JPH1072607A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the erosion of a brick and to prolong the service life of a blast furnace by always lowering blasting quantity from a tuyere at the upper part, and also, blowing water from the tuyere to a position where the erosion of the brick at the side wall part of a furnace bottom is predicted. SOLUTION: At the side wall part of the furnace bottom in the blast furnace, the blasting quantity of the tuyere 4 positioned at the upper part to the position where the local erosion of the brick caused by molten iron is predicted, is reduced. At the same time, water or steam is blown from this tuyere 4 and the temp. in the front of the tuyere is restrained to that equal to or lower than the temp. in the front of the other tuyeres. At this time, the water or steam quantity blown from the tuyere 4 is desirably made to about 60g/Nm<3> . By this method, the raising of the temp. of the molten iron 6 dripped to the furnace bottom from this position can efficiently be restrained to also restrain the damage to the refractory brick.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a blast furnace for suppressing erosion of bricks on a bottom wall of a blast furnace.

[0002]

2. Description of the Related Art In recent years, the technology for repairing a blast furnace furnace body has been advanced, so that the portion above the tuyere is repaired even if the furnace is in operation, periodically or as required when the wind is shut off.
The furnace body can be maintained. However, for the lower part of the blast furnace below the tuyere,
Due to the presence of slag and the difficulty of removing the contents at this site, it is almost impossible to repair the damaged part during operation.

[0003] Therefore, it can be considered that the degree of damage to the lower part of the blast furnace determines the life of the blast furnace. In order to extend the life of the blast furnace, it is necessary to suppress damage to the lower part of the blast furnace, and in particular, to prevent damage to the lower part of the blast furnace. It is a very important task to prevent further damage to bricks at the site where the remaining thickness is locally reduced. The damage to the lower part of the blast furnace means mainly the wear of refractory bricks installed on the inner surface of the furnace by hot metal, and the suppression of the damage means to suppress the wear of the bricks.

Various methods have been implemented as means for suppressing the wear of the refractory bricks. For example, the following method can be used.

[0005] a) Protecting the brick by enhancing the furnace bottom cooling and forming a solidified layer on the surface of the brick, and suppressing its wear.

B) Increasing the charging amount of the titanium-containing iron source material into the furnace or blowing the titanium-containing ore from the tuyere to increase the viscosity of the hot metal, thereby reducing the flow rate of the hot metal, Control wear.

C) The amount of hot air is adjusted by adjusting the opening of the tuyere diameter or adjusting the hot air control valve to reduce the amount of hot metal dripped near the bottom wall of the furnace, thereby suppressing brick wear.

[0008] Among them, the method a) requires a long time for the effect to be realized, and in many cases, the effect is not clear, and it is difficult to take local countermeasures for the damaged portion. There is. B)
In addition to the cost increase and the danger of hindering the operation of the blast furnace, the method of (1) has the following local measures, as in a), except for the injection of titanium-containing ore from the tuyeres. There is a problem that it cannot be adopted.

[0009] On the other hand, in the method c), by adjusting or completely closing the tuyere diameter, it is possible to reduce the amount of air blow or to stop the air blow. This is effective in suppressing wear of the furnace bottom side wall bricks, and there is no particular problem in terms of cost. Normally, the adjustment of the opening of the tuyere diameter or complete closing can be performed only when the wind is shut off. However, according to the method using the hot air control valve disclosed in Japanese Patent Application Laid-Open No. 60-243207, the stop of the air blowing is not possible. Although it is not possible, it is possible to freely adjust the amount of air blow even when the wind is not closed. Also, since it is not necessary to apply to all tuyeres, this method can be implemented as a local measure.

As described above, the above-mentioned method c) is advantageous in many respects, but the use of a hot air control valve requires an initial investment for it, and also requires high PCI (pulverized coal injection). During operation, the following problems also surface.

[0011] Under the recent high PCI operation, oxygen is enriched in the hot air to be blown.
Equipment for controlling the amount of C (pulverized coal) injected and the amount of oxygen enrichment for each tuyere is not usually provided. Therefore,
If the blow volume is reduced by the hot air control valve at a specific tuyere, the PC blows the same amount as the other tuyere at that specific tuyere, or stops blowing PC only at that tuyere. Will be either. When PC injection is performed, the combustion rate of PC is significantly reduced at the specific tuyere, and when PC injection is stopped, the tuyere front temperature is expected to rise extremely at the tuyere, In the former,
Accumulation of furnace powder (unburned coal), in the latter case, there is a concern that the cohesive zone (the region where the ore is softened and melted and reduced to drop hot metal) and the temperature of the dropped hot metal may increase accordingly.

