Method for improving the utilization of coal gas in blast furnace ironmaking

Abstract

This invention discloses a method for improving gas utilization in blast furnace ironmaking, employing a center-funnel charging pattern. This pattern first reserves a certain gas flow channel, and then strengthens the edge airflow, albeit to a lesser extent, but still promotes smooth channel flow, facilitates gas flow improvement, and promotes smooth blast furnace operation. Unlike methods that rely solely on central coke, this method directly sets the center angle at the end of the coke charging angle. Based on adjustments to the upper charging system, this invention regulates the charging angle and number of charging rings, the charging method and standards, and adjusts the lower blast system, including the length of the tuyeres, the inlet blast temperature, and the furnace top pressure. It also incorporates certain external raw material conditions and the slag and iron composition outside the furnace. This comprehensive process, based on existing conditions, improves gas utilization without additional investment.

Description

Technical Field

[0001] This invention relates to the field of blast furnace gas, specifically a method for improving the utilization rate of gas in blast furnace ironmaking. Background Technology

[0002] In recent years, China's steel industry has faced overcapacity, intensified environmental governance, and normalized environmental protection-related production restrictions. A weak downstream market and persistently high coke prices influenced by pulverized coal resources have continuously squeezed the profits of steel companies. To ensure their survival and development, steel companies need to constantly research and explore methods to reduce production costs. Blast furnace gas utilization rate is a crucial indicator of blast furnace fuel consumption and operational efficiency; improving this rate is one of the main ways for companies to reduce blast furnace fuel consumption and production costs. Changgang Steel's blast furnace gas utilization rate is around 48%, with a fuel ratio of around 528 kg / t. Compared to advanced blast furnaces under similar conditions in China, which achieve a gas utilization rate of around 0.50 and a fuel ratio of around 515 kg / t, there is significant room for improvement. To reduce consumption, optimize technical and economic indicators, and lower costs, exploring technologies to improve blast furnace gas utilization rate under existing process equipment conditions is imperative.

[0003] Currently, the main methods used in the industry to improve the utilization rate of blast furnace gas include:

[0004] 1. Suppress the gas flow at the edge; increase the material distribution angle and increase the number of material distribution rings at large angles; during the suppression process, the gas flow path at the edge is suppressed, which will cause the air pressure to rise and increase the risk of difficult furnace operation.

[0005] 2. Increase ore batch weight; increasing the ore batch weight reduces the number of ore and coke layers inside the blast furnace, which helps increase the thickness of the coke window in the softening zone, ensuring smooth gas flow through the softening zone, improving the permeability of the lower part of the blast furnace, expanding the indirect reduction reaction zone, and enabling the heat of the gas to be fully transferred to the burden, thereby improving gas utilization. However, increasing the ore batch weight is limited by the volume of the blast furnace top receiving tank; furthermore, increasing the ore batch weight increases the thickness of the burden layer, making it more difficult for the gas flow through the burden column, reducing permeability, and potentially causing furnace instability.

[0006] 3. Increasing oxygen content lowers the direct reduction reaction zone; increasing the oxygen content in the blast furnace can raise the theoretical combustion temperature before the tuyeres, causing the high-temperature section at the bottom of the blast furnace to shift downwards, thereby reducing the direct reduction reaction zone and improving gas utilization. This requires an oxygen source and will increase investment.

[0007] 4. Increasing the blast temperature lowers the direct reduction reaction zone. Increasing the blast temperature also shifts the high-temperature zone in the furnace downwards, reducing the direct reduction reaction zone and lowering the blast furnace fuel ratio. Changgang's blast furnace is currently equipped with four hot blast stoves. Through process optimization, the blast temperature can reach 1200–1220℃. Large fluctuations in blast temperature can cause fluctuations in the position of the softening zone, thus affecting furnace conditions and the permeability of the charge column. Therefore, it is generally necessary to maintain a stable blast temperature and ensure the blast furnace is subjected to high blast temperatures. Currently, the blast furnace blast temperature is used at the 1200℃ level. Summary of the Invention

