Blast furnace for ironmaking production

Abstract

The invention relates to a blast furnace for iron production, in which iron ore is at least partially reduced by means of a reducing gas which is injected into the shaft of the blast furnace. The blast furnace comprises an outer wall and an inner wall, the inner wall having a thickness Tint, the inner wall being in contact with a substance charged into the blast furnace. The thickness Tint of the inner wall is substantially constant above and below the injection region of the reducing gas.

Description

[0001] This invention patent application is a divisional application of the invention patent application with application date of September 15, 2020, application number 202080103197.5, and invention name “Blast furnace for ironmaking production”. Technical Field

[0002] The present invention relates to a blast furnace for iron production. Background Art

[0003] In a blast furnace, the conversion of iron-containing charge materials (sinter, pellets and iron ore) into cast iron is conventionally achieved by the reduction of iron oxides by reducing gases (comprising in particular CO, H2 and N2) formed by the combustion of coke at tuyeres located in the bottom part of the blast furnace, where air preheated to a temperature between 1000°C and 1300°C, called hot blast, is injected.

[0004] To increase productivity and reduce costs, auxiliary fuel, such as coal in powdered form, fuel oil, natural gas or other fuels, combined with the oxygen enrichment of the hot air is also injected at the tuyere.

[0005] The gas recovered in the upper part of the blast furnace, called top gas, consists mainly of CO, CO2, H2 and N2 in the corresponding proportions of 20%v-28%v, 17%v-25%v, 1%v-5%v and 48%v-55%v. These gases are usually used as fuel in other parts of the plant and / or in power plants for electricity production. Therefore, blast furnaces are important producers of CO2.

[0006] In view of the significant increase in the CO 2 concentration in the atmosphere since the beginning of the last century and the consequent greenhouse effect, it is of vital importance to reduce CO 2 emissions wherever CO 2 is produced in large quantities, and therefore in particular in blast furnaces.

[0007] For this purpose, the consumption of reducing agents in blast furnaces has been reduced by half during the last 50 years, so that the carbon consumption in blast furnaces of conventional configuration has now reached a low limit associated with the laws of thermodynamics.

[0008] A further known method of reducing CO2 emissions is to reintroduce the CO2-free and CO-enriched top gas into the blast furnace. Thus, the use of CO-enriched gas as reducing agent makes it possible to reduce coke consumption and thus CO2 emissions. This injection can be done at two levels: at the typical tuyere level, replacing the hot blast; and in the reduction zone of the blast furnace, for example near and above the shaft-waist corner of the blast furnace (lower shaft of the blast furnace). Such blast furnaces are particularly known as top gas recovery blast furnaces (TGRBF).

[0009] Currently there is no second injection level in the blast furnace, so a new injection level must be created without adversely affecting the operation of the blast furnace. For example, the reducing gas injection must not disturb the material flow inside the blast furnace, which is key to productivity.

[0010] There is a need for a blast furnace having a reduced environmental impact at the same or increased productivity level compared to prior art blast furnaces. Summary of the invention

[0011] This problem is solved by a blast furnace according to the invention, comprising an outer wall and an inner wall having a thickness T int An injection device for injecting a reducing gas through an injection outlet in an injection region, wherein the thickness of the inner wall is T int The injection outlet is aligned with the inner wall at a substantially constant velocity above and below the injection area, and the injection device is capable of injecting the reducing agent at a velocity of less than 120 m / s.

[0012] The blast furnace of the present invention may also include the following optional features considered individually or in all possible technical combinations:

[0013] -Inner wall thickness T int is substantially constant over a height of at least 400 mm above the injection area and at least 400 mm below the injection area,

[0014] the blast furnace has a working height H and the injection of reducing gas is carried out at a height comprised between 20% and 70% of said working height H, starting from the tuyere level,

[0015] The blast furnace has a working height H and the injection of reducing gas is carried out at a height comprised between 20% and 70% of said working height H, starting from the tuyere level.

