Method for improving gas utilization rate in blast furnace damping-down material loading process and air supply initial stage

Abstract

The invention relates to a blast furnace ironmaking technology, in particular to a method for improving the gas utilization rate in the blowing-down material loading process and the blowing-in initial stage of a blast furnace. The method aims at the phenomenon that the gas utilization rate is reduced by 4%-5% in the blowing-down material loading process before long-term blowing-down of the blast furnace and the blowing-in initial stage of the blast furnace due to the fact that the coke consumption is increased and the ore-coke ratio is reduced. By adjusting parameters such as a damping-down material distribution mode, a furnace top material distribution matrix and air supply speed during air supply recovery, distribution of gas flow in a material column is improved and optimized, contact and reaction conditions of gas and ore are improved, the minimum value of the gas utilization rate is improved from 42% to 44% or above, the average value is improved from 44% to 46% or above, the indirect reduction degree of the ore is increased, fuel consumption is reduced, and the service life of the ore is prolonged. And smooth recovery of the furnace condition is promoted.

Description

Technical Field

[0001] This invention relates to blast furnace ironmaking technology, specifically to a method for improving the utilization rate of gas during the blast furnace shutdown process and the initial blast gas supply. Background Technology

[0002] After several months of continuous operation, blast furnaces undergo planned shutdowns for maintenance and repairs. During the shutdown, there is no coke or pulverized coal combustion or heat from the hot blast, causing the furnace temperature to gradually decrease. Therefore, before a planned shutdown, during the charging process and at the initial stage of blast recovery, various measures are taken to increase the slag and iron heat to ensure sufficient temperature for flow. The main measure is to increase fuel consumption, especially coke consumption.

[0003] As coke consumption increases, the ore-to-coke ratio in the furnace gradually decreases, improving the permeability of the burden. This allows the gas to more easily reach the furnace top through the coke layer, reducing its chance of contact and reaction with the ore. Consequently, CO in the gas cannot be fully converted into CO2, resulting in lower gas utilization. With this reduced utilization, iron oxides in the ore cannot be fully reduced by CO and must be directly reduced by carbon upon entering the hearth, leading to increased fuel consumption and decreased hearth heat. Under normal production conditions, blast furnace gas utilization is typically 48%–50%. Traditional operations during blast furnace shutdown charging and the initial recovery phase generally reduce gas utilization by 4%–5%, dropping it to 43%–45%, resulting in a fuel ratio increase of 20–30 kg / t.

[0004] By optimizing and adjusting the process, improving the utilization rate of gas during the charging of blast furnace materials and the initial stage of blast furnace recovery can effectively reduce fuel consumption, increase slag and iron calorific value, and promote the smooth recovery of furnace conditions.

[0005] This method aims to improve the gas utilization rate during the blast furnace shutdown charge process and the initial blasting stage. It addresses the significant decrease in gas utilization rate caused by increased coke consumption during the shutdown charge process and the initial blasting stage before a long-term shutdown. By adjusting parameters such as the arrangement of the shutdown charge, the furnace top charge matrix, and the blasting speed during blasting recovery, the gas utilization rate can be increased from 44% to over 46%, reducing fuel consumption by 10-15 kg / tFe, thereby ensuring a smooth recovery of furnace conditions. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned problems by providing a method to improve the utilization rate of blast furnace gas during the blast furnace shutdown charge process and the initial blast gas supply.

