JP2000192122A - Structure of auxiliary fuel blowing tuyere in blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of an auxiliary fuel blowing tuyere in a blast furnace, in which the auxiliary fuel can be stably blown into the blast furnace, e.g. in the case of using pulverized fine coal, in the pulverized fine coal blowing ratio of >=150 kg/ton of pig-iron. SOLUTION: In the structure of the auxiliary fuel blowing tuyere in the blast furnace containing the neighborhood of the connecting part of a blow pipe 3 connected with the tuyere 1, this tuyere has the reduced diameter part 4 of the diameter smaller than the inner diameter of the blow pipe 3 and the inner diameter of the tip part of the tuyere 1 in the tube between the neighborhood of the connecting part of the blow pipe 3 and the tip part of the tuyere 1 and an auxiliary fuel blowing lance 2 is arranged so that the tip part 7 of the lance 2 is positioned at the tip part side of the tuyere from the reduced diameter part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary fuel injection tuyere structure in a blast furnace.

[0002]

2. Description of the Related Art As is well known, in a conventional blast furnace, iron ore (including pellets, sintered ore, etc.), coke, auxiliary materials (limestone, etc.) and the like are charged from the upper part, while high-temperature Coke as fuel (heat source) by supplying air
Iron ore has been reduced and dissolved as a reducing agent, and pig iron has been manufactured.However, in order to reduce the use of coke, which is expensive to manufacture, and to counteract the aging of coke ovens, the operating rate of coke ovens was reduced. In order to reduce the amount of fuel, for example, the method of injecting auxiliary fuel into a blast furnace through which auxiliary fuel is injected from a blast furnace tuyere as fuel instead of coke has been widely practiced.

As an auxiliary fuel, a liquid fuel such as heavy oil having excellent flammability was initially used. However, since the oil shock, the price of heavy oil has soared. In recent years, pulverized coal obtained by pulverizing coal has been used as coke. The so-called pulverized coal injection operation (hereinafter, referred to as PCI operation), which is blown from tuyeres, is becoming common as a part alternative fuel. Furthermore, recently, as a part of addressing environmental issues, waste synthetic resin material represented by waste plastic and solid fuel derived from waste have been supplied into the blast furnace through tuyeres, and a heat source and a reducing agent have been supplied. It has also been proposed to serve as

In order to reduce the cost of hot metal, the most effective method is to increase the injection ratio of auxiliary fuel such as pulverized coal and heavy oil to reduce coke. The tuyere that has been commonly used by connecting it (for example, Iron and Steelmaking, Vol. II, 3rd Edition Iron and Steel Handbook (Page 306, FIG. 5, 170), JP-A-64-4410, JP-A-3-240908)
(Hereinafter referred to as the tuyere), when the auxiliary fuel injection ratio from the tuyere is increased, the auxiliary fuel devolatilizes in the tuyere and becomes a combustion gas to increase the gas volume. It has been confirmed that the head pressure loss increases, and that the replacement rate with coke deteriorates due to the deterioration of the combustibility in the raceway at the tuyere tip. Have been done.

[0005] In order to solve the above problem, when pulverized coal is blown as auxiliary fuel using the normal tuyere, for example, the tip position of a pulverized coal blowing lance is set to an optimum position. Improve the number and structure of lances,
Improvements have also been made in the selection of appropriate coal types (volatiles, ash, etc.) and the optimization of the particle size composition. However, even if these improvements are made, pulverized coal that can be stably injected from the above-mentioned normal tuyere Is about 150 kg / t of pig iron in pulverized coal injection ratio.

On the other hand, Japanese Patent Publication No. 53-19442,
Japanese Patent Application Laid-Open No. 28804 and Japanese Patent Application Laid-Open No. 2-104604 propose a Laval-type tuyere (hereinafter referred to as Laval tuyere) used as a tuyere of a blast furnace (blast furnace).

For example, Japanese Patent Publication No. 53-19442 (especially page 1, column 2, line 8 to page 2, column 3, line 1) discloses solid fuel such as coke used in shaft furnaces such as blast furnaces. Due to its high price, Laval tuyere has been proposed as a tuyere used for a technique in which a part of the auxiliary fuel is replaced with a liquid hydrocarbon auxiliary fuel and the auxiliary fuel is injected into a blower pipe opened in a shaft furnace. I have. The Laval tuyere is a replaceable first member having a tapered portion constituting a sonic furnace port, a divergent portion, and an injection pipe for injecting fuel in the tuyere,
It is basically composed of a fixed second member connected to the first member and extending to the divergent portion of the first member to form the divergent portion. In this Laval tuyere, a condition for transition from a supersonic flow state to a subsonic state in the flared portion of the tuyere, that is, a condition in which a shock wave is formed in the flared portion, is created, and fuel is provided upstream of the shock wave. By injecting
When the injected fuel passes through the shock wave band, the dispersing action into the combustion medium becomes effective, and the fuel injection rate can be increased without generating soot. It is explained. In order to generate a shock wave in the divergent portion of the Laval tuyere, it is necessary to design a furnace port (contraction section) in accordance with the supply speed of the combustion medium of the shaft furnace. Focusing on the point, the first member can be replaced so that the shape of the furnace port can be changed according to the combustion medium supply speed.