[0008] The purpose of this invention is to provide a method for improving the utilization rate of gas in blast furnace ironmaking, so as to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A method for improving gas utilization in blast furnace ironmaking includes an upper charging system, which is a basic measure that can be fine-tuned during production, specifically including:

[0011] The fabric pattern adopts a center-funnel design, and the specific fabric pattern is: C34(3)32(2)29(2)27(2)22(2)O32(3)31(3)30(3)29(2);

[0012] Where C represents coke and O represents ore, the ring angle of C is 4+1, where 4 represents the first four ring angles and 1 represents the last ring angle, generally called the center angle, i.e., the center angle of coke. The outermost ring angle, i.e., the first ring angle, generally does not exceed 35°, and is 1~3° larger than the outermost ring angle of O, decreasing by 2° thereafter. The outermost ring angle of O is 1~3° smaller than the outermost ring angle of C, decreasing by 1° thereafter. The purpose of choosing 4 rings is to appropriately widen the feeding platform. The center angle of coke is generally chosen to be 23~21°, and the angle is less than 1°. 9°, to prevent insufficient feeding accuracy or detachment due to an excessively small angle, this feeding pattern forms a platform + funnel material surface shape. This pattern first reserves a certain gas flow channel, and then takes measures to strengthen the edge airflow, which is relatively weaker, but more conducive to smooth channel flow, facilitates gas flow improvement, and promotes smooth blast furnace operation. Unlike separate center coke, the center angle is set directly in the coke feeding angle at the end. The furnace feeding method adopts [n(A+B)+C], where A represents the coke material sequence. B represents the ore sequence. Under normal feeding conditions, it's an A+B sequence, meaning one batch of coke is followed by one batch of ore in a cycle. Similarly, C represents coke, D represents ore, and C+D means one batch of coke is followed by one batch of ore in a cycle. A / B = coke load, C / D = coke load. In the [n(A+B)+C] feeding pattern, n represents the cycle multiple, typically chosen as 3-5. A represents coke, B represents ore, and C represents ore. When n=3, it means (A+B) goes through 3 rounds. After the 3rd round of B, C goes directly. The two sequences representing ore are connected... Together, the coke load = 3B + C / 3A, and the amount of A = 3B + C / coke load, which means that the coke supporting C is evenly distributed to the three cokes represented by A. Unequal material line feeding is adopted. The zero position of the material line at the top of the bellless furnace is generally the upper edge of the furnace throat steel brick. During the production process, when the material line reaches the set material line depth, the lifting line starts to feed material into the furnace. The coke material line is 0.3 meters above the height of the furnace throat steel brick, and the ore material line is 0.2 meters above the height of the furnace throat steel brick. The two material line heights are different, differing by 0.1 meters. Feeding is carried out according to this material line.

[0013] It also includes a lower air supply system, which is a supporting measure used to match the upper and lower sections, specifically including:

[0014] A 450mm long, 5° angled tuyeres are used for air supply, extending the outlet position appropriately into the blast furnace to reduce the effective belly angle. This increases and stabilizes the inlet blast temperature, raising it from 1180℃ to 1200℃ and maintaining it at this level. The blast temperature is increased within the equipment's allowable range, avoiding the use of the maximum limit, and allowing for appropriate adjustment to minimize fluctuations. The temperature difference between the final temperature at the end of the hot blast stove's air supply and the initial temperature at the beginning of the air supply should be ≤30℃. The oxygen enrichment is increased and stabilized, using the maximum allowable oxygen level, generally not as a means of adjustment, but maintained at the maximum limit. The furnace top pressure is increased and stabilized, with the blast furnace top pressure ≥190kPa, reaching more than 86% of the design top pressure.

[0015] Further including auxiliary measures, which are used to assist in production, specifically including:

[0016] The raw material conditions must meet the following requirements:

[0017] a. The quality is relatively good; the main sintering quality indicators and coke quality indicators meet the requirements.

[0018] b. Raw material screening control mainly refers to optimizing the feed distribution and feed rate by adjusting the amplitude of the vibrating screen and controlling the material flow under the blast furnace trough, reducing the thickness of the material layer on the screen plate, and improving the screening effect. The raw materials fed into the furnace mainly include sintered ore + pellets + raw ore. The main content of screening control is that the powder of sintered ore less than 5mm is ≤3.5%, and the powder of raw ore less than 8mm is ≤3.5%. The fuel fed into the furnace mainly includes coke + coke particles + pulverized coal. The main content of screening control is that the powder of coke less than 25mm is ≤3.5%.