[0007] The objective of this invention is achieved as follows: a method for improving the utilization rate of gas during the charging process of blast furnace shutdown materials and the initial stage of blasting, comprising the following steps: Step 1: Before the blast furnace shutdown, the weight of the ore batch remains unchanged for two smelting cycles, and the coke batch is increased by 10 kg / t on the basis of the normal production coke ratio. The normal coke ratio is determined according to the actual operation of the blast furnace, ranging from 320 to 360 kg / t; Step 2: The basic coke ratio of the shutdown material is determined according to the length of the shutdown time using formula (1): K 休风料 =K 正常料 +h 休风时 ×1.0(1), where: K 休风料 —Coke ratio during shutdown, kg / t; K 正常料 —Normal coke ratio, kg / t; h 休风时长 —The number of hours from the start of the planned shutdown to the resumption of operation, in hours; for every additional hour of shutdown, the coke ratio of the entire furnace during shutdown is increased by 1.0 kg / t, and the coke ratio charged in the previous smelting cycle before shutdown is K. 休风料 The rest-time feed should be prepared until the ventilation stops. The weight of the ore batch in the rest-time feed should be consistent with the weight of the ore batch during normal production, which is 40t~180t. Step 3: Add coke according to the length of the rest-time, the amount of coke added being n. 空焦 Calculate using formula (2): n 空焦 =h 休风时长 / 16+0.5(2), where: n 空焦 —Number of hollow coke in the idle air feed, rounded to the nearest integer, in units; h 休风时长 —The number of hours from the start of the planned shutdown to the resumption of the shutdown, h; After the addition of the shutdown material, the empty coke is added in 12 batches, and the shutdown is carried out 6~8 hours later. The first batch of empty coke is located in the upper part of the furnace belly. The quantity of empty coke is calculated according to formula (2). One empty coke is added every 3 batches of ore. The angle of the empty coke and the coke in the normal material is consistent; Step 4: Maintain a coke ratio of 15~20kg / t Fe in the shutdown material; Step 5: After the empty coke is added in the shutdown material, the furnace top material distribution matrix should be adjusted accordingly when the shutdown material is loaded due to the large change in the ore-coke ratio. For blast furnaces that adopt the center coke addition method, reduce the number of center coke rings by 0.2~0.3 rings, reduce the center coke ratio by 1.0%~2.0%, and keep the total weight of the center coke consistent with that before the shutdown and normal production, with a weight of 3.5~6.5t, until the shutdown; Step 6: Quickly add air in the early stage of air supply recovery.

[0008] In step six, during the initial stage of air supply recovery, the air supply ratio is rapidly increased to reach 0.55~0.65, i.e., the air volume / furnace volume ratio reaches 0.55~0.65.

[0009] The beneficial effects of this invention are as follows: For the 1800m³ blast furnace at Taiyuan Iron & Steel Plant, using this method, during scheduled maintenance shutdowns of up to 48 hours, the fuel ratio is reduced from 560kg / t to 545kg / t during the initial stages of blast furnace refueling and blast furnace recovery, saving 60 tons of fuel and reducing costs by 150,000 yuan. For the 4350m³ blast furnace, using this method, the fuel ratio is reduced from 550kg / t to 535kg / t during scheduled maintenance shutdowns of up to 48 hours, saving 150 tons of fuel and reducing costs by 300,000 yuan. Taiyuan Iron & Steel Plant has one 1800m³ blast furnace and two 4350m³ blast furnaces. Assuming each blast furnace shuts down four times a year, the annual smelting cost reduction is 3 million yuan, while also significantly reducing carbon emissions, demonstrating strong potential for widespread application. Detailed Implementation

[0010] This invention proposes a method to improve the gas utilization rate during the blast furnace shutdown charge process and the initial stage of blast furnace ventilation. Addressing the phenomenon of a 4%–5% decrease in gas utilization rate due to increased coke consumption and a lower ore-to-coke ratio during the shutdown charge process before a long-term blast furnace shutdown and the initial stage of ventilation recovery, this method optimizes the gas flow distribution within the charge column by adjusting parameters such as the arrangement of the shutdown charge, the furnace top charge matrix, and the blast acceleration rate during ventilation recovery. This improves the conditions for gas-ore contact and reaction, increasing the minimum gas utilization rate from 42% to over 44%, and the average from 44% to over 46%. This also increases the degree of indirect ore reduction, reduces fuel consumption, and facilitates a smooth recovery of furnace conditions. The first technical feature of this invention is increasing the coke ratio by 10 kg / t by maintaining the same ore batch and increasing the coke batch two smelting cycles before the shutdown. The second technical feature is increasing the basic coke ratio by 1.0 kg / t per hour, depending on the shutdown duration. The third technical feature of this invention is that the number of empty coke in the resting batch is calculated by adding one empty coke every 16 hours, plus 0.5 batches, and rounding up to the nearest whole number. The fourth technical feature is maintaining a coke-to-coke ratio of 15-20 kg / t Fe in the resting batch. The fifth technical feature is maintaining a constant weight of central coke in each batch by reducing the proportion of central coke added during batch expansion in a center-coke-fed blast furnace. The sixth technical feature is restoring the air volume after blasting resumption by increasing the air volume by 300-500 m³ / min every 10-15 minutes, depending on the furnace volume.