Further, Japanese Patent Publication No. 28804/1989 proposes that the blowing tuyere used for the blast furnace is a so-called Laval tuyere whose central portion is formed smaller in diameter than the inlet diameter and the outlet diameter. I have. According to the official gazette, "In this Laval tuyere, the subsonic wind flows in the center (throat) at the entrance of the tuyere.
In this case, the Mach number M = 1, and a supersonic flow occurs on the exit side of the tuyere. The supersonic velocity at the exit side is determined by the wind pressure at the entrance and exit of the tuyere. Then, the supersonic flow from the Laval tuyere becomes a turbulent compressible free jet, the energy of which is transmitted deep into the blast furnace while maintaining the velocity of the outlet of the Laval tuyere. The longer is the longer. It is further described that the Laval tuyere has the following effects. :
An inactive furnace core called a deadman is narrowed, and the amount of blown air can be increased due to an increase in the operating internal volume, thereby increasing the amount of tapping. : The reactivity of the lower part of the blast furnace increases, and the fuel ratio due to the increase in the direct reduction rate can be reduced. : The central operation of the blast furnace can be achieved, the fuel ratio can be reduced by reducing the heat loss of the furnace body, and the furnace body and bottom can be protected by centralizing the hearth iron slag flow.
: The number of tuyere breakage decreases due to an increase in kinetic energy in front of the tuyere and deepening of the raceway. : It is said that the raceway becomes shallow when recessive coke is used, but the raceway can be maintained.

Japanese Patent Application Laid-Open No. 2-104604 relates to a tuyere structure of a blast furnace in which a large amount of pulverized coal is blown, wherein a front pipe and a rear pipe are formed with a throat (throat) as a boundary. The so-called Laval tuyere is proposed in which the length of the tuyere is 0.2 to 0.6 of the tuyere length. The publication also states, "Hot air mixed with pulverized coal enters the front pipe from the rear pipe, but has a flow velocity of 105 m / s or more when passing through the throat, and is blown into the blast furnace from the tip of the front pipe.""The gas flow velocity at the throat is set to 105 m / s or more, which is the flashback limit velocity.
Pulverized coal combustion does not occur inside the rear pipe. "
Further, according to this Laval tuyere, since the length of the front tube is set to 0.2 to 0.6 of the tuyere length, the flow velocity at the tuyere tip is increased to prevent a flashback phenomenon and to reduce the wear of the front tube. Can be reduced. "

By the way, in the case of the above-mentioned Laval tuyere,
For example, in the Laval tuyere described in Japanese Patent Publication No. 53-19442, a combustion medium (hot air) is supplied under conditions that generate a shock wave in the divergent portion, and fuel (auxiliary fuel) is injected upstream of the shock wave. Although it can be expected that the injected auxiliary fuel is dispersed and supplied into the hot air when passing through the shock wave band, and it can be expected that the fuel injection rate can be increased without generating soot, the following problems occur. Is concerned. That is, since two members, the first and second members, are required, replacement / recovery work becomes complicated in the case of trouble such as tuyere breakage as compared with the conventional normal tuyere, and it may take a long time. Danger such as furnace cooling increases. :
At the time of auxiliary fuel injection, in order to form a shock wave in the divergent part, it is necessary to re-install the tapered part suitable for the blast condition (production condition), the divergent part, and the first member having the sonic furnace diameter at each time. . : In recent years, in the high pressure blast furnace operation for maintaining the furnace top pressure high, it is necessary to increase the pressure of the combustion medium to the pressure at the inlet of the first member to the pressure required to form a shock wave in the divergent portion. As a result, the load on equipment such as blowers and pipes increases. : Since the auxiliary fuel injection holes are formed in the inner peripheral surface of the Laval tuyere, the auxiliary fuel is not always dispersed and supplied into the hot air. : Since the first member has a tapered part constituting the sonic furnace port, an injection pipe for injecting fuel in the divergent part and the tuyere, and is configured to be replaceable,
In addition to being complicated in shape, it must be configured to generate a shock wave in the divergent portion, and there is a concern about practicality.

Further, in the Laval tuyere described in Japanese Patent Publication No. 1-2804, the supersonic flow from the Laval tuyere becomes a turbulent compressible free jet, and the speed of the outlet of the Laval tuyere is maintained, and the blast furnace is maintained. Although the energy is transmitted to the interior of the car, there is no mention of using the Laval tuyere to inject auxiliary fuel.

Also, in the pulverized coal injection Laval tuyere described in Japanese Patent Application Laid-Open No. 2-104604, a large amount of pulverized coal is expected to be injected because the flow velocity at the tuyere tip can be increased to prevent the flashback phenomenon. Although it is possible, the supply of pulverized coal is
In the lower left of the page, lines 7-11, "The hot air mixed with pulverized coal enters the front pipe from the rear pipe, but the gas passing through the throat
It is set to 105 m / s or more, and is blown into the blast furnace from the tip of the front pipe. The pulverized coal is mixed with hot air upstream of the Laval tuyere and supplied from the Laval tuyere, so that even if the flashback phenomenon can be prevented, Good combustion conditions (production conditions) cannot be expected because of the intense combustion at the exit of the pipe and the increase in back pressure.

