JPH0978111A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the fluidization of charged material charged into a blast furnace and to achieve the stable operation by obtaining starting velocity of the fluidization of the charged material in the furnace in each charging butch and gas flowing speed distribution in the furnace and maintaining so that the starting speed of fluidization becomes higher than the gas flowing speed. SOLUTION: At the time of charging the charging material from the furnace top of the blast furnace by dividing into plural times, sampling is executed in a fixed period or when the condition of charging material varies. Grain size distribution and density distribution of the charged material are measured, and based on these, the starting speed of fluidization umf of the charged material is obtd. At the same time, the gas flowing speed distribution ug in the furnace diameter direction is measured, and at least one of the grain size distribution and density distribution of charged material, charged material distribution and hot blast quantity blown from tuyeres of the blast furnace is adjusted. The operation is executed while maintaining so that the starting speed of fluidization umf is higher than the gas flowing speed ug in the furnace. By this method, the stable blast furnace operation is continuously executed in a low fuel ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace operating method for preventing fluidization of a charge charged into a blast furnace and achieving stable operation.

[0002]

2. Description of the Related Art In a blast furnace operation, it is not possible to maintain an appropriate distribution of the charge in the furnace radial direction at the top of the blast furnace, and to maintain the gas flow velocity distribution in the furnace and the reduction state of the charged raw material within an appropriate range. , Is extremely important in achieving stable operation. In order to achieve stable operation of this blast furnace, at least the fluidization phenomenon of the charged raw fuel (in the mixture of solid and gas or liquid, the drag force exerted by the moving fluid on the solid particles overcomes gravity and moves as if it were a fluid). It is necessary to prevent this. Therefore, the following three types of methods have been conventionally proposed.

First, the proposal 1 measures the gas composition and / or temperature distribution in the furnace in the diameter or height direction of the furnace by using a sonde, estimates the in-furnace state from the measured value, and based on this, the equipment is installed. It controls the distribution of incoming particles and the blowing conditions. Proposal 2 also measures the layer thickness distribution of the charge using an ultrasonic profile meter, estimates the in-furnace state from the measured values, and controls the charge distribution and blast state based on this. It is a thing. Furthermore, Proposal 3 measures the fluidized state of the charged material using the image fiber in the furnace, and controls the air permeability of the fluidized site based on this.

As an example of the above three proposals, Japanese Patent Publication No. 61-21
No. 284, Japanese Patent Publication No. 62-224608, and Japanese Patent Publication No. 64-8207. Japanese Patent Publication 61-2
In 1284, the observation data relating to the in-reactor gas at an arbitrary point in the in-reactor radial direction obtained in the past is divided into a central flow group, a peripheral flow group, and an arbitrary number of gas flow groups in between, and each observation is performed. A method of detecting the gas flow velocity distribution in the blast furnace from the data group by the discriminant function method is disclosed.

In Japanese Patent Publication No. 224608/1987, the deposition angle of the raw material, the gas flow velocity distribution in the radial direction of the blast furnace, the unloading velocity distribution, and the particle size distribution of the raw material in the radial direction of the blast furnace are measured and based on the measured values. There is disclosed a method of estimating the cohesive zone shape in the furnace and controlling the charging of the raw fuel so that the estimated cohesive zone shape becomes a preset cohesive zone shape. Further, Japanese Examined Patent Publication (Kokoku) No. 64-8207 discloses a method of controlling the air permeability at a place where a charge layer having a small particle size is charged to be below the fluidization start air permeability.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to the methods disclosed in JP-A 1-212284 and JP-B-62-224608, it is difficult to determine or predict the fluidization of the furnace interior contents. That is, in the method proposed in Japanese Patent Publication No. 61-21284, the discriminant function method using the estimation calculation using the gas composition and the gas temperature is adopted as the means for detecting the gas flow velocity in the specific gas flow group in the furnace. Therefore, even if the charged raw fuel is fluidized, the gas composition and temperature may be normal and the fluidization could not be determined. The reason is that the measured values of the gas composition and the gas temperature used in the estimation calculation are affected by the gas flow rate and the ore / coke layer thickness ratio of the same gas flow group, and the gas flow rate may vary depending on the ore / coke layer thickness ratio. It is to show a normal value even if the fluidization start speed is exceeded.