[0011] This invention employs the following basic technical concept: Addressing the phenomenon of a 4%–5% decrease in gas utilization due to increased coke consumption and a lower ore-to-coke ratio during the pre-long-term blast furnace shutdown process and the initial stage of blast furnace recovery, this invention improves gas utilization by adjusting parameters such as the arrangement of the shutdown charge, the furnace top charge matrix, and the blast speed during blast furnace recovery. This optimizes the distribution of gas flow within the charge column, improves the conditions for gas-ore contact and reaction, thereby increasing gas utilization, enhancing the degree of indirect ore reduction, reducing fuel consumption, and facilitating a smooth recovery of furnace conditions.

[0012] The specific technical solution of the present invention is as follows: 1. Before the blast furnace shuts down, the ore batch remains unchanged for two smelting cycles. The coke ratio is increased by 10 kg / t by increasing the coke batch to regulate the distribution of gas flow and avoid a decrease in gas utilization rate due to large changes in gas flow.

[0013] 2. Use formula (1) to determine the coke ratio of the resting material based on the length of the resting time: K 休风料 =K 正常料 +h 休风时 ×1.0(1), where: K 休风料 —Coke ratio for idle coke (excluding empty coke), kg / t; K 正常料 —Normal coke ratio, kg / t; h 休风时长 —The number of hours from the start of the planned shutdown to the resumption of operation, in hours; based on statistical data on heat loss during the shutdown period and the heat deficit caused by the inability to inject coal after the start of ventilation, the basic coke ratio of the entire furnace should be increased by 1.0 kg / t for every hour of shutdown. The coke ratio charged in the previous smelting cycle before the shutdown was K. 休风料 The weight of the ore batch in the rest-time batch should be consistent with the size of the ore batch during normal production, until the rest-time batch is shut down.

[0014] 3. Add empty focus according to the length of the wind cessation period. The amount of empty focus, n, is calculated using formula (2): n 空焦 =h 休风时长 / 16+0.5(2), where: n 空焦 —Number of hollow coke in the idle air feed, rounded to the nearest integer, in units; h 休风时长 —The number of hours from the start of the planned shutdown to the resumption of the shutdown, h; after the addition of the shutdown material, the empty coke is added 12 batches. After the shutdown is scheduled, the first batch of empty coke is located in the upper part of the furnace belly. The quantity of empty coke is calculated according to formula (2). One empty coke is added every 3 batches of ore. When loading, the material distribution matrix is ​​loaded according to the material distribution matrix of the normal coke batch in the shutdown material.

[0015] 4. To avoid excessive coke batch size and to maintain the permeability of the ore in the feed column, maintain a coke-to-roasting ratio of 15~25 kg / t Fe in the resting feed.

[0016] 5. After adding hollow coke to the blast furnace charge for shutdown, the gas utilization rate is prone to decrease due to the significant change in the ore-to-coke ratio. The charging matrix at the top of the furnace should be adjusted accordingly when charging the shutdown charge. For blast furnaces using the center coke charging method, the number of center coke rings should be reduced, the proportion of center coke should be lowered, and the total weight of center coke should be kept constant to avoid a significant drop in gas utilization rate until shutdown. For example, during normal production, the coke batch weight is 25.5t, the number of charging rings is 333222 4.5, the total number of rings is 19.5, the number of center coke rings is 4.5, and the weight of center coke is 5.88t. During shutdown, the coke batch weight is 26.2t, and the number of center coke rings should be reduced to 4.3, maintaining the center coke weight at 5.88t. Blast furnaces using the platform hopper charging method can raise the charge line by 0.1~0.2m to control the central airflow and avoid a significant drop in gas utilization rate until shutdown.

