ≤0.0018%, and the mass fraction of O is 0.03% to 0.05%; the tapping temperature of the molten steel from the converter is 1550℃ to 1700℃.

[0021] Optionally, the carbon addition is achieved by adding carbonaceous material to the bottom of the first semi-molten steel; wherein the carbonaceous material includes one or more of biomass particles and coal powder, the mass fraction of C in the carbonaceous material is 50% to 99%, and the amount of carbonaceous material added is 5 kg / t steel to 15 kg / t steel.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] This application provides a method for smelting high-scrap-ratio, low-nitrogen molten steel. By employing a double-tank converter process, the scrap ratio is increased while the smelting cycle can be controlled. Bottom-injection of pulverized coal enhances carbon and heating, improving heat output and denitrification. Utilizing CO2 as a carrier gas generates twice the volume of CO, strengthening agitation and achieving better denitrification with improved kinetics. This results in lower O content at the converter endpoint and reduced T and Fe content in the slag. The method provided in this application can increase the scrap ratio to 35%–75%, resulting in molten steel with a nitrogen mass fraction ≤0.0018%, thus reducing the nitrogen content of the molten steel while maintaining a high scrap ratio during smelting. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart of a smelting method for high scrap ratio, low nitrogen molten steel, provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0029] Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] The inventive concept of this application:

[0032] The technical difficulties in smelting under existing technology are as follows: (1) At present, the high scrap ratio process is mainly achieved by preheating scrap steel and adding silicon and carbon heat-replenishing agents. After preheating scrap steel, although increasing the scrap steel temperature can increase the scrap ratio, the amount of molten iron is reduced, making it difficult to control nitrogen. Similarly, adding silicon heat-replenishing agents can increase the heat, but the total carbon-oxygen reaction weakens, and the nitrogen content is difficult to control. The thermal efficiency of adding carbon heat-replenishing agents is low, and the CO bubbles generated cannot play a role in the molten steel pool. (2) The bottom blowing CO2 process is used to reduce nitrogen, mainly by using CO2 and molten iron C to generate CO with twice the volume. Due to the reduction of the total source of carbon caused by the high scrap ratio, the denitrification capacity also becomes worse under the high scrap ratio condition. (3) Denitrification by RH after converter. The denitrification capacity of RH has a limit. When the nitrogen content at the converter endpoint is high, the nitrogen content at the RH endpoint increases.

[0033] In this application, a twin-cell converter process is used to smelt steel. The first converter adds 250-450 kg / t of scrap steel, and CO2 is used as the carrier gas for pulverized coal injection at the bottom of the converter during the smelting process, resulting in semi-finished steel. Pulverized coal and carbon powder are added to the bottom of the semi-finished steel ladle, and the strong impact and agitation of the molten steel during tapping increases the carbon content of the semi-finished steel. The carbonized semi-finished steel then enters the second converter, which adds 100-300 kg / t of scrap steel, and CO2 is used as the carrier gas for pulverized coal injection at the bottom. The amount of pulverized coal injected is dynamically increased as the carbon content of the molten steel decreases. This process utilizes bottom-injected pulverized coal to increase carbon and supplement heat, thereby enhancing heat output and denitrification. Adjusting the injection volume of carbonaceous raw materials based on the carbon content of the molten steel improves the utilization rate of carbonaceous raw materials and the carburizing rate. Using CO2 as a carrier gas generates twice the volume of CO, strengthening agitation and achieving better denitrification. The oxygen content in the molten steel and the total nitrogen (T.Fe) in the slag at the converter endpoint are both reduced. The method provided in this application can increase the scrap ratio to 35%–75%, resulting in molten steel with a nitrogen mass fraction ≤0.0018%, thus reducing the nitrogen content of the molten steel while maintaining a high scrap ratio during smelting.

[0034] Figure 1 This is a schematic flowchart of a smelting method for high scrap ratio, low nitrogen molten steel, provided in an embodiment of this application.

[0035] Please see Figure 1 This application provides a method for smelting high scrap ratio, low nitrogen molten steel, the method comprising:

[0036] By employing a converter duplex process for steelmaking, the scrap ratio can be increased to 35%–75%, while simultaneously controlling the smelting cycle. For example, this method can increase the scrap ratio to 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, etc.

[0037] S1. Molten iron and first scrap steel are smelted in the first converter to obtain the first semi-steel molten steel;

[0038] In some embodiments, the amount of the first scrap steel added is 250 kg / t steel to 450 kg / t steel.

