Production method for optimizing smelting of low-silicon molten iron

Abstract

The invention discloses a production method for optimizing smelting of low-silicon molten iron, and belongs to the technical field of steel smelting. The method comprises the following steps: 1) optimizing a raw material ratio: selecting high-quality iron ore, coke and a flux as main raw materials; the flux is a mixture of limestone and dolomite in a mass ratio of (0.9-1.1): (0.9-1.1); 2) smelting process parameter optimization: controlling the air volume, air pressure and air temperature of the blast furnace in the blast furnace smelting process; meanwhile, the coke load is reasonably adjusted and is kept between 2.5 and 3.0; when the low-silicon molten iron is smelted, converter slag charge is added in three batches; (3) improving an in-furnace operation technology; (4) molten iron pretreatment; and 5) quality detection and feedback control. The invention aims to realize stable production of the low-silicon molten iron, reduce the production cost and improve the smelting efficiency and the molten iron quality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel smelting, and particularly relates to a production method for optimizing smelting of low-silicon molten iron. BACKGROUND

[0002] In 2024, the molten iron was implemented to reduce cost and increase efficiency, and the silicon content of the molten iron was reduced by 0.14% compared with the original. In the early stage of smelting of low-silicon molten iron, the heat is low, the slag-making material of the converter cannot be completely melted, and the smelting dry-back phenomenon is easily caused. At the same time, the converter needs to be overblown to increase the temperature, the consumption of steel materials is increased, and the purity of the molten iron is reduced. In the process of converter steelmaking, silicon is an important heat-generating element. When the silicon content in the molten iron is high, silicon will be oxidized in the initial stage of converter blowing, generating silicon dioxide (SiO2), and releasing a large amount of heat, thereby increasing the temperature in the furnace. For example, the oxidation reaction of silicon, which is an exothermic reaction, can significantly increase the temperature in the furnace by oxidizing 1% of silicon. If the silicon content of the molten iron is low, this exothermic process is weakened, making it difficult to increase the temperature in the early stage of the converter. Insufficient heat input: low silicon content in the molten iron means a decrease in heat sources in the initial stage of converter blowing. Converter steelmaking mainly relies on the physical heat of the molten iron and the chemical heat released by the oxidation reaction of the elements in the molten iron. The physical heat refers to the temperature of the molten iron itself, and the chemical heat refers to the heat released by the oxidation reaction of the elements in the molten iron. Low silicon content reduces the chemical heat, and the physical heat is gradually lost during the blowing process, so it is difficult to maintain a high temperature in the early stage of the converter.

[0003] In the steel production process, molten iron is an important intermediate product, and its quality directly affects the quality and efficiency of subsequent steelmaking and rolling. Low-silicon molten iron refers to molten iron with a silicon content of less than 0.3%, which is suitable for producing high-strength steel, high-quality alloy steel and other high-end products. However, the reduction of Si content in the molten iron causes poor slagging in the converter under the existing process, and the converter needs to be overblown to increase the temperature, increasing the consumption of steel materials and reducing the purity of the molten iron. In the early stage of smelting of low-silicon molten iron, the heat is low, the slag-making material of the converter cannot be completely melted, and the smelting dry-back phenomenon is easily caused, leading to accidents such as sticking of the lance and increasing the labor intensity of workers. Low-silicon molten iron causes a lack of heat in the converter smelting, and the converter needs to be overblown to increase the temperature, increasing the consumption of steel materials. Due to the lack of chemical heat, low-silicon molten iron needs to be overblown to increase the temperature in the converter, resulting in a high oxygen content in the steel, an increase in the consumption of deoxidizers, an increase in deoxidation products, and an increase in inclusions in the molten iron, which seriously affects the purity of the molten iron and reduces the quality of the molten iron. At the same time, the early heat of the molten iron is insufficient, and the slagging is poor, and the existing slag-making system and lance position system cannot meet the existing molten iron conditions. However, the traditional smelting method of low-silicon molten iron has some problems, such as unstable control of silicon content, high smelting cost, and large fluctuations in furnace conditions. Therefore, it is of great practical significance to develop a smelting method for optimizing low-silicon molten iron. SUMMARY

[0004] The purpose of the present application is to provide a production method for optimizing the smelting of low-silicon molten iron, optimizing the converter slagging system and adjusting the oxygen lance position system, making the converter slag early, reducing the poor slagging due to insufficient heat in the early stage, improving the early dephosphorization efficiency, reducing the converter point blowing rate, and improving the purity of the molten iron. At the same time, through the improvement of raw material ratio, optimization of smelting process parameters and the use of advanced in-furnace operation technology, stable production of low-silicon molten iron is realized, production cost is reduced, and smelting efficiency and molten iron quality are improved.