Further, in the method proposed in Japanese Patent Publication No. 62-224608, the shape of the cohesive zone in the furnace is determined based on the measurement data of the gas flow velocity distribution in the furnace radial direction, the unloading speed and the particle size distribution of the raw material. From the estimation, if the measurement data fluctuates due to the fluidization phenomenon, it cannot be used for the operation. Further, the Japanese Patent Publication No. 64-82
In the method disclosed in Japanese Patent Publication No. 07, since the air permeability is controlled only at the place where the charge layer having a small particle size is charged, other places such as a charge having a relatively large particle size are charged. It was impossible to suppress fluidization of the central part in the radial direction of the furnace.

According to the present invention, the fluidization initiation speed is obtained by using the measured values of the particle size distribution and the density distribution of the raw fuel charged from the furnace top, while the sonde is used to determine the radial direction of each charging batch. By measuring the gas flow velocity distribution in the furnace, it is possible to accurately detect the signs of fluidization of the furnace interior charge and adjust the particle size of the charge or the distribution in the furnace radial direction to achieve stable operation of the blast furnace. It is what

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the means therefor is a blast furnace operating method in which the charge is divided into a plurality of times and charged from the top of the blast furnace. The particle size distribution and density distribution of the charge in each charging batch are measured, the fluidization start speed u _mf of the furnace internal charge is determined based on the measured values, and the gas flow velocity distribution u in the furnace in the radial direction is also measured. _{It is characterized} by measuring _g and adjusting at least one of the particle size distribution of the charge, the density distribution, the charge distribution, and the amount of hot air blown from the tuyere of the blast furnace to maintain the following relationship while operating. According to the blast furnace operating method. _Fluidization start velocity u _mf ＞ Furnace gas flow velocity u _g

At this time, the particle size distribution and the density distribution of the charged material may be measured periodically or when the charged material conditions are changed. Then, this particle size distribution is measured, for example, by using a plurality of sieve screens having different meshes in a relationship between the amount on the screen and the amount under the screen, and the density distribution is the true specific gravity for each particle size of the charge. Can be measured and determined using a hydrometer.

The particle size and density of the charge charged from the furnace top are
This is an important factor in determining the fluidization initiation rate, and generally, the smaller the particle size and the greater the density, the easier the fluidization.
Further, the fluidization start speed u _mf can be obtained by the following equation (1), for example. u _mf = {gφ _s ² D _p ² / 2k} × {(ρ _p −ρ) / μ} × {ε _mf ² / (1−ε _mf )} (1) ρ _p : Charge Density ρ: Density of the gas in the furnace g: Acceleration of gravity μ: Viscosity of the gas in the furnace φ _s : Shape factor of the charge D _p : Average diameter of the charge ε _mf : Porosity in the packed bed of the charge k :constant

From this, the particle size distribution and density distribution of each of the sinter, agglomerated iron ore, ore such as pellets or coke charged from the furnace top of the blast furnace are measured, and these measured values are referred to the above ( Substituting into equation 1), the fluidization start speed u _mf for each charging batch is determined. The fluidization initiation speed is, for example, 14.0 m / s when the coke has a density of 1000 kg / m ³ and a particle size of 50 mm, and is 8.1 m / s when the ore has a density of 3600 kg / m ³ and a particle size of 20 mm. Furnace gas flow velocity distribution u _g of Ro径direction is measured using a furnace top Zondegasu anemometer provided in the blast furnace top.

[0013]

[Operation] During operation of the blast furnace,
For example, the fluidization start velocity u _mf obtained by the above equation (1)
And the in-furnace gas flow rate u measured by the above-mentioned furnace top sonde gas anemometer
comparing _g, if u _mf> u _g, charge does not cause fluidization, operation is normal. However, when u _g rises to u _mf = u _g , the charge at that site starts to fluidize. If a u _mf <u _g more u _g is increased, charge is vigorously fluidized, finally blow (the charge in the furnace is discharged from the furnace top is conveyed to the gas flow rate) And caused inoperability.

[0014] The fluidization can detect the signs in advance by managing u _mf and u _g during operation. That is, when u _g / u _mf rises and approaches 1 during operation,
In order to prevent the liquidation expected in the near future,
than is to maintain fluidization velocity u _mf> furnace gas velocity u _g in lowering the u _g / u _mf.