[0013]

Therefore, according to the present invention, if the normal tuyere is used as described above, for example, when inexpensive pulverized coal is used as an auxiliary fuel, the amount of pulverized coal that can be stably blown in is reduced. Is at most 150kg / pig iron in pulverized coal injection ratio
It is difficult to further increase the amount of pulverized coal to be injected, and the amount of expensive coke used is reduced (reduction of coke ratio)
Is difficult to expect, and the applicant has also
As proposed in Japanese Patent Publication No. 04, the use of a Laval tuyere was focused on the fact that hot air could be supplied deep inside the blast furnace depending on the blast conditions (production conditions). The present invention provides an auxiliary fuel injection tuyere structure in a blast furnace capable of stably injecting pulverized coal at a pulverized coal injection ratio of 150 kg / t or more in the case of pulverized coal.

[0014]

In order to achieve the above object, an auxiliary fuel injection tuyere structure in a blast furnace according to the present invention comprises an auxiliary fuel in a blast furnace including a vicinity of a connection portion of a blow pipe connected to the tuyere. A blow tuyere structure with a reduced diameter portion smaller than the inner diameter of the blow pipe and the inner diameter of the tuyere tip in the pipe from the vicinity of the connection of the blow pipe to the tuyere tip, and auxiliary fuel injection The lance is disposed with its tip position located closer to the tuyere tip than the reduced diameter portion.

In the above-mentioned configuration, the structure of the Laval tuyere of the prior application is used. However, in consideration of the case where the inner diameter of the tuyere is large or the total length of the tuyere is relatively short, It is said that the Laval tuyere may be configured including the vicinity of the connection part of the blow pipe connected to the tuyere. (Hereinafter, the tuyere of the present invention is referred to as a Laval tuyere). At the Laval tuyere, the flow exiting the reduced diameter portion has a high-speed central flow and a widening flow along the divergent portion downstream of the reduced diameter portion, thereby providing a deep and deep race in the blast furnace. A way can be formed.

Further, in the above configuration, an auxiliary fuel injection lance is provided for the Laval tuyere,
The lance tip position is disposed closer to the tuyere tip than the reduced diameter portion. In other words, if the tip position of the auxiliary fuel injection lance is disposed behind the upstream of the reduced diameter portion of the Laval tuyere (upstream in the blowing direction), the auxiliary fuel will be mixed upstream of the reduced diameter portion, As a result, the fuel burns violently in the divergent portion downstream of the reduced diameter portion or in the vicinity of the divergent portion, and the back pressure (internal pressure loss in the tuyere) increases, so that good blast conditions (production conditions) cannot be expected. Therefore, the tip position of the auxiliary fuel injection lance is located closer to the tuyere tip than the diameter-reduced portion of the Laval tuyere. The auxiliary fuel is injected into the blast furnace at a high speed while being agitated and dispersed in the hot air, so that the auxiliary fuel is injected into the blast furnace at a high speed downstream of the reduced diameter portion or in the divergent portion. Tuyere without violent burning near the exit It can be burnt by blowing the blast furnace deeply auxiliary fuel to lower the pressure loss.

Further, as described above, the tip of the auxiliary fuel injection lance is disposed closer to the tip of the tuyere than the reduced diameter portion of the Laval tuyere, so that the hot air passing through the reduced diameter portion can be used as the auxiliary fuel injection lance. As a result, the injected auxiliary fuel is stirred and dispersed in the hot air before the reduced diameter portion of the Laval tuyere, so that the hot air velocity at the divergent portion ahead of the reduced diameter portion is
It is not necessary to stir and disperse even at a supersonic speed (M> 1) which generates a shock wave as described in JP-B-53-19442, and at a subsonic speed (0.3 <M <0.8),
The auxiliary fuel can be sufficiently dispersed to ignite, and a wide and long good raceway can be formed to blow the auxiliary fuel into the blast furnace and burn. Further, in the case of subsonic speed, since the blowing pressure may be lower than in the case of supersonic speed, the cost of blowing equipment such as a blower and a blowing pipe and the energy cost required for blowing can be suppressed.

In the auxiliary fuel injection tuyere structure for a blast furnace according to the first aspect of the present invention, the curvature R may be formed on the inner diameter side of the tip of the Laval tuyere. By providing R, the hot air containing the auxiliary fuel that has flowed out of the vicinity of the tip of the Laval tuyere is less likely to generate a vortex on the outside of the tuyere tip. A stable raceway is formed and the blast furnace operation can be stabilized. In order to obtain such an effect, the curvature R is preferably R = 2 to 100 mm, and more preferably R = 10 to 60 mm.