[0005] To solve the above technical problems, the present application adopts the following technical solutions:

[0006] The present application is a production method for optimizing the smelting of low-silicon molten iron, comprising:

[0007] 1) Raw material ratio optimization: high-quality iron ore, coke and flux are selected as the main raw materials; the flux is a mixture of limestone and dolomite, with a mass ratio of 0.9-1.1:0.9-1.1; the mass ratio of iron ore, coke and flux is 4-5:0.8-1.2:0.4-0.6, preferably 4.5:1:0.5;

[0008] 2) Smelting process parameter optimization: during the blast furnace smelting process, the blast furnace air volume, blast pressure and blast temperature are controlled; the air volume is controlled at 1000-1200 m 3 / min, the blast pressure is controlled at 150-180 kPa, and the blast temperature is controlled at 1100-1200℃; at the same time, the coke load is reasonably adjusted and maintained at 2.5-3.0; by optimizing these process parameters, the reduction reaction in the blast furnace is ensured to proceed fully, the reduction amount of silicon is reduced, and thus the silicon content in the molten iron is controlled;

[0009] A low-silicon molten iron smelting slagging system is developed, and the converter slag is added in three batches during the smelting of low-silicon molten iron; the first batch of slag is added before the molten iron is mixed or when the blowing starts, and the addition amount is 1 / 2-1 / 3 of the total amount; the second batch of slag is added after the first batch of slag is fully melted, and the addition amount is 1 / 3 of the total amount; the last batch of slag must be added completely 3 minutes before the carbon is drawn and the furnace is emptied, otherwise the slag cannot be melted in time;

[0010] 3) In-furnace operation technology improvement: the layered charging technology is adopted, and the iron ore and coke are charged in layers in the blast furnace, so that the material distribution in the furnace is more uniform, the permeability and reduction efficiency in the furnace are improved; at the same time, cooling walls are arranged on the inner wall of the blast furnace to prevent the formation of clinkers in the furnace and the erosion of the furnace wall, and to maintain the stable operation of the blast furnace;

[0011] 4) Molten iron pretreatment: after the molten iron flows out of the blast furnace, the molten iron is pretreated by spraying desiliconizing agent, which further reduces the silicon content in the molten iron and ensures that the silicon content in the molten iron is stably below 0.3%.

[0012] 5) Quality inspection and feedback control: During the smelting process, the molten iron is sampled and tested regularly to analyze its chemical composition and temperature. According to the test results, the raw material ratio, process parameters and furnace operation are adjusted in time to realize dynamic control of the low-silicon molten iron smelting process. The converter oxygen lance position is optimized. The lance position is raised in the early stage to increase the FeO in the slag to meet the FeO required for the rapid dissolution of the white ash in the early stage and ensure the dephosphorization rate. After slagging, the lance position is raised in time to avoid drying out and overflowing slag. Increasing the FeO in the slag promotes the dissolution of the second batch of white ash. When the carbon-oxygen reaction weakens, the high-low-high lance position mode is adopted in time to promote the slag penetration. In the later stage, when the temperature is high, dolomite is added appropriately. The cooling agent, iron oxide scale and other iron-containing oxides must be added before 10 minutes. The lance pressure time is greater than 60 seconds to promote the reduction of FeO in the slag, protect the slag system, and improve the effect of splashing slag to protect the furnace.

[0013] Furthermore, the grade of the iron ore is not less than 60%, and the sulfur content is less than 0.05%; the ash content of the coke is less than 12%, and the sulfur content is less than 0.6%.

[0014] Furthermore, the mass ratio of the limestone to dolomite is 1:1.

[0015] Furthermore, the second batch of slag is usually added in small batches multiple times. Multiple additions are beneficial to the dissolution of lime, and small batches can also be used to control the outflow of foam slag in the furnace.

