JP3644862B2 - Auxiliary fuel injection operation method to blast furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for injecting auxiliary fuel into a blast furnace.
[0002]
[Prior art]
As is well known, in conventional blast furnaces, iron ore (including pellets and sintered ore), coke, limestone, etc. are charged from the top, while high temperature air is supplied from the lower tuyere to fuel coke. Iron ore has been reduced and dissolved as a (heat source) and reducing agent, and pig iron has been manufactured. Thereafter, in order to reduce the use of coke, which has a high manufacturing cost, and as a countermeasure for aging of coke ovens, In order to reduce the operation rate, for example, an auxiliary fuel injection operation method into a blast furnace in which auxiliary fuel is injected from a blast furnace tuyere as a fuel to replace coke has been widely implemented.
[0003]
As a supplementary fuel, liquid fuel such as heavy oil with excellent combustibility was initially used, but the price of heavy oil has soared since the previous oil shock, and in recent years, pulverized coal obtained by pulverizing coal has become a partial substitute for coke. So-called pulverized coal injection operation (hereinafter referred to as PCI operation) that is injected from the tuyere is becoming common. Furthermore, recently, as part of dealing with environmental problems, waste synthetic resin materials represented by waste plastics and waste-derived solid fuel are supplied into the blast furnace through the tuyere, and the heat source and reducing agent are supplied. It has also been proposed to serve as
[0004]
By the way, in order to reduce the hot metal cost, it is the most effective method to increase the injection ratio of auxiliary fuel such as pulverized coal and heavy oil and reduce the coke. The tuyere that has been used normally (see, for example, 3rd Edition Steel Handbook, Volume II Steelmaking and Steelmaking (Figure 306 on page 306), JP-A 64-4410, JP-A-3-240908) (Hereinafter referred to as normal tuyere), when the auxiliary fuel injection ratio from the tuyere is increased, the auxiliary fuel is converted into combustion gas in the tuyere and the gas volume increases and tuyere pressure loss increases. Furthermore, it has been confirmed that the combustibility in the raceway at the tuyere deteriorates and the replacement rate with coke deteriorates, and these are said to limit the increase in the auxiliary fuel injection ratio.
[0005]
Therefore, in order to improve the above problem, when the pulverized coal is blown as auxiliary fuel using the normal tuyere, for example, the tip position of the pulverized coal blowing lance is set to the optimum position, or the volatile content is high. Improvements such as using pulverized coal or pulverized coal whose particle size configuration has been changed from fine particles have been attempted, but even if these improvements are made, the amount of pulverized coal that can be stably blown from the above tuyere is fine powder The charcoal blowing ratio is about 150kg / t.
[0006]
On the other hand, JP-B-53-19442, JP-B-1-28804, and JP-A-2-104604 disclose Laval type tuyere (hereinafter referred to as Laval tuyere) used as tuyeres for blast furnaces (blast furnaces). Proposed).
[0007]
For example, Japanese Patent Publication No. 53-19442 (especially page 1, column 2, line 8 to page 2, column 3, line 1) describes the price of solid fuel such as coke used in shaft furnaces such as blast furnaces. Due to the high cost, Laval tuyere has been proposed as a tuyere used in a technique in which part of the fuel is replaced with a liquid hydrocarbon auxiliary fuel and the auxiliary fuel is injected into a blow pipe opened to the shaft furnace. This Laval tuyere has a replaceable first member having a tapered portion and a divergent portion constituting the sonic furnace throat and an injection pipe for injecting fuel in the tuyere, and a divergent portion of the first member connected to the first member. This is basically composed of a fixed second member that extends to the end and forms the divergent portion. In this Laval tuyere, a condition for transitioning from a supersonic flow state to a subsonic speed state in the divergent part of the tuyere, that is, a condition in which a shock wave is formed in the divergent part, fuel is generated upstream of the shock wave. When the injected fuel passes through the shock wave band, the dispersion action into the combustion medium becomes effective, and the fuel injection rate can be increased without generating soot. It is explained. In this Laval tuyere, in order to generate a shock wave in the divergent part, it is necessary to design the furnace mouth (constriction part) according to the supply speed of the combustion medium of the shaft furnace. Focusing on this 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.