[0016] The present invention also relates to an ironmaking method performed in a blast furnace according to the aforementioned embodiment, wherein the reducing gas comprises a portion of the top gas discharged from the blast furnace during the ironmaking process. The method may also include the following optional features considered separately or in all possible technical combinations:

[0017] - the reducing gas is injected at a temperature comprised between 850° C. and 1200° C.,

[0018] The reducing gas preferably contains between 65%v and 75%v of carbon monoxide CO, between 8%v and 15%v of hydrogen H2, between 1%v and 5%v of carbon dioxide CO2, the remainder being mainly nitrogen N2. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other characteristics and advantages of the invention will clearly emerge from the description of the invention, which is given below by way of indication and which is in no way limiting, with reference to the accompanying drawings, in which:

[0020] - Figure 1 Side view of a blast furnace showing reducing gas injection in the reduction zone

[0021] - Figure 2 Picture shows Figure 1 Top view of the blast furnace

[0022] - Figure 3 A blast furnace according to an embodiment of the present invention is shown in FIG.

[0023] Elements in the drawings are illustrative and may not be drawn to scale. DETAILED DESCRIPTION

[0024] Figure 1 1 is a side view of a blast furnace according to the present invention. Starting from the top, the blast furnace 1 comprises: a throat 11, a furnace body or breast 12, a furnace waist 13, a furnace belly 14 and a furnace hearth 15, wherein the furnace throat 11 is loaded with materials and exhausts gases. The loaded materials are mainly iron-containing materials such as sintered ore, pellets or iron ore and carbon-containing materials such as coke. The hot air injection necessary for carbon combustion and thus iron reduction is performed through the tuyere 16 located between the furnace belly 14 and the furnace hearth 15. In terms of structure, as shown in FIG. Figure 3 As shown in FIG. 1 , the blast furnace has an outer wall or shell 2 which is covered on the inside of the blast furnace by a refractory lining and a shield 3 forming an inner wall 5. The blast furnace has an inner diameter D int , the inner diameter D int It varies from top to bottom. In order to reduce the consumption of coke, the main carbon provider for iron reduction, it has been envisaged to inject reducing gases in the blast furnace in addition to the hot blast. This reducing gas injection is performed in the shaft of the blast furnace, preferably in the lower part of the shaft.

[0025] In a preferred embodiment, the reducing gas injection is performed at a height corresponding to 20% and 70% of the working height H of the furnace from the typical tuyere level. In a most preferred embodiment, the reducing gas injection is performed between 30% and 60% of the working height H of the furnace. Figure 1 As illustrated in , the working height H of the blast furnace is the distance between the level of hot blast injection through a typical tuyere and the zero level of the charge.

[0026] In a preferred embodiment, the reducing gas introduced into the shaft furnace is the top gas discharged from said furnace, which has been subjected to gas treatment to remove dust and obtain a suitable composition, pressure and temperature. This reducing gas preferably contains between 65%v and 75%v of carbon monoxide CO, between 8%v and 15%v of hydrogen H2, between 1%v and 5%v of carbon dioxide CO2, the remainder being mainly nitrogen N2. This reducing gas is preferably injected at a temperature comprised between 850°C and 1200°C.

[0027] The injection is performed by several injection devices 4 provided with injection outlets 6 around the circumference of the furnace, such as Figure 2 As shown in the figure, Figure 2 is a top view of the blast furnace 1 at the level of the injection of reducing gas. In a preferred embodiment, there are as many injection devices 4 as there are shields forming the inner wall 5. 200 Nm2 of gas is injected into the blast furnace for every ton of hot metal. 3 Up to 700Nm 3 The reducing gas between.

[0028] Figure 3 The figure shows a side view of a blast furnace 1 in the injection area according to an embodiment of the invention. The injection device 4 is inserted into the blast furnace 1 through the shell 2 and the shield 3 forming the inner wall 5. The shield above and below the injection device has a substantially constant thickness T int , and the injection outlet 6 is aligned with the inner wall 5. Since the shield is subject to wear due to the material falling into the blast furnace, the thickness of the shield cannot be accurately known and controlled, so substantially constant means that the variation of the thickness is less than or equal to 2%. In a preferred embodiment, the thickness T of the inner wall int The injection outlet 6 is substantially constant at a height of at least 400 mm above the injection outlet and at least 400 mm below the injection outlet. Furthermore, according to the invention, the injection device 4 is designed so that the injection outlet 6 is aligned with the inner wall 5 and the reducing gas is injected at a speed lower than 120 m / s, and preferably at a speed lower than 100 m / s. By doing so, the reducing gas injection does not push the material falling into the blast furnace and therefore does not create any cavities that would affect the good distribution of the charge due to the formation of a mixed layer of coke and iron-containing material and therefore affect the productivity of the ironmaking process.

