Device for injecting reducing gas into a shaft furnace

Abstract

A device for injecting reducing gas into a shaft furnace, the device comprising: an outer housing having a front face provided with an outlet for gas injection into the shaft furnace; an inner housing positioned within the outer housing, wherein the reducing gas is circulated. The inner housing has an opening that matches the gas injection outlet of the front face of the outer housing. The front face of the outer housing comprises an upper portion and a lower portion, and the gas injection outlet is located in the lower portion and inwardly relative to the upper portion.

Description

Technical Field

[0001] This invention relates to an apparatus for injecting reducing gases into a vertical shaft furnace. Background Technology

[0002] In a blast furnace, the conversion of iron-containing furnace charge (sinter, pellets, and iron ore) into cast iron or hot metal is conventionally achieved by reducing iron oxides with reducing gases (specifically including CO, H2, and N2). The reducing gases are generated by burning coke at the tuyeres located in the bottom part of the blast furnace. Air preheated to a temperature between 1000°C and 1300°C is injected at the tuyeres; this is called hot blast.

[0003] To improve productivity and reduce costs, auxiliary fuels, such as coal, fuel oil, natural gas, or other fuels in powder form, are injected into the vents to combine with the oxygen-rich hot air.

[0004] The gas recovered in the upper part of the blast furnace, known as top gas, mainly consists of CO, CO2, H2, and N2 in proportions of 20% v–28% v, 17% v–25% v, 1% v–5% v, and 48% v–55% v, respectively. Although these gases are partially used as fuel in other plants, such as power plants, blast furnaces remain a significant producer of CO2.

[0005] Given the significant increase in atmospheric CO2 concentration since the beginning of the last century and the resulting greenhouse effect, reducing CO2 emissions is crucial in places where CO2 is produced in large quantities, and therefore especially in blast furnaces.

[0006] To this end, the consumption of reducing agents in blast furnaces has been reduced by half in the last 50 years, so that carbon consumption in conventionally configured blast furnaces has now reached the minimum limit related to the laws of thermodynamics.

[0007] Another known method for reducing CO2 emissions is to reintroduce CO2-free and CO-rich top gas into the blast furnace, known as a TGRBAF (Top Gas Recovery Blast Furnace). The use of CO-rich gas as a reducing agent allows for reduced coke consumption and thus reduced CO2 emissions. This injection can be performed at two levels: at the typical tuyeres level, replacing hot blast; and in the reduction zone of the blast furnace, for example, in the lower part of the furnace shaft.

[0008] Injection at the tuyer level can be performed at the location of existing equipment. However, in current practice, injection at the reduction zone level is not available, and therefore new equipment must be installed. This equipment will come into contact with the charge in the furnace and will therefore be subject to impact and abrasion. Furthermore, the charge may contain fine and volatile substances that could clog or contaminate the injection outlet, thus necessitating modifications to the equipment.

[0009] Therefore, a device is needed that allows the injection of reducing gases and has an extended service life. Notably, a device is needed that has a limited risk of clogging due to the substances introduced into the furnace. A lightweight and easy-to-implement device is also required. Summary of the Invention

[0010] This problem is solved by a device according to the invention, which includes: an outer housing having a rear surface and a front surface, the front surface being provided with an outlet for gas injection into a vertical furnace; and an inner housing positioned within the outer housing, wherein a reducing gas is circulated, the inner housing having an opening matching the gas injection outlet of the front surface of the outer housing, wherein the front surface includes an upper portion and a lower portion, the gas injection outlet being located in the lower portion, and the lower portion and the upper portion being designed such that the injection outlet is positioned inward relative to the upper portion.

[0011] The apparatus of the present invention may also include the following optional features, either individually or according to all possible combinations of technologies:

[0012] - The fire-resistant layer is positioned between the outer shell and the inner shell.

[0013] - The inner shell is made of steel with a temperature resistance up to 1200°C.

[0014] - The device does not include any cooling system.

[0015] - A vertical shaft furnace is a type of blast furnace.

[0016] - The device is bolted to the vertical furnace.

[0017] - The device includes a reinforcing plate for supporting the inner housing.

[0018] - The internal shell is designed to allow the injection of reducing gas into the vertical furnace to proceed downwards.

