Blast furnace for ironmaking production

Abstract

A blast furnace for the production of steel, wherein iron ore is at least partially reduced by reducing gas injected into a stack of the blast furnace. The blast furnace has an outer wall and a stack of thickness T int The inner wall has a thickness T int is approximately constant above and below the reducing gas injection region.

Description

Technical Field

[0001] The present invention relates to blast furnaces for ironmaking production.

Background Art

[0002] In blast furnaces, the conversion of iron-containing inputs (sinter, pellets, and iron ore) to cast iron has conventionally been carried out by the reduction of iron oxide by a reducing gas (containing in particular CO, H2, and N2) generated by the combustion of coke at tuyeres located at the bottom of the blast furnace into which air preheated to a temperature of 1000°C to 1300°C, called hot blast, is blown.

[0003] To increase productivity and reduce costs, in addition to oxygen enrichment of the hot blast, auxiliary fuels such as pulverized coal, fuel oil, natural gas, or other fuels are also injected into the tuyeres.

[0004] The gas recovered at the top of the blast furnace, called top gas, mainly consists of CO, CO2, H2, and N2, in proportions of 20 - 28%v, 17 - 25%v, 1 - 5%v, and 48 - 55%v respectively. These gases are generally used as fuel in other parts of the plant and / or for power production in power plants. Therefore, blast furnaces are a major source of CO2 emissions.

[0005] Considering the significant increase in atmospheric CO2 concentration since the beginning of the previous century and the subsequent greenhouse effect, it is essential to reduce CO2 emissions, particularly in blast furnaces where large amounts of CO2 are generated.

[0006] For this purpose, the consumption of reducing agents in blast furnaces has been reduced by half over the past 50 years. Therefore, currently, in blast furnaces of conventional configuration, the carbon consumption has reached the lower limit related to the laws of thermodynamics.

[0007] As one method for further reducing CO2 emissions, a method of reintroducing CO2-purified and CO-rich top gas into a blast furnace is known. Therefore, by using the CO-rich gas as a reducing agent, it becomes possible to reduce coke consumption and thus CO2 emissions. This injection may be carried out at the classical tuyere level instead of hot air, and also at two levels in the reduction zone of the blast furnace, for example, near the corners of the shaft-bellows of the blast furnace and above it (lower stack of the blast furnace). This type of blast furnace is particularly known as a top gas recycling blast furnace (TGRBF).

[0008] Since the second level of injection does not currently exist in the blast furnace, a new level of injection must be created, which must not harmfully impair the operation of the blast furnace. For example, the injection of the reducing gas must not interfere with the flow of substances inside the blast furnace, which is important for productivity.

Summary of the Invention

Problems to be Solved by the Invention

[0009] There is a need for a blast furnace that has productivity equal to or higher than that of prior art blast furnaces and reduces the environmental impact.

Means for Solving the Problems

[0010] This problem is solved by the blast furnace according to the present invention. The blast furnace includes an outer wall, an inner wall having a thickness T int and an injection device for injecting a reducing gas through an injection outlet in the injection area. The thickness T int of the inner wall is substantially constant above and below the injection area. The injection outlet is aligned with the inner wall, and the injection device can inject the reduction at a speed of less than 120 m / s.

[0011] The blast furnace of the present invention may also have the following optional features, considered separately or in any possible technical combination: - The thickness T int of the inner wall is substantially constant over a height of at least 400 mm above and at least 400 mm below the injection area. - The blast furnace has an operating height H, and the reducing gas injection is carried out at a height between 20% and 70% of the operating height H from the tuyere level. - The blast furnace has an operating height H, and the reducing gas injection is carried out at a height between 20% and 70% of the operating height H from the tuyere level.

[0012] The present invention also relates to a steelmaking method carried out in a blast furnace according to the foregoing embodiments, wherein the reducing gas contains a part of the top gas discharged from the blast furnace during the steelmaking process. The method may also have the following optional features, which are considered according to all technically possible combinations separately: - The reducing gas is injected at a temperature between 850 °C and 1200 °C. - The reducing gas preferably contains 65%v - 75%v carbon monoxide CO, 8%v - 15%v hydrogen H2, 1%v - 5%v carbon dioxide CO2, and the remainder is mainly nitrogen N2.

[0013] Other features and advantages of the present invention will become apparent from the description of the present invention, which is given below for illustrative purposes with reference to the accompanying drawings and is in no way limiting.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0015] The elements in the figures are illustrative and may not be drawn to scale.