[0029] According to an embodiment of the present invention, the following additional notes are also disclosed:

[0030] Notes 1. A blast furnace 1 for iron production, wherein iron ore is at least partially reduced by a reducing gas, the reducing gas being injected into a shaft 12 of the blast furnace, the blast furnace comprising:

[0031] - an outer wall 2 and an inner wall 5, said inner wall 5 being in contact with the material charged into the blast furnace, said inner wall 5 having a thickness T int ,

[0032] - an injection device 4 for injecting the reducing gas in an injection zone through an injection outlet 6,

[0033] in,

[0034] - the thickness Tint of the inner wall 5 is substantially constant above and below the injection area,

[0035] - the injection outlet 6 is aligned with the inner wall,

[0036] The injection device 4 is capable of injecting the reducing agent at a speed lower than 120 m / s.

[0037] Note 2. The blast furnace according to Note 1, wherein the thickness T of the inner wall is int is substantially constant over a height of at least 400 mm above the injection area and at least 400 mm below the injection area.

[0038] Note 3. The blast furnace according to any one of the preceding notes, wherein the blast furnace has a working height H, and the injection of the reducing gas is performed at a height comprised between 20% and 70% of the working height H, starting from the level of the tuyere 16 .

[0039] Supplement 4. An ironmaking method performed in a blast furnace according to any one of Supplements 1 to 3, wherein the reducing gas contains a portion of top gas discharged from the blast furnace during the ironmaking process.

[0040] Note 5. The ironmaking method according to Note 4, wherein the reducing gas is injected at a temperature comprised between 850°C and 1200°C.

[0041] Supplement 6. The ironmaking method according to Supplement 4 or 5, wherein the reducing gas has the following composition:

[0042] 65%v≤CO≤75%v

[0043] 8%v≤H2≤15%v

[0044] 1%v≤CO2≤5%v

[0045] The rest is N2.

Claims

1. A blast furnace (1) for iron production, wherein: The iron ore is at least partially reduced by a reducing gas which is injected in the shaft (12) of the blast furnace, the blast furnace (1) comprising: - a housing (2); - an inner wall (5), which is formed by the guard plate (3); - an injection device (4) which is inserted into the blast furnace (1) by passing through the housing (2) and the shield (3), in, - the injection device (4) is capable of injecting the reducing gas through the injection outlet (6) in the injection zone at a speed lower than 120 m / s, - the blast furnace (1) comprises a hot blast injection level at the level of the tuyere (16), and the blast furnace (1) has a working height H and the reducing gas injection is carried out at a height ranging between 20% and 70% of the working height H starting from the tuyere (16) level; the working height H is the distance between the injection level of the hot blast through the tuyere (16) and the zero level of the charge of the blast furnace (1).

2. The blast furnace (1) according to claim 1, wherein: The inner wall (5) has a thickness T int , the thickness T int It is substantially constant above and below the injection area.

3. The blast furnace (1) according to claim 1 or 2, wherein: The injection device (4) is designed so that the injection outlet (6) is aligned with the inner wall (5).

4. The blast furnace (1) according to claim 1 or 2, wherein the injection device (4) is capable of injecting the reducing gas at a speed lower than 100 m / s.

5. The blast furnace (1) according to claim 1 or 2, wherein: The reducing gas injection is performed at a height comprised between 30% and 60% of the working height H, starting from the level of the tuyere (16).

6. The blast furnace (1) according to claim 1 or 2, wherein: The thickness T of the inner wall (5) int is substantially constant over a height of at least 400 mm above the injection area and at least 400 mm below the injection area.

7. The blast furnace (1) according to claim 1 or 2, wherein: The number of the injection devices (4) is equal to the number of the guard plates (3).

8. An ironmaking method performed in a blast furnace according to any one of claims 1 to 7, wherein: The reducing gas comprises a portion of the top gas exhausted from a blast furnace during the ironmaking process.

9. The ironmaking method according to claim 8, wherein: The reducing gas is injected at a temperature comprised between 850°C and 1200°C.

10. The ironmaking method according to claim 9, wherein: The reducing gas contains between 65% and 75% by volume of carbon monoxide, between 8% and 15% by volume of hydrogen, between 1% and 5% by volume of carbon dioxide, and the remainder being mainly nitrogen.

11. The ironmaking method according to claim 9 or 10, wherein: The reducing gas has the following composition: 65%v≤CO≤75%v 8%v≤H2≤15%v 1%v≤CO2≤5%v The rest is N2.

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