Smelting method for greatly controlling production of large blast furnace

Abstract

The invention provides a smelting method for greatly controlling the production of a large blast furnace, which adopts the technical conception of oxygen reduction and air addition to reduce the oxygen enrichment rate to the minimum value 1% allowed by equipment so as to ensure that the theoretical combustion temperature is higher than 2200 DEG C and the air volume is as large as possible; according to the method, the standard air speed of 210-220 m / s and the actual air speed of 250-270 m / s are taken as targets, the area of an air supply tuyere and the appropriate coal injection ratio are calculated through a formula, and adjustment and optimization of a charging system are combined, so that a set of complete production control process system is obtained, the working uniformity of the whole hearth is ensured, and smooth operation of the whole furnace condition under large-scale production control can be ensured.

Description

Technical Field

[0001] The invention relates to the field of blast furnace steelmaking, and in particular to a smelting method for large-scale blast furnace production control. Background Art

[0002] Blast furnace production is based on wind. In daily operation, there is a saying that "strong wind can cure all diseases". Only with sufficient wind volume can the molten iron in the furnace be driven to circulate and make the furnace work actively. Generally, artificial wind control within 10% has little effect on the production of the entire blast furnace. Once the control exceeds 10%, the wind volume is too small to blow through the center. Over time, the furnace will accumulate, the airflow distribution is poor, and the material flow is not smooth, which eventually affects the smooth operation of the entire blast furnace.

[0003] Due to the downturn in the steel industry in recent years, low back-end demand, high product inventory, and long-term large-scale losses in steel companies, in order to win the battle for survival, most steel companies choose to control production or stop production to reduce losses. There are a total of 22 tuyere air supply in the blast furnace. Generally, production control is carried out in the form of blocking individual tuyere and reducing wind speed (also known as "slow wind") when the blast furnace is working. Long-term blocking of individual tuyere will produce dead zones and local accumulation in the blast furnace hearth, which is not conducive to the smooth operation of the blast furnace, and will also cause the small sleeves on both sides of the blocked tuyere to burn out easily. The long-term slow wind pulverized coal also burns incompletely, which on the one hand deteriorates the permeability of the charge, which is not conducive to the smooth operation of the blast furnace, and on the other hand, it also causes waste of raw materials such as pulverized coal. Summary of the invention

[0004] The object of the present invention is to provide a smelting method for greatly controlling the production of a large blast furnace.

[0005] A smelting method for controlling the production of a large blast furnace comprises the following steps: (1) Calculate the air volume during production control: Calculate the air volume during production control according to formula I: A / B*{air volume before production control*(1+0.035*(oxygen enrichment rate before production control-oxygen enrichment rate during production control)*100}=air volume during production control; In formula I: A-the output of molten iron in blast furnace during production control, unit: t; B-the output of molten iron in blast furnace before production control, unit: t; the unit of air volume before production control and air volume during production control: m³ / min; the unit of oxygen enrichment rate before production control and oxygen enrichment rate during production control: %; and the oxygen enrichment rate during production control is 1%; (2) Calculate the air outlet area and air pressure during production control: During production control, the standard wind speed is guaranteed to reach 210-220m / s and the actual wind speed is guaranteed to reach 250-270m / s. The air outlet area and wind pressure during production control corresponding to the wind speed during production control are calculated according to formulas II and III; Formula II: V = air volume during production control / S / 60; Formula III: C = {air volume during production control / S / 60*(273+hot air temperature)*0.1013} / {273*(0.1013+air pressure during production control*0.001)}; In formula II: V-standard wind speed during production control, unit: m / s; air volume during production control, calculated by formula I, unit: m³ / min; S-air outlet area during production control, unit: m²; In formula III: C-actual wind speed during production control, unit: m / s; air volume during production control, calculated by formula I, unit: m³ / min; hot air temperature, unit: ℃; S-air outlet area during production control, calculated by formula II, unit: m²; wind pressure during production control, unit: kpa; (3) Calculate the air outlet diameter during production control: Calculate the air outlet diameter during production control according to Formula IV: S=π*r 2 ; In formula IV: S-the area of ​​the air outlet during production control, calculated by formula II, unit: m²; π-pi; r-the diameter of the air outlet during production control, unit: mm; (4) When charging the blast furnace, ore and coke are distributed in a circular manner along the radial direction from the outside to the center of the blast furnace, and when distributing ore, central coking is performed near the center of the blast furnace; the distribution chute corresponding to the central coking is inclined at an angle of 20 to 24°, and the coke distribution amount / total coke distribution amount when the distribution chute is inclined at an angle of 20 to 24° is controlled at 10 to 16%; at the same time, the depth of the ore line is controlled at (1.5±0.1) m, and the depth of the coke line is controlled at (1.3±0.1) m; (5) Calculation of coal injection ratio during production control: With the theoretical combustion temperature > 2200°C, calculate the coal injection ratio during production control according to formula V; Formula V: T=1563+0.7938*hot air temperature+4.3*oxygen enrichment rate during production control*100-2*coal injection ratio during production control; In formula V: T-theoretical combustion temperature, unit: °C; hot air temperature unit: °C; oxygen enrichment rate during production control: consistent with the oxygen enrichment rate during production control in formula I, unit: %; coal injection ratio during production control is in kg / t; (6) During the blast furnace smelting process, the molten iron temperature is controlled at 1480~1520℃.