There are three control means for reducing u _g / u _mf . One of them is a gas flow velocity in a portion where fluidization occurs in the furnace radial direction or has a symptom thereof by controlling the distribution of the charge from the furnace top in the furnace radial direction, for example, by using an armor plate. Is to lower. By lowering the furnace gas flow rate u _g, it is possible to decrease the u _g / u _mf when fluidization velocity u _mf is the same.

The second is to improve the particle size or density of the charge from the furnace top. According to the above equation (1), the fluidization initiation speed u _mf increases in proportion to the square of the particle size of the charge and is proportional to the density of the charge. Accordingly, when improving the particle size or density of the charge, since the u _mf is increased, it can be the same u _g to reduce u _g / u _mf.

The third is to reduce the superficial gas velocity in the furnace. By this method, since the furnace gas flow rate is decreased over the Ro径direction throughout over the Ro径direction throughout u _g
/ _Umf can be reduced.

In the case of a bell-armor type blast furnace, the charge distribution control in the furnace radial direction is generally performed by changing the angle of the armor. In addition, the particle size and density of the charge can be controlled by further increasing the particle size of the raw fuel at a specific part, that is, the part with a relatively large particle size that flows into the central part of the furnace where fluidization is easy, or by using a dense material such as pellets or a large size. There is a method of increasing the mixing ratio of a raw material having a high particle size such as a lump ore.
The decrease of the superficial gas velocity in the furnace is to avoid fluidization by decreasing the air flow rate or increasing the furnace top pressure at the expense of the productivity of the blast furnace.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described in detail with reference to FIGS. First, a sonde for directly measuring the gas flow velocity distribution in the furnace radial direction of the blast furnace will be described with reference to FIGS. 2 and 3. This is to install a plurality of venturis 3 and 4 on a sonde 1 which is movable in the furnace radial direction on the upper surface of the massive zone of the blast furnace shaft, and to measure the gas flow velocity distribution immediately after charging the raw fuel. It is provided so that it can be inserted into and taken out of the furnace at an insertion angle of 25 ° from the above, whereby the streamline direction of the gas in the furnace that has risen in the charging material 2 in the blast furnace (may be considered to be almost perpendicular to the charging material) and The angles formed by the center lines a and b of both venturis 3 and 4 can be made substantially parallel.

The venturi 3 is a high speed type with a diaphragm ratio of 2.5, which is provided at the tip of the sonde 1, and the venturi 4 is a low speed type with a diaphragm ratio of 4.0, which is provided in the middle of the sonde 1. 3
a is a temperature measuring sensor projecting from the outlet side 3o of the high-speed venturi 3 and 3b is a static pressure side conduit whose one end communicates with the throttle 3s of the high-speed venturi 3 and the other end communicates with the differential pressure transmitter 8a. 3c has an end portion 3i of the high-speed venturi 3 at one end.
To the differential pressure transmitter 8a, and a pressure measuring sensor 4a projecting from the outlet side 4o of the low-speed venturi 4 and one end of the low-speed venturi 4b.
Of the static pressure side conduit 4c, which communicates with the throttle portion 4s and the other end of which communicates with the differential pressure transmitter 8b. One end of the static pressure conduit 4c communicates with the inlet side part 4i of the low-speed venturi 4 and the other end communicates with the differential pressure transmitter 8b. All pressure side conduits, 7a and 7b are pressure equalizing valves, 9a and 9b are N
₂ Purge gas introduction valve, 10 is a differential pressure converter, 11 is a gas flow rate calculator, 12 is a furnace top pressure gauge, and 13 is a large bell.

[0021] Then, the blast furnace internal volume: 5,245m ³ blowing amount: 7,900Nm ³ / minute blower moisture: 25g / Nm ³ oxygen addition amount: 10,000Nm ³ / time pulverized coal blown amount: 120kg / t-pig tapping amount: 12,000 t / day Charge mode of charge: C (coke) C (coke) O
(Ore) O (Ore).

