A smelting method for increasing the proportion of lump ore in a blast furnace

Abstract

The application provides a smelting method for increasing the proportion of lump ore in a blast furnace, comprising the following steps: S1, raw material preparation, drying and preheating the lump ore, then mixing the lump ore with sintered ore, pellet ore, coke and coke butter to form ore raw material, and transporting the ore raw material to the top of the blast furnace by a belt conveyor; S2, blast furnace charging, alternately distributing the coke and the ore raw material into the blast furnace through a rotating distribution chute to form an alternating layered structure of ore layers and coke layers; S3, air supply system, reducing the original tuyere area by 1% to 3% during smelting, and adjusting the equivalent bosh angle to 75 degrees by installing a tuyere small sleeve at the tuyere; S4, slag making system, adding serpentine into the ore raw material according to the aluminum content in the slag, and controlling the magnesium-aluminum ratio in the slag to be 0.55 to 0.6. The application fully considers the whole process of blast furnace ironmaking, so that the blast furnace can still guarantee moderate permeability and low blast furnace pressure difference, the gas channel in the blast furnace is unobstructed, the slag viscosity is low, and the blast furnace can be stably smelted when the proportion of lump ore in the blast furnace is increased to 15% to 17%.

Description

Technical Field

[0001] This invention relates to the field of blast furnace ironmaking technology, and in particular to a smelting method for increasing the proportion of lump ore in blast furnaces. Background Technology

[0002] Blast furnaces are a crucial component of modern steel production processes. They use ore as raw material for smelting, reducing it to produce molten iron. Blast furnaces have the highest energy consumption and carbon emissions among all steel production processes. Therefore, blast furnace ironmaking faces significant economic and environmental challenges.

[0003] Sinter, pellets, and lump ore are the main iron-containing raw materials for blast furnace smelting. Among them, lump ore is a raw material with the lowest overall cost. Moreover, lump ore does not require high-temperature roasting before being fed into the furnace, which significantly reduces carbon emissions. Therefore, the scientific and rational addition of lump ore to the blast furnace can significantly reduce the coke ratio, alleviate the economic and environmental burden of the ironmaking process, and is of great significance for reducing the cost of the steel industry and achieving energy conservation and emission reduction. However, due to the influence of multiple factors such as the moisture content, bursting rate, and reducibility of lump ore, the current proportion of lump ore in the furnace is only between 5% and 10%.

[0004] Increasing the proportion of lump ore in a blast furnace leads to several issues. Lump ore's metallurgical properties, particularly its softening and dripping properties, are significantly inferior to sinter / pelletized ore. This results in increased pressure differential, decreased permeability, higher slag viscosity, and poor liquid permeability of the dead charge column, severely impacting the blast furnace's stability and smooth operation. Therefore, appropriate technical measures must be implemented to address these problems and minimize the impact of lump ore on the blast furnace, providing technical support for increasing the lump ore proportion.

[0005] Chinese Patent 202010643897.5 discloses a method for increasing the proportion of lump ore in blast furnace smelting. This method utilizes sintering waste gas to pre-treat the lump ore, increasing its feed ratio. Lump ore with a particle size of 11mm-17mm replaces part of the sintering bottom material during sintering. The replacement ratio is determined based on the lump ore's bursting index. Lump ore with a particle size of 18mm-40mm is fed into the sintering ring cooler at the tail of the sintering machine along with hot sintered ore, utilizing the waste heat of the sintered ore and the hot waste gas from the sintering ring cooler for pre-treatment. Coke and blast furnace iron are alternately fed into the blast furnace, forming an alternating layered structure of ore and coke layers. The sintered ore composite material is positioned at the bottom of the ore layer, while the pellet and lump coke composite material is positioned at the top. The advantages are: it utilizes sintering waste gas to pre-treat the lump ore, improving its metallurgical properties; it saves bottom material, increases the quality of the finished ore, and improves the hourly output of the sintering machine. However, this method involves a complex pretreatment process for lump ore, and the placement of sintered ore composite material must be strictly controlled during ore layer placement. The entire material preparation and filling process involves numerous steps, and the operation of related equipment is cumbersome, which is not conducive to on-site operation.

