JP7348518B2 - How to operate a blast furnace - Google Patents

Description

The present invention relates to a method for operating a blast furnace, and more particularly, to a method for preventing thermal deterioration of blast furnace top equipment during blast furnace operation in which coke is centrally charged.

Generally, in order to continue stable operation of a blast furnace, it is necessary to form an inverted V-shaped cohesive zone. To achieve this, it is necessary to keep the O/C (ore/coke) in the furnace center low to develop a gas flow and maintain the temperature in the furnace center higher than in other areas. Therefore, the shape of the cohesive zone is controlled by charging a part of the coke into the furnace into the center of the furnace mouth (coke center charging) to locally lower the O/C in the furnace center region. A method may be adopted.

Normally, coke charged into a furnace undergoes a solution loss reaction due to CO ₂ gas generated by a reduction reaction of ore during the descending process, and generates a large amount of powder. The large amount of powder generated deteriorates the air permeability and liquid permeability in the furnace, but when coke center charging is performed, the amount of ore in the center of the furnace decreases, resulting in the generation of _CO2 gas in the center of the furnace. quantity decreases. As a result, solution loss reactions are suppressed and a healthy core with less generated powder is formed.

However, when center charging of coke is performed, high-temperature exhaust gas is intensively discharged from the center of the furnace to the outside of the blast furnace, so deterioration of the top equipment of the blast furnace due to heat becomes significant.
Therefore, Patent Document 1 discloses an invention that lowers the gas temperature in the furnace when the space in the furnace above the raw fuel level increases significantly when performing a reduced air suspension to lower the raw fuel level in the blast furnace. Disclosed. In this invention, a water spray nozzle oriented toward the top of the furnace is fixed directly above the raw fuel, and the water sprayed toward the top of the furnace rises in the furnace and then descends, thereby cooling the gas in the furnace.
Additionally, Patent Document 2 discloses an invention in which when water is sprayed downward from a water nozzle installed at the top of the blast furnace, the maximum temperature of the blast furnace top gas is lowered by setting the water spray particle size to such an extent that water does not adhere to the raw fuel. has been done.

Japanese Patent Application Publication No. 4-362108 Japanese Patent Application Publication No. 2003-064407

When the present inventors verified the methods described in Patent Document 1 and Patent Document 2, it was found that the following problems existed.
The method described in Patent Document 1 does not assume cooling of furnace gas during blast furnace operation. Therefore, when the method described in Patent Document 1 is carried out during blast furnace operation, the distance between the rise and fall of the sprayed water (the cooling time associated with the distance) is insufficient, and the gas in the furnace is insufficiently cooled. In particular, in the center charging operation of coke in blast furnaces, which has been frequently used in recent years, the gas in the furnace that blows up from the core tends to reach a high temperature. In the water spraying range of the shaded area in FIG. 1(b) of Patent Document 1, the cooling effect of the blast furnace top equipment is insufficient (temperature reduction of the blast furnace top equipment located in the reactor core is insufficient).
Further, in the method described in Patent Document 2, since the amount of water sprinkled is limited, the cooling effect of the blast furnace top equipment is insufficient when central coke charging operation is performed.

The present invention has been made in view of the above circumstances, and provides a blast furnace operating method that can suppress the temperature rise of the blast furnace top equipment during blast furnace operation and prevent deterioration of the blast furnace top equipment due to heat. The purpose is to

In order to achieve the above object, the present invention provides the following advantages:
The positions of both end points of a virtual line segment with the center of the blast furnace as its midpoint, or each vertex of a virtual regular polygon that is rotationally symmetrical about the center of the blast furnace when viewed from above within the furnace space above the raw fuel surface of the furnace. An injection hole for injecting water is provided at the position of
Injecting water from each injection hole toward the center of the blast furnace during blast furnace operation in a direction with an elevation angle of 0° to 10°;
It is characterized in that the difference in the amount of water (ton/h) injected from each of the injection holes is within 5% by mass of the total amount of water to be injected from each of the injection holes.

In the present invention, in response to the high-temperature rising gas that blows up from the core during blast furnace operation, an equal amount of water (or (vaporized steam) is injected to stir the high-temperature gas rising inside the furnace. As a result, the high-temperature rising gas in the reactor is mixed with relatively low-temperature in-furnace gas existing in a region other than the reactor core, and the temperature of the rising gas in the reactor blown up from the reactor core is lowered.