[0008]
Further, Japanese Patent Publication No. 1-28284 proposes that the blower tuyere itself used in the blast furnace is a so-called Laval tuyere having a central portion formed smaller than the inlet diameter and the outlet diameter. According to the publication, “In this Laval tuyere, the subsonic wind at the entrance side of the tuyere is Mach number M = 1 at the central part (throat part) and the supersonic flow is at the exit side of the tuyere. However, the supersonic speed of the exit side is determined by the wind pressure at the entrance and exit of the tuyere, and the supersonic flow from this Laval tuyere becomes a turbulent compressible free jet, The speed at the exit of the Laval tuyere is maintained and the energy is transmitted deep into the blast furnace, and the speed core is longer as the Mach number is larger. " According to the mouth, there are the following effects. {Circle around (1)} An inactive furnace core called dead man is narrowed, and the amount of blown air can be increased by increasing the operating internal volume, increasing the amount of output. {Circle around (2)} The reactivity at the bottom of the blast furnace is increased, and the fuel ratio can be reduced by directly increasing the reduction rate. {Circle around (3)} The central operation of the blast furnace can be performed, and the furnace body and the bottom of the furnace can be protected by reducing the fuel ratio by reducing the heat loss of the furnace body and by centralizing the core flow. {Circle around (4)} The number of tuyere breaks decreases due to an increase in kinetic energy before tuyere and deepening of the raceway. {Circle around (5)} Although it is said that the raceway becomes shallower when the recessive coke is used, the raceway can be maintained.
[0009]
JP-A-2-104604 relates to a blast furnace tuyeres structure in which a large amount of pulverized coal is blown into a front tube and a rear tube with a throat portion (throat portion) as a boundary, and the length of the front tube. A so-called Laval tuyere with a tuyere length of 0.2 to 0.6 has been proposed. According to the publication, “hot air mixed with pulverized coal enters the front pipe from the rear pipe, but when passing through the throat part, the flow velocity is set to 105 m / s or more and is blown into the blast furnace from the front end of the front pipe.” Also, “Because the gas flow velocity at the throat section is 105 m / s or more, which is the critical speed for backfire, combustion of pulverized coal does not occur inside the rear pipe.” Furthermore, 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 rate at the tuyere tip can be increased to prevent the flashback phenomenon and to reduce the wear of the front tube. " Has been.
[0010]
By the way, in the case of the Laval tuyere described above, for example, in the Laval tuyere described in Japanese Patent Publication No. 53-19442, the combustion medium (hot air) is supplied in a condition that generates a shock wave in the divergent section, and upstream of the shock wave. The fuel (auxiliary fuel) is injected into the fuel, so that the injected auxiliary fuel can be expected to be distributed and supplied into the hot air when passing through the shock wave band, and the fuel injection rate can be increased without generating soot. However, there are concerns about the following problems. That is, (1): Since the first and second members are required, the replacement / recovery operation becomes complicated and troublesome in the event of trouble such as damage to the tuyere compared to the conventional normal tuyere. Because of the possibility, the risk of furnace cooling increases. (2): When the auxiliary fuel is injected, in order to form a shock wave in the divergent part, it is installed on the first member that has a tapered part suitable for blast conditions (production conditions), divergent part, and sonic furnace aperture. I need to fix it. (3): Also, in high-pressure blast furnace operation that keeps the furnace top pressure high, which is the mainstream in recent years, the pressure of the combustion medium is increased to the pressure required to form a shock wave in the divergent section at the first member inlet. Because it is necessary, the equipment load such as blower and piping increases. {Circle around (4)} Since the auxiliary fuel injection holes are formed on the inner peripheral surface of the Laval tuyere, the auxiliary fuel is not necessarily dispersedly supplied into the hot air. {Circle over (5)} The first member has a complicated shape because the first member has a tapered portion forming the sonic furnace port, a divergent portion, and an injection pipe for injecting fuel in the tuyere. It must be configured in a shape that generates a shock wave in the divergent part, and there is a concern about practicality.
[0011]
In the Laval tuyere described in JP-B-1-28804, the supersonic flow from the Laval tuyere becomes a turbulent compressible free jet, and the speed of the Laval tuyere exit is maintained deep into the blast furnace. Although the energy is transmitted, there is no description about injecting auxiliary fuel together with this Laval tuyere.