[0039] By employing a converter duplex process for steelmaking, the scrap steel ratio in the smelting process can be increased, while the smelting cycle can be controlled. For example, the amount of the first scrap steel added can be 250 kg / t steel, 280 kg / t steel, 300 kg / t steel, 320 kg / t steel, 350 kg / t steel, 380 kg / t steel, 420 kg / t steel, 450 kg / t steel, etc.

[0040] In some embodiments, the smelting time in the first converter is t1, where t1 is 10 min to 15 min; wherein,

[0041] When the smelting time in the first converter is less than 5 minutes, pure CO2 is blown from the bottom of the converter.

[0042] When the smelting time of the first converter is 5 min to t1, CO2 is used as the carrier gas for injecting pulverized coal at the bottom of the converter.

[0043] In some implementations, the CO2 flow rate is 2500 Nm³ relative to a 300-ton converter. 3 / h~4500Nm 3 The flow rate of the pulverized coal is 200 kg / min to 400 kg / min.

[0044] The flow rates of CO2 and pulverized coal can be adjusted appropriately according to the converter's tonnage. Bottom blowing of pulverized coal increases carbon content, resulting in a high absorption rate. However, the high carbon content of the semi-steel limits the carbon increase rate, so the pulverized coal quantity cannot be too high; conversely, too low a quantity will have no carbon increase effect. For example, t1 can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, etc.; the CO2 flow rate can be 2500 Nm³. 3 / h, 3000Nm 3 / h, 3500Nm 3 / h, 4000Nm 3 / h, 4500Nm 3 / h, etc.; the flow rate of the pulverized coal can be 200Kg / min, 250Kg / min, 300Kg / min, 350Kg / min, 400Kg / min, etc.

[0045] S2. Carbonize the first semi-steel molten steel to obtain a second semi-steel molten steel; and,

[0046] In some embodiments, the mass fraction of C in the second semi-steel molten steel is 1.5% to 2.5%; the tapping temperature of the second semi-steel molten steel is 1350℃ to 1450℃.

[0047] The carbon content in the molten steel of the second half is increased by adding carbon to improve the denitrification effect. For example, the mass fraction of carbon in the molten steel of the second half can be 1.5%, 1.6%, 1.8%, 2.0%, 2.1%, 2.2%, 2.4%, 2.5%, etc.; the tapping temperature of the molten steel of the second half can be 1350℃, 1370℃, 1390℃, 1400℃, 1420℃, 1440℃, 1450℃, etc.

[0048] In some embodiments, the carbon addition is achieved by adding carbonaceous material to the bottom of the first semi-steel molten steel; wherein the carbonaceous material includes one or more of biomass pellets and coal powder, the mass fraction of C in the carbonaceous material is 50% to 99%, and the amount of carbonaceous material added is 5 kg / t steel to 15 kg / t steel.

[0049] Carbonaceous materials such as pulverized coal and carbon powder are added to the bottom of the semi-steel ladle. During the tapping process, the strong impact and agitation of the molten steel increase the carbon content of the semi-steel. This carbonization is achieved by utilizing the favorable kinetics of tapping, with the carbonaceous raw materials located at the bottom of the ladle. For example, the amount of carbonaceous material added can be 5 kg / t steel, 7 kg / t steel, 9 kg / t steel, 11 kg / t steel, 12 kg / t steel, 14 kg / t steel, 15 kg / t steel, etc.

[0050] S3. The second semi-steel molten steel and the second scrap steel are smelted in a second converter, and CO2 is used as the carrier gas to inject pulverized coal to reduce the nitrogen content of the molten steel, thereby obtaining converter molten steel.

[0051] In some embodiments, the amount of the second scrap steel added is 100 kg / t steel to 300 kg / t steel.

[0052] By employing a converter duplex process for steelmaking, the scrap steel ratio in the smelting process can be increased, while the smelting cycle can be controlled. For example, the amount of the second scrap steel added can be 100 kg / t steel, 130 kg / t steel, 150 kg / t steel, 180 kg / t steel, 200 kg / t steel, 220 kg / t steel, 250 kg / t steel, 300 kg / t steel, etc.

[0053] In some embodiments, the smelting time in the second converter is t2, which is 13 min to 20 min; wherein,

[0054] When the smelting time in the second converter is less than 12 minutes, CO2 is used as the carrier gas for injecting pulverized coal at the bottom of the converter.

[0055] When the smelting time in the second converter is 12 min to t2, pure argon gas is blown into the bottom of the converter.

