Method for recycling liquid refining white slag from a converter

Abstract

This invention relates to the field of comprehensive resource utilization technology, specifically to a method for recycling liquid refined white slag in a converter. The specific steps are as follows: Before adding molten iron to the converter, liquid refined white slag with a basicity R≥3.0, FeO content≤1.0%, P content≤0.05%, and temperature≥1500℃ is added to the molten iron ladle, covered with carbonized rice husks, and added to the converter within 0.5 hours; the physical heat of the white slag is included as an independent variable in the heat balance calculation, and the amount of coolant and slag-forming material is dynamically adjusted; during the blowing process, staged slag forming and staged oxygen lance control are adopted, and the final carbon content is controlled to ≥0.09wt% and the final slag basicity is controlled to ≥3.0%; after continuous casting, the remaining white slag and remaining molten steel in the ladle are returned to the ladle of the next heat for secondary recycling. This invention can suppress converter splashing and sulfur reversion, improve the resource utilization rate of refined white slag, and reduce the consumption of slag-forming materials and metal materials.

Description

Technical Field

[0001] This invention relates to the field of comprehensive resource utilization technology, specifically to a method for recycling liquid refining slag in a converter. Background Technology

[0002] In the converter-LF refining-continuous casting steel production process, the LF refining process typically generates a certain amount of refining white slag, approximately 30 kg / t of steel. This type of refining white slag generally features high temperature, high basicity, high CaO content, low FeO content, and low phosphorus content. The temperature typically reaches above 1500℃, the basicity (CaO / SiO2) is greater than 3.0, the CaO content is approximately 50%–60%, the FeO content is usually less than 1%, and it also contains a certain amount of Al2O3 and MgO. Due to the high CaO content and physical heat of the refining white slag, from a metallurgical and energy utilization perspective, it has potential value for reuse in the steelmaking process.

[0003] Currently, steel companies primarily handle LF (sulfurized sulfide) refining slag through water cooling, stockpiling and aging, crushing and screening, outsourcing disposal, or partial reuse as building material raw materials. While these methods can stabilize the refining slag, the high-temperature physical heat carried by the liquid refining slag is largely lost during the process. Furthermore, water cooling easily leads to high Ca(OH)2 concentration materials, increasing the burden on subsequent transportation, stockpiling, and environmental treatment. Although some companies have attempted to crush, briquette, or process the cold refining slag into slag for reuse in the steelmaking process, these methods typically require additional cooling, crushing, screening, pressing, or drying equipment, resulting in longer process flows, higher costs, and difficulty in fully utilizing the original high-temperature liquid characteristics of the refining slag.

[0004] Existing technologies for recycling liquid refined white slag mainly focus on replacing some slag-forming materials with cold slag, or on single-use recycling of residual slag from steel ladles. While these technologies can reduce the consumption of auxiliary materials such as lime and fluorite to some extent, they typically only focus on the utilization of the chemical composition of the refined white slag, lacking systematic control over its impact on the high-temperature physical heat during converter smelting. When high-temperature liquid refined white slag directly enters the converter smelting system, the large amount of physical heat it carries alters the early-stage thermal balance of the converter, causing an increase in the initial furnace temperature. This may lead to premature and concentrated carbon-oxygen reactions, increasing the risk of splashing during the early blowing stage and affecting the stability and operational safety of converter smelting.

[0005] Meanwhile, existing technologies are mostly single-stage methods for utilizing refined white slag, such as returning cold refined white slag to the converter, reusing slag from ladle pouring, or replacing some auxiliary materials with refined white slag. A multi-stage closed-loop utilization system covering pre-addition to the ladle, dynamic smelting control in the converter, and secondary reuse of slag from ladle pouring has not yet been formed. Due to the lack of comprehensive control over the physical, thermal, and chemical composition and metallurgical reaction processes of liquid refined white slag, existing treatment methods still suffer from low resource utilization rates, insufficient physical and thermal utilization, difficulties in splash control, and insufficient stability in the reuse process.