[0016] Furthermore, the water temperature difference of the cooling wall is controlled between 10-15°C.

[0017] Furthermore, the desiliconizing agent is a magnesium-based composite desiliconizing agent.

[0018] Furthermore, the injection rate of desiliconizing agent is controlled at 1.0-1.5 kg / t molten iron.

[0019] Furthermore, the air volume of the blast furnace is 1100m 3 / min, wind pressure is 160kPa, wind temperature is 1150℃, coke load is 2.8.

[0020] Furthermore, the injection amount of the desiliconizing agent is controlled at 1.2 kg / t molten iron.

[0021] Furthermore, the water temperature difference of the cooling wall is controlled at 12°C.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The method for smelting low-silicon molten iron by a small slag process is optimized, the addition of slag material in the early stage is reduced, a small amount of slag material is added in multiple batches, the gun position is optimized, the early slag material is fully melted, the dephosphorization effect in the early stage is increased, the terminal slag basicity requirement is met, the converter point blowing rate is reduced, the deoxidizer consumption is reduced, and the molten steel purity is improved.

[0024] The smelting method has the following advantages: 1. By optimizing the raw material ratio and smelting process parameters, the silicon content in the molten iron is effectively controlled to ensure stable production of low-silicon molten iron. 2. Advanced in-furnace operation technology and molten iron pretreatment method are adopted to improve the smelting efficiency and molten iron quality, and reduce the production cost. 3. Dynamic control of the smelting process is realized, the flexibility and stability of production are improved, and it has important significance for the technical upgrading and product structure adjustment of steel enterprises. BRIEF DESCRIPTION OF DRAWINGS

[0025] The application will be further described below in conjunction with the drawings.

[0026] Figure 1 Comparison before and after position optimization. DETAILED DESCRIPTION

[0027] A production method for optimizing the smelting of low-silicon molten iron, comprising:

[0028] 1) Raw material ratio optimization: high-quality iron ore, coke and flux are selected as main raw materials, and the mass ratio of iron ore, coke and flux is 4.5:1:0.5. The grade of iron ore is not less than 60%, and the sulfur content is less than 0.05%; the ash content of coke is less than 12%, and the sulfur content is less than 0.6%; the flux uses a mixture of limestone and dolomite, and the ratio is 1:1. By accurately controlling the chemical composition and physical properties of the raw materials, a good foundation is provided for the smelting of low-silicon molten iron.

[0029] C(％) Si (%) Mn (%) P(％) S(％) Temperature (°C) 3.2-4.0 0.2-0.5 0.3-0.57 0.120-0.150 0.020-0.040 1240-1320

[0030] 2) Smelting process parameter optimization: in the blast furnace smelting process, the blast furnace air volume, blast pressure and blast temperature are controlled; the air volume is controlled at 1000-1200 m 3 / min, the blast pressure is controlled at 150-180 kPa, and the blast temperature is controlled at 1100-1200℃. At the same time, the coke load is reasonably adjusted and maintained at 2.5-3.0. By optimizing these process parameters, the reduction reaction in the blast furnace is ensured to proceed fully, the reduction amount of silicon is reduced, and thus the silicon content in the molten iron is controlled.

[0031] According to the low silicon content and low physical heat of the hot metal in our plant, a low-silicon hot metal smelting and slagging system is developed. The slag material is added in three batches when smelting low-silicon hot metal. The first batch of slag material is added before the hot metal is mixed or at the beginning of blowing, and the amount is 1 / 2-1 / 3 of the total amount (1000-2000 kg is reduced under normal circumstances). The second batch of slag material is added after the first batch of slag material is melted and the silicon and manganese oxidation of the hot metal is basically completed. The amount of the second batch of slag material is 1 / 3 of the total amount of slag, and the second batch of slag material is usually added in small batches and multiple times, which is beneficial to the dissolution of lime and can also control the foam slag in the furnace. The last batch of slag material must be added completely 3 minutes before the carbon is drawn and the furnace is tapped, otherwise the slag cannot be melted in time. The comparison of the amount of slag added in the early stage of the low-slag process is shown in Table 1.

