Blast furnace for iron and steel production
The blast furnace design with inner wall expansion and controlled reducing gas injection addresses the challenge of high productivity and reduced CO2 emissions by optimizing gas injection, achieving efficient iron reduction and environmental sustainability.
Patent Information
- Application Number
- JP2025167207
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-10-03
- Publication Date
- 2026-01-06
AI Technical Summary
Blast furnaces face a challenge in achieving high productivity while reducing their environmental impact, particularly in terms of CO2 emissions, despite conventional methods already minimizing coke consumption.
A blast furnace design with an inner wall expansion and controlled reducing gas injection below this expansion, utilizing CO2-rich top gas as a reducing agent, injected at specific angles and velocities to enhance iron reduction efficiency.
This design effectively reduces coke consumption and CO2 emissions without impairing the steelmaking process, maintaining or enhancing productivity.
Smart Images
Figure 2026001176000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a blast furnace for the production of iron and a process for injecting a reducing gas into said blast furnace. [Background technology]
[0002] In blast furnaces, the conversion of iron-bearing charges (sinter, pellets and iron ore) into cast iron, or hot metal, is traditionally carried out by the reduction of iron oxide with reducing gas (containing, among other things, CO, H2 and N2) produced by the combustion of coke in tuyeres at the bottom of the furnace, into which preheated air, known as hot blast, is blown at temperatures between 1000 and 1300°C.
[0003] To increase productivity and reduce costs, supplemental fuels such as pulverized forms of coal, fuel oil, natural gas or other fuels are also injected into the tuyere in conjunction with oxygen enrichment of the hot blast.
[0004] The gas recovered at the top of the blast furnace, known as top gas, is composed primarily of CO, CO2, H2, and N2, with proportions of 20-28%v, 17-25%v, 1-5%v, and 48-55%v, respectively. Although some of this gas is used as fuel in other plants, such as power plants, blast furnaces remain a significant source of CO2.
[0005] Given the significant increase in atmospheric CO2 concentrations since the beginning of the last century and the subsequent greenhouse effect, it is essential to reduce CO2 emissions where CO2 is produced in large quantities, and therefore in particular in blast furnaces.
[0006] To this end, the consumption of reducing agents in blast furnaces has been reduced by half over the last 50 years, so that today, in conventionally configured blast furnaces, the carbon consumption has reached the lower limit associated with the laws of thermodynamics.
[0007] One way to further reduce CO2 emissions is to reinject CO2-rich top gas purified from CO2 back into the blast furnace, known as TGRBF (Top Gas Circulation Blast Furnace). Thus, using CO2-rich gas as a reducing agent allows for a reduction in coke consumption and therefore CO2 emissions. This injection can be carried out at two levels: at the classical tuyere level instead of hot air, and in the reducing zone of the blast furnace, for example at the bottom of the blast furnace stack.
[0008] However, this so-called reducing gas shaft injection must not interfere with the execution of the steelmaking process and must not impair productivity. Summary of the Invention [Problem to be solved by the invention]
[0009] There is a need for blast furnaces that are as productive as or more productive than conventional blast furnaces, while reducing their impact on the environment. [Means for solving the problem]
[0010] This problem is solved by a blast furnace according to the invention, in which iron ore is at least partially reduced by reducing gas injected into the stack of the blast furnace in an injection zone, said blast furnace having an outer wall and an inner wall in contact with the materials charged into the blast furnace, in said injection zone the inner wall having a local inward expansion, and the reducing gas injection taking place below said inward expansion.
[0011] The blast furnace of the invention may also be equipped with the following optional features, which are considered separately and according to all possible technical combinations: The widened portion has a width W comprised between 50 and 250 mm. - The reducing gas is injected near the bottom of the expansion section. The reducing gas is injected at a distance L below the expansion, the distance L being less than or equal to the width W of said expansion. Local enlargements are performed by adding protrusions to the inner walls. The inner wall is formed by staves that come into contact with the material fed into the blast furnace, and local enlargements are formed using staves with a trapezoidal cross section. The reducing gas is injected by means of a blowing device that can blow the gas downwards. The reducing gas is injected by an injection device capable of injecting the gas at an angle α comprised between 15° and 30° with respect to a plane X perpendicular to the inner wall of the blast furnace. The blast furnace has a working height H, and the reducing gas injection is carried out at a height comprised between 20% and 70% of said working height H from the tuyere level. The blast furnace has a working height H, and the reducing gas injection is carried out at a height comprised between 30% and 60% of said working height H from the tuyere level.
[0012] The present invention also relates to a method for making iron preformed in a blast furnace according to the aforementioned embodiment, wherein the reducing gas injection is carried out at a speed comprised between 75 m / s and 200 m / s.