[0006] Therefore, there is an urgent need to provide a method for recycling liquid refining white slag suitable for converter smelting processes. This method should fully utilize the high-temperature physical heat and high alkalinity characteristics of the refining white slag, while coordinating the adjustment of converter heat balance, slag formation system, oxygen supply system, and endpoint control. This will enable the safe, efficient, and closed-loop recycling of liquid refining white slag, and reduce the pressure of solid waste treatment and the consumption of steelmaking auxiliary materials. Summary of the Invention

[0007] To address the technical problems of insufficient physical heat utilization, easy splashing in the early stage of converter, and low resource utilization rate in the recycling of liquid refining white slag in existing LF refining processes, this invention provides a method for recycling liquid refining white slag in converters. By pre-adding liquid refining white slag to the molten iron ladle, adjusting the amount of coolant and slag-forming material, and synergistically controlling slag formation, oxygen supply, and the blowing endpoint, the residual slag in the ladle is recycled for a second time, thereby achieving safe, efficient, and closed-loop utilization of liquid refining white slag.

[0008] The technical solution of this invention is as follows: A method for recycling liquid refining slag in a converter includes the following steps: (1) Before the molten iron is poured into the converter, liquid refined white slag is added to the molten iron ladle; after adding, carbonized rice husks are covered on the surface of the molten iron ladle, and the molten iron is poured into the converter within 0.5 hours after adding the liquid refined white slag. (2) Determine the physical heat brought into the converter based on the temperature and amount of liquid refining slag, and adjust the amount of converter coolant and slag-forming material accordingly; (3) During the converter blowing process, blowing is carried out in accordance with the phased slag-forming material addition system and the phased oxygen lance position control system; (4) Control the carbon content and slag basicity at the end of converter blowing; (5) After the continuous casting is completed, the remaining liquid refining slag in the ladle is returned to the next cycle for reuse.

[0009] Furthermore, in step (1), the alkalinity R=CaO / SiO2≥3.0, FeO content≤1.0%, P content≤0.05%, and temperature≥1500℃ of the liquid refining white residue.

[0010] Furthermore, in step (1), the amount of liquid refining slag added is 7.7~15.4 kg / t steel.

[0011] Furthermore, the amount of liquid refining residue added is determined according to the following conditions: When the basicity R of the liquid refining slag is ≥3.5 and the proportion of molten iron in the furnace is >85%, the amount of liquid refining slag added is 11.5~15.4kg / t steel; When the basicity R of the liquid refining slag meets the condition of 3.0≤R<3.5, or the proportion of molten iron in the furnace is ≤85%, the amount of liquid refining slag added is 7.7~11.5kg / t steel.

[0012] Furthermore, in step (2), the specific method for adjusting the amount of converter coolant and slag-forming material added is as follows: (a) Based on the CaO content of the liquid refining slag, calculate the reduction in active lime according to material balance: Δm 石灰 =m 渣 ×ω CaO-渣 / ω CaO-石灰 In the formula m 渣 The amount of liquid refining residue added, ω CaO-渣 ω represents the mass fraction of CaO in liquid refining residue. CaO-石灰 This represents the effective CaO mass fraction in active lime. (b) Based on the physical heat introduced by the liquid refining slag, calculate the increase in limestone according to the heat balance: Δm 石灰石 =(Q 渣 -m 白云石 ×H 白云石 ) / H 石灰石 In the formula Q 渣 =m 渣 ×c 渣 ×(T 渣 -25), c 渣 The specific heat capacity of liquid white slag, T 渣 The measured temperature of liquid refining white residue, m 白云石 H represents the quality of raw dolomite added during the scrap steel stage. 白云石 The decomposition of dolomite units is endothermic, H 石灰石 The decomposition of limestone units is endothermic.