[0012]
In addition, in the pulverized coal injection laval tuyere described in JP-A-2-104604, although a large amount of pulverized coal can be expected by increasing the flow velocity of the tuyere and preventing the flashback phenomenon, The supply of the pulverized coal is as follows: “Hot air mixed with pulverized coal enters the front pipe from the rear pipe, but the gas passing through the throat part has a flow rate of 105 m / As described above, the pulverized coal is mixed with hot air upstream from the Laval tuyere and supplied from the Laval tuyere. For this reason, even if the flashback phenomenon can be prevented, a strong blast condition (production condition) cannot be expected because intense combustion occurs in the front tube and the exit from the front tube and the back pressure increases.
[0013]
[Problems to be solved by the invention]
Therefore, in the present invention, when the normal tuyere is used as described above, the amount of pulverized coal that can be stably injected when using inexpensive pulverized coal as an auxiliary fuel, for example, is at most 150 kg / It is about pig iron t, and it is difficult to increase the amount of pulverized coal injection, and it is difficult to expect a reduction in the amount of coke used (a reduction in the coke ratio). As proposed in the official gazette, the use of Laval tuyere has focused on the fact that hot air can be supplied deep inside the blast furnace depending on the blast conditions (production conditions). Auxiliary fuel injection, for example, in the case of pulverized coal, provides a pulverized coal injection ratio of 150 kg / pig iron t or more, and provides a method for injecting auxiliary fuel into a blast furnace while minimizing the use of expensive coke. To do.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have conducted intensive investigations and examinations, grasped the current situation as described in the section of the prior art, and further, the present applicant previously issued Japanese Patent Publication No. 1-28804. The present invention has been made by paying attention to the Laval tuyere proposed in (1) and to the auxiliary fuel injection lance normally used for the tuyere. The gist (Claim 1) is that the inner diameter of the blow pipe and the reduced diameter portion smaller than the inner diameter of the tuyere tip are formed in the pipe between the vicinity of the connecting portion of the blow pipe connected to the tuyere and the tip of the tuyere. Auxiliary fuel injection into the blast furnace in which auxiliary fuel is injected from the auxiliary fuel injection tuyere having a configuration in which the tip position of the auxiliary fuel injection lance is disposed on the tip side of the tuyere from the reduced diameter portion A method of operating auxiliary fuel injection into a blast furnace, wherein the auxiliary fuel injection tuyere having the above-described configuration is provided with 10% or more of the auxiliary fuel injection tuyere of the entire blast furnace to inject auxiliary fuel, and To do.
[0015]
In the above configuration, the Laval tuyere structure of the previous application is used, but considering the case where the tuyere's inner diameter is large or the tuyere's overall length is relatively short, It is said that the Laval tuyere may be configured including the vicinity of the connected part of the connected blowpipe, and if the Laval tuyere can be configured by the tuyere itself, the Laval tuyere is configured by the tuyere itself. Also good. In this Laval tuyere, the flow exiting the reduced diameter part can be a high-speed central flow and a widening flow along the divergent part downstream of the reduced diameter part, thereby allowing the blast furnace to have a deep and deep race. Ways can be formed. And in the said structure, the front-end | tip position of an auxiliary | assistant fuel blowing lance is arrange | positioned with respect to this Laval tuyere on the tuyere tip side rather than a reduced diameter part. That is, when the tip position of the auxiliary fuel injection lance is disposed behind the diameter-reduced portion of the Laval tuyere (upstream side in the blowing direction), the auxiliary fuel is mixed on the upstream side of the reduced-diameter portion, As a result, it burns violently in the vicinity of the divergent part downstream of the reduced diameter part or in the vicinity of the divergent part, resulting in a high back pressure (pressure loss in the tuyere), and good blast conditions (production conditions) cannot be expected. . On the other hand, when the tip position of the auxiliary fuel blowing lance is disposed closer to the tuyere tip side than the reduced diameter portion of the Laval tuyere, the hot air passing through the reduced diameter portion is heated to the tip portion of the auxiliary fuel blowing lance. Therefore, the injected auxiliary fuel is blown into the blast furnace at a high speed while being stirred and dispersed in the hot air, so that in the divergent part downstream of the reduced diameter part or in the vicinity of the divergent part. Auxiliary fuel can be injected deeply into the blast furnace with low pressure loss in the tuyere without burning intensely.