[0013] The iron making process may also comprise the following optional features, considered separately or according to all possible technological combinations: - Reducing gas contains a portion of the furnace top gas discharged from the blast furnace during the steelmaking process. The reducing gas is injected at a temperature comprised between 850°C and 1200°C. The reducing gas contains preferentially 65%v-75%v carbon monoxide CO, 8%v-15%v hydrogen H2, 1%v-5%v carbon dioxide CO2, the remainder being mainly nitrogen N2.
[0014] Other characteristics and advantages of the present invention will become apparent from the description of the invention given below by way of illustration and in no way limiting, with reference to the accompanying drawings, in which: FIG. [Brief explanation of the drawings]
[0015] [Figure 1] FIG. 1 is a side view of a blast furnace with reducing gas injected in the reducing zone. [Figure 2] FIG. 2 is a top view of the blast furnace of FIG. 1. [Figure 3] FIG. 1 illustrates a shaft furnace according to an embodiment of the present invention. [Figure 4] FIG. 10 shows a DEM-CFD simulation of the inside of a shaft furnace according to the present invention with varying reducing gas injection positions. [Figure 5] FIG. 10 shows DEM-CFD simulations of the inside of a shaft furnace according to the present invention with varying reducing gas injection angles. DETAILED DESCRIPTION OF THE INVENTION
[0016] Elements in the figures are illustrative and may not be drawn to scale.
[0017] FIG. 1 is a side view of a blast furnace according to the present invention. The blast furnace 1 comprises, from top to bottom, a furnace throat 11, through which raw materials are introduced and gases are discharged, a stack (also called a shaft) 12, a furnace belly 13, a bosh 14, and a hearth 15. The introduced raw materials are primarily iron-containing materials such as sinter, pellets, or iron ore, and carbon-containing materials such as coke. Hot air injection, necessary for carbon combustion and therefore iron reduction, is performed through tuyere 16 located between the bosh 14 and the hearth 15. Structurally, the blast furnace has an outer wall or shell 2. As shown in FIG. 3, this shell 2 is surrounded by a refractory lining and staves 3 inside the blast furnace, forming an inner wall 5. To reduce the consumption of coke, the primary carbon source for reducing iron, it is envisioned that reducing gas is injected into the blast furnace in addition to hot air. This reducing gas injection occurs within the blast furnace stack, preferentially at the bottom of the stack 12, e.g., directly above the belly 13. In a preferred embodiment, the reducing gas injection is carried out at a distance from the classical tuyere level comprised between 20% and 70%, preferentially between 30 and 60%, of the working height H of the furnace. As shown in Figure 1, the working height H of the blast furnace is the distance between the level of hot air injection through the classical tuyere and the zero level of injection.
[0018] Injection is through a number of injection ports 4 around the periphery of the furnace, as shown in Figure 2, which is a top view of the blast furnace 1 at the level of reducing gas injection. In a preferred embodiment, there are as many injection ports as there are staves forming the inner wall 2. The injection port is 200-700 Nm3 per tonne of hot metal in the blast furnace. 3 A reducing gas of 1000 ppm is blown into the reaction vessel.
[0019] FIG. 3 illustrates a blowout opening 4 in a furnace according to one embodiment of the present invention. In this embodiment, the stave 3 is provided with a protrusion 6 that forms a localized expansion of the inner wall 2, and the blowout opening 4 is located below this localized expansion. While the protrusion is one embodiment of the localized expansion, other ways of achieving this are possible, such as implementing a trapezoidal stave in which the bottom of the stave is larger than the top and the blowout opening is located below the bottom. A localized expansion refers to a local increase in the width of the inner wall. By blowing below the localized expansion, a material-free zone, or cavity, can be formed, which protects the blowing area from material movement within the furnace and therefore improves the durability of the blowing equipment. Furthermore, the material does not approach the blowout opening, preventing clogging of the blowing equipment. In a preferred embodiment, the width W is between 50 and 250 mm, providing a cavity large enough to protect the blowout opening. The blowout opening is located a distance L from the expansion. In a preferred embodiment, this distance L is closest to zero and is preferentially smaller than the width W of the expansion. Similar to the width, this parameter allows for control of the size of the cavity formed. The gas inlet 4 is designed so that the reducing gas is ejected at an angle α with respect to a plane X perpendicular to the inner wall at the location of the expansion. In a preferred embodiment, the angle α is between 0 and 30°. This particular range increases the depth to which the reducing gas penetrates into the furnace, thus improving contact with the internal load. If the angle exceeds 30°, a larger amount of gas will be cooled by contact with the inner wall and will not provide the expected reduction effect.
[0020] When the steelmaking process is carried out in the shaft furnace according to the present invention, the reducing gas is preferably injected at a velocity comprised between 75 and 200 m / s to provide a cavity size sufficient to protect the blowing equipment. In the range of 120 to 200 m / s, the size of the cavity does not increase further, and above 200 m / s, the cavity is not controlled and the formation of a mixed layer of coke and iron-containing raw materials may impair the good distribution of the load, thus impairing the productivity of the steelmaking process.