Further, in the auxiliary fuel injection tuyere structure for a blast furnace according to the first aspect of the present invention, the minimum diameter portion of the reduced diameter portion is provided.
When D2, the outer diameter OD of the auxiliary fuel injection lance, and the number of auxiliary fuel injection lances N, the formula [(OD / D2) ² × N <0.15]
The ratio of the cross-sectional area of the auxiliary fuel injection lance to the area of the minimum diameter portion D2 of the reduced diameter portion is less than 15%, so that the hot air is supplied to the Laval tuyere. When the air is blown, the turbulence of the hot air flowing through the reduced diameter portion and the increase in the pressure loss in the tuyere are suppressed, and in particular, the pressure loss in the tuyere can be suppressed to an allowable range, and the vibration of the auxiliary fuel injection lance is also suppressed. Can be. Further, the auxiliary fuel injected from the auxiliary fuel injection lance can be appropriately stirred and dispersed and injected into the blast furnace. In this case, the diameters of the tuyere and the lance are indicated by a diameter in order to facilitate the calculation, but the cross-sectional shape of these is preferably, but not necessarily, circular.

Further, in the auxiliary fuel injection tuyere structure for a blast furnace according to the first aspect of the present invention, the minimum diameter portion of the reduced diameter portion is provided.
D2, D2 when the inner diameter of the blow pipe on the inlet side of the reduced diameter part is D1
/ D1 satisfies 0.5 to 0.9, or the aperture angle β on the entrance side of the reduced diameter portion satisfies 10 to 60 degrees. By providing such a configuration, hot air can be supplied to the Laval tuyere. When blown, the tuyere pressure loss can be kept within an allowable range, and within this allowable range, an increase in the amount of air blown and / or the amount of auxiliary fuel injected can be expected. A reduction in manufacturing costs can be expected. Further, in the auxiliary fuel injection tuyere structure in the blast furnace according to claim 1,
When the minimum diameter part D2 of the reduced diameter part and the exit inner diameter D3 of the tuyere are D2
The same operation and effect can be expected even in a configuration in which / D3 satisfies 0.55 to 0.95 or the divergence angle θ on the exit side of the reduced diameter portion satisfies 1 to 15 degrees.

Although not particularly limited, in the auxiliary fuel injection tuyere structure in the blast furnace according to the first aspect, the curvature R may be formed at the minimum diameter portion of the reduced diameter portion. . When the curvature R is provided in the minimum diameter portion in this manner,
When hot air is blown into the Laval tuyere, after the hot air passes through the minimum diameter portion of the Laval tuyere, a vortex is less likely to be generated on the downstream inner peripheral surface side, so that the increase in the tuyere pressure loss is suppressed. Stable blast furnace operation can be expected. In order to obtain such an effect, the magnitude of the curvature R depends on the aperture angle on the tuyere entrance side and the spread angle on the tuyere exit side.
It is preferably about 2 to 100 mm.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory sectional view of an auxiliary fuel injection tuyere structure in a blast furnace according to the present invention. In FIG. 1, reference numeral 1 denotes a Laval tuyere, reference numeral 2 denotes an auxiliary fuel injection lance, and reference numeral 3 denotes a blow pipe. .

In the present embodiment, the Laval tuyere 1 is an example in which a Laval type is formed in the tuyere itself, and a reduced diameter portion 4 is formed in the center portion, and the upstream side of the reduced diameter portion 4 (on the blow pipe 3 side). An inlet portion 5 formed to be tapered, an outlet portion 6 formed to be divergent on the downstream side, an inner diameter D2 of the reduced diameter portion 4, an inner diameter D1 of the inlet portion 5,
When the inside diameter D3 of the outlet part 6 is set, it is formed in a shape that satisfies the relationship of D1> D2 <D3. A blow pipe 3 is connected to the inlet portion 5 side of the Laval tuyere 1, and two pulverized coal blowing lances 2 are pierced through the blow pipe 3, and the position of the tip 7 is reduced in diameter. It is mounted slightly out of the part 4 to the outlet part 6 side.

The auxiliary fuel injection tuyere structure in the blast furnace having the above-described configuration was installed in the combustion test apparatus shown in FIG. 2, and the change in air flow in the tuyere branch pipe when pulverized coal was cut off was investigated. For comparison, a normal tuyere H having an inlet inner diameter equal to the inner diameter D1 of the inlet portion 5 of the Laval tuyere 1 and an outlet inner diameter equal to the inner diameter D2 of the reduced diameter portion 4 was used. A similar investigation was conducted under the same conditions. FIG. 3 shows the result of the investigation.

As is apparent from FIG. 3, the change in the tuyere branch pipe airflow is greatly improved in the Laval tuyere 1 compared to the normal tuyere H. The reason for this is that, as shown in FIG. 4, the tuyere H is usually tapered, so that the volume expansion due to the combustion in the tuyere causes a large back pressure, which greatly affects the air volume in the tuyere branch pipe. Tuyere 1
Since the outlet 6 is formed so as to be widened at the end, almost no back pressure is applied. As a result, the pulverized coal stream P blown out at the tuyere H is thin and short, whereas the Laval tuyere 1
In this case, the blown pulverized coal stream P becomes thick and long, and a raceway can be formed in the blast furnace where wide and long pulverized coal is dispersed and burned.