In general blast furnace operation, the gas flow velocity near the center of the furnace is the highest, and there is a high possibility that ores will be fluidized in this region. During the operation of the blast furnace, it was often observed that the gas flow velocity at this site fluctuated greatly, and a more detailed analysis revealed that at this time, the ore was present on the top of the charge, and normal-quality coke was extremely fluid. It turned out to be difficult to turn into. Fig. 1 is an example of measurement of the top gas velocity in the center of the furnace measured using the top sonde 1 installed at the top of the blast furnace.
Shown in

Immediately after charging the coke, the gas flow velocity is about 12 m /
s is less than 14 m / s, which is the fluidization start speed, and the amount of fluctuation is small and stable, indicating that no fluidization phenomenon has occurred. However, the gas flow velocity immediately after charging the ore is about 8 m / s, and the fluctuation range is large. Therefore, when the fluidization start speed of 8.1 m / s is exceeded, fluidization may occur. I understand. Therefore,
If the properties of the charge are not changed, it is necessary to keep the gas flow rate in this part during operation to 8.1 m / s or less in order to maintain the production amount.

Since the blast furnace adopts a 4-batch charging method by the bell method, the correlation tendency between η _CO and the gas flow rate differs for each charging batch. For stable operation of the blast furnace, it is necessary to minimize the gas flow rate fluctuation amount for each batch.
About 8 m / s at gas flow rate, 7 to 17% for η _CO
Is found to be appropriate.

In order to reduce the fuel ratio of the blast furnace, it is necessary to increase η _CO at this portion, but if it exceeds 17%, the gas flow velocity fluctuation for each batch becomes large, and
In particular, immediately after charging the second batch (O2) of the ore, the gas flow velocity exceeds the fluidization start speed of 8.1 m / s and fluidization of the ore occurs, which makes stable operation difficult. On the contrary, when η _CO is lower than 7%, the gas flow velocity immediately after charging the first batch (O1) of the ore may be equal to or higher than the fluidization start speed of the ore of 8.1 m / s. However, since coke collapses in the center of the furnace, the fluidization phenomenon is unlikely to occur like ore. However, in this case, stable operation becomes difficult because the difference in gas flow velocity between batches becomes large.

The control value of the gas flow velocity at the center of the blast furnace is 8 because the average particle size of the ore is 20 mm.
m / s ± 1 m / s. In case of deviation from this control range, the stable operation of the blast furnace will be continued by taking the measures described below. Since the relationship between the gas flow velocity and η _{CO at} the same site varies depending on the target blast furnace, raw material quality and blowing conditions, it is desirable to determine the above control values by collecting data in advance.

(Example 1) Table 1 shows an example of particle size distribution of O2 charged in a blast furnace. In Table 1, O charged in the center of the furnace
2 is a relatively large particle size portion, and the ratio of the ore particle size +35 mm is usually about 6.5%, and the particle size is 35 to 25.
The ratio of mm is about 10.0%. However, when changing to a sintered ore having a different grain size composition, the grain size decreases as shown in Table 1, and accordingly, the fluidization start speed of the furnace center immediately after O2 charging is from 8.1 m / s to 7. It was 5 m / s, which was lower than the in-reactor gas flow rate of 8.1 m / s actually measured by the Sonde 1, so it was judged to be a fluidization phenomenon (point in FIG. 4A).

For this reason, in order to increase the portion of the O2 particle size having a relatively large proportion, the agglomerates are mixed at a mixing ratio of 11% to 1
It increased to 4% (in Table 1) and increased the fluidization initiation speed in the center of the furnace. As a result, the fluidization start speed in the central part of the furnace became 8.1 m / s, the fluidization phenomenon became calm, the reducing gas utilization rate in that part became around 10%, and the fuel ratio was 483 kg / t-pig. To 479 kg / tp
ig, and the furnace conditions were stable (point in Figure 4B).

[0029]

[Table 1]

(Example 2) O2 pellet compounding ratio was 4%
During operation of the blast furnace at 8, the gas flow velocity in the furnace (measured value at Sonde 1) in the center of the furnace immediately after O2 charging was 8.
It increased from 1 m / s to 9.9 m / s, and exceeded the fluidization initiation speed of 8.1 m / s calculated by the above formula (1) (Fig. 4C).
point). For this reason, the pellet mixing ratio of O2 is 7% (Table 2
) To 9% (Table 2), the fluidization start speed in the central part of the furnace is increased to 9.0 m / s and
The gas flow velocity in the furnace was lowered to 6.5 m / s. As a result, the fluidization phenomenon in the central part of the furnace disappeared, the reducing gas utilization rate in that part was around 12%, and the fuel ratio was 479 kg /
It decreased from t-pig to 469 kg / t-pig, and the furnace condition was stable (point in FIG. 4D).