[0021] In a preferred embodiment, the reducing gas introduced into the blast furnace is the top gas discharged from said furnace, which has been subjected to gas treatment to remove dust and to obtain the appropriate composition, pressure and temperature. This reducing gas preferentially contains 65%v-75%v carbon monoxide CO, 8%v-15%v hydrogen H, 1%v-5%v carbon dioxide CO, the remainder being mainly nitrogen N. It is preferentially injected at a temperature comprised between 850 and 1200°C.
[0022] FIG. 4 shows the results of a DEM-CFD (Discrete Element Method and Computational Fluid Dynamics) simulation of the material movement in a blast furnace according to the present invention, depending on the position of the reducing gas injection relative to the expansion. In FIG. 4A, the gas is injected near the local inward expansion, and the distance L can be considered equal to zero. In FIG. 4B, the distance L is equal to 200 mm, and in FIG. 4C, it is equal to 400 mm. In the simulation, the width of the expansion is constant in all figures and equal to 200 mm, the velocity of the reducing gas is also constant and equal to 120 m / s, and the injection angle α is fixed at 30°. From the simulation, it can be observed that the further away from the expansion, the smaller the cavitation. At 400 mm, there is even no cavitation. Therefore, for this particular configuration, having the injection located between 0 and 200 mm is a preferred embodiment.
[0023] Figure 5 shows the results of a CFD simulation of gas injection into a blast furnace according to the present invention, varying the injection angle α. In Figures 5A, 5B, 5C, 5D, and 5E, the angle α is equal to 0°, 15°, 30°, 45°, and 60°, respectively. In the simulations, the width of the expansion section is constant in all figures, equal to 200 mm, and the velocity of the reducing gas is also constant, equal to 120 m / s, respectively. The injection occurred near the expansion section (L = 0 mm). The reducing gas is represented by squares; the darker the squares, the greater the amount of reducing gas. From the simulations, it can be observed that, starting from an angle of 15°, more gas penetrates deeper into the load injected into the blast furnace. However, for angles greater than 30°, the gas tends to flow toward the inner wall of the furnace where it is cooled and does not come into contact with the load.
[0024] Therefore, in the blast furnace according to the present invention, it is possible to effectively inject reducing gas, and therefore it is possible to suppress coke consumption and CO2 emissions without impairing the load flowing into the furnace, and it is possible to reduce the productivity of the blast furnace.
Claims
1. 1. A blast furnace (1) for steel production, in which iron ore is at least partially reduced by reducing gas injected into a stack (12) of the blast furnace in an injection zone, said blast furnace (1) comprising an outer wall (2) and an inner wall (5) in contact with materials charged into the blast furnace, said inner wall (5) comprising a local inward expansion (6) in said injection zone, and reduction gas injection taking place below said inward expansion.
2. 2. The blast furnace according to claim 1, wherein the expansion (6) has a width (W) comprised between 50 and 250 mm.
3. 3. The blast furnace according to claim 1, wherein the reducing gas is injected into the vicinity of the lower part of the expanded section.
4. 3. The blast furnace according to claim 1, wherein the reducing gas is injected below the expansion at a distance L which is equal to or less than the width W of the expansion.
5. A blast furnace according to any one of claims 1 to 4, wherein the local enlargement is produced by adding a protrusion (6) to the inner wall (2).
6. The inner wall 5 is formed of a stave 3 that contacts the material charged into the blast furnace, and the local expansion portion 6 is formed using a stave 3 having a trapezoidal cross section. A blast furnace according to any one of claims 1 to 5.
7. 7. A blast furnace according to claim 1, wherein the reducing gas is injected by means of an injection device (4) designed to inject the gas downwards.
8. 8. The blast furnace according to claim 7, wherein the reducing gas is injected by an injection device designed to inject the gas at an angle α comprised between 15° and 30° relative to a plan X perpendicular to the inner wall 5 of the blast furnace.
9. The blast furnace according to any one of claims 1 to 8, wherein the blast furnace has a working height H, and the reducing gas injection is carried out at a height from the level of the tuyere 16 that is comprised between 20% and 70% of the working height H.
10. The blast furnace according to any one of claims 1 to 8, wherein the blast furnace has a working height H, and the reducing gas injection is carried out at a height from the level of the tuyere 16 that is comprised between 30% and 60% of the working height H.
11. 11. The method for making iron performed in a blast furnace according to claims 1 to 10, wherein the reducing gas is injected at a speed comprised between 75 m / s and 200 m / s.
12. 12. The method of claim 11, wherein the reducing gas contains a portion of the top gas discharged from the blast furnace during the iron making process.
13. 13. The method for making iron according to claim 11 or 12, wherein the reducing gas is injected at a temperature comprised between 850°C and 1200°C.
14. The method for making iron according to claims 11 to 13, wherein the reducing gas has the following composition: 65%v≦CO≦75%v 8%v≦H ２ ≦15%v 1%v≦CO ２ ≦5%v The rest is N ２ .