[0017] 6. In the initial stage of blast furnace recovery, rapidly increase the blast volume to achieve an air-to-volume ratio of 0.6, i.e., blast volume / furnace volume of 0.6. Taking a 4000m³ blast furnace as an example, the initial blast volume should reach 2400m³ / min. Subsequently, increase the blast volume in small increments every 10-15 minutes by 300-500m³ / min. Use the lower limit for 1000m³ blast furnaces and the upper limit for 5000m³ blast furnaces. Maintain the normal descent of the furnace charge and keep the slag skin adhering to the cooling equipment stable to prevent it from falling off, thereby maintaining a stable gas flow distribution in the furnace and preventing a significant drop in gas utilization.

[0018] 7. After taking steps 1 to 6, the minimum gas utilization rate during the blast furnace shutdown process of charging shutdown materials and the initial stage of blast furnace recovery increased from 42% to over 44%, and the average value increased from 44.4% to over 46%. Based on the calculation that each 1% increase in gas utilization rate reduces the fuel ratio by 5 kg / t, fuel consumption is reduced by 10~15 kg / tFe, which is conducive to the rapid recovery of furnace conditions. Example 1

[0019] This method has been successfully applied at Taiyuan Iron & Steel Group's ironmaking plant.

[0020] Taking the shutdown of an 1800m³ blast furnace on April 29, 2025 as an example, the shutdown time is from 0:30 on April 29 to 4:45 on April 30, with a shutdown duration of 28 hours and 15 minutes. The specific implementation plan is as follows: 1. The ore batch before the shutdown is 51t. The ore batch remains unchanged for the two smelting cycles before the shutdown. The coke ratio is increased by 10kg / t by increasing the coke batch, from 350kg / t to 360kg / t.

[0021] 2. The normal coke ratio is 350 kg / t, the downtime is 28 hours, the basic coke ratio of the downtime material is increased by 28 kg / t, and the basic coke ratio is increased to 378 kg / t.

[0022] 3. The rest period is 28 hours, and two empty cokes are added. After the rest period material is loaded, the first empty coke is added to the 12th batch of material, and the second empty coke is added to the 15th batch of material.

[0023] 4. Maintain 18 kg / t Fe coke in the idle feed.

[0024] 5. The coke batch weight in the rest blast furnace is increased from 10.6t to 11.5t, which is the normal weight. Because the 1800m³ blast furnace adopts the center coke feeding method, the number of coke feeding rings is 33221 3.8, the number of center coke rings is 3.8, and the proportion of center coke is 25.7%. During normal production, the amount of center coke is 2.72t. In order to keep the weight of center coke unchanged, when the coke batch is increased to 11.5t, the number of center coke rings is reduced to 3.4.

[0025] 6. At 4:45 on April 30, the air supply was started. During the initial recovery period, the air volume was rapidly increased. After 30 minutes, the air volume reached 1000 m³ / min. Subsequently, the air volume was increased by 300 m³ / min every 15 minutes. After 3 hours of air supply, the air volume reached 3600 m³ / min, which is close to the normal production air volume.

[0026] During this ventilation shutdown and ventilation recovery process, the lowest gas utilization rate was 45%, and the average was 47.5%, which is 2.3% higher than the gas utilization rate during previous long-term ventilation shutdowns. This resulted in a reduction of fuel consumption by 11 kg / t, a reduction of coke consumption by 55 t, and an economic benefit of 110,000 yuan. Example 2

[0027] Taking the shutdown of a 4350m³ blast furnace on June 29, 2025 as an example, the shutdown time is from 3:51 on June 29 to 13:38 on June 30, with a shutdown duration of 33 hours and 47 minutes. The specific implementation plan is as follows: 1. The ore batch before the shutdown is 124t. The ore batch remains unchanged for the two smelting cycles before the shutdown. The coke ratio is increased by 10kg / t by increasing the coke batch, from 355kg / t to 365kg / t.

[0028] 2. The normal coke ratio is 355 kg / t, the downtime is 33 h, the basic coke ratio of the downtime material is increased by 33 kg / t, and the basic coke ratio is increased to 388 kg / t.

[0029] 3. The rest period is 33 hours, and 3 empty cokes are added. After the rest period material is loaded, the first empty coke is added to the 12th batch of material, the second empty coke is added to the 15th batch of material, and the second empty coke is added to the 18th batch of material.