[0006] The technical effects of the smelting method for large-scale blast furnace production control of the present invention are as follows: ① In order to ensure the theoretical combustion temperature is greater than 2200℃ and the air volume is as large as possible, oxygen is reduced and air is added. The oxygen enrichment rate is reduced to the minimum value of 1% allowed by the equipment. Reducing the oxygen enrichment rate will increase the air volume by 3.5%. Based on this, the air volume and air pressure during production control are calculated by combining Formula I and Formula III; ② The standard wind speed during production control reaches 210-220m / s and the actual wind speed reaches 250-270m / s, which can avoid the wind speed being too small to penetrate the center and the wind speed being too large to blow the coke into pieces; therefore, the present invention takes "obtaining a standard wind speed of 210-220m / s and an actual wind speed of 250-270m / s" as the goal, and continues to calculate the diameter of the air supply port during production control according to formula II; so that the present invention does not adopt the production control method of "blocking individual air ports" to prevent the formation of local accumulation and uneven furnace operation, but adopts full air port air supply to reduce the air port area and ensure the uniformity of furnace operation; ③ Although the wind speed is guaranteed by reducing the air vents during production control, the air volume entering the furnace will be smaller than that before production control. Therefore, the present invention also adjusts the coking system (the inclination angle of the coking chute is above 26° during coking before production control) and increases the center coking (20-24° coking, and the center coking ratio is controlled at 10-16%), which not only ensures the center airflow, but also avoids excessive center coking, which leads to a decrease in the utilization rate of the center airflow and an increase in the fuel ratio, thereby affecting the smooth operation and production efficiency of the blast furnace; and, when the material is spread, it is like a cone from top to bottom during distribution. The deeper the material line, the more furnace materials are distributed on the inner and outer edges of the furnace, and the more the edge airflow can be suppressed. Therefore, the mine adopts a (1.5±0.1)m material line to suppress the edge, and the coke adopts a (1.3±0.1)m material line to distribute the material inward to guide the airflow to the center; ④ In order to ensure the smooth operation of the blast furnace, the temperature of the blast furnace molten iron needs to be controlled at 1480-1520℃, which can prevent the blast furnace molten iron temperature from being too low, which will reduce the working activity of the production control furnace and cause accumulation, and also prevent the molten iron temperature from being too high, which will increase costs. Therefore, in operation, the molten iron temperature is controlled at 1480-1520℃ by controlling the molten iron composition system, slag basicity and cooling water temperature. ⑤ The smelting method for large-scale blast furnace production control of the present invention adopts the technical concept of reducing oxygen and adding air. The air supply port area and the appropriate coal injection ratio are calculated through wind speed, theoretical combustion temperature and wind index, and combined with the adjustment and optimization of the charging system, a complete production control process system is obtained. While ensuring the uniformity of the operation of the entire furnace, it can also ensure the smooth operation of the entire furnace condition under large-scale production control.