Further, in the method for operating a blast furnace according to the present invention, the position of each of the injection holes is spaced apart from the center of the blast furnace by 1.0 m or more in the horizontal direction, and the amount of water injected from each of the injection holes is 2 tons/h to 10 tons/h. h is preferable.

According to this configuration, since the injected water droplets do not adhere to the blast furnace top equipment, dust is suppressed from adhering and depositing on the blast furnace top equipment together with the water droplets, preventing failure of the blast furnace top equipment, and preventing dust from adhering to the top equipment. Periodic cleaning of deposits can be made unnecessary.

In the method of operating a blast furnace according to the present invention, an equal amount of water is injected in a generally horizontal direction toward the center of the blast furnace from each position that is rotationally symmetrical when viewed from above, and high-temperature water that blows up from the core during blast furnace operation is removed. By mixing the rising gas in the furnace with the relatively low-temperature gas existing in parts other than the core, the temperature rise in the blast furnace top equipment is suppressed and the deterioration of the blast furnace top equipment due to heat is prevented. Can be done.
Furthermore, in the blast furnace operating method according to the present invention, since water is injected in the direction of an elevation angle of 0° to 10°, it is possible to prevent an adverse effect on the raw fuel due to water spraying.

1 is a longitudinal cross-sectional view of the furnace top of a bellless blast furnace that implements a blast furnace operating method according to an embodiment of the present invention. FIG. 3 is a plan cross-sectional view of the top of the furnace. FIG. 7 is a plan cross-sectional view of the top of the furnace according to a first modification. FIG. 7 is a plan cross-sectional view of the top of the furnace according to a second modification.

Next, embodiments embodying the present invention will be described with reference to the attached drawings to provide an understanding of the present invention. Note that in this specification and the drawings, constituent elements having substantially the same functions are designated by the same reference numerals, and redundant explanation will be omitted.

[Current status of blast furnace operation]
Traditionally, the main raw materials for blast furnaces have been ore and the fuel coke, but over the past few decades, low-cost pulverized coal, which is made by pulverizing coal, has gradually come to be used as a fuel instead of coke. ing. In recent years, the amount of coke used has decreased as the amount of pulverized coal has increased.

The charge from the top of the furnace, such as coke, is itself a coolant and functions to cool the furnace gas through heat exchange with the furnace gas. However, as mentioned above, since the amount of coke input has been decreasing in recent years, the temperature of the furnace gas tends to rise as the amount of pulverized coal used increases.

In addition, as the amount of pulverized coal used increases and the amount of coke used decreases, the permeability of gas in the furnace deteriorates. The furnace condition is stabilized by converting it into a central flow and maintaining the shape of the softened cohesive zone in an inverted V-shape. On the other hand, due to the central flow of the rising gas in the furnace, the gas temperature in the horizontal section of the blast furnace has a temperature distribution where the temperature at the center of the furnace top (core part) is the peak.

In this way, the heat load on the blast furnace top equipment increases due to the rise in the temperature of the gas in the furnace due to the increase in the amount of pulverized coal used and the reduction in the amount of coke charged compared to the past, and the central flow of the rising gas in the furnace. ing. As a result, problems such as thermal damage to blast furnace top equipment, shortened service life, and shortened maintenance cycles have arisen.

[Technical idea of the present invention]
In order to verify the effectiveness of the method described in Patent Document 1 in a blast furnace operation where coke center charging is implemented, the method described in Patent Document 1 was applied to an operating blast furnace that employs coke center charging. Although it was possible to cool the gas in the furnace, the cooling capacity was insufficient and the temperature could not be lowered enough to prevent damage to the blast furnace top equipment. As a result of various studies on the causes, we found that the high-temperature rising gas in the furnace blowing up from the central charging area (core) directly collides with the blast furnace top equipment without being sufficiently cooled, resulting in a decrease in the temperature of the blast furnace top equipment. It was found that this was insufficient.

Therefore, the present inventors have developed a method for improving blast furnace top equipment, especially the core, by promoting agitation of the relatively low-temperature in-furnace gas existing in areas other than the core and the high-temperature in-furnace rising gas that blows up from the core. We decided to lower the temperature of the equipment. Specifically, water (or steam evaporated from water) is injected approximately horizontally into the high-temperature gas rising inside the reactor that is blown up from the core, stirring the high-temperature rising gas inside the reactor, and destroying parts other than the core. The temperature of the rising gas in the furnace is lowered by mixing it with the furnace gas existing in the furnace. At that time, if water is injected from only one direction, only the direction in which the gas rising in the furnace flows will change, so it will flow approximately horizontally evenly from each position that is rotationally symmetrical in plan view toward the center of the blast furnace. A large amount of water is injected to stir the rising gas in the furnace.