[0019] The slag and iron composition outside the furnace must meet the following standards:

[0020] a. Tap flow velocity ≥ 3.5d / min, iron content difference ≤ 8%;

[0021] b. Slag removal time after tapping should be ≤15 minutes;

[0022] c. The interval between opening the taphole is ≤25 minutes;

[0023] Controlling appropriate furnace temperature and slag basicity is crucial to avoid high slag-iron viscosity, which would affect fluidity and permeability. The furnace temperature Si should be controlled at 0.25–0.55%, the physical heat at 1460–1500℃, and the slag R2 at 1.16–1.22.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention is based on the adjustment of the upper charging system, and controls the feeding angle and number of feeding rings of the furnace charge, the feeding method and feeding standard of the furnace charge, and adjusts the lower air supply system, the length of the tuyeres, the level of the inlet air temperature, and the level of the furnace top pressure. It is also assisted by certain external raw material conditions and the slag and iron structure outside the furnace. The whole process is controlled based on the current situation, and improves the gas utilization rate without additional investment.

[0026] 2. The material distribution mode of the present invention first reserves a certain gas flow channel, and then takes measures to strengthen the edge airflow. The degree of strengthening is relatively weak, which is more conducive to smooth channel flow, facilitates the increase of gas flow, and is conducive to the smooth operation of the blast furnace. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the top charging system in a method for improving gas utilization in blast furnace ironmaking according to the present invention;

[0028] Figure 2 This is a schematic diagram of the lower air supply system in a method for improving gas utilization in blast furnace ironmaking according to the present invention;

[0029] Figure 3 This is a schematic diagram of auxiliary measures in a method for improving gas utilization in blast furnace ironmaking according to the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] like Figure 1 As shown, the present invention provides a technical solution:

[0032] A method for improving gas utilization in blast furnace ironmaking includes an upper charging system, which is a basic measure that can be fine-tuned during production. Specifically, it includes:

[0033] The fabric pattern adopts a center-funnel design, and the specific fabric pattern is: C34(3)32(2)29(2)27(2)22(2)O32(3)31(3)30(3)29(2);

[0034] Where C represents coke and O represents ore, the ring angle of C is 4+1, where 4 represents the first four ring angles and 1 represents the last ring angle, generally called the center angle, i.e., the center angle of coke. The outermost ring angle, i.e., the first ring angle, generally does not exceed 35°, and is 1~3° larger than the outermost ring angle of O, decreasing by 2° thereafter. The outermost ring angle of O is 1~3° smaller than the outermost ring angle of C, decreasing by 1° thereafter. The purpose of choosing 4 rings is to appropriately widen the feeding platform. The center angle of coke is generally chosen to be 23~21°, and the angle is less than 1°. 9°, to prevent insufficient feeding accuracy or detachment due to an excessively small angle, this feeding pattern forms a platform + funnel material surface shape. This pattern first reserves a certain gas flow channel, and then takes measures to strengthen the edge airflow, which is relatively weaker, but more conducive to smooth channel flow, facilitates gas flow improvement, and promotes smooth blast furnace operation. Unlike separate center coke, the center angle is set directly in the coke feeding angle at the end. The furnace feeding method adopts [n(A+B)+C], where A represents the coke material sequence. B represents the ore sequence. Under normal feeding conditions, it's an A+B sequence, meaning one batch of coke is followed by one batch of ore in a cycle. Similarly, C represents coke, D represents ore, and C+D means one batch of coke is followed by one batch of ore in a cycle. A / B = coke load, C / D = coke load. In the [n(A+B)+C] feeding pattern, n represents the cycle multiple, typically chosen as 3-5. A represents coke, B represents ore, and C represents ore. When n=3, it means (A+B) goes through 3 rounds. After the 3rd round of B, C goes directly. The two sequences representing ore are connected... Together, the coke load = 3B + C / 3A, and the amount of A = 3B + C / coke load, which means that the coke supporting C is evenly distributed to the three cokes represented by A. Unequal material line feeding is adopted. The zero position of the material line at the top of the bellless furnace is generally the upper edge of the furnace throat steel brick. During the production process, when the material line reaches the set material line depth, the lifting line starts to feed material into the furnace. The coke material line is 0.3 meters above the height of the furnace throat steel brick, and the ore material line is 0.2 meters above the height of the furnace throat steel brick. The two material line heights are different, differing by 0.1 meters. Feeding is carried out according to this material line.