[0007] Furthermore, in step (6), the silicon content of the molten iron smelted in the blast furnace is controlled at 0.4-0.45%, the sulfur content is controlled at 0.015-0.030%, and the slag basicity is controlled at 1.18-1.2 to ensure that the physical heat of the molten iron is greater than 1480°C.

[0008] Furthermore, the carbon content in the dry ash produced after blast furnace combustion is ≤30%, indicating that the pulverized coal is burned completely. DETAILED DESCRIPTION

[0009] The preferred embodiment of the smelting method for large-scale blast furnace production control of the present invention is described in detail below. Example 1

[0010] Taking the 1500m³ blast furnace with 40% production control as an example, the daily output of molten iron in the blast furnace during normal production (i.e. the output of molten iron in the blast furnace before production control) is 5000t, the wind pressure (i.e. the wind pressure before production control) is 430Kpa, the air volume (i.e. the air volume before production control) is 3300m³, and the oxygen enrichment rate (i.e. the oxygen enrichment rate before production control) is 3.7%. In order to ensure the theoretical combustion temperature during production control, the air volume is as large as possible, and oxygen is reduced and air is added (the fan cannot work at full load under the production control state. In this case, reducing oxygen enrichment and increasing the fan workload is more economical), and the oxygen enrichment rate is reduced to the minimum value allowed by the equipment, that is, the oxygen enrichment rate is 1% during production control, which corresponds to an increase in air volume of 3.5%. The daily output of molten iron in the blast furnace during production control is 3000t.

[0011] A smelting method for controlling the production of a large blast furnace comprises the following steps: (1) Calculate the air volume during production control: Calculate the air volume during production control according to formula I: A / B*{air volume before production control*(1+0.035*(oxygen enrichment rate before production control-oxygen enrichment rate during production control)*100}=air volume during production control; In formula I: A-the output of molten iron in blast furnace during production control, unit: t; B-the output of molten iron in blast furnace before production control, unit: t; the unit of air volume before production control and air volume during production control: m³ / min; the unit of oxygen enrichment rate before production control and oxygen enrichment rate during production control: %; and the oxygen enrichment rate during production control is 1%; (2) Calculate the air outlet area and air pressure during production control: During production control, the standard wind speed is guaranteed to reach 210-220m / s and the actual wind speed is guaranteed to reach 250-270m / s. The air outlet area and wind pressure during production control corresponding to the wind speed during production control are calculated according to formulas II and III; Formula II: V = air volume during production control / S / 60; Formula III: C = {air volume during production control / S / 60*(273+hot air temperature)*0.1013} / {273*(0.1013+air pressure during production control*0.001)}; In formula II: V-standard wind speed during production control, unit: m / s; air volume during production control, calculated by formula I, unit: m³ / min; S-air outlet area during production control, unit: m²; In formula III: C-actual wind speed during production control, unit: m / s; air volume during production control, calculated by formula I, unit: m³ / min; hot air temperature, unit: ℃; S-air outlet area during production control, calculated by formula II, unit: m²; wind pressure during production control, unit: kpa; (3) Calculate the air outlet diameter during production control: Calculate the air outlet diameter during production control according to Formula IV: S=π*r 2 ; In formula IV: S-the area of ​​the air outlet during production control, calculated by formula II, unit: m²; π-the pi, the value is 3.14159; r-the diameter of the air outlet during production control, unit: mm; (4) When charging the blast furnace, ore and coke are distributed in a circular manner along the radial direction from the outside to the center of the blast furnace. The specific charging system is: When distributing ore, the inclination angle of the distribution chute and the corresponding number of rotations of the distribution chute are: 38.5° / 4 turns, 36° / 3 turns, 33.5° / 2 turns, 31° / 2 turns, so that the distribution is carried out in a circular manner from the outside to the center of the blast furnace; During coke distribution, the inclination angle of the distribution chute and the corresponding number of rotations of the distribution chute are: 36° / 3 turns, 34° / 2 turns, 31° / 2 turns, 28° / 2 turns, 23° / 3 turns, so that the distribution is carried out in a circular manner from the outside to the center of the blast furnace; When the inclination angle of the distribution chute and the corresponding distribution chute rotation number of distribution circles is 23° / 3 circles, the coke distribution amount / total coke distribution amount is controlled at 10-16%; The depth of the ore material line is controlled at (1.5±0.1)m, and the depth of the coke material line is controlled at (1.3±0.1)m; (5) Calculation of coal injection ratio during production control: With the theoretical combustion temperature > 2200°C, calculate the coal injection ratio during production control according to formula V; Formula V: T=1563+0.7938*hot air temperature+4.3*oxygen enrichment rate during production control*100-2*coal injection ratio during production control; In formula V: T-theoretical combustion temperature, unit: °C; hot air temperature unit: °C; oxygen enrichment rate during production control: 1%; coal injection ratio during production control: kg / t; (6) During the blast furnace smelting process, the molten iron temperature is controlled at 1480~1520℃.