[0013] Furthermore, in step (3), the phased slag-forming material addition system is as follows: 0-3 minutes after the start of blowing, the amount of the first batch of slag material added is controlled to be 80%-85% of the total amount of slag-forming material added in the whole furnace, so that the slag can quickly form good fluidity and covering ability in the early stage of smelting, effectively suppressing the premature concentrated outbreak of carbon-oxygen reaction caused by the high temperature physical heat brought in by the liquid refining white slag; 3 minutes after the start of blowing, the remaining slag-forming material is added to gradually increase the slag basicity to 2.5-3.5, ensuring the continuous efficient dephosphorization and desulfurization. This phased feeding system delays the start time of the violent carbon-oxygen reaction to more than 3 minutes after the start of blowing, reduces the splashing frequency by more than 80%, and creates stable slag system conditions for the dephosphorization reaction.

[0014] Furthermore, in step (3), the phased oxygen lance position control system is specifically as follows: 0–3 min after the start of blowing: oxygen lance position ≤ 1.5 m; 3–10 minutes after the start of blowing: the oxygen lance position is lowered to 1.3–1.4 m; From the start of blowing to the end of blowing: the oxygen lance position is 1.2m.

[0015] By employing a low lance position of ≤1.5m in the initial stage of blowing (0-3 min) combined with rapid temperature increase for slag formation; lowering the lance position to 1.3-1.4m in the early to mid-stage of blowing (3-10 min) to suppress splashing by utilizing the good fluidity and foaming characteristics of liquid refined white slag; and further lowering the lance position to 1.2m in the late stage of blowing (10 min to the end) to complete the deep decarburization task, this lance position control system is matched with the slag characteristics under the condition of white slag recycling. Al2O3 in white slag can effectively lower the slag melting point and enhance the degree of foaming. Therefore, in the mid-stage of blowing, it is necessary to actively lower the lance position to avoid splashing caused by excessive foaming of the slag layer. Through the above-mentioned staged and precise control, both dephosphorization efficiency and splashing are ensured.

[0016] Furthermore, step (3) also includes the control of oxygen flow rate, specifically: 0-3 minutes after the start of blowing: oxygen flow rate is 91%-94% of the nominal flow rate; 3–10 minutes after the start of blowing: oxygen flow rate is reduced to 71–74% of the nominal flow rate; From the start of blowing to the end of blowing: the oxygen flow rate is restored to 91% of the nominal flow rate.

[0017] Furthermore, in step (4), the carbon content at the end of the converter blowing process is ≥0.09%. By controlling the carbon content at the end of the converter blowing process to ≥0.09%, the oxidizability of the molten steel at the end of the blowing process is reduced. Moreover, by increasing the carbon content at the end, the conditions for the sulfur reversion reaction are reduced from the thermodynamic source, so that the sulfur reversion increment caused by the white slag recycling is controlled within 0.005%.

[0018] Furthermore, in step (4), the final slag basicity is ≥3.0. By controlling the final slag basicity of the converter to ≥3.0, it is ensured that the slag has a sufficiently high desulfurization capacity. High basicity slag is conducive to the transfer and fixation of sulfur from molten steel to slag. At the same time, combined with the low oxidation control strategy of final carbon content ≥0.09%, the two work together to suppress the sulfur reversion problem in the white slag recycling process and ensure that the final sulfur content of molten steel meets the requirements of specialty steel.

[0019] The beneficial effects of this invention are as follows: (1) This invention screens qualified white slag by detecting the basicity, FeO content and P content of the liquid refining white slag after LF refining; before the converter is added to the molten iron ladle, covered with carbonized rice husks and added to the converter within 0.5 hours; the physical heat of the white slag is included as an independent variable in the heat balance calculation, and the amount of coolant and slag-forming material is dynamically adjusted; staged slag-forming and staged oxygen lance control are adopted, and the carbon content and slag basicity at the blowing endpoint are controlled; after continuous casting, the remaining white slag and remaining molten steel are returned to the ladle of the next heat, realizing the closed-loop utilization of liquid refining white slag from screening, primary reuse, converter collaborative control to secondary reuse, improving the stability of reuse and resource utilization rate.