[0031]

[Table 2]

(Embodiment 3) As shown in FIG. 5, the armor plate modes (2411) and (2418) are used together (the degree of use is 2: 3) (to the CCOO in the charging mode of the charging material). Correspondingly, it is a value indicating the number of each notch of the armor plate, and the larger the value, the closer the dropping position of the charge kicked and charged by this is closer to the center of the furnace.) The gas flow velocity (measured value with sonde 1) in the center of the furnace immediately after charging O1 exceeds 14.0 m / s, which is the fluidization start speed of the coke calculated by the equation (1), and is 15.0 m / s.
And a fluidization phenomenon was observed in the center of the furnace (Fig. 4E
point). Therefore, as shown in FIG. 4, the use mode of the armor plate was changed to the combined use of (2511) and (2518), and the use degree was changed to 1: 3 to promote the kick amount of C2 to the center of the furnace. (Fig. 5). As a result, the fluidization phenomenon in the central part of the furnace disappeared, the reducing gas utilization rate in that part became around 10%, and the fuel ratio increased from 469 kg / t-pig to 471 kg / t-pig, but the reactor condition remained unsatisfactory. It escaped (point in Figure 4B).

(Example 4) During operation at an air flow rate of 7900 Nm ³ / min, the gas flow velocity in the central part of the furnace immediately after the introduction of O 2 increased to 10 m / s (point G in FIG. 4). At that time, since there was not enough time to take the above-mentioned three examples, as a measure for emergency evacuation, the air flow rate was reduced to 7570 Nm ³ / min, so that the gas flow velocity in the central part of the furnace immediately after O 2 charging was about 9 m / s. To below the fluidization initiation rate. After that, the air flow rate was adjusted to 79 while using the third embodiment together.
Recovered up to 00 Nm ³ / min, fuel ratio 471 kg / t-
Stable operation was possible with the pig as it was (point H in Fig. 4).

[0034]

EFFECTS OF THE INVENTION According to the present invention, it is possible to easily understand the fluidization phenomenon of the charge and the stable state of the gas flow velocity in the furnace, and it is possible to continuously perform stable blast furnace operation at a low fuel ratio. Is played.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a gas flow velocity in a furnace and a fluidization start speed.

FIG. 2 is a vertical sectional view of a blast furnace according to this embodiment.

[Figure 3] Side sectional view of the sonde

[Fig. 4] Flow velocity of reducing gas and reducing gas utilization rate (η
_CO ) relationship diagram

FIG. 5 is a diagram showing the relationship of the relative layer thickness of C2 in the furnace diameter method when the armor plate is adjusted.

[Explanation of symbols] 1 Sonde 2 Charge in blast furnace 3 Sonde tip Venturi part 3a Temperature sensor 3b Total pressure side conduit 3c Static pressure side conduit 3o Venturi outlet side 3i Venturi inlet side 3s Venturi throttle 4 Sonde middle Venturi part 4a Temperature sensor 4b Full pressure side conduit 4c Static pressure side conduit 4o Venturi outlet side 4i Venturi inlet side 4s Venturi throttle part 7a Pressure equalizing valve 7b Pressure equalizing valve 8a Differential pressure transmitter 8b Differential pressure transmitter 9a Purge gas introducing valve 9b Purge gas introduction valve 10 Differential pressure converter 11 Gas flow rate calculator 12 Furnace top pressure gauge 13 Large bell MA Armor plate BF Blast furnace

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinroku Matsuzaki 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Takeshi Nakayama 1st Nishinosu, Oita City, Oita Prefecture New Japan Oita Steel Works, Ltd.

Claims (1)

[Claims] 1. In a blast furnace operating method in which the charge is divided into a plurality of times and charged from the top of the blast furnace, the particle size distribution and density distribution of the charge in each charging batch are measured, and the measured values are used as the basis. with obtaining the fluidization velocity u _mf of the furnace interior container to measure the Ro径direction of the in-furnace gas flow velocity distribution u _g, particle size distribution of the charge density distribution, burden distribution, blast furnace tuyeres A method for operating a blast furnace, characterized in that at least one of the hot air volumes blown from is adjusted to operate while maintaining the following relationship. _Fluidization start velocity u _mf ＞ Furnace gas flow velocity u _g