[0016]
In addition, as described above, the tip position of the auxiliary fuel blowing lance is disposed closer to the tip of the tuyere than the diameter reducing portion of the Laval tuyere, so that the hot air that has passed through the reduced diameter portion is moved to the tip of the auxiliary fuel blowing lance. As a result, the injected auxiliary fuel is agitated 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 supersonic speeds (M> 1) that generate shock waves as described in Japanese Patent No. 19442, and sufficient auxiliary fuel is supplied at subsonic speeds (0.3 <M <0.8). The auxiliary fuel can be injected into the blast furnace by dispersing and forming a good wide and long raceway. Further, in the case of subsonic speed, the blowing pressure may be lower than in the case of supersonic speed, so that the cost of blower equipment such as a blower and a blow pipe can be kept low.
[0017]
In the present invention, the Laval tuyere having the above-described configuration is provided with 10% or more of the auxiliary fuel blowing tuyere of the entire blast furnace, and the auxiliary fuel is blown, and by providing the Laval tuyere, Auxiliary fuel can be agitated and dispersed from the tuyere into the raceway without impairing the combustibility of the auxiliary fuel, and blown deep into the blast furnace. By the action of such Laval tuyere, the pressure loss of the blast furnace is suppressed, Blast furnace operation with improved air permeability and less occurrence of air pressure fluctuations and slipping of charge is possible, which makes it possible to inject auxiliary fuel into the blast furnace, for example, in the case of pulverized coal, a pulverized coal injection ratio of 150 kg / More than pig iron t, and even pulverized coal injection ratio 200kg / pig iron t to 300kg / pig iron t or more can be stably injected, so the use of expensive coke can be reduced and the coke ratio can be lowered. .
[0018]
In the method for injecting auxiliary fuel into the blast furnace according to the present invention, a plurality of auxiliary fuel injection lances may be set in the Laval tuyere and the same or different types of auxiliary fuel may be injected from each of them. By doing so, auxiliary fuel can be injected into the blast furnace more effectively.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
FIG. 1 is a cross-sectional view showing an outline of a Laval tuyere applied to the method of the present invention. A Laval tuyere 1 has a reduced diameter portion 2 formed at the center thereof, and an inner diameter D2 of the reduced diameter portion 2; When the inner diameter D1 of the inlet portion 3 and the inner diameter D3 of the outlet portion 4 are set, they are formed in a shape that satisfies the relationship D1> D2 <D3. A blow pipe 5 is connected to the inlet 3 side of the Laval tuyere 1, and two pulverized coal blowing lances 6 are passed through the blow pipe 5 at symmetrical positions, and the position of the tip 7 is reduced in diameter. It is attached to the outlet part 4 side slightly from the part 2.
[0021]
The Laval tuyere configured as shown in Fig. 1 above is installed in a large blast furnace (total number of tuyere of 40 tuyere) with an internal volume of 4500m ³ and an output volume of 9000t / d instead of the normal tuyere to inject auxiliary fuel. Carried out. FIG. 2 shows the pulverized powder obtained when the pulverized coal is blown only with the normal tuyere, and the pulverized coal is blown with 60% (24) of all tuyere replaced with the laval tuyere. Relative value of charcoal injection ratio and fluctuation in descent speed of blast furnace interior [relative relative to the fluctuation range of descent speed when pulverized coal injection ratio at normal tuyere is 200kg / pig iron t (= 1) It is a graph which shows the relationship with [value]. Note that the blowing speed before the tuyere at this time is a normal speed, and the subsonic speed of M = 0.4 is calculated in the divergent part on the tip side of the laval tuyere.
[0022]
As can be seen from Fig. 2 above, in the normal tuyere, in the process of pulverized coal injection ratio 150kg / pig iron t to 200kg / pig iron t, the descent speed fluctuation of the blast furnace interior linearly increases, Furnace heat controllability deteriorated. However, when the Laval tuyere according to the present invention is applied to 60% of all tuyere and operated under the same pulverized coal injection conditions, the pulverized coal injection ratio of 150 kg / pig iron t As a result of the stabilization, the pulverized coal ratio is more than about 25% of the maximum pulverized coal injection ratio when only the tuyere is used (at this test stage). The maximum pulverized coal injection ratio was 250 kg / pig iron (t), and the amount could be stably increased.