That is, in the auxiliary fuel injection tuyere structure of the blast furnace having the configuration shown in FIG. 1, the position of the tip 7 of the auxiliary fuel injection lance 2 with respect to the Laval tuyere 1
Since it is disposed slightly to the outlet 6 side, it is installed in the blast furnace to supply hot air, and when pulverized coal is supplied from the auxiliary fuel injection lance 2, the hot air passes through the reduced diameter portion 4. By the way, the flow is about subsonic (0.3 <Mach number M <0.8) to supersonic (M = 1), but the flow becomes a high-speed central flow and a flow that spreads along the divergent shape of the outlet portion 6. As a result, a deep and deep raceway is formed in the blast furnace, and the high-speed central flow exiting the reduced diameter portion 4 is stirred by the tip of the auxiliary fuel injection lance 2. The pulverized coal blown from 2 is ignited while being stirred and dispersed in hot air, and blown into the blast furnace at a high speed.
The pulverized coal can be blown deep into the blast furnace and burned without lowering the pressure loss in the tuyere without violent combustion inside or near the outlet 6 thereof. By such an operation, the auxiliary fuel can be injected into the blast furnace stably at a pulverized coal injection ratio of 150 kg / pig iron t or more in the case of pulverized coal, for example. As a result of operating the blast furnace with the tuyere structure changed to the normal tuyere and installing about 60% in the blast furnace, the pulverized coal ratio is about 25% or more of the maximum pulverized coal injection ratio when only the normal tuyere is used ( Pulverized coal injection ratio 250kg /
It was possible to stably increase the amount up to about pig iron t).

FIG. 2 is a schematic view of a combustion test apparatus, which is designed to have a structure imitating an actual blast furnace tuyere. Pulverized coal 8 is transferred from ground hopper 9 to screw conveyor 10
Is transferred to the coal bin 11. A pulverized coal feeder 12 is provided below the coal bin 11, and the pulverized coal 8 quantitatively cut out at this portion is sent to the pulverized coal injection lance 2 through a transport pipe 14 together with a transport gas 13. On the other hand, the hot air obtained in the high-temperature hot-blast furnace 15 is sent from the blowing pipe 16 to the combustion test furnace 17 through the blow pipe 3 and the Laval tuyere 1. Reference numeral 18 denotes a chimney.

The fuel injection section of the blast furnace is completely different from a general combustion apparatus, and is constituted by a blow pipe 3 and a normal tuyere (in this experiment, the Laval tuyere 1 according to the present invention). Is approximated to the actual blast furnace injection section. In addition, the combustion test furnace 17 is provided with a large number of viewing windows for observing the combustion state and the ignition state of the powder fuel, and is used for measuring the furnace temperature, the furnace gas composition, the furnace dust, the flame radiation amount, and the like. An inspection hole is provided, and a viewing window 19 for observing the state of adhesion of ash to the wall surface of the blow pipe 3 is provided at the upstream bent portion of the blow pipe 3.

FIG. 5 shows a blade having a curvature R (R = 2 to 100 mm) on the inner diameter side of the tip of the outlet portion 6 of the Laval tuyere 1 in the auxiliary fuel injection tuyere structure in the blast furnace having the structure shown in FIG. FIG. 4 is an explanatory view showing the mouth structure, in which the curvature R is provided on the inner diameter side, so that the hot air containing the auxiliary fuel that has exited the periphery of the tip of the outlet 6 generates a vortex at the outside of the tip of the outlet 6. Since it is difficult to suppress, the turbulence of the hot air flow into the blast furnace can be reduced, and stable blast furnace operation can be performed.

In FIG. 5, the length of the Laval tuyere 1 is 500 mm, the inner diameter D1 of the blow pipe 3 is 175 mm, the minimum diameter D2 of the reduced diameter portion 4 is 135 mm, the inner diameter D3 of the outlet 6 is 168 mm,
Laval tuyere 1 with divergent angle θ = 6 degrees on the exit side of reduced diameter portion 4
Was used to simulate the relationship between the curvature R and the local loss coefficient when the curvature R was changed toward the inner diameter of the tip of the outlet portion 6 of the Laval tuyere 1. FIG. 6 shows the simulation results. As is apparent from FIG. 6, the curvature R is
It can be seen that if it is less than 2 mm, the local loss coefficient is large, and it is almost meaningless to provide the curvature R. When the curvature R exceeds 2 mm, the local loss coefficient sharply decreases and eddy currents are less likely to be generated outside the tip. On the other hand, the effect is sufficient even if the curvature R exceeds 100 mm, but the upper limit of the curvature R is preferably set to 100 mm due to the structure of the tuyere cooling water chamber.
In view of this, the auxiliary fuel injection tuyere structure in the blast furnace according to the present invention may have a structure in which a curvature R (R = 2 to 100 mm) is provided on the inner diameter side of the tuyere tip as a preferred embodiment. is there.