[0056] In some implementations, the CO2 flow rate relative to a 300t converter is (3500 + t² × 500) Nm³. 3 The flow rate of the pulverized coal is (300 + t² × 50) kg / min, and the flow rate of the argon gas is 1000 Nm³. 3 / h~3000Nm 3 / h.

[0057] The flow rates of CO2 and pulverized coal can be adjusted appropriately based on the converter's tonnage. Bottom-blowing with pulverized coal increases carbon content, resulting in high absorption rates. Based on the characteristics of the decarburization reaction in the molten pool, the amount of pulverized coal injected is dynamically increased as the carbon content of the molten steel decreases, further enhancing the carbon absorption rate. Argon gas is switched at the end stage to stop further carbon increase. Argon gas is then switched back at the final carbon content to prevent the injection of CO2 from causing an increase in the final oxygen content. For example, t2 can be 13min, 14min, 15min, 16min, 17min, 18min, 19min, 20min, etc.; the CO2 flow rate can be 10000 Nm³. 3 / h, 10200Nm 3 / h, 10500Nm 3 / h, 10800Nm 3 / h, 11000Nm 3 / h, etc.; the flow rate of pulverized coal can be 950 kg / min, 960 kg / min, 980 kg / min, 1000 kg / min, 1020 kg / min, 1050 kg / min, etc.; the argon flow rate can be 1000 Nm 3 / h, 1200Nm 3 / h, 1500Nm 3 / h, 1800Nm 3 / h, 2000Nm 3 / h, 2500Nm 3 / h, 3000Nm 3 / h etc.

[0058] In some embodiments, the mass fraction of C in the converter molten steel is 0.02% to 0.06%, the mass fraction of N is ≤0.0018%, and the mass fraction of O is 0.03% to 0.05%; the tapping temperature of the converter molten steel is 1550℃ to 1700℃.

[0059] By injecting pulverized coal at the bottom to increase carbon and supplement heat, the heat output and denitrification effect are enhanced. Utilizing CO2 as a carrier gas generates twice the volume of CO, strengthening agitation and achieving better denitrification with improved kinetic conditions. This results in lower O content at the converter endpoint and reduced T and Fe content in the slag. The method provided in this application can increase the scrap steel ratio to 35%–75%, resulting in a nitrogen mass fraction in the molten steel ≤0.0018%, thus reducing the nitrogen content in the molten steel while maintaining a high scrap steel ratio during smelting. For example, the mass fraction of C can be 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, etc.; the mass fraction of N can be 0.0010%, 0.0012%, 0.0013%, 0.0014%, 0.0015%, 0.0017%, 0.0018%, etc.; the mass fraction of O can be 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, etc.; and the tapping temperature of the converter molten steel can be 1550℃, 1580℃, 1600℃, 1620℃, 1650℃, 1680℃, 1700℃, etc.

[0060] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0061] Example 1

[0062] In a 300t converter, 105t of scrap steel was charged into the first converter, and the smelting time was 10 minutes. From 0 to 5 minutes of smelting, pure CO2 was bottom-blown. From 5 to 10 minutes, CO2 was injected using pulverized coal at a flow rate of 3000 Nm³. 3 The coal powder flow rate was 210 kg / min, the carbon content of the molten steel was 2.0%, and the temperature was 1406℃. Steel tapping began. Biomass pellets and coal powder, containing carbon, were added to the bottom of the semi-steel ladle at a rate of 11 kg / t of steel. During the smelting process in the second converter, 66 tons of scrap steel were added, and the blowing time was 13 minutes. From 0 to 12 minutes of smelting, CO2 was injected into the coal powder at a flow rate of 10000 Nm³. 3 The coal powder flow rate is 950 kg / min; from the 12th to the 13th minute, bottom-blown pure argon gas is used at a flow rate of 3000 Nm³. 3 The steel melt carbon content was 0.036% at 1646℃, and the steel was tapped from the converter. The final nitrogen content was 13ppm, carbon content was 0.036%, oxygen content was 0.039%, and slag T.Fe content was 14%.