As described above, suppressing the wear of the refractory bricks installed on the inner surface of the furnace bottom side wall due to the hot metal,
This is an extremely important issue in extending the life of the blast furnace. Moreover, in order to prevent further damage to bricks where the remaining brick thickness has been locally reduced due to the damage that has already occurred, as a local measure, it is effective to wear effectively over a long period instead of a short period. It is necessary to continue taking restraint measures. However, the conventional measures for suppressing the damage to bricks have not always been satisfactory.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation. In the furnace bottom side wall, a portion where a local erosion due to hot metal of brick is predicted is considered. Effectively suppresses brick wear quickly and, for parts where the remaining thickness of refractory bricks has already been reduced locally due to hot metal wear, effectively prevents further wear of the bricks in that part for a long period of time. It is an object of the present invention to provide a method of operating a blast furnace that can be suppressed to a minimum.

[0014]

Means for Solving the Problems As a result of repeated studies to achieve the above object, the present inventors have found that, as will be described in detail later, a portion where brick erosion is predicted or a remaining thickness of brick is considered. The present inventors have confirmed that it is effective to reduce the amount of air blown from the tuyere in the vicinity of the portion determined to be less and to blow water or water vapor, and have accomplished the present invention.

The gist of the present invention resides in the following blast furnace operating methods (1) to (3).

(1) For a part where brick erosion is expected on the bottom wall of the blast furnace, the amount of air blown from the tuyere located above the part is constantly reduced, and water or steam is blown from the tuyere. By controlling the amount and temperature of hot metal dropped on the furnace bottom at this site,
A method of operating a blast furnace to suppress erosion of bricks on the bottom wall of the blast furnace.

(2) The furnace bottom wall temperature is measured by a plurality of thermometers installed on the blast furnace bottom wall, and when the measured temperature exceeds a control value, the tuyere located above the temperature rising point is sent. The erosion of bricks on the blast furnace bottom wall is characterized by controlling the amount and temperature of hot metal dropped on the furnace bottom at this location by lowering the air volume and blowing water or steam from the tuyere. How to operate blast furnace to control.

(3) For the part where the brick thickness on the bottom wall of the blast furnace is locally small, the amount of air blown from the tuyere located above this part is reduced, and water or steam is blown from the tuyere. By controlling the amount and temperature of hot metal dropped on the furnace bottom at this site,
A method of operating a blast furnace to suppress erosion of bricks on the bottom wall of the blast furnace.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The method of operating a blast furnace according to the present invention (methods (1) to (3) above) will be described in detail below.

FIG. 1 is a view schematically showing a state of a lower part of a blast furnace. As shown in the figure, the lower part of the blast furnace is composed of carbon bricks 2 protected by a steel shell 1 and chamotte bricks 3 laid on the furnace bottom. A PC injection lance 5 is attached to the furnace bottom side wall 8. Tuyere 4 is provided.

At the bottom of the furnace, a coke packed bed and hot metal dropped from the cohesive zone are stored. At the time of tapping, a taphole is provided at a portion indicated by reference numeral 7 and tapping is performed. In addition, the broken line in the figure is the brick surface at the time of furnace construction. In the state shown in the figure, as shown by the maximum erosion line 10, the bottom wall of the furnace is greatly eroded, and the remaining thickness of the refractory brick is significantly reduced locally. It has been done.

Although the mechanism of wear of refractory bricks at the bottom wall of the blast furnace is not completely elucidated, the wear of the bricks occurs at the contact surface with the hot metal, and depends on the temperature and flow rate of the hot metal. It is known to be greatly affected. When the hot metal temperature is high and the hot metal flow rate is high, the wear becomes severe.

Therefore, in a portion where local erosion of the refractory brick is predicted, wear of the brick in that portion is promptly suppressed, or in a portion where the remaining thickness of the brick is locally reduced, a further increase is made. In order to suppress the wear over a long period of time, it is considered effective to lower the temperature and the flow velocity of the hot metal at the location and in the vicinity thereof.

The present inventors have conducted many actual furnace tests,
If the amount of air blown from the tuyere located above the place where it is particularly desired to prevent wear of the refractory brick at the lower part of the blast furnace is reduced by reducing the tuyere diameter or reducing the opening of the hot air control valve, the vicinity of the wall side It was confirmed that the amount of hot metal dripped at the part was reduced, the amount of heat flowing down the part and entering the furnace bottom was reduced, and the temperature of the hot metal at the part was lowered, effectively acting on brick wear control.

By the way, when the amount of air blown from the tuyere is reduced, the charge descending speed at the upper part of the tuyere is reduced, so that the heat flow ratio is reduced and the cohesive zone on the side wall side (here, the furnace wall) is used. (Refers to the position of the cohesive zone on the side). In addition,
The heat flow ratio is represented by the following equation.