[0032]

[0033] By analyzing the composition of the slag and based on the material balance and heat balance in the early stage, when the silicon content of the hot metal is 0.15%-0.30%, the amount of lime added in the early stage is controlled at 1500 kg-3000 kg, which can meet the requirement of the early stage basicity. The specific situation is shown in Table 2.

[0034] Table 2 Comparison of converter slag

[0035]

[0036] Compared with the normal smelting method, the low-silicon hot metal smelting method has a lower basicity, but the basicity of 2.72 can meet the process requirements, and the Σ(FeO) in the slag is reduced, which improves the slag system and is beneficial to the slag splashing and furnace protection.

[0037] 3) Improvement of furnace operation technology: The layered charging technology is adopted, and the iron ore and coke are charged in layers in the blast furnace, so that the material distribution in the furnace is more uniform, the permeability and reduction efficiency in the furnace are improved. At the same time, cooling walls are arranged on the inner wall of the blast furnace, and the water temperature difference of the cooling walls is controlled between 10-15℃, which prevents the formation of nodules in the furnace and the erosion of the furnace wall, and maintains the stable operation of the blast furnace.

[0038] 4) Hot metal pretreatment: After the hot metal flows out of the blast furnace, the method of spraying desiliconizing agent is used for pretreatment. The desiliconizing agent is a magnesium-based composite desiliconizing agent, and the spraying amount is controlled at 1.0-1.5 kg / t of hot metal. By spraying the desiliconizing agent, the silicon content in the hot metal is further reduced, and the silicon content of the hot metal is ensured to be stable below 0.3%.

[0039] 5) Quality detection and feedback control: During the smelting process, regular sampling and testing of molten iron is carried out to analyze the chemical composition and temperature of the molten iron. According to the test results, timely adjustment of raw material ratio, process parameters and furnace operation is realized to achieve dynamic control of the low-silicon molten iron smelting process. Before the optimization of the oxygen lance position, the lance position is increased to increase the (FeO) in the slag, meet the needs of the early stage of white ash fast dissolution, ensure the dephosphorization rate, and timely increase the lance position after slagging to avoid dry return and slag overflow, increase the (FeO) in the slag to promote the dissolution of the second batch of added white ash. When the carbon-oxygen reaction is weakened, timely high-low-high lance position mode operation is adopted to promote slag penetration, and dolomite can be added appropriately in the later stage when the temperature is high. The iron oxides such as cooling agent and iron oxide scale must be added completely 10 minutes before, the lance pressure time is greater than 60 seconds, the reduction of (FeO) in the slag is promoted, the slag system is protected, and the effect of slag splashing is improved. The comparison of the optimized lance position is as follows Figure 1 .

[0040] Verification of the effect of the less slag process:

[0041]

[0042] The smelting method has the following advantages:

[0043] 1. By optimizing the raw material ratio and smelting process parameters, the silicon content in the molten iron is effectively controlled, and the stable production of low-silicon molten iron is ensured.

[0044] 2. The use of advanced furnace operation technology and molten iron pretreatment method improves the smelting efficiency and molten iron quality, and reduces the production cost.

[0045] 3. Dynamic control of the smelting process is realized, which improves the flexibility and stability of production, and has important significance for the technical upgrading and product structure adjustment of steel enterprises.

[0046] After the optimization of the method of smelting low-silicon molten iron by the less slag process, the addition of slag material in the early stage is reduced, a small amount of slag material is added in multiple batches, and the lance position is optimized, so that the early stage slag material is fully melted, the dephosphorization effect is improved, the terminal slag alkalinity requirement is met, the converter point blowing rate is reduced, the deoxidizer consumption is reduced, and the steel purity is improved.