[Blast furnace operating method according to an embodiment of the present invention]
A method of operating a blast furnace according to an embodiment of the present invention uses a bellless blast furnace. FIG. 1 shows a vertical cross-section of a furnace top 10 of a bellless blast furnace that implements the blast furnace operating method according to the present embodiment, and FIG. 2 shows a planar cross-section of the furnace top 10.
The bellless blast furnace is equipped with a rotating cone 12 and a rotating chute 13 as top equipment of the blast furnace. In the operation of a bellless blast furnace, a drive device (not shown) in a rotating cone 12 installed at the mouth of the furnace top 10 rotates the furnace in the circumferential direction, and feeds raw fuel through a rotating chute 13 that tilts vertically. 20 coke and ore are charged into the furnace. In a blast furnace operation in which coke is centrally charged, coke and ore are charged in layers while coke is preferentially charged into the center 21 of the furnace.

In this embodiment, water is sprayed to inject water at both end points of an imaginary line segment 22 with the blast furnace center 15 as the midpoint when viewed from above in the in-furnace space 11 above the upper surface of the in-furnace raw fuel 20. A nozzle 16 (an example of an injection hole) is installed (see FIG. 2). Water is supplied to each water sprinkling nozzle 16 via a water sprinkling pipe 17 . The temperature of the supplied water is about 20°C to 50°C.
Further, in order to measure the temperature of the gas in the furnace, a temperature measuring probe 18 is installed directly below each water spray nozzle 16 and water spray pipe 17.

It is desirable that each water spray nozzle 16 be installed at a position separated from the blast furnace center 15 by 1.0 m or more in the horizontal direction. If the separation distance from the blast furnace center 15 is less than 1.0 m, there is a possibility that the nozzle hole will come into direct contact with the rising gas in the furnace, and there is a risk that the water spray nozzle 16 will have to be replaced more frequently.

The angle of the central axis of the water stream that is injected from the water spray nozzle 16 toward the blast furnace center 15 and supplied to the blast furnace center 15 is in the range of an elevation angle of 0° to an elevation angle of 10°.
When the angle of elevation becomes negative, that is, the angle of inclination, the water spray nozzle 16 is directed downward, which may cause the nozzle hole to be clogged by dust contained in the gas rising in the furnace. For this reason, it is preferable that the water jet direction has an elevation angle of 0° or more. On the other hand, when the elevation angle exceeds 10°, the stirring performance for the rising gas in the furnace decreases, and the water injected toward the rising gas in the furnace tends to flow along with the rising gas in the furnace. As a result, a superior stirring effect cannot be obtained.

The difference in the amount of water (ton/h) sprayed from each water spray nozzle 16 is within 5% by mass of the total amount of water sprayed from each water nozzle 16.
If the difference in the amount of water injected from each water nozzle 16 is large, the flow direction of the rising gas in the furnace will only change. do.

The amount of water sprayed from each water nozzle 16 is preferably 2 ton/h to 10 ton/h.
If the amount of water injected from each water nozzle 16 exceeds 10 ton/h, part of the injected water may not be vaporized and water droplets may adhere to the blast furnace top equipment. In that case, dust and water droplets may adhere to the top equipment of the blast furnace, so the top equipment of the blast furnace needs to be cleaned regularly.
On the other hand, if the amount of water injected from each water nozzle 16 is small, the phenomenon of water vaporization within the water sprinkling pipe 17 becomes noticeable, and the adhesion and accumulation of foreign matter within the water sprinkling pipe 17 becomes noticeable. Moreover, the effort of covering the water sprinkling pipe 17 with a heat insulating material increases. According to the findings of the present inventors, when the amount of water sprayed from each water nozzle 16 was set to 2 tons/h or more, no significant accumulation of foreign matter was observed in the water spray pipe 17.

In the above embodiment, the water spray nozzles 16 are arranged at the positions of both end points of the virtual line segment 22 whose midpoint is the blast furnace center 15 when viewed from above, The water spray nozzle 16 may be arranged at each vertex of the rectangle. FIG. 3 shows a first modification example in which water nozzles 16 are arranged at each vertex of a virtual equilateral triangle 23 that is rotationally symmetrical about the blast furnace center 15 when viewed from above. A second modification example in which the water spray nozzles 16 are arranged at each vertex of the virtual square 24 is shown in FIG. 4, respectively.