[0012] The values ​​corresponding to the parameters in the above formulas Ⅰ to Ⅳ are shown in Table 1 below: Table 1

[0013] The blast furnace was controlled from 5,000 tons per day to 3,000 tons, and the production control rate was maintained at 40% for up to one year. After testing, the carbon content in the dry ash produced during the blast furnace production of Example 1 was ≤30%, indicating that the coal powder was completely burned. In addition, since Example 1 can ensure the uniformity of the furnace operation during production control and maintain the highest possible air volume, it ensures that the key indicators affecting the blast furnace condition, such as wind speed ≥260m / s, theoretical combustion temperature >2220℃, and physical heat >1480℃, are guaranteed, thereby ensuring that the blast furnace condition is smooth.

[0014] Example 2 The difference from Example 1 is that the daily output of molten iron in the blast furnace during production control is 4000t, that is, the production control is 20%, and the corresponding values ​​of the parameter indicators in the above formulas I to IV are shown in Table 2 below: Table 2

[0015] After testing, the carbon content of the dry ash produced during the blast furnace production of Example 2 is ≤30%, indicating that the pulverized coal is completely burned. Since Example 2 can ensure the uniformity of the furnace operation during production control and maintain the highest possible air volume, it ensures that the key indicators affecting the blast furnace condition, such as wind speed ≥260m / s, theoretical combustion temperature >2220℃, and physical heat >1480℃, ensures that the blast furnace condition is smooth.

[0016] Example 3 The difference from Example 1 is that the daily output of molten iron in the blast furnace during production control is 3500t, that is, the production control is 30%, and the corresponding values ​​of the parameter indicators in the above formulas I to IV are shown in Table 3 below: Table 3

[0017] After testing, the carbon content of the dry ash produced during the blast furnace production of Example 3 is ≤30%, indicating that the pulverized coal is completely burned. Since Example 3 can ensure the uniformity of the furnace operation during production control and maintain the highest possible air volume, it ensures that the key indicators affecting the blast furnace condition, such as wind speed ≥260m / s, theoretical combustion temperature >2220℃, and physical heat >1480℃, are ensured, thereby ensuring that the blast furnace condition is smooth.

[0018] In blast furnace operation, due to the decrease in the working activity of the hearth during production control, it is easy to accumulate, and the operation should be mainly based on ensuring physical heat. In order to ensure the requirement of physical heat > 1480℃, the silicon content in the molten iron is increased by 0.1 compared with before production control, and controlled at 0.4-0.45%; the sulfur content is 0.015-0.030%; and the slag basicity is appropriately lowered and controlled at 1.18-1.2.

[0019] In addition, the cooling intensity of the blast furnace is controlled to be small to avoid taking away too much heat from the furnace.