[0035] It also includes a bottom-supply air system, which is a supporting measure used to match the upper and lower levels, specifically including:

[0036] A 450mm long, 5° angled tuyeres are used for air supply, extending the outlet position appropriately into the blast furnace to reduce the effective belly angle. This increases and stabilizes the inlet blast temperature, raising it from 1180℃ to 1200℃ and maintaining it at this level. The blast temperature is increased within the equipment's allowable range, avoiding the use of the maximum limit, and allowing for appropriate adjustment to minimize fluctuations. The temperature difference between the final temperature at the end of the hot blast stove's air supply and the initial temperature at the beginning of the air supply should be ≤30℃. The oxygen enrichment is increased and stabilized, using the maximum allowable oxygen level, generally not as a means of adjustment, but maintained at the maximum limit. The furnace top pressure is increased and stabilized, with the blast furnace top pressure ≥190kPa, reaching more than 86% of the design top pressure.

[0037] Further, it includes auxiliary measures, which are used to assist in production, specifically including:

[0038] The raw material conditions must meet the following requirements:

[0039] a. The quality is relatively good; the main sintering quality indicators and coke quality indicators meet the requirements.

[0040] b. Raw material screening control mainly refers to optimizing the feed distribution and feed rate by adjusting the amplitude of the vibrating screen and controlling the material flow under the blast furnace trough, reducing the thickness of the material layer on the screen plate, and improving the screening effect. The raw materials fed into the furnace mainly include sintered ore + pellets + raw ore. The main content of screening control is that the powder of sintered ore less than 5mm is ≤3.5%, and the powder of raw ore less than 8mm is ≤3.5%. The fuel fed into the furnace mainly includes coke + coke particles + pulverized coal. The main content of screening control is that the powder of coke less than 25mm is ≤3.5%.

[0041] The slag and iron composition outside the furnace must meet the following standards:

[0042] a. Tap flow velocity ≥ 3.5d / min, iron content difference ≤ 8%;

[0043] b. Slag removal time after tapping should be ≤15 minutes;

[0044] c. The interval between opening the taphole is ≤25 minutes;

[0045] Controlling appropriate furnace temperature and slag basicity is crucial to avoid high slag-iron viscosity, which would negatively impact fluidity and permeability. The furnace temperature (Si) should be controlled at 0.25–0.55%, the physical heat at 1460–1500℃, and the slag R2 at 1.16–1.22.

[0046] When all of the above conditions are met simultaneously, the gas utilization rate will be significantly improved;

[0047] The before-and-after comparison images are shown below:

[0048] Statistics on blast furnace gas utilization rate before implementation

[0049] name CO <![CDATA[CO2]]> <![CDATA[O2]]> <![CDATA[H2]]> <![CDATA[CH4]]> <![CDATA[N2]]> <![CDATA[CO / CO2]]> <![CDATA[CO2 / (CO+CO2)]]> 1 21.68 19.93 0.60 0.495 1.56 54.47 1.09 0.479 2 21.27 19.80 0.54 0.34 1.62 56.50 1.07 0.482 3 21.45 19.71 0.54 0.57 1.56 56.14 1.09 0.479 average 21.47 19.81 0.56 0.47 1.58 55.70 1.08 0.480