[0006] Chinese Patent 202111313910.1 discloses a blast furnace ironmaking method for increasing the proportion of lump ore, including: step S1, material preparation and transportation; step S2, blast furnace filling; step S3, powder and oxygen conveying; and step S4, molten iron tapping. In step S2, the present invention controls the amount and position of each raw material during blast furnace filling by setting up a material distribution device, detects the material layer height by setting up an infrared ranging device, compares the material layer height with the standard material layer height set inside by setting up a central control module to adjust the material distribution speed, and adjusts the material distribution rotation speed according to the thickness of the material layer in the center and edge of the blast furnace, and controls the amount of material distribution by detecting the top temperature of the material. This allows the charging process to be adjusted and changed according to the actual situation when using the blast furnace for ironmaking, so that the raw materials can be melted and reduced more quickly in the blast furnace, thereby increasing the proportion of lump ore used in blast furnace ironmaking. However, this method relies on infrared ranging devices to measure the height of each material layer, and the high temperature of smelting will reduce the measurement accuracy and service life of the infrared ranging devices, which is not conducive to long-term use. Moreover, adjusting the charging system cannot guarantee the smooth operation of the blast furnace. The blast furnace blowing system and slagging system also need to be adjusted simultaneously, resulting in many improvement points and too much coordination.

[0007] Therefore, how to increase the proportion of lump ore in the blast furnace and reduce the operational difficulty of matching it while ensuring stable blast furnace smelting, so as to meet the requirements of ironmaking plants to improve quality and efficiency and reduce costs, has become an urgent problem to be solved. Summary of the Invention

[0008] To address the aforementioned problems in the existing technology, the present invention aims to provide a smelting method for increasing the proportion of lump ore in blast furnaces that is simple to operate and provides stable blast furnace smelting.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0010] A smelting method for increasing the proportion of lump ore in blast furnaces includes the following steps:

[0011] S1. Raw material preparation

[0012] After drying and preheating the lump ore, it is mixed with sinter, pellets, coke, and coke to form ore raw materials, which are then transported to the top of the blast furnace by belt conveyor.

[0013] S2, Blast Furnace Charging

[0014] Coke and ore are alternately fed into the blast furnace through a rotating feeding chute, forming an alternating layered structure of ore and coke layers. The coke layer feeding adopts a three-batch circulating coke feeding process, namely the first two batches of normal feeding batches + the third batch of small-angle feeding batches. Every three batches constitute a small coke feeding cycle, and the coke feeding is repeated in a cycle.

[0015] S3, Air Supply System

[0016] During smelting, the original tuyeres area is reduced by 1% to 3%, and the equivalent furnace belly angle is adjusted to 75° by adding a small tuyeres sleeve at the tuyeres.

[0017] S4, Slag Formation System

[0018] Add an appropriate amount of serpentine to the ore raw material according to the aluminum content in the slag, and control the magnesium-aluminum ratio in the slag to be between 0.55 and 0.6.

[0019] In step S1

[0020] The pretreatment method for lump ore is as follows: a hot air pipe is connected to the bottom of the lump ore bin, so that hot air is blown over the lump ore from bottom to top to dry the moisture on the outer surface of the lump ore and preheat the lump ore to 30℃~50℃; then screening is carried out to remove lump ore powder and small-diameter lump ore, and only lump ore with a particle size of 5mm~20mm is retained for use as raw material for ironmaking.

[0021] The temperature of the hot air used for drying is 160℃~180℃; the dried lump ore is screened using a multi-frequency screen, and the screening flow rate of the multi-frequency screen is controlled to be ≤20kg / s.

[0022] In step S1, the ore raw materials include sinter, pellets, and lump ore, wherein the mass percentage of lump ore in the ore raw materials is 15% to 17%. After the sinter, lump ore, and pellets are mixed, 2% of the total amount of coke and coke briquettes from the sinter, pellets, and lump ore is added to the mixture via a vibrating screen. Appropriate amounts of smelting additives may also be added to the ore raw materials according to smelting requirements.

[0023] Furthermore, the coke has a particle size of 20mm to 40mm, and the coke granules have a particle size of ≤20mm.

[0024] In step S2, the fabric matrix of the normal fabric batch of the coke layer is 39-37.5-36-34-32 / 3-2-2-2-2, and the fabric matrix of the small-angle fabric batch of coke is 39-37.5-36-34-27 / 3-2-2-2-2.