[0030] 4. Maintain 25 kg / t Fe coke in the idle air feed.

[0031] 5. The coke batch weight in the rest blast furnace is increased from 25.8t to 28.4t, which is normal. Because the 4350m³ blast furnace adopts the center coke feeding method, the number of coke feeding rings is 333222 4.2, the number of center coke rings is 4.2, and the proportion of center coke is 21.9%. During normal production, the amount of center coke is 5.65t. In order to keep the weight of center coke constant, when the coke batch is increased to 28.4t, the number of center coke rings is reduced to 3.8.

[0032] 6. At 13:38 on June 30, the air supply was started. During the initial recovery period, the air volume was rapidly increased. After 30 minutes, the air volume reached 2600 m³ / min. Subsequently, the air volume was increased by 400 m³ / min every 15 minutes. After 5 hours of air supply, the air volume reached 6700 m³ / min, which is close to the normal production air volume.

[0033] During this ventilation shutdown and ventilation recovery process, the lowest gas utilization rate was 44.5%, and the average was 46.8%, which is 2.4% higher than the gas utilization rate during previous long-term ventilation shutdowns. This resulted in a reduction of fuel consumption by 12 kg / t, a reduction of coke consumption by 120 t, and an economic benefit of 240,000 yuan.

[0034] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for improving the utilization rate of blast furnace gas during the downtime charge process and the initial blast stage, characterized in that: Includes the following steps: Step 1: Before the blast furnace shuts down, maintain the weight of the ore batch unchanged for the two smelting cycles. Increase the coke batch by 10 kg / t on the basis of the normal production coke ratio. The normal coke ratio is determined according to the actual operation of the blast furnace, ranging from 320 to 360 kg / t. Step 2: Use formula (1) to determine the coke ratio of the resting material based on the length of the resting time: K 休风料 =K 正常料 +h 休风时 ×1.0(1), where: K 休风料 —Coke ratio during shutdown, kg / t; K 正常料 —Normal coke ratio, kg / t; h 休风时长 —The number of hours from the start of the planned shutdown to the resumption of operation, in hours; for every additional hour of shutdown, the coke ratio of the entire furnace during shutdown is increased by 1.0 kg / t, and the coke ratio charged in the previous smelting cycle before shutdown is K. 休风料 The weight of the ore batch in the rest-time material should be consistent with the weight of the ore batch during normal production, which is 40t~180t. Step 3: Add empty focus based on the length of the wind cessation period, the quantity of empty focus being n. 空焦 Calculate using formula (2): n 空焦 =h 休风时长 / 16+0.5(2), where: n 空焦 —Number of hollow coke in the idle air feed, rounded to the nearest integer, in units; h 休风时长 —The number of hours from the start of the planned shutdown to the resumption of the shutdown, h; After the addition of the shutdown material, the coke is added in 12 batches, and the shutdown is resumed after 6~8 hours. The first batch of coke is located in the upper part of the furnace belly. The number of coke is calculated according to formula (2). One coke is added every 3 batches of ore. The angle of the coke and the coke in the normal material are consistent. Step 4: Maintain a coke-butane ratio of 15-20 kg / t Fe in the resting feed; Step 5: After adding hollow coke to the blast furnace charge, due to the significant change in the ore-to-coke ratio, the top charging matrix should be adjusted accordingly when charging the blast furnace charge. For blast furnaces using the center coke charging method, reduce the number of center coke rings by 0.2 to 0.3 and reduce the proportion of center coke by 1.0% to 2.0%. Keep the total weight of center coke consistent with that during normal production before the blast furnace shutdown, which is 3.5 to 6.5 tons, until the blast furnace shutdown. Step Six: Rapidly increase airflow during the initial stage of air supply recovery.

2. The method for improving the utilization rate of blast furnace shutdown charge and initial blast gas during the initial blast period, as described in claim 1, is characterized in that: In step six, during the initial stage of air supply recovery, the air supply ratio is rapidly increased to reach 0.55~0.65, i.e., the air volume / furnace volume ratio reaches 0.55~0.65.