[0019] - The internal shell is designed so that the injection of reducing gas into the vertical shaft furnace is performed at an angle α between 0° and 30°, which is perpendicular to the inner wall of the vertical shaft furnace.

[0020] - The device includes a stone box located in the upper part of the front surface.

[0021] - The front surface has a triangular shape.

[0022] - The lower part is recessed relative to the upper part.

[0023] - The lower part is cut diagonally starting from the upper part. Attached Figure Description

[0024] Other features and advantages of the invention will become apparent from the description of the invention with reference to the accompanying drawings, which are given below by way of indication and are in no way limiting, in which:

[0025] - Figure 1 The illustration shows a side view of a blast furnace equipped with a reducing gas injection device;

[0026] - Figure 2 The illustration shows a top view of a blast furnace with reducing gas injection.

[0027] - Figure 3 The illustration shows an injection device according to a first embodiment of the present invention;

[0028] - Figure 4 The illustration shows an injection device according to a second embodiment of the present invention;

[0029] - Figure 5 The illustration shows an injection device according to a second embodiment of the present invention.

[0030] The elements in the accompanying drawings are for illustrative purposes and may not be drawn to scale. The same reference numerals are used for the same elements from one drawing to another. Detailed Implementation

[0031] Figure 1 This is a side view of a blast furnace according to the present invention. Starting from the top, the blast furnace 1 includes a throat 11, a furnace body (also called a chest) 12, a waist 13, a belly 14, and a hearth 15, wherein the throat 11 is used to load materials and discharge gases. The loaded materials are mainly iron-containing materials such as sinter, pellets, or iron ore, and carbon-containing materials such as coke. Carbon combustion, and therefore the injection of hot blast necessary for iron reduction, is performed through a tuyer 16 located between the belly 14 and the hearth 15. Structurally, as... Figure 3As illustrated, 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 protective plates 3, thus forming an inner wall. To reduce the consumption of coke, the primary carbon provider for iron reduction, it has been envisioned to inject reducing gases into the blast furnace in addition to hot blast. This injection of reducing gases is preferably performed in the lower portion of the furnace body 12, for example, directly above the waist 13. In a preferred embodiment, the reducing gas injection is performed at a distance from the typical tuyeres level, this distance being between 20% and 70% of the furnace's working height H, preferably between 30% and 60%. Figure 1 As shown in the diagram, the working height H of the blast furnace is the distance between the injection level of hot blast through a typical tuyer and the zero level of the charge.

[0032] Injection is performed through several injection outlets surrounding the circumference of the furnace, such as... Figure 2 As shown in the diagram, Figure 2 This is a top view of blast furnace 1 at the injection level of reducing gas. In a preferred embodiment, there are as many injection outlets as the lining plates forming the inner wall. 200 Nm³ of hot metal is injected into the blast furnace per ton of hot metal. 3 With 700 Nm 3 Reducing gases between them.

[0033] Figures 3 to 5 The illustration shows an injection device 4 according to different embodiments of the present invention. In all embodiments, the injection device 4 includes an outer housing 20 having a front surface 21 and a rear surface 22. The front surface 21 is a surface positioned inside a furnace and is provided with an outlet 23 for injecting reducing gas into the furnace. The injection device 4 also includes an inner housing 24 positioned within the outer housing 20. The inner housing 24 is preferably made of steel capable of withstanding temperatures up to 1200°C, preferably stainless steel. The inner housing 24 may also be made of copper. The inner housing 24 has an opening that matches the gas injection outlet 23 of the front surface 21 of the outer housing 20.

[0034] The front surface 21 of the injection device 4 includes at least two parts: an upper part 21A and a lower part 21B, with the lower part 21B including a gas injection outlet 23. These upper and lower parts are designed such that the gas injection outlet 23 is positioned inward relative to the upper part 21A, thereby protecting the gas injection outlet 23 from the impact of furnace charge falling into the furnace. This allows a material-free cavity to form around the gas injection outlet 23 during gas injection, thus preventing the injection outlet from becoming dirty and / or blocked. This extends the service life of the injection device 4.