[0025] In step S2, the ore layer adopts a 33-30-27-30 / 3-3-3-1 material distribution method, and the last ring of small-diameter ore is distributed in the middle ring with better air permeability.

[0026] In step S4, when the aluminum content in the slag is >16.5%, the magnesium-aluminum ratio is controlled at 0.6; when the aluminum content in the slag is between 15% and 16.5%, the magnesium-aluminum ratio is controlled at 0.55 to 0.6. If the magnesium-aluminum ratio in the slag is lower than 0.55, serpentine is added at 1% of the ore batch.

[0027] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0028] This invention provides a smelting method for increasing the proportion of lump ore in blast furnaces. It fully considers the entire blast furnace ironmaking process, detailing key control steps in four stages: raw material preparation, blast furnace charging, blast system, and slag formation. This minimizes the impact of lump ore on the blast furnace. Even with a lump ore proportion increased to 15%–17%, it still ensures adequate permeability and a low blast furnace pressure differential, unobstructed gas channels, and low slag viscosity. It also solves the problem of poor permeability in the dead charge column, ensuring the stability of blast furnace smelting. Experiments show that using this smelting method significantly increases daily blast furnace iron production, reduces the fuel ratio, and achieves remarkable increases in production and reductions in energy consumption. The cost per ton of molten iron decreases by more than 18 yuan, demonstrating a considerable improvement.

[0029] This invention introduces sintering waste heat (160℃~180℃) into the bottom of the lump ore bin for drying and preheating. The lump ore is then sieved using a multi-frequency screen to remove powdered ore, reducing its amount fed into the furnace and ensuring good blast furnace permeability. The lump ore pretreatment step only requires connecting the sintering waste heat to the bottom of the lump ore bin and installing a mesh air supply pipe inside the bin. This requires minimal equipment modification and allows for effective reuse of sintering waste heat without increasing energy consumption. The low-frequency, high-amplitude stable vibration provided by the multi-frequency screen effectively improves the separation efficiency of lump powder, reduces residual powder in the lump ore, and ensures a particle size of 5mm~20mm. Preheated lump ore fed into the blast furnace is more likely to undergo smelting reactions, improving smelting efficiency, reducing energy consumption, and decreasing blast furnace load.

[0030] In the blast furnace charging step, this invention simultaneously defines the distribution matrix of the coke layer and the ore layer in detail. Specifically, the ore layer distribution matrix is ​​33-30-27-30 / 3-3-3-1. During the chute feeding process, larger-diameter ore is first distributed normally from the periphery of the blast furnace inwards, while smaller-diameter ore in the final ring is distributed in the more permeable middle ring, preventing dense accumulation in the blast furnace center and thus improving the permeability of the ore layer in the center of the blast furnace. The coke layer distribution adopts a three-batch cyclic coke distribution process: two normal distribution batches followed by a third small-angle distribution batch, with each three batches constituting a small coke feeding cycle, which is repeated cyclically. The fabric matrix for a normal coke charging batch is 39-37.5-36-34-32 / 3-2-2-2-2, while the fabric matrix for a small-angle coke charging batch is 39-37.5-36-34-27 / 3-2-2-2-2. It can be seen that during small-angle coke charging, a raised coke heap forms at the center of the coke layer. The coke itself has high porosity and good permeability, and this raised coke heap forms the supporting framework of the blast furnace's central material layer. When the ore layer is added, it reduces the accumulation of ore powder towards the blast furnace center, achieving the goal of activating the central airflow with the lowest possible coke ratio. Because the small-diameter powder from the ore layer is not distributed in the blast furnace center, the porosity and permeability of the coke heap are maintained stably, ensuring that the gas flow generated in the furnace belly passes smoothly through the blocky material layer.

[0031] During the smelting process, this invention adjusts the kinetic energy and velocity of the blast furnace tuyeres by slightly altering their area, thereby improving the penetration of the blast furnace lining. Simultaneously, by adjusting the equivalent belly angle of the blast furnace, the impact of the gas flow on the belly is reduced, ensuring a reasonable furnace configuration for smelting after increasing the proportion of lump ore. Through these operations, the airflow angle and velocity can be adjusted, allowing the air blown in through the tuyeres to pass smoothly through the blast furnace, thus improving gas utilization.