[0047] The above-described embodiments are only descriptions of preferred modes of the present application and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A production method for optimizing the smelting of low-silicon molten iron, characterized by: include: 1) Optimization of raw material ratio: Select high-quality iron ore, coke and flux as the main raw materials; the flux is a mixture of limestone and dolomite with a mass ratio of 0.9-1.1:0.9-1.1; the mass ratio of iron ore, coke and flux is: 4-5:0.8-1.2:0.4-0.6; 2) Optimization of smelting process parameters: During the blast furnace smelting process, control the air volume, air pressure and air temperature of the blast furnace; the air volume is controlled at 1000-1200m 3 / min, wind pressure controlled at 150-180kPa, and wind temperature controlled at 1100-1200℃; at the same time, the coke load was reasonably adjusted to maintain between 2.5-3.0; by optimizing these process parameters, the reduction reaction in the blast furnace was ensured to proceed fully, the amount of silicon reduced was reduced, and thus the silicon content in the molten iron was controlled; Establish a slag-making system for smelting low-silicon hot metal. When smelting low-silicon hot metal, converter slag is added in three batches. The first batch of slag is added before adding hot metal or when blowing starts, and the amount added is 1 / 2-1 / 3 of the total amount. The second batch of slag is added in small batches after the first batch of slag has been melted and the oxidation of silicon and manganese in the hot metal has basically completed. The amount added is 1 / 3 of the total slag. The last batch of slag must be added 3 minutes before carbon pulling and pouring the furnace, otherwise there will be no time to melt the slag. 3) Improvements to furnace operation technology: Layered charging technology is used to load iron ore and coke into the blast furnace in layers, resulting in more even distribution of materials within the furnace, improved air permeability, and reduction efficiency. Furthermore, cooling staves are installed on the inner walls of the blast furnace to prevent nodules and erosion, maintaining stable operation. 4) Hot metal pretreatment: After the hot metal flows out of the blast furnace, it is pretreated by spraying a desiliconizing agent. By spraying the desiliconizing agent, the silicon content in the hot metal is further reduced to ensure that the silicon content of the hot metal is stabilized below 0.3%; 5) Quality inspection and feedback control: During the smelting process, the molten iron is sampled and tested regularly to analyze its chemical composition and temperature. According to the test results, the raw material ratio, process parameters and furnace operation are adjusted in time to realize dynamic control of the low-silicon molten iron smelting process. The converter oxygen lance position is optimized. The lance position is raised in the early stage to increase the FeO in the slag to meet the FeO required for the rapid dissolution of the white ash in the early stage and ensure the dephosphorization rate. After slagging, the lance position is raised in time to avoid drying out and overflowing slag. Increasing the FeO in the slag promotes the dissolution of the second batch of white ash. When the carbon-oxygen reaction weakens, the high-low-high lance position mode is adopted in time to promote the slag penetration. In the later stage, when the temperature is high, dolomite is added appropriately. The cooling agent, iron oxide scale and other iron-containing oxides must be added before 10 minutes. The lance pressure time is greater than 60 seconds to promote the reduction of FeO in the slag, protect the slag system, and improve the effect of splashing slag to protect the furnace.

2. The production method for optimizing the smelting of low-silicon molten iron according to claim 1, characterized in that: The grade of iron ore shall not be less than 60% and the sulfur content shall be less than 0.05%; the ash content of coke shall be less than 12% and the sulfur content shall be less than 0.6%.

3. The production method for optimizing the smelting of low-silicon molten iron according to claim 1, characterized in that: The mass ratio of the limestone to the dolomite is 1:

1.

4. The production method for optimizing the smelting of low-silicon molten iron according to claim 1, characterized in that: The second batch of slag is usually added in small batches multiple times. Multiple additions are beneficial to the dissolution of lime. Small slag can also be used to control the outflow of foam slag in the furnace.

5. The production method for optimizing the smelting of low-silicon molten iron according to claim 1, characterized in that: Control the water temperature difference of the cooling wall between 10-15℃.

6. The production method for optimizing the smelting of low-silicon molten iron according to claim 1, characterized in that: The desiliconizing agent is a magnesium-based composite desiliconizing agent.

7. The production method for optimizing the smelting of low-silicon molten iron according to claim 6, characterized in that: The desiliconizing agent injection amount is controlled at 1.0-1.5kg / t molten iron.

8. The production method for optimizing the smelting of low-silicon molten iron according to claim 1, characterized in that: The air volume of the blast furnace is 1100m 3 / min, wind pressure is 160kPa, wind temperature is 1150℃, and coke load is 2.

8.

9. The production method for optimizing the smelting of low-silicon molten iron according to claim 7, characterized in that: The desiliconizing agent injection rate is controlled at 1.2 kg / t molten iron.

10. The production method for optimizing the smelting of low-silicon molten iron according to claim 5, characterized in that: Control the water temperature difference of the cooling wall at 12℃.

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