FIG. 7 shows the lance of the auxiliary fuel injection lance when an experiment was conducted using a 1/17 scale cold model furnace having an auxiliary fuel injection tuyere structure in the blast furnace having the structure shown in FIG. FIG. 4 is a graph showing the relationship between the ratio [(OD / D2) ² × N] of the cross-sectional area to the area at the minimum diameter of the Laval tuyere and the pressure loss in the tuyere. In this experiment, the length of the Laval tuyere 1 (27.4 mm), the inner diameter D1 of the blow pipe 3 (11.4 mm), the minimum diameter D2 of the reduced diameter portion 4 (6 mm to 10 mm), and the inner diameter D3 of the outlet 6
(11.0mm), Outer diameter OD of auxiliary fuel injection lance 2 (2mm),
When the number of auxiliary fuel injection lances 2 is N = 2,
The pressure loss in the tuyere when D2 was changed was measured, and the result is shown in FIG. As is apparent from FIG. 7, the sectional area of the auxiliary fuel injection lance 2 and the Laval tuyere 1
Ratio to the area at the minimum diameter of ｛π (OD / 2) ² × N / [π (D2 /
2) ² ] = (OD / D2) ² × N｝ is less than 0.15, it can be seen that the pressure loss in the tuyere is greatly reduced as compared with the case where the ratio is 0.15 or more. In addition, fine vibration of the auxiliary fuel injection lance 2 can be suppressed, and thereby stable blast furnace operation can be performed. Therefore, in the auxiliary fuel injection tuyere structure in the blast furnace according to the present invention, as preferred embodiments, the minimum diameter portion D2 of the reduced diameter portion, the outer diameter OD of the auxiliary fuel injection lance, the number of auxiliary fuel injection lances N and (OD / D2) ² × N
A structure satisfying <0.15 may be adopted. In this experiment, the auxiliary fuel injection lance 2 used was one having a circular cross-sectional shape, but it is not necessarily required to be circular.

FIG. 8 shows the minimum diameter portion of the Laval tuyere when an experiment was conducted using a 1/17 scale cold model furnace having an auxiliary fuel injection tuyere structure in the blast furnace having the configuration shown in FIG.
It is a graph which shows the relationship between the ratio (D2 / D1) of D2 and the inner diameter D1 of a blow pipe, and the tuyere pressure loss. In this experiment, the length of Laval tuyere 1 (27.4 mm), blow pipe 3
Inner diameter D1 (11.4mm), the minimum diameter part D2 of the reduced diameter part 4 (3mm ~ 1
1.4 mm), the inner diameter D3 of the outlet 6 (11.0 mm), the outer diameter OD of the auxiliary fuel injection lance 2 (1 mm to 2 mm), and when the number of auxiliary fuel injection lances 2 is N (2), D2 The pressure loss in the tuyere when the pressure was changed was measured, and the result is shown in FIG. As is apparent from FIG. 8, if the ratio (D2 / D1) of the minimum diameter D2 of the reduced diameter portion 4 of the Laval tuyere 1 to the inner diameter D1 of the blow pipe 3 is 0.5 or more, the ratio is 0.5 or more. It can be seen that the pressure loss in the tuyere is greatly reduced as compared with the case where the pressure is small. Also, as shown in FIG. 10, D2 / D1 must be smaller than 0.9 in order to generate a contraction at the tuyere tip. In other words, by providing a configuration in which D2 / D1 satisfies 0.5 to 0.9, when hot air is blown into the Laval tuyere, the tuyere pressure loss can be suppressed within an allowable range, and within this allowable range. As a result, an increase in the amount of air blown and / or the amount of auxiliary fuel blow-in can be expected, and an increase in the amount of extracted tap iron and a reduction in the cost of hot metal production can be expected.

FIG. 9 is a diagram showing a throttle at the inlet side of the reduced diameter portion when an experiment was conducted using a 1/17 scale cold model furnace having an auxiliary fuel injection tuyere structure in the blast furnace having the configuration shown in FIG. Angle β
FIG. 6 is a graph showing the relationship between the pressure loss in the tuyere and the tuyere. In this experiment, the length of the Laval tuyere 1 (27.4 mm), the inner diameter D1 of the blow pipe 3 (11.4 mm), and the minimum diameter D2 of the reduced diameter portion 4 (6 m)
m to 10 mm), the inner diameter D3 of the outlet part 6 (11.0 mm), the throttle angle β on the entrance side of the reduced diameter part 4, and the outer diameter OD of the auxiliary fuel injection lance 2.
(2mm), when the number of auxiliary fuel injection lances 2 was N (2), the pressure loss in the tuyere was measured when β was changed by changing D2 and the throttle position, and the results are shown in FIG. It is shown. As is clear from FIG. 9, when the throttle angle β on the inlet side of the reduced diameter portion is 60 degrees or less, the pressure loss in the tuyere is greatly reduced as compared with the case where the angle becomes larger than 60 degrees. . The angle β can be configured at 10 degrees or more in relation to the length of the Laval tuyere 1. Further, as shown in FIG. 10, since the contraction at the tuyere tip occurs at 10 degrees or more, The lower limit is 10 degrees. Therefore, by providing a configuration in which the aperture angle β on the inlet side of the reduced diameter portion satisfies 10 to 60 degrees, the D2 / D1 is 0.5 to 0.5.
As with the case where the configuration that satisfies 0.9 is provided, when hot air is blown into the Laval tuyere, the tuyere pressure loss can be suppressed within the allowable range, and the air flow rate and / or auxiliary fuel It is expected that the amount of molten iron blown will increase, and it is expected that the amount of tapping will increase and the cost of hot metal production will decrease.