[0032] The present invention also limits the MgO content and magnesium-aluminum ratio range of the slag, which effectively reduces the viscosity of the slag, improves the slag fluidity, reduces gas resistance, maintains the porosity of the coke skeleton, and ensures the smooth operation of the blast furnace and the quality of pig iron. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the embodiments.

[0034] A smelting method for increasing the proportion of lump ore in blast furnaces specifically includes the following steps:

[0035] S1. Raw material preparation

[0036] The lump ore is pre-treated and then mixed with sinter, pellets, coke, and coke-butane to form raw ore, which is then transported to the top of the blast furnace by belt conveyor. This coke-butane mixed loading method improves the permeability of the ore layer within the blast furnace.

[0037] The pretreatment method for the lump ore is as follows:

[0038] A hot air pipe is connected to the bottom of the lump ore bin, so that hot air blows over the lump ore from bottom to top, drying the moisture on the outer surface of the lump ore and preheating the lump ore to 30℃~50℃; then screening is carried out to remove lump ore powder and small-diameter lump ore, retaining only lump ore with a particle size of 5mm~20mm for use as raw material for ironmaking.

[0039] Generally, the temperature of the hot air used for drying is 160℃~180℃. If the temperature of the hot air is too high, on the one hand, the surface moisture of the lump ore will become too dry, making it prone to pulverization; on the other hand, the high temperature of the hot air can easily lead to excessively high ore temperatures, posing a risk of damaging the screen. Experiments have shown that when the temperature of the lump ore reaches 30℃~50℃, the surface moisture content can be stably controlled at a low level, which can meet the needs of ironmaking production. Otherwise, because the evaporation of surface moisture requires the absorption of heat, the temperature of the lump ore cannot stably rise to 30℃~50℃ when the surface moisture content is high.

[0040] Typically, the block ore bin is a square bin with a conical bottom. Hot air pipes are introduced below the block ore bin, and several cross-shaped air supply pipes are installed inside the block ore bin so that the air supply network can cover the cross-section of the block ore bin. Air outlets are evenly opened on the air supply pipes to ensure that the hot air can fully contact the block ore in the block ore bin to achieve drying and preheating.

[0041] For the purpose of making full use of energy and saving energy and reducing consumption, the hot air used for drying can be the waste heat of sintering. That is, the hot air generated by high-temperature sintering is extracted and poured into the hot air pipe at the bottom of the lump ore bin by an induced draft fan. As the hot air travels from bottom to top along the gap between the ore blocks, the hot air comes into full contact with the outer surface of the lump ore, so as to achieve rapid drying of the surface moisture of the lump ore and preheating of the lump ore.

[0042] The dried lump ore is screened using a multi-frequency screen, with the screening flow rate controlled to be ≤20kg / s. Compared with the traditional lump ore under-trough vibrating screen, the multi-frequency screen uses low-frequency, large-amplitude stable vibration, which can effectively improve the separation efficiency of lump powder, reduce the residue of lump powder in the lump ore, and ensure that the particle size of the lump ore is 5mm to 20mm as much as possible.

[0043] The preferred particle size of the lump ore is 10mm to 15mm, which can fully improve the permeability between the material layers in the blast furnace and ensure the ironmaking effect.

[0044] Generally, the ore raw materials include sinter, pellets, and lump ore, wherein the mass percentage of lump ore in the ore raw materials is 15% to 17%, preferably 17%. After the sinter, lump ore, and pellets are mixed, appropriate amounts of coke and coke briquettes are added through a vibrating screen. The mass of each type of coke and coke briquettes added is 2% of the total mass of the sinter, pellets, and lump ore. Appropriate smelting additives may also be added to the ore raw materials according to specific needs.

[0045] Of the sintered ore, the content of sintered ore with a particle size <5mm does not exceed 3%, the content of sintered ore with a particle size of 5mm to 10mm does not exceed 30%, and the content of sintered ore with a particle size of 25mm to 40mm exceeds 50%.

[0046] The coke has a particle size of 20mm to 40mm, and the coke granules have a particle size of ≤20mm.

[0047] S2, Blast Furnace Charging

[0048] Coke and ore are alternately fed into the blast furnace via a rotating feeding chute, forming an alternating layered structure of ore and coke layers. The coke load of this invention is 4.5–5.0, preferably 4.5–4.7.