[0020] (2) This invention utilizes the high alkalinity, high CaO content and high temperature physical heat of refined white slag to replace part of the active lime, and increases the amount of lower-priced limestone, thereby reducing the slag-making cost by about RMB 0.85 / ton of steel; through heat balance pre-regulation and staged oxygen lance control, the splashing frequency is reduced by more than 80%; through endpoint carbon control and LF deoxidation slag-making, the sulfur return increment is controlled within 0.005%, which is conducive to improving smelting safety and maintaining stable steel quality.

[0021] (3) This invention recovers the residual molten steel carried by the white slag through pre-addition to the molten iron ladle and secondary reuse of the molten steel in the ladle, reducing metal loss caused by remelting blow-off and splashing, thus reducing metal consumption by approximately 0.168 kg / t of steel; at the same time, it achieves a white slag resource utilization rate of 90%, reducing the pressure of solid waste transportation and disposal. Based on an annual steel production of 1.7 million tons, the annualized comprehensive benefit is approximately RMB 2.1682 million, and no new large-scale equipment is required, demonstrating good economic benefits and promotional value. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention are clearly and completely described. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0023] Example 1 The technical solution of this invention was applied to the entire process of a 120-ton converter in a steel plant.

[0024] 1. Basic conditions Nominal converter capacity: 120 tons; average annual output: 1.7 million tons; main steel grades: slab specialty steel (refined ratio above 95%).

[0025] The previous method for treating liquid refining slag was to transport it to the preparation workshop for water treatment and then outsource the treatment, resulting in a resource utilization rate of less than 30%. Consumption of quicklime before implementation: 23.97 kg / t steel; Limestone consumption before implementation: 18.82 kg / t steel; Before implementation, the amount of slag generated was approximately 2.53 kg / t of steel.

[0026] 2. Typical components of white residue (based on sampling data from the production day) are shown in Table 1: Table 1 Typical components of liquid refining residue

[0027] 3. Typical conditions for molten iron Molten iron temperature: 1320℃; Si content in molten iron: 0.50%; P content in molten iron: 0.145%; S content in molten iron: 0.035%.

[0028] 4. Specific Implementation Steps A method for recycling liquid refining slag in a converter includes the following steps: (1) Acquisition and detection of white residue After LF refining, about 4 tons of liquid refining slag were generated in the ladle. After sampling and testing, the slag had an alkalinity R=3.22, a temperature of 1550℃, and FeO=0.45%. All indicators met the conditions for reuse, and this batch of liquid refining slag was selected for reuse.

[0029] (2) Pre-filling of molten iron into the ladle Before the molten iron is poured into the converter, 1.38 tons of the aforementioned 4 tons of liquid refined white slag are poured into the molten iron ladle, with the amount of liquid refined white slag added being 11.5 kg / t of steel. After addition, carbonized rice husks are placed on the surface of the molten iron in the ladle, and the molten iron is poured into the converter within 0.5 hours after the addition of the liquid refined white slag.

[0030] (3) Heat balance calculation and adjustment Before the molten iron is poured into the converter, a heat balance calculation model is established that includes the physical heat input of liquid refined white slag. The physical heat calculation formula for liquid refined white slag is as follows: Q 渣 =m 渣 ×c 渣 ×(T 渣 -25) In the formula m 渣 The mass of liquid refined white residue is expressed in kg; cresidue is taken as having an average specific heat capacity of 1.2 kJ / (kg2). ℃); T 渣 The measured temperature of the white residue is in °C.

[0031] Based on the calculation of 1.38t of liquid refined white slag at 1550℃ in this embodiment, the physical heat introduced is: Q 渣 =1.38×1000×1.2×(1550-25)=2.53×10 6 kJ.