In addition, each position to be rotated (i.e., the position of both end points of a virtual line segment whose midpoint is the center of the blast furnace, or the position of each vertex of a virtual regular polygon that is rotationally symmetrical about the center of the blast furnace) When providing the water spray nozzle 16, it may be provided at a geometrically relevant position (both end points or each vertex), or a predetermined error may exist. In this embodiment, the distance between the location where the water spray nozzle 16 is installed and the corresponding geometric position is set to 5% or less of the diameter of the blast furnace at the location (height position) where the water spray nozzle 16 is installed. It has been confirmed that the effect of the present invention can be obtained even if there is a difference in diameter (if the blast furnace volume is about 5000 ^m3 , the diameter is about 30 m, and the error is 1.5 m or less). In this embodiment, the height difference between each water spray nozzle 16 (height difference between the highest and lowest water spray nozzles) is set to 0.5 m or less, and even within this range, the The effects of the invention have been obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the above-described embodiments, and can be considered within the scope of the claims. It also includes other embodiments and modifications. For example, in the above embodiment, a bellless type blast furnace is used, but a bell type blast furnace may be used. Further, in the above embodiment, a water spray nozzle is used as the injection hole, but a metal pipe or the like may also be used.

A verification test conducted to verify the effects of the present invention will be described.
The effects of the present invention were verified using an operating blast furnace that employs coke center charging. Temperature changes at the top of the blast furnace were measured using the spray nozzle spray angle, spray position (symmetrical, asymmetrical), distance from the center of the blast furnace to the water nozzle, water volume per spray nozzle, and water volume difference between the spray nozzles as parameters. .

The quality of the blast furnace top equipment temperature was judged as follows.
The temperature of the blast furnace top equipment without watering is approximately 1200°C, and if the reduction in the temperature of the blast furnace top equipment is 600°C or more, ◎ (excellent), if it is 500°C or more and less than 600°C, ○ (good), 500. If the temperature was less than ℃, it was marked as × (not possible).
The test results are shown in Table 1.

The matters revealed from the verification test are listed below.
- In all Examples, the temperature quality was ○ or higher. Within the scope of the conditions of claim 1 of the present invention, the temperature reduction amount varies depending on the amount of water and the distance between the injection positions, but evaluations of ◎ or ◎ were obtained.
・In contrast to Example 1, where the water nozzle was replaced every six months to one year, in Examples 5 to 8, where the distance from the center of the blast furnace to the water nozzle was 1.0 m or more, the water nozzle was replaced frequently over one year. Met. In addition, although the separation distance in Example 9 was also 1.0 m, since the amount of water per water nozzle was 15.0 ton/h, significant dust adhesion to the blast furnace top equipment was observed.

・Comparative Example 1 with one water spray nozzle on one side, Comparative Examples 2 and 3 where the spray angle was outside the range of elevation angle of 0° to elevation angle of 10°, and the difference in water amount between the water spray nozzles was 20% by mass In Comparative Example 4, the temperature was evaluated as poor. In particular, in Comparative Example 3 where the injection angle was -45° in elevation, nozzle clogging suddenly occurred and the cooling performance decreased.

10: Furnace top, 11: Furnace space, 12: Swivel cone (blast furnace top equipment), 13: Swivel chute (blast furnace top equipment), 15: Center of blast furnace, 16: Water nozzle (injection hole), 17: Water spray Piping, 18: Temperature measurement sonde, 20: Raw fuel, 21: Center inside the reactor, 22: Virtual line segment, 23: Virtual equilateral triangle, 24: Virtual square

Claims (2)

In the operation of blast furnaces that carry out central coke charging,
The positions of both end points of a virtual line segment with the center of the blast furnace as its midpoint, or each vertex of a virtual regular polygon that is rotationally symmetrical about the center of the blast furnace when viewed from above within the furnace space above the raw fuel surface of the furnace. An injection hole for injecting water is provided at the position of
Injecting water from each injection hole toward the center of the blast furnace during blast furnace operation in a direction with an elevation angle of 0° to 10°;
A method for operating a blast furnace, characterized in that the difference in the amount of water (ton/h) injected from each of the injection holes is within 5% by mass of the total amount of water injected from each of the injection holes. 2. The method of operating a blast furnace according to claim 1, wherein each injection hole is spaced apart from the center of the blast furnace by 1.0 m or more in the horizontal direction, and the amount of water injected from each injection hole is 2 ton/h to 10 ton/h. A method of operating a blast furnace characterized by the following.

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