[0049] The ore layer fabric matrix is ​​33-30-27-30 / 3-3-3-1, that is:

[0050] Ore ring number 3 3 3 1

[0051] During the chute feeding process, larger-diameter ore is fed first, while smaller-diameter ore is fed last due to gravity. A 33-30-27-30 / 3-3-3-1 feeding method is used, placing the last ring of smaller-diameter ore in a more permeable middle ring to prevent dense accumulation in the blast furnace center and thus maintain its permeability. Compared to the original 33-30-27 / 3-4-3 feeding matrix, the ore layer feeding matrix of this invention effectively improves the permeability of the ore layer in the blast furnace center.

[0052] The coke layer is laid using a three-batch cyclic coke laying process, namely, the first two batches of normal laying batches + the third batch of small-angle laying batches, with each three batches forming a small coke-adding cycle, and the coke material is laid repeatedly in this cycle.

[0053] The fabric distribution matrix for a normal coke batch is 39-37.5-36-34-32 / 3-2-2-2-2, and the fabric distribution matrix for a small-angle coke batch is 39-37.5-36-34-27 / 3-2-2-2-2, i.e.

[0054]

[0055] When the coke is fed at a small angle, approximately 18% of the total coke content is directly added to the center of the blast furnace, forming a raised coke heap at the center. Coke itself has high porosity and good permeability; this raised heap forms the supporting framework of the blast furnace's central burden. When the ore layer is added, it reduces the accumulation of ore powder in the blast furnace center, achieving the goal of activating the central airflow with the lowest possible coke ratio. Furthermore, coke has high thermal strength, enabling it to form gas channels and ensuring the smooth flow of gas generated in the furnace belly through the lumpy burden layer.

[0056] In conventional center-coke charging methods, the amount of coke added to the center is often 50% to 60% of the total coke volume to ensure unobstructed gas flow in the center of the blast furnace. However, this charging method significantly increases blast furnace fuel consumption and leads to excessively high iron production costs. Reducing the amount of coke added to the center does not improve the permeability of the blast furnace center, restricts the gas flow in the center, and causes unstable furnace conditions. This invention, based on pretreatment of lump ore and adjustments to the ore layer charging method, achieves effective control of the permeability of the blast furnace burden layer through only intermittent, small-proportion center-coke addition. This improves the permeability of the blast furnace center and ensures unobstructed gas flow in the central area of ​​the blast furnace.

[0057] Experiments showed that if a small-angle charging method was used for each batch of coke, the coke ratio would increase significantly, failing to maximize the coke's performance. Therefore, after multiple trials, a three-batch cycle was adopted, with each cycle consisting of two normal charging batches plus one small-angle charging batch. This resulted in moderate air permeability within the blast furnace and more stable blast furnace smelting performance.

[0058] S3, Air Supply System

[0059] During smelting, preheated air is blown in from the tuyeres located at the bottom of the blast furnace along the furnace perimeter, reducing the original tuyeres area by 1% to 3%. By adding tuyeres sleeves at the tuyeres, the equivalent furnace belly angle is adjusted to 75°, thereby activating the hearth, improving the blast furnace blowing effect, and solving the problems of high blast furnace pressure differential and poor permeability after increasing the proportion of lump ore.

[0060] By appropriately reducing the tuyeres area, the kinetic energy and velocity of the blast can be moderately increased, thereby improving the penetration of the blast into the blast furnace burden. However, if the tuyeres area is reduced too much, resulting in excessively high blast velocity, it will affect the furnace temperature and gas utilization rate, which is detrimental to the stability of the blast furnace conditions.

[0061] This invention alters the blowing angle of the blast furnace by adding an extended tuyere sleeve, thereby appropriately reducing the equivalent belly angle. The length of the tuyere sleeve is adjusted according to the specific design structure of the blast furnace; the designed belly angle of this plant's blast furnace is 77.366°. By adding a 480mm tuyere sleeve, the belly angle is reduced to 75°, thereby reducing the impact of the gas flow on the belly and ensuring a reasonable furnace operation for blast furnace smelting after increasing the proportion of lump ore.

[0062] S4, Slag Formation System

[0063] Because lump ore has a relatively high Al2O3 content, increasing the proportion of lump ore will increase the Al2O3 content in the slag, leading to increased slag viscosity and poor permeability of the dead stock. To address this issue, the aluminum content of the blast furnace slag is monitored in real time during the smelting process. Based on the aluminum content, appropriate amounts of serpentine are added to the ore raw materials to control the magnesium-aluminum ratio in the slag at 0.55–0.6, thereby reducing blast furnace slag viscosity and improving the permeability of the dead stock in the hearth.