[0016] Figure 1 is a side view of a blast furnace according to the present invention. The blast furnace 1 includes, in order from the top, a furnace mouth 11 into which raw materials are charged and gas is discharged, a stack - or shaft - 12, a bosh 13, a tuyere 14, and a hearth 15. The charged raw materials are mainly iron - containing raw materials such as sintered ore, pellets or iron ore and carbon - containing raw materials such as coke. The hot air blowing required for carbon combustion and thus iron reduction is carried out by tuyeres 16 located between the tuyere 14 and the hearth 15. Regarding the structure, the blast furnace has an outer wall or shell 2, and as shown in Figure 3, this shell 2 is covered inside the blast furnace by an inner - lining refractory and staves 3 to form an inner wall 5. The blast furnace has an inner diameter D that varies from the top to the bottom. int In order to reduce the consumption of coke, which is the main carbon source for reducing iron, it is envisaged to blow reducing gas into the blast furnace in addition to hot air. This reducing gas injection is carried out preferentially in the lower part of the stack within the blast furnace stack.

[0017] In a preferred embodiment, the reducing gas injection is carried out at a height corresponding to 20% - 70% of the working height H of the furnace, starting from the classical tuyere level. In the most preferred embodiment, the reducing gas injection is carried out between 30% - 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 hot - air blowing level through the classical tuyere and the zero - level of the charge.

[0018] In a preferred embodiment, the reducing gas introduced into the shaft furnace is the top - gas discharged from the furnace, which has been subjected to gas treatment to remove dust and obtain an appropriate composition, pressure and temperature. This reducing gas preferably contains 65%v - 75%v carbon monoxide CO, 8%v - 15%v hydrogen H2, 1%v - 5%v carbon dioxide CO2, and the remainder is mainly nitrogen N2.

[0019] This is blown in at a temperature preferably included between 850 and 1200 °C.

[0020] The blowing is carried out through a plurality of blowing devices 4 provided with blowing outlets 6 around the furnace, as shown in FIG. 2 which is a top view of the blast furnace 1 at the level of the reducing gas blowing. In a preferred embodiment, there are the same number of blowing devices 4 as the number of staves forming the inner wall 5. 200 to 700 Nm 3 of reducing gas is blown per ton of hot metal in the blast furnace.

[0021] FIG. 3 is a side view of the blast furnace 1 in the blowing region according to an embodiment of the present invention. The blowing device 4 is inserted into the blast furnace 1 by penetrating through the shell 2 and the staves 3 forming the inner wall 5. The staves above and below the blowing device have a substantially constant thickness T int . The blowing outlet 6 is aligned with the inner wall 5. Since the staves are worn by substances falling into the blast furnace, its thickness cannot be accurately grasped or controlled. Therefore, being substantially constant means that the variation in thickness is 2% or less. In a preferred embodiment, the thickness T int of the inner wall is substantially constant over a height of at least 400 mm above and at least 400 mm below the blowing outlet. Further, according to the present invention, the blowing device 4 is designed such that the blowing outlet 6 is aligned with the inner wall 5 and the reducing gas is blown at a speed of less than 120 m / s, preferably less than 100 m / s. By doing so, the reducing gas blowing does not push aside the substances falling into the blast furnace, so that a good distribution of the load is achieved by forming a mixed layer of coke and iron-containing raw materials, and thus cavities that would impair the productivity of the hot metal production process are not formed.

Claims

1. A blast furnace 1 for ironmaking production, in which iron ore is at least partially reduced by a reducing gas blown into the stack 12 of the blast furnace. In the blast furnace, the blast furnace has a working height H which is the distance between the blowing level of the hot blast through the tuyere 16 and the zero level of the charge. The blast furnace, - An outer wall 2 and an inner wall 5 that comes into contact with a substance charged into the blast furnace, where the inner wall 5 has a thickness T ｉｎｔ having the inner wall 5, and - a blowing device 4 for blowing the reducing gas through a blowing outlet 6 in a blowing region at a height included between 20% and 70% of the working height H from the blowing level of the tuyere 16, and is provided with, - Thickness T of the inner wall 5 ｉｎｔ is substantially constant over a height of at least 400 mm above and at least 400 mm below the blowing region, - the blowing outlet 6 is aligned with the inner wall, - the blowing device 4 can blow the reducing gas at a speed of less than 120 m / s, blast furnace 1.

2. The reducing gas contains a part of the top gas discharged from the blast furnace during the steelmaking process. A steelmaking method carried out in the blast furnace according to Claim 1.

3. The reducing gas is blown at a temperature included between 850 °C and 1200 °C. The steelmaking method according to Claim 2.

4. The reducing gas has the following composition. The steelmaking method according to Claim 3: 65% v ≤ CO ≤ 75% v 8% v ≤ H ２ ≤ 15% v 1% v ≤ CO ２ ≤ 5% v The remainder is N ２ .

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