[0050] Statistics on blast furnace gas utilization rate after implementation

[0051] name CO <![CDATA[CO2]]> <![CDATA[O2]]> <![CDATA[H2]]> <![CDATA[CH4]]> <![CDATA[N2]]> <![CDATA[CO / CO2]]> <![CDATA[CO2 / (CO+CO2)]]> 1 21.00 19.93 0.60 0.40 1.66 56.43 1.05 0.487 2 21.09 20.30 0.60 0.40 1.65 55.95 1.04 0.490 3 20.29 19.53 0.60 0.55 1.55 57.48 1.04 0.490 average 20.79 19.92 0.60 0.45 1.62 56.62 1.04 0.489

[0052] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the utilization of coal gas in blast furnace ironmaking, characterized by: This includes an upper loading system, which is a basic measure that is fine-tuned during production. Specifically, it includes: The fabric pattern adopts a center-funnel design, and the specific fabric pattern is: C34(3)32(2)29(2)27(2)22(2)O32(3)31(3)30(3)29(2); Where C represents coke and O represents ore, the ring angle of C is 4+1, where 4 represents the first four ring angles and 1 represents the last ring angle. This feeding pattern forms a platform + hopper material surface shape. This pattern first reserves a certain gas flow channel, and then takes measures to strengthen the edge airflow, adopting the [n(A+B)+C] feeding method, where A represents the coke material sequence and B represents the ore material sequence. Under normal feeding conditions, the material sequence is A+B, that is, a batch of coke is fed into the furnace. A batch of ore is fed in a circulating manner. In the feeding pattern [n(A+B)+C], n represents the circulation multiple, which is selected from 3 to 5. Unequal feeding lines are used. The zero position of the feed line at the top of the bellless furnace is the position of the upper edge of the furnace throat steel brick. During the production process, when the feed line reaches the set feed line depth, the lifting line starts to feed into the furnace. The feed line for coke is 0.3 meters above the height of the furnace throat steel brick, and the feed line for ore is 0.2 meters above the height of the furnace throat steel brick. The two feed line heights are different, differing by 0.1 meters. Feeding is carried out according to this feed line.

2. A method for increasing the utilization of coal gas in a blast furnace ironmaking process according to claim 1, characterized in that: It also includes a lower air supply system, which is a supporting measure used to match the upper and lower sections, specifically including: A 450mm long, 5° angled tuyeres are used for air supply, extending the outlet position appropriately into the blast furnace, reducing the effective belly angle, increasing and stabilizing the inlet blast temperature. The inlet hot blast temperature is increased from 1180℃ to 1200℃ and stabilized at this level. The blast temperature is increased within the equipment's allowable range, without using the maximum limit, leaving appropriate adjustment margin to stabilize and reduce fluctuations. The difference between the final temperature at the end of the hot blast stove's air supply and the initial temperature at the beginning of the air supply should be ≤30℃. The oxygen enrichment is increased and stabilized, using the maximum allowable oxygen level. The furnace top pressure is increased and stabilized, with the blast furnace top pressure ≥190kPa, reaching more than 86% of the design top pressure.

3. A method for increasing the utilization of coal gas in a blast furnace iron-making process according to claim 1, characterized in that: Further including auxiliary measures, which are used to assist in production, specifically including: The raw material conditions must meet the following requirements: a. The main quality indicators of sintered ore meet the requirements, and the main quality indicators of coke meet the requirements. b. Raw material screening control mainly involves adjusting the amplitude of the vibrating screen under the blast furnace trough to control the material flow, optimize the feed distribution and feed rate, reduce the thickness of the material layer on the screen plate, and improve the screening effect. The raw materials fed into the furnace mainly include sinter + pellets + raw ore. The main content of screening control is that the powder smaller than 5mm in sinter is ≤3.5%, and the powder smaller than 8mm in raw ore is ≤3.5%. The main content of fuel screening control is that the powder smaller than 25mm in coke is ≤3.5%. The slag and iron composition outside the furnace must meet the following standards: a. Tap flow velocity ≥ 3.5 t / min, iron quantity difference ≤ 8%; b. The slag removal time after the taphole is opened shall be ≤15 minutes; c. The interval between opening the taphole is ≤25 minutes; Control the furnace temperature and slag basicity, avoid the viscosity of slag iron, affect the fluidity and permeability, control the Si in 0.25-0.55%, the physical heat in 1460-1500℃, the slag R2 in 1.16-1.22.

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