[0064] The online magnesium-aluminum ratio (MgA ratio) is generally used to represent the degree of change in slag fluidity, with a reasonable range of 0.55-0.6. When the aluminum content in the slag is >16.5%, the MgA ratio is controlled at 0.6; when the aluminum content is between 15% and 16.5%, the MgA ratio is controlled at 0.55-0.6. The required MgO content in the slag is calculated by using the aluminum content and MgA ratio, and then the amount of serpentine to be added is determined, supplementing the subsequent ore raw materials with an appropriate amount of serpentine. If the MgA ratio in the slag is below 0.55, serpentine is added at 1% of the ore batch to increase the MgO content in the slag, keeping the MgO content between 8.5% and 9.5% and the MgA ratio between 0.55 and 0.6, thereby reducing slag viscosity.

[0065] Through the combined effect of the above steps, the proportion of blast furnace lump ore can be increased from 5% to 10% to 15% to 17%, and stable smelting is achieved.

[0066] The present invention will be further described below through embodiments.

[0067] In the following embodiments, the blast furnace used has a volume of 816 m³. 3 The equivalent furnace belly angle is 77.366°; the blast furnace has a total of 18 tuyeres with a total tuyere area of ​​0.176 m². 2 ~0.182m 2 The air outlets are available in two diameters: 110mm and 115mm. They can be used in combination according to production needs and operational conditions.

[0068] Examples 1 to 6 are batches of blast furnaces put into production with an increased proportion of lump ore using the method of the present invention, while Comparative Example 1 is a batch of conventional blast furnaces put into production without using the method of the present invention.

[0069] The composition and content of the blast furnace ore raw materials in Examples 1 to 6 and Comparative Example 1 are shown in the table below.

[0070] Example 1 75％ 13.5％ 11.5％ 2％ 2％ Example 2 75％ 15％ 10％ 2％ 2％ Example 3 75％ 16.22％ 8.78％ 2％ 2％ Example 4 75％ 17％ 8％ 2％ 2％ Example 5 75％ 17％ 8％ 2％ 2％ Example 6 75％ 17％ 8％ 2％ 2％ Comparative Example 1 75％ 10％ 15％ 2％ 2％

[0071] The detailed parameter control of the blast furnace in Examples 1 to 6 and Comparative Example 1 is shown in the table below.

[0072]

[0073] The particle size control of sinter, pellets, coke, and coke briquettes, as well as the blast furnace coke load, are all controlled in the same way.

[0074] The technical effects of Examples 1 to 6 and Comparative Example 1 are shown in the table below.

[0075]

[0076] The technical comparison data above shows that by implementing the method of the present invention, the proportion of blast furnace lump ore can be gradually and stably increased from 10% to 17%, and stable smelting of the blast furnace can be achieved. After three batches of repeated smelting with a lump ore proportion of 17%, the smelting is stable and reproducible, proving that the method of the present invention can effectively ensure the smooth operation of the blast furnace after the proportion of blast furnace lump ore is increased.

[0077] The permeability index and pressure difference indicators show that after adopting the series of related operations of this invention, the adverse consequences such as increased blast furnace pressure difference and decreased permeability that occur after increasing the proportion of lump ore were overcome. The permeability index and pressure difference in the blast furnace were maintained within a good range, basically the same as those of Comparative Example 1 with conventional low lump ore feeding. This indicates that the blast furnace has good permeability, unobstructed gas channels, and good working conditions, making it easy to intensify smelting. In addition, the gas utilization rate shows that compared with Comparative Example 1, the gas utilization rate of Examples 4 to 6 is higher, and the gas utilization rate values ​​of multiple batches are relatively stable, proving that the blast furnace smelting reaction is stable and effectively reduces coke and increases production.

[0078] The data in the table also shows that after increasing the proportion of lump ore in the blast furnace, the daily iron production also increased, from 3408.42 t / d (Comparative Example 1) to 3432.72 t / d (Example 4), an increase of 24.3 t / d. Simultaneously, the fuel ratio decreased from 533.40 kg / t (Comparative Example 1) to 531.34 kg / t (Example 4), a decrease of 2.06 kg / t, demonstrating a significant effect of increasing production and reducing consumption. Calculations show that when the proportion of lump ore increases to 17%, the cost per ton of molten iron decreases by more than 18 yuan, a considerable improvement in cost. Furthermore, after multiple batches of smelting, the smelting stability is excellent.