[0023]
Further, the influence of the tip position of the auxiliary fuel injection lance was investigated using heavy oil and pulverized coal as auxiliary fuel, and the results of the investigation are shown in FIG. Figure 3 shows the relative value of the tip position of the auxiliary fuel injection lance and the wind pressure fluctuation [relative to the standard (= 1) wind pressure fluctuation when the pulverized coal injection ratio at the tuyere is 200 kg / pig iron t FIG. 3 is a graph showing the relationship between the tip position of the auxiliary fuel injection lance and the outside of the furnace when the tip position of the auxiliary fuel injection lance is on the inside of the furnace from the most contracted diameter portion. The fluctuation range of the wind pressure is clearly different. Considering the reason, when the tip of the lance is between the outer diameter of the laval tuyere and the most reduced diameter part, the auxiliary fuel for injection (heavy oil, pulverized coal) is partially The volume of gas passing through this region increases for gasification and combustion, and the unreacted auxiliary fuel interacts with the inner surface of the tuyere and the surrounding gas mass to increase pressure loss and unsteady. This causes a large fluctuation range of the blowing pressure. On the other hand, when the tip of the lance is between the most contracted diameter part of the Laval tuyere and the inside of the furnace, the gasification of the auxiliary fuel and the increase in gas volume due to combustion are caused by the expansion of the flow cross-sectional area of the divergent part. Since the back pressure and its fluctuation are reduced because it is relaxed, it is considered that the fluctuation range of the blowing pressure becomes small. Note that the horizontal axis in FIG. 3 indicates that the most contracted diameter portion of the Laval tuyere is 0 point, the position of the inlet portion is -1, and the position of the outlet portion is 1.
[0024]
In addition, Fig. 4 shows the number of applications of the Laval tuyere configured as shown in Fig. 1 to the large blast furnace from the beginning when 2% of all normal tuyers were replaced and used up to 60%. Ratio and relative value of blast furnace interior descent rate fluctuation (relative value when the fluctuation range of descent rate when the pulverized coal injection ratio at the tuyere is 200 kg / pig iron t is the standard (= 1)) It is a graph which shows the relationship. In addition, when replacing the Laval tuyere, when considering the circumferential balance of the blast furnace (replacement at a substantially symmetrical position with respect to the center of the blast furnace) and when exchanging concentrated in a part of the circumferential direction, Since it became clear that there was a difference in how the effects of the blast furnace operating state appeared, the increase in the pulverized coal injection ratio and the increase in the number of Laval tuyere were carried out in consideration of the circumferential balance of the former blast furnace.
[0025]
As is clear from FIG. 4 above, when the Laval tuyere is replaced by 10% or more of the whole tuyere, it can be seen that the fluctuation range of the descending speed of the blast furnace interior decreases and the descent behavior starts to be improved.
[0026]
According to the method for injecting auxiliary fuel into the blast furnace according to the present invention, pulverized coal injection is performed in the case of pulverized coal as described above by replacing the Laval tuyere with 10% or more of all tuyere. In addition to the function and effect of stably blowing a ratio of 150 kg / pig iron t or more, the following function and effect can be expected.
[0027]
{Circle around (1)} Low-strength coke can be used. That is, when the coke strength is reduced, the generation of powder in the furnace increases, the air permeability deteriorates and the pressure loss in the furnace increases greatly, but by replacing the Laval tuyere with 10% or more of all tuyere, A low-strength coke can be expected because a raceway with a deep extension can be formed in front of the Laval tuyere in the furnace, and the peripheralization of the gas flow can be suppressed.
[0028]
(2): Use of small coke is possible. Using small coke (particle size of 15 mm or less) reduces the average particle size of the blast furnace charge, greatly increases the pressure loss in the furnace, and peripheralizes the gas flow in the furnace. By exchanging more than 50%, it is possible to form a raceway that extends deeply in front of the Laval tuyere and to suppress the peripheralization of the gas flow, so the use of small coke is expected to increase. it can.
[0029]
{Circle around (3)} It is possible to increase the lump ore blending ratio. That is, a lump ore (raw ore), which is one of blast furnace raw ores, has a unique property such as thermal cracking, and cracks are generated in a relatively low temperature region in the furnace to generate a large amount of powder. For this reason, the same problems as in the above (1) and (2) occur. Conventionally, a lump ore with less heat cracking is selected and the lump ore blending ratio (weight ratio of lump ore in the charged ore) is 10 to 20%. However, by replacing the Laval tuyere with 10% or more of all tuyere, it is possible to form a raceway that extends deeply forward in the furnace of the Laval tuyere, and around the gas flow. It can be expected to increase the lump ore blending ratio because it can be expected to suppress crystallization.