[0032] During the scrap steel addition stage, 1 ton of raw dolomite is added in advance. The heat absorbed by the decomposition of dolomite carbonates initially offsets part of the excess heat from the liquid refining slag. The remaining heat load is balanced by increasing the heat absorbed by the decomposition of limestone. The simplified calculation formula for heat balance compensation is as follows: Δm 石灰石 = (Q) 渣 -m 白云石 ×H 白云石 ) / H 石灰石 In the formula m 白云石 =1000kg is the mass of dolomite added during the scrap steel period, H 白云石 =1550kJ / kg is the unit endothermic heat of decomposition of raw dolomite, H 石灰石 =1780kJ / kg is the unit heat of heat absorbed during the decomposition of limestone; Calculated: Δm 石灰石 =(2.53×10 6 -1000×1550) / 1780=548kg, meaning this furnace requires approximately 548kg more limestone. Regarding material alkalinity compensation, CaO in the white slag can replace quicklime; the replacement amount is calculated using the following formula: Δm 石灰 =m 渣 ×ωCaO-渣 / ω CaO-石灰 In this embodiment, the CaO content of the white slag is 56.05%, and the effective CaO content of the active lime is 90%. The calculated value is: Δm 石灰 =1380×0.5605 / 0.90=859kg, meaning the amount of active lime reduced is approximately 859kg (about 0.86t) / furnace.

[0033] It should be noted that in the above single-furnace calculation, Δm 石灰石 The 548 kg figure is only a theoretical value for heat balance compensation, considering only the heat absorbed by limestone decomposition to offset the physical heat of the white slag. In actual production, because this invention changes the addition of dolomite from multiple stages of the original smelting process to adding 1 t at the scrap steel stage, and only the remaining dolomite is added during the smelting process, the heat required to offset the reduced amount of original dolomite needs to be compensated by adding more limestone. Therefore, the actual increase in limestone is higher than the theoretical value for heat balance. In addition, fluctuations in the composition of white slag in different furnaces and the secondary reuse of residual white slag also lead to deviations between the annual statistical value and the theoretical value for a single furnace. The average increase in limestone in the workshop's annual statistics is 13.53 kg / t steel (approximately 1624 kg / furnace), of which heat balance compensation (offsetting the physical heat of white slag) accounts for about 34%, and heat compensation after the reduction of dolomite and other factors such as CaO compensation account for about 66%.

[0034] Overall thermal balance control logic: In the scrap steel period, 1 ton of dolomite is added first to absorb heat, and then limestone is added and active lime is reduced to counteract the high-temperature physical heat brought in by the liquid refining slag and suppress the concentrated burst of carbon and oxygen splashing in the early stage of the converter.

[0035] (4) Converter iron charging and blowdown The molten iron (including the pre-added liquid refined white slag) in the iron ladle is added into the converter, along with scrap steel and the adjusted amount of limestone, and the blowing process begins.

[0036] 0-3 minutes after the start of blowing: This stage is the initial smelting stage - slag formation stage. After adding scrap steel, add 1 t of dolomite to balance the heat.

[0037] The amount of the first batch of slag-forming material added is controlled to be 82% of the total amount of slag-forming material added in the whole furnace, so as to promote slag formation and make the slag have basic fluidity and covering ability. Three minutes after the start of blowing, the remaining slag-forming material is added to gradually increase the slag basicity to 2.5-3.5 and enter the efficient dephosphorization stage.

[0038] (5) Gun position and flow control To suppress splashing and ensure dephosphorization efficiency, the oxygen lance position and oxygen flow rate are controlled in stages according to the following time series: 0-3 minutes (initial smelting stage): Gun position 1.5 meters, oxygen flow rate 32000-33000 Nm³ 3 / h (nominal flow rate 35000 Nm) 3 (91% to 94% of the oxygen flow rate), using low gun position and high oxygen flow rate can promote rapid temperature increase and slag formation, creating conditions for dephosphorization; 3–10 minutes (early and middle stages of smelting): Due to the presence of white slag, good fluidity, and good slag foaming, the lance position needs to be gradually lowered to 1.3–1.4 meters and the flow rate reduced to 25,000–26,000 Nm³ to suppress splashing. 3 / h (nominal flow rate 35000 Nm) 3 (71%~74% of / h), promoting the dephosphorization reaction and inhibiting splashing; 10 minutes until the end of the blowing process (decarburization period): Return to low lance position 1.2 meters, flow rate 32000 Nm 3 / h (nominal flow rate 35000 Nm) 3 (91% of / h), completing the decarbonization task.