[0020] The distribution of the distribution chute inclination angle, the distribution chute inclination angle and the corresponding number of distribution circles when distributing ore and coke during blast furnace charging of the present invention can be, but not limited to, the specific parameters of Examples 1 to 3. The distribution chutes of different types of blast furnaces have different lengths, and the corresponding inclination angles of each distribution chute need to be adaptively adjusted. In addition, the number of distribution angles of the distribution chutes of ore and coke and the total number of distribution circles also need to be adaptively adjusted according to the size of the batch; the larger the total amount of the batch, the more total number of distribution circles; the smaller the total amount of the batch, the fewer total number of distribution circles. For the technical solution of the present invention, the key improvement in the blast furnace charging link is that when distributing ore, central coking is performed near the center position in the blast furnace; the distribution chute inclination angle corresponding to the central coking is: 20 to 24°, and the coke distribution amount of the central coking / the total amount of coke distribution is controlled at 10 to 16%, so as to ensure that the central airflow is opened while maintaining a high utilization rate of the central airflow.

[0021] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent process changes made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A smelting method for large-scale blast furnace production control, characterized in that: The following steps are involved: (1) Calculate the air volume during production control: Calculate the air volume during production control according to formula I: A / B*{air volume before production control*(1+0.035*(oxygen enrichment rate before production control-oxygen enrichment rate during production control)*100}=air volume during production control; In formula I: A-the output of molten iron in blast furnace during production control, unit: t; B-the output of molten iron in blast furnace before production control, unit: t; the unit of air volume before production control and air volume during production control: m³ / min; the unit of oxygen enrichment rate before production control and oxygen enrichment rate during production control: %; and the oxygen enrichment rate during production control is 1%; (2) Calculate the air outlet area and air pressure during production control: During production control, the standard wind speed is guaranteed to reach 210-220m / s and the actual wind speed is guaranteed to reach 250-270m / s. The air outlet area and wind pressure during production control corresponding to the wind speed during production control are calculated according to formulas II and III; Formula II: V = air volume during production control / S / 60; Formula III: C = {air volume during production control / S / 60*(273+hot air temperature)*0.1013} / {273*(0.1013+air pressure during production control*0.001)}; In formula II: V-standard wind speed during production control, unit: m / s; air volume during production control, calculated by formula I, unit: m³ / min; S-air outlet area during production control, unit: m²; In formula III: C-actual wind speed during production control, unit: m / s; air volume during production control, calculated by formula I, unit: m³ / min; hot air temperature, unit: ℃; S-air outlet area during production control, calculated by formula II, unit: m²; wind pressure during production control, unit: kpa; (3) Calculate the air outlet diameter during production control: Calculate the air outlet diameter during production control according to Formula IV: S=π*r 2 ; In formula IV: S-the area of ​​the air outlet during production control, calculated by formula II, unit: m²; π-pi; r-the diameter of the air outlet during production control, unit: mm; (4) When charging the blast furnace, ore and coke are distributed in a circular manner along the radial direction from the outside to the center of the blast furnace, and when distributing ore, central coking is performed near the center of the blast furnace; the distribution chute corresponding to the central coking is inclined at an angle of 20 to 24°, and the coke distribution amount / total coke distribution amount when the distribution chute is inclined at an angle of 20 to 24° is controlled at 10 to 16%; at the same time, the depth of the ore line is controlled at (1.5±0.1) m, and the depth of the coke line is controlled at (1.3±0.1) m; (5) Calculation of coal injection ratio during production control: With the theoretical combustion temperature > 2200°C, calculate the coal injection ratio during production control according to formula V; Formula V: T=1563+0.7938*hot air temperature+4.3*oxygen enrichment rate during production control*100-2*coal injection ratio during production control; In formula V: T-theoretical combustion temperature, unit: °C; hot air temperature unit: °C; oxygen enrichment rate during production control: consistent with the oxygen enrichment rate during production control in formula I, unit: %; coal injection ratio during production control is in kg / t; (6) During the blast furnace smelting process, the molten iron temperature is controlled at 1480~1520℃.

2. The smelting method for large-scale blast furnace production control according to claim 1, characterized in that: In step (6), the silicon content of the molten iron smelted in the blast furnace is controlled at 0.4-0.45%, the sulfur content is controlled at 0.015-0.030%, and the slag basicity is controlled at 1.18-1.

2.

3. The smelting method for large-scale blast furnace production control according to claim 1, characterized in that: The carbon content in the dry ash produced after blast furnace combustion is ≤30%.

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