[0030]
(4): It is possible to increase the pellet content. Pellets have a spherical shape and therefore have a smaller inclination angle than sintered or massive ores. When multiple pellets are mixed, pellets flow into the center of the furnace, making the gas flow peripheral and softening fusion. Although the pressure loss in the furnace greatly increases due to the W-shaped belt, the raceway has a deep expansion in front of the Laval tuyere in the furnace by replacing 10% or more of the Laval tuyere. And can be expected to increase the blending ratio of pellets because it can be expected to suppress the peripheralization of the gas flow.
(5): Long terrace operation in the bell-less blast furnace becomes possible. In the bell-less blast furnace, the long terrace operation that lengthens the coke terrace (the part where the upper surface of the coke layer is flatly deposited from the furnace wall to the furnace center) has been directed from the viewpoint of controllability of the charge distribution. . However, on the other hand, if the terrace length is increased, the tilt distance of the charge is shortened, the segregation of the charge is weakened, the particle diameter at the center of the furnace is reduced, the central gas flow is lowered, and the gas flow is peripheralized. However, by replacing the Laval tuyere with 10% or more of all tuyere, it is possible to form a raceway that extends deeply in front of the Laval tuyere in the furnace, and suppresses the peripheralization of the gas flow. The long terrace operation in the bell-less blast furnace can be expected from what can be expected.
[0032]
【The invention's effect】
As described above, according to the method for injecting auxiliary fuel into the blast furnace according to the present invention, auxiliary fuel injection into the blast furnace is performed in a larger amount than in the past, for example, in the case of pulverized coal, a pulverized coal injection ratio of 150 kg. / Pile iron t or more, and further, pulverized coal injection ratio 200 kg / pile iron t to 300 kg / pile iron t or more can be stably injected, and the use of expensive coke can be reduced. In addition to these effects, the use of low-strength coke, which has been suppressed by increasing the pressure loss in the furnace, the use of small coke, the increase of the lump ore content, and the increase of the pellet content are expected. it can.
[0033]
In addition, by disposing the tip position of the auxiliary fuel blowing lance closer to the tip of the tuyere than the diameter reducing portion of the Laval tuyere, the hot air passing through the diameter reducing portion is agitated by the tip of the auxiliary fuel blowing lance. Therefore, since the injected pulverized coal is stirred and dispersed in the hot air, the operation is performed by sufficiently dispersing the pulverized coal at the subsonic speed (0.3 <M <0.8) at the divergent part at the tip of the reduced diameter part. It is possible to operate with a low cost of blower equipment such as a blower and a blower pipe.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an outline of a Laval tuyere applied to a method of the present invention.
[Fig.2] The ratio of pulverized coal injection and the blast furnace interior in the case where pulverized coal is blown only with normal tuyere and when pulverized coal is blown instead of Laval tuyere for 60% of all tuyere It is a graph which shows the relationship with the relative value of descent speed fluctuation.
FIG. 3 is a graph showing the relationship between the tip position of an auxiliary fuel injection lance and the relative value of fluctuations in wind pressure.
FIG. 4 is a graph showing the relationship between the ratio of the number of applied Laval tuyere to the blast furnace and the relative value of the descent speed fluctuation of the blast furnace interior.
[Explanation of symbols]
1: Laval tuyere 2: Reduced diameter part 3: Inlet part 4: Outlet part 5: Blow pipe 6: Pulverized coal blowing lance 7: Lance tip

Claims (2)

The pipe between the vicinity of the connection portion of the blow pipe connected to the tuyere and the tip of the tuyere has a reduced diameter portion smaller than the inner diameter of the blow pipe and the inner diameter of the tuyere tip, and the auxiliary fuel blowing lance An auxiliary fuel injection operation method into a blast furnace in which auxiliary fuel is injected from an auxiliary fuel injection tuyere having a tip position disposed closer to the tip of the tuyere than the reduced diameter portion, the auxiliary fuel having the above-described configuration A method for injecting auxiliary fuel into a blast furnace, characterized in that an auxiliary fuel is injected by providing at least 10% of the auxiliary fuel injection tuyere of the entire blast furnace. The method for injecting auxiliary fuel into a blast furnace according to claim 1, wherein a plurality of auxiliary fuel injection lances are set, and the same or different types of auxiliary fuel are injected from each of the auxiliary fuel injection lances.

Images