[0063] Example 2

[0064] In a 150t converter, 42t of scrap steel was charged into the first converter, and the smelting time was 12 minutes. From 0 to 5 minutes of smelting, pure CO2 was bottom-blown. From 5 to 12 minutes, CO2 was injected using pulverized coal at a flow rate of 1750 Nm³. 3 The coal powder flow rate is 140 kg / min, the carbon content of the molten steel is 1.8%, and the temperature is 1390℃. Steel tapping begins. Biomass pellets and coal powder, containing carbon, are added to the bottom of the semi-steel ladle at a rate of 6 kg / t steel. During the smelting process in the second converter, 26 tons of scrap steel are added, and the blowing time is 14 minutes. From 0 to 12 minutes of smelting, CO2 is injected through the coal powder at a flow rate of 5250 Nm³. 3 The coal powder flow rate is 500 kg / min; from the 12th to the 14th minute, bottom-blown pure argon gas is used at a flow rate of 1500 Nm³. 3 The steel melt carbon content was 0.04% at 1640℃, and the steel was tapped from the converter. The final nitrogen content was 12 ppm, carbon content was 0.04%, oxygen content was 0.035%, and slag T.Fe content was 13%.

[0065] Example 3

[0066] In the 210t converter, 86t of scrap steel was charged into the first converter, and the smelting time was 13 minutes. From 0 to 5 minutes of smelting, pure CO2 was blown in from the bottom. From 5 to 13 minutes, CO2 was injected using pulverized coal at a flow rate of 2940 Nm³. 3 The coal powder flow rate was 224 kg / min, the carbon content of the molten steel was 1.9%, and the temperature was 1387℃. Steel tapping began. Biomass pellets and coal powder, containing carbon, were added to the bottom of the semi-steel ladle at a rate of 9 kg / t steel. During the smelting process in the second converter, 53 tons of scrap steel were added, and the blowing time was 15 minutes. From 0 to 12 minutes of smelting, CO2 was injected into the coal powder at a flow rate of 7700 Nm³. 3 The coal powder flow rate is 735 kg / min; from the 12th to the 15th minute, bottom-blown pure argon gas is used at a flow rate of 2100 Nm³. 3 The steel melt carbon content was 0.038% at 1660℃, and the steel was tapped from the converter. The final nitrogen content was 11 ppm, carbon content was 0.038%, oxygen content was 0.038%, and slag T.Fe content was 15%.

[0067] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for smelting high scrap steel ratio, low nitrogen molten steel, characterized in that, The method of increasing the scrap steel ratio to 35%~75% includes: Molten iron and first scrap steel are smelted in a first converter to obtain first semi-steel molten steel. The amount of first scrap steel added is 250 kg / t·steel to 450 kg / t·steel. The smelting time in the first converter is t1, which is 10 min to 15 min. When the smelting time in the first converter is less than 5 min, pure CO2 is blown into the bottom of the converter. When the smelting time in the first converter is 5 min to t1, CO2 is used as the carrier gas to inject pulverized coal at the bottom of the converter. The first semi-steel molten steel is carbonized to obtain a second semi-steel molten steel, wherein the mass fraction of carbon in the second semi-steel molten steel is 1.5%~2.5%; the tapping temperature of the second semi-steel molten steel is 1350℃~1450℃; and, The second semi-steel molten steel and the second scrap steel are smelted in a second converter, and CO2 is used as the carrier gas to inject pulverized coal to reduce the nitrogen content of the molten steel, resulting in converter molten steel. The amount of the second scrap steel added is 100 kg / t steel to 300 kg / t steel. The smelting time in the second converter is t2, which is 13 min to 20 min. When the smelting time in the second converter is less than 12 min, CO2 is used as the carrier gas to inject pulverized coal at the bottom of the converter. When the smelting time in the second converter is between 12 min and t2, pure argon gas is blown into the bottom of the converter. In the molten steel from the converter, the mass fraction of C is 0.02%~0.06%, the mass fraction of N is ≤0.0018%, and the mass fraction of O is 0.03%~0.05%; the tapping temperature of the molten steel from the converter is 1550℃~1700℃.

2. The method according to claim 1, characterized in that, The CO2 flow rate is 2500 Nm³ relative to a 300-ton converter. 3 / h~4500Nm 3 / h, the flow rate of the pulverized coal is 200kg / min~400kg / min.

3. The method according to claim 1, characterized in that, For a converter with a capacity of 300 tons, the CO2 flow rate is (3500 + t2 × 500) Nm³. 3 The flow rate of the pulverized coal is (300 + t² × 50) kg / min, and the flow rate of the argon gas is 1000 Nm³. 3 / h~3000Nm 3 / h.

4. The method according to claim 1, characterized in that, The carbon addition is achieved by adding carbonaceous material to the bottom of the first semi-steel molten steel; wherein the carbonaceous material includes one or more of biomass particles and coal powder, the mass fraction of C in the carbonaceous material is 50%~99%, and the amount of carbonaceous material added is 5kg / t·steel to 15kg / t·steel.

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