[0039] (6) Endpoint control The carbon content at the end of the blowing process was controlled at 0.10%, which is 0.04% higher than the conventional control value (0.06%). The slag basicity at the end was controlled at 3.2, and the sulfur content at the end was measured at 0.038%, which is only 0.003% higher than the sulfur content of the molten iron entering the furnace (0.035%), and the sulfur return increment was controlled within 0.005%.

[0040] (7) Secondary reuse of ladle injection residue After continuous casting is completed, about 2.5 tons of white slag and a small amount of molten steel are left in the ladle. Before the next heat of steel is tapped from the converter, the ladle containing the remaining white slag is hoisted to the tapping bay. During the tapping process, the strong impact force and high temperature of the molten steel are used to mix the white slag, which melts rapidly and forms top slag.

[0041] (8) Steel tapping and LF-assisted desulfurization After tapping, the steel enters the LF process. Based on the oxygen content at the station (approximately 400 ppm), about 200 meters of aluminum wire are fed in at a ratio of 1 ppm oxygen to 0.5 meters of aluminum wire to remove dissolved oxygen from the steel. The steel is then heated to 1590℃ and calcium carbide is added to create white slag. The steel is then bottom-blown and stirred for 7 minutes, and the final sulfur content is reduced to 0.008%, meeting the requirements for specialty steel.

[0042] 5. Implementation Effect Analysis The implementation effect of the technical solution in this embodiment is shown in Table 2: Table 2 Implementation Effect Analysis

[0043] As can be seen from the data in Table 2, after applying the technical solution of this invention, the resource utilization rate of white slag increased from less than 30% to 90%, the consumption of active lime decreased by 5.21 kg / t steel, the metal consumption decreased by 0.168 kg / t steel, the number of splashing accidents decreased from 12 times per month to 2 times, the sulfur recovery increment was controlled at 0.003%, and it did not have an adverse impact on the quality of molten steel.

[0044] The project benefits are calculated as follows: (1) Annualized benefits for the whole year: Based on the prices of quicklime (311 yuan / t) and limestone (57 yuan / t), and an annual output of 1.7 million tons, the calculation formula is: (Decrease in quicklime price × quicklime unit price - Increase in limestone price × limestone unit price) × 1.7 million tons = (5.21 × 0.311 - 13.53 × 0.057) × 1.7 million tons = 1.4435 million yuan / year.

[0045] (2) Transportation and disposal costs: Reduced transportation costs per ton of steel: 0.114 yuan / t - 0.065 yuan / t = 0.05 yuan / t; Annualized benefit: 0.05 yuan / t × 1.7 million tons = 85,000 yuan / year; (3) Consumption of metal materials: Metal consumption decreased by 1068.852 kg / t - 1068.684 kg / t = 0.168 kg / t; Annualized benefit: 0.168 kg / t × 1.7 million tons × 2.24 yuan / kg = 639,700 yuan.

[0046] In summary, implementing the technical solution of this invention reduces slag-making material costs by RMB 1.4435 million per year, metal consumption by RMB 639,700 per year, and transportation and disposal costs by RMB 85,000 per year, resulting in a total annualized comprehensive benefit of RMB 2.1682 million. This benefit is achieved through process optimization alone, without increasing investment in large-scale equipment, demonstrating an extremely high return on investment.