[0079] In summary, under the comprehensive control of a series of steps in this invention, the proportion of blast furnace lump ore can be increased from 5%–10% to 15%–17% while still ensuring high permeability and good smelting stability within the blast furnace. It also exhibits technical advantages such as low cost and low carbon content, fully demonstrating the effectiveness and reliability of the method.

[0080] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A smelting method for increasing the proportion of lump ore in blast furnaces, characterized in that... Includes the following steps: S1. Raw material preparation After drying and preheating the lump ore, it is mixed with sinter, pellets, coke, and coke to form ore raw materials, which are then transported to the top of the blast furnace by belt conveyor. S2, Blast Furnace Charging Coke and ore are alternately fed into the blast furnace through a rotating feeding chute, forming an alternating layered structure of ore and coke layers. The coke layer feeding adopts a three-batch circulating coke feeding process, namely the first two batches of normal feeding batches + the third batch of small-angle feeding batches. Every three batches constitute a small coke feeding cycle, and the coke feeding is repeated in a cycle. S3, Air Supply System During smelting, the original tuyeres area is reduced by 1% to 3%, and the equivalent furnace belly angle is adjusted to 75° by adding a small tuyeres sleeve at the tuyeres. S4, Slag Formation System Add an appropriate amount of serpentine to the ore raw material according to the aluminum content in the slag, and control the magnesium-aluminum ratio in the slag to be between 0.55 and 0.

6. In step S1, the ore raw materials include sinter, pellets and lump ore, wherein the mass percentage of lump ore in the ore raw materials is 15%~17%; after the sinter, lump ore and pellets are mixed, coke and coke briquettes of 2% of the total mass of the sinter, pellets and lump ore are added to the vibrating screen. In step S2, the fabric matrix of the normal fabric batch of the coke layer is 39-37.5-36-34-32 / 3-2-2-2-2, and the fabric matrix of the small-angle fabric batch of coke is 39-37.5-36-34-27 / 3-2-2-2-2.

2. The smelting method for increasing the proportion of lump ore in blast furnace according to claim 1, characterized in that: In step S1, the pretreatment method for lump ore is as follows: a hot air pipe is connected to the bottom of the lump ore bin, so that hot air blows over the lump ore from bottom to top, drying the moisture on the outer surface of the lump ore and preheating the lump ore to 30℃~50℃; then screening is performed to remove lump ore powder and small-diameter lump ore, retaining only lump ore with a particle size of 5mm~20mm for use as raw material for ironmaking.

3. The smelting method for increasing the proportion of lump ore in blast furnace according to claim 2, characterized in that: The temperature of the hot air used for drying is 160℃~180℃; the dried lump ore is screened using a multi-frequency screen, and the screening flow rate of the multi-frequency screen is controlled to be ≤20kg / s.

4. The smelting method for increasing the proportion of lump ore in blast furnace according to claim 1, characterized in that: The ore raw material also includes an appropriate amount of smelting additives.

5. A smelting method for increasing the proportion of lump ore in a blast furnace according to claim 1, characterized in that: The coke has a particle size of 20mm to 40mm, and the coke granules have a particle size of ≤20mm.

6. A smelting method for increasing the proportion of lump ore in a blast furnace according to claim 1, characterized in that: In step S2, the ore layer adopts a 33-30-27-30 / 3-3-3-1 material distribution method, with the last ring of small-diameter ore distributed in the middle ring with better air permeability.

7. A smelting method for increasing the proportion of lump ore in a blast furnace according to claim 1, characterized in that: In step S4, when the aluminum content in the slag is >16.5%, the magnesium-aluminum ratio is controlled at 0.6; when the aluminum content in the slag is between 15% and 16.5%, the magnesium-aluminum ratio is controlled at 0.55 to 0.

6.

8. A smelting method for increasing the proportion of lump ore in a blast furnace according to claim 7, characterized in that: If the magnesium-aluminum ratio in the slag is less than 0.55, add serpentine at 1% of the ore batch.

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