FIG. 11 shows the minimum diameter portion of the Laval tuyere when an experiment was conducted using a 1/17 scale cold model furnace having an auxiliary fuel injection tuyere structure in the blast furnace having the configuration shown in FIG.
It is a graph which shows the relationship between the ratio (D2 / D3) of D2 and the exit inner diameter D3 of Laval tuyere, and the tuyere friction loss. In this experiment, the length of the Laval tuyere 1 (27.4 mm), the inner diameter D1 of the blow pipe 3 (11.4 mm), the minimum diameter D2 of the reduced diameter portion 4 (8 mm),
The inner diameter D3 of the outlet 6 (8 mm to 16 mm), the outer diameter OD of the auxiliary fuel injection lance 2 (2 mm), and the number of auxiliary fuel injection lances 2
When N (2 pieces) was set, the friction loss in the tuyere when D3 was changed was measured, and the results are shown in FIG. As is clear from FIG. 11, the reduced diameter portion 4 of the Laval tuyere 1
The ratio (D2 / D3) of the minimum diameter part D2 of the above to the inner diameter D3 of the outlet part 6 is 0.
If within the range of 55 to 0.95, the ratio is less than 0.55 or
It can be seen that the friction loss in the tuyere is much smaller than that in the case of the conventional structure shown in FIG. That is, this allows D2 / D3
With a configuration satisfying 0.55 to 0.95, when hot air is blown into the Laval tuyere, the pressure loss in the tuyere can be suppressed within the allowable range, that is, below the normal tuyere,
Within this allowable range, an increase in the amount of air blown and / or the amount of auxiliary fuel injected can be expected, and an increase in the amount of tapping and a reduction in the cost of hot metal production can be expected.

FIG. 12 shows the expansion at the exit side of the reduced diameter portion when an experiment was performed using a 1/17 scale cold model furnace having an auxiliary fuel injection tuyere structure in the blast furnace having the configuration shown in FIG. It is a graph which shows the relationship between angle (theta) and the tuyere friction loss. In this experiment, the length of the Laval tuyere 1 (27.4 mm), the inner diameter D1 of the blow pipe 3 (11.4 mm), and the minimum diameter D2 of the reduced diameter portion 4
(8 mm), inner diameter D3 of outlet 6 (8 mm to 16 mm), divergence angle θ on the exit side of reduced diameter section 4, outer diameter OD of auxiliary fuel injection lance 2
(2mm), when the number of auxiliary fuel injection lances 2 was N (2), the tuyere friction loss was measured when θ was changed by changing D3 and the throttle position, and the results are shown in Fig. 12. It is shown. As is apparent from FIG. 12, when the divergent angle θ on the exit side of the reduced diameter portion 4 is 1 to 15 degrees, the friction loss in the tuyere becomes smaller than when the angle is less than 1 degree or exceeds 15 degrees. It can be seen that the friction loss in the tuyere of the conventional structure shown in FIG. If the angle θ exceeds 15 degrees, the connection with the cooling flow path in the Laval tuyere 1 becomes poor, and the structure becomes difficult, so the upper limit value is set.
15 degrees. By providing the configuration in which the divergent angle θ on the exit side of the reduced diameter portion satisfies 1 to 15 degrees, similarly to the case in which the configuration in which D2 / D3 satisfies 0.55 to 0.95 is used, hot air is applied to the Laval tuyere. When the air is blown, the pressure loss in the tuyere can be suppressed within an allowable range, that is, below the normal tuyere, and within this allowable range, an increase in the amount of air blown and / or the amount of auxiliary fuel injected can be expected. An increase in the amount of pig iron and a reduction in the cost of hot metal production can be expected.

In the above example, the basic structure has been described as an example, but the present invention is not limited to this example. For example, the auxiliary fuel injection tuyere in the blast furnace having the structure shown in FIG. In the structure, the reduced diameter portion 4 of the Laval tuyere 1
In addition to forming the minimum diameter portion as a straight portion or a top portion having a small length, the portion may be formed to have a curvature (r = about 2 to 100 mm) that smoothly connects the entrance and exit sides. With such a curvature (r), the hot air containing the auxiliary fuel around the minimum diameter portion of the reduced diameter portion 4 is more likely to be swirled on the exit side of the reduced diameter portion 4 than when formed at the straight portion or the top portion. Is suppressed, friction loss is suppressed, the turbulence of the hot air flow into the blast furnace can be reduced, and stable blast furnace operation can be expected.

[0037]

As described above, the auxiliary fuel injection tuyere structure in the blast furnace according to the present invention can reduce the tuyere pressure loss and reduce the auxiliary fuel injection into the blast furnace as compared with the conventional one. For pulverized coal in large quantities, for example pulverized coal injection ratio 1
It is possible to stably inject 50 kg / pig iron or more, and further, pulverized coal injection ratio 200 kg / pig t to 300 kg / pig iron t or more, thereby reducing the use of expensive coke.