[0035] The inner shell 24 is capable of conveying reducing gas with a temperature between 800°C and 1200°C to the gas injection outlet 23, so that the reducing gas is injected into the blast furnace 1. The inner shell 24 and the gas injection outlet 23 are designed such that the injection of reducing gas into the blast furnace body is performed downwards, preferably at an angle α between 0° and 30° with respect to the perpendicular to the inner wall. The diameter of the inner shell 24 is selected to meet the required injection speed in the blast furnace. In a preferred embodiment, this speed is between 75 m / s and 200 m / s. In another embodiment, this speed is less than 60 m / s. The refractory layer 25 allows for mitigation of temperature changes in the reducing gas circulating into the inner shell.

[0036] In addition, a fire-resistant layer 25 may be provided between the outer shell 20 and the inner shell 24.

[0037] exist Figure 3 In one embodiment, the lower portion 21B is recessed relative to the upper portion 21A, and the gas injection outlet 23 is located in the recessed lower portion 21B and is therefore protected by the upper portion 21A, which serves as a cover.

[0038] exist Figure 4 In one embodiment, the lower portion 21B is obliquely cut from the upper portion 21A, and the gas injection outlet 23 is located in the inwardly obliquely cut lower portion 21B.

[0039] exist Figure 5 In the embodiments, the outer housing 20 has a similar Figure 3 The implementation method is the same design, but the injection outlet 23 is located at a different position in the lower part 21B.

[0040] In all embodiments, the injection device 4 may have a stone box structure on its front surface, which is designed to locally reinforce the outer housing 20 and protect the outer housing 20 from the furnace charge falling into the furnace, and thus extend the service life of the injection device 4.

[0041] The injection device according to any of the foregoing embodiments is attached to the outer shell of the blast furnace 1. The injection device may be bolted or welded to the outer shell.

[0042] The injection apparatus according to any of the foregoing embodiments is preferably used to inject a reducing gas at breast height in a blast furnace, and more specifically, a top gas recovery blast furnace. This reducing gas preferably contains carbon monoxide (CO) at a volume percentage between 65% and 75% v, hydrogen (H2) at 8% and 15% v, carbon dioxide (CO2) at 1% and 5% v, with the remainder being primarily nitrogen (N2). This reducing gas is preferably injected at a temperature between 850°C and 1200°C.

Claims

1. An apparatus (4) for injecting a reducing gas into a vertical shaft furnace (1), the injection being performed within the furnace body of the vertical shaft furnace (1), the apparatus comprising: a. An outer casing (20) having a rear surface (22) and a front surface (21), the front surface (21) being provided with an outlet (23) for injecting gas into the vertical furnace. b. An inner housing (24) positioned inside the outer housing (20), wherein the reducing gas is circulated, and the inner housing (24) has an opening that matches the gas injection outlet (23) of the front surface (21) of the outer housing. The front surface (21) includes an upper portion (21A) and a lower portion (21B), the gas injection outlet (23) is located in the lower portion (21B), and the lower portion (21B) and the upper portion (21A) are designed such that the injection outlet (23) is positioned inward relative to the upper portion (21A), and the inner housing (24) is made of steel with a temperature resistance of up to 1200°C; The device (4) further includes a fire-resistant layer (25) positioned between the outer housing (20) and the inner housing (24), and does not include any cooling system.

2. The apparatus according to claim 1, wherein, The vertical shaft furnace is a blast furnace.

3. The apparatus according to claim 1 or 2, wherein, The device (4) is bolted to the vertical furnace.

4. The apparatus according to claim 1 or 2 further includes a reinforcing plate for supporting the inner housing (24).

5. The apparatus according to claim 1 or 2, wherein, The inner shell (24) is designed such that the injection of the reducing gas into the vertical furnace is performed at an angle α between 0° and 30°, which is perpendicular to the inner wall of the vertical furnace.

6. The device according to claim 1 or 2, further comprising a stone box located in the upper portion (21A) of the front surface.

7. The apparatus according to claim 1 or 2, wherein, The front surface (21) of the outer housing (20) has a triangular shape.

8. The apparatus according to claim 1 or 2, wherein, The lower portion (21B) is recessed relative to the upper portion (21A).

9. The apparatus according to claim 1 or 2, wherein, The lower portion (21B) is obliquely cut from the upper portion (21A).

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