[0047] Although the present invention has been described in detail with reference to preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for recycling liquid refining slag in a converter, characterized in that, Includes the following steps: (1) Before the molten iron is poured into the converter, liquid refined white slag is added to the molten iron ladle; after adding, carbonized rice husks are covered on the surface of the molten iron ladle, and the molten iron is poured into the converter within 0.5 hours after adding the liquid refined white slag. (2) Determine the physical heat brought into the converter based on the temperature and amount of liquid refining slag, and adjust the amount of converter coolant and slag-forming material accordingly; (3) During the converter blowing process, blowing is carried out in accordance with the phased slag-forming material addition system and the phased oxygen lance position control system; (4) Control the carbon content and slag basicity at the end of converter blowing; (5) After the continuous casting is completed, the remaining liquid refining slag in the ladle is returned to the next cycle for reuse.

2. The method as described in claim 1, characterized in that, In step (1), the alkalinity R=CaO / SiO2≥3.0, FeO content≤1.0%, P content≤0.05%, and temperature≥1500℃ of the liquid refining white residue.

3. The method as described in claim 1, characterized in that, In step (1), the amount of liquid refining slag added is 7.7~15.4 kg / t steel.

4. The method as described in claim 3, characterized in that, The amount of liquid refining residue added is determined according to the following conditions: When the basicity R of the liquid refining slag is ≥3.5 and the proportion of molten iron in the furnace is >85%, the amount of liquid refining slag added is 11.5~15.4kg / t steel; When the basicity R of the liquid refining slag meets the condition of 3.0≤R<3.5, or the proportion of molten iron in the furnace is ≤85%, the amount of liquid refining slag added is 7.7~11.5kg / t steel.

5. The method as described in claim 1, characterized in that, In step (2), the specific method for adjusting the amount of converter coolant and slag-forming material added is as follows: (a) Based on the CaO content of the liquid refining slag, calculate the reduction in active lime according to material balance: Δm 石灰 =m 渣 ×ω CaO-渣 / ω CaO-石灰 In the formula: m 渣 The amount of liquid refining residue added, ω CaO-渣 ω represents the mass fraction of CaO in liquid refining residue. CaO-石灰 This represents the effective CaO mass fraction in active lime. (b) Based on the physical heat introduced by the liquid refining slag, calculate the increase in limestone according to the heat balance: Δm 石灰石 =(Q 渣 -m 白云石 ×H 白云石 ) / H 石灰石 In the formula Q 渣 =m 渣 ×c 渣 ×(T 渣 -25), c 渣 The specific heat capacity of liquid white slag, T 渣 The measured temperature of liquid refining white residue, m 白云石 H represents the quality of raw dolomite added during the scrap steel stage. 白云石 The decomposition of dolomite units is endothermic, H 石灰石 The decomposition of limestone units is endothermic.

6. The method as described in claim 1, characterized in that, In step (3), the phased slag-forming material addition system is as follows: 0 to 3 minutes after the start of blowing, the amount of the first batch of slag-forming material added is controlled to be 80% to 85% of the total amount of slag-forming material added in the whole furnace; 3 minutes after the start of blowing, the remaining slag-forming material is added to gradually increase the slag basicity to 2.5 to 3.

5.

7. The method as described in claim 1, characterized in that, In step (3), the phased oxygen lance position control system is specifically as follows: 0–3 min after the start of blowing: oxygen lance position ≤ 1.5 m; 3–10 minutes after the start of blowing: the oxygen lance position is lowered to 1.3–1.4 m; From the start of blowing to the end of blowing: the oxygen lance position is 1.2m.

8. The method as described in claim 7, characterized in that, Step (3) also includes controlling the oxygen flow rate, specifically: 0-3 minutes after the start of blowing: oxygen flow rate is 91%-94% of the nominal flow rate; 3–10 minutes after the start of blowing: reduce the oxygen flow rate to 71%–74% of the nominal flow rate; From the start of blowing to the end of blowing: the oxygen flow rate is restored to 91% of the nominal flow rate.

9. The method as described in claim 1, characterized in that, In step (4), the carbon content at the end of the converter blowing process is ≥0.09%.

10. The method as described in claim 1, characterized in that, In step (4), the final slag alkalinity is ≥3.0.

Images