Further, by disposing the tip of the auxiliary fuel injection lance on the tip side of the tuyere from the reduced diameter portion of the Laval tuyere, the hot air passing through the reduced diameter portion is moved by the tip of the auxiliary fuel injection lance. Since the pulverized coal injected is stirred and dispersed in the hot air, the pulverized coal is sufficiently dispersed at the subsonic speed (0.3 <M <0.8) at the divergent portion ahead of the reduced diameter portion. Accordingly, in the actual furnace operation, the cost of the blower equipment such as the blower and the blower tube can be reduced and operated.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of an auxiliary fuel injection tuyere structure in a blast furnace according to the present invention.

FIG. 2 is a schematic diagram of a combustion test apparatus.

FIG. 3 is an explanatory diagram showing a comparison of changes in the tuyere branch pipe air volume between the Laval tuyere according to the present invention and a normal tuyere.

FIG. 4 is a schematic diagram showing a comparison of pulverized coal injection states between the Laval tuyere according to the present invention and a normal tuyere, wherein a is the case of the Laval tuyere and b is the case of the normal tuyere.

FIG. 5 is an explanatory sectional view showing another example of the auxiliary fuel injection tuyere structure in the blast furnace according to the present invention.

6 is a graph showing a relationship between a curvature R on an inner diameter side of a tip end of an outlet portion and a local loss coefficient at the outlet portion in the auxiliary fuel injection tuyere structure shown in FIG.

FIG. 7 is a graph showing the relationship between the ratio [(OD / D2) ² × N] of the cross-sectional area of the auxiliary fuel injection lance to the area at the minimum diameter of the Laval tuyere and the pressure loss in the tuyere. .

FIG. 8 is a graph showing the relationship between the ratio (D2 / D1) between the minimum diameter D2 of the Laval tuyere and the inner diameter D1 of the blow pipe and the pressure loss in the tuyere.

FIG. 9 is a graph showing the relationship between the throttle angle β on the inlet side of the reduced diameter portion and the pressure loss in the tuyere.

FIG. 10 is a graph schematically showing the flow velocity (dynamic pressure) distribution at the tip of the tuyere when the normal tuyere and the Laval tuyere according to the present invention are used.

FIG. 11 is a graph showing the relationship between the ratio (D2 / D3) between the minimum diameter portion D2 of the Laval tuyere and the outlet inner diameter D3 of the Laval tuyere, and the friction loss in the tuyere.

FIG. 12 is a graph showing a relationship between a divergence angle θ on the exit side of the reduced diameter portion and a friction loss in the tuyere.

[Explanation of Signs] 1: Laval tuyere 2: auxiliary fuel injection lance 3: blow pipe 4: reduced diameter portion
5: Inlet 6: Outlet 7: Lance tip

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kentaro Nozawa 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Inside the Kobe Steel Works Kakogawa Works (72) Inventor Jun Sato 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Kobe Corporation Inside the Steel Works Kakogawa Works (72) Inventor Yoshiyuki Matsui 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Inside Kobe Steel Works Kakogawa Steel Works, Ltd. (72) Ryuichi Hori 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Kobe Steel Works, Ltd. F-term in Kakogawa Works (reference) 4K015 FC01 FC02 FC03

Claims (5)

[Claims] 1. An auxiliary fuel injection tuyere structure in a blast furnace including a vicinity of a connection portion of a blow pipe connected to a tuyere, wherein a blower is provided in a pipe extending from the vicinity of the connection portion of the blow pipe to the tip of the tuyere. It has a reduced diameter portion smaller than the inner diameter of the pipe and the inner diameter of the tuyere tip, and the auxiliary fuel injection lance is arranged such that the tip position is located closer to the tuyere tip side than the reduced diameter portion. Auxiliary fuel injection tuyere structure in a blast furnace. 2. The tuyere structure according to claim 1, wherein the tuyere tip has a curvature R at an inner diameter side thereof.
(R = 2 to 100 mm) Auxiliary fuel injection tuyere structure in a blast furnace formed. 3. The auxiliary fuel injection tuyere structure for a blast furnace according to claim 1, wherein the minimum diameter portion D2 of the reduced diameter portion, the outer diameter OD of the auxiliary fuel injection lance, and the number N of auxiliary fuel injection lances.
And an auxiliary fuel injection tuyere structure in a blast furnace having a configuration satisfying the following expression. (OD / D2) ² × N <0.15 4. The auxiliary fuel injection tuyere structure for a blast furnace according to claim 1, wherein D2 / D1 is equal to a minimum diameter portion D2 of the reduced diameter portion and an inner diameter D1 of a blow pipe on the side of the reduced diameter portion. 0.5
0.9, or the aperture angle β on the inlet side of the reduced diameter part is 10-60.
Auxiliary fuel injection tuyere structure in a blast furnace having a configuration satisfying the temperature. 5. The auxiliary fuel injection tuyere structure for a blast furnace according to claim 1, wherein D2 / D3 satisfies 0.55 to 0.95 when the minimum diameter portion D2 of the reduced diameter portion and the exit inner diameter D3 of the tuyere are set. ,
Alternatively, an auxiliary fuel injection tuyere structure in a blast furnace having a configuration in which a divergence angle θ at the outlet side of the reduced diameter portion satisfies 1 to 15 degrees.