Heat flow ratio = heat capacity of falling charge / heat capacity of rising gas (≡Cs · Ws / Cg · Vg) where Cs: specific heat of charge (kcal / kg · ° C.) Cg: specific heat of gas (kcal / Nm ³ · ° C) Ws: Amount of charge drop (kg / h) Vg: Amount of gas rise (Nm ³ / h) The above cohesive zone reduces ore that has been softened and fused by heating. The hot metal liquefied in this cohesive zone rises due to heat exchange with hot gas while dropping toward the hearth while traveling between the particles in the lower coke layer. Therefore, it is considered that the longer the dropping distance and the higher the tuyere front temperature, the higher the dropping hot metal temperature.

Therefore, the rise of the cohesive zone described above is an unfavorable phenomenon from the viewpoint of suppressing the wear of the refractory brick.

In recent years, since high PCI operation has become popular and oxygen is being enriched, measures are taken to reduce the amount of air blown from the tuyere, and the accumulation of unburned coal in the furnace is prevented. Therefore, when PC blowing is stopped, as described above, the tuyere front temperature of the tuyere with the reduced air flow increases, and the rise of the cohesive zone and the accompanying rise in the temperature of the dropping hot metal are further accelerated.

However, by reducing the amount of air blown from the tuyere and blowing water or steam from the tuyere, the temperature before the tuyere is suppressed to be equal to or lower than the temperature before the tuyere of another tuyere. Combined with the decrease in the amount of hot metal dripped due to the decrease in the amount of blown air and the resulting drop in hot metal temperature, the rise in temperature of hot metal dripped from the location to the furnace bottom is significantly suppressed, effectively reducing the wear of refractory bricks. It was found that it could be suppressed.

In this case, the amount of water or steam blown from the tuyere is preferably limited to 60 g / Nm ^{3 in view} of oxygen enrichment, and it is not necessary to simply blow a large amount. This is because, if the amount of water or steam blown is too large, unreduced FeO may fall in front of the tuyere due to a local decrease in the cohesive zone. Specifically, it is preferable to control the amount of water or steam blown from the tuyere so as to be equal to the tuyere pre-temperature of the tuyere for which the air volume is not controlled. It varies slightly depending on the blast furnace, but 0-60
It is preferably in the range of g / min.

As described above, the reduction in the amount of air blown at the specific tuyere and the injection of water or steam have a remarkable effect on the prevention of wear of the brick located below the tuyere at the lower part of the furnace. Therefore, the tuyere located above the part where the local erosion of the refractory brick in the lower part of the blast furnace is predicted (the part where the wear of the brick is likely to progress) is reduced and the blowing of water or steam is reduced. Performing the operation is effective as a preventive measure against brick erosion on the bottom wall of the blast furnace. This is the operation method (1).

It is effective to always carry out the above-mentioned reduction in the amount of blown air and blowing of water or steam as a preventive measure against brick wear.

In the above method (2), thermometers are installed at a plurality of locations on the bottom wall of the blast furnace, and when the temperature rises at a specific portion of the bottom wall of the furnace and this temperature exceeds a control value, This is an operation method in which the amount of air blown from the tuyere located above the temperature rising portion is reduced and water or steam is blown from the tuyere. According to this method, it is possible to accurately grasp a place where the brick is likely to be worn on the furnace bottom side wall,
This is advantageous because efficient and precise measures can be taken.

According to the method (3), the amount of air blown from the tuyere located above the portion of the blast furnace bottom side wall portion where the brick thickness is locally small is reduced and the tuyere is removed from the tuyere. This is an operation method that blows water or steam. Thereby, further wear of the brick in that part can be effectively suppressed for a long period of time.

In this case, the determination of a portion where the remaining brick thickness is thinner than the other portions can be made by calculation using temperature measurement data by a thermometer installed at the same portion, measurement using elastic waves, or the like.

In carrying out the method of the present invention, the tuyere for reducing the amount of blown air and blowing steam or the like is a tuyere located above a portion where erosion of refractory bricks is predicted or a portion where the remaining brick thickness is small. If you take measures such as reducing the amount of steam blown when the solidification layer has developed,
Naturally, the effect can be maintained for a long time.

In addition, when several tuyeres for reducing the amount of air blow and for blowing steam or the like are continuous, the unloading speed of the charge becomes slow, and a circumferential deviation occurs. Since the effect of controlling the distribution of the charged material at the mouth is lost, in such a case, it is preferable to keep the amount of air blown to 1/2 or more of the normal tuyere without extremely decreasing.

[0038]

【Example】

(1) Example of model calculation First, a blast furnace integrated simulator (3D mathematical model of blast furnace) to confirm the effect of the method of the present invention by model calculation.
Was calculated. In this calculation, it is assumed that the temperature rise of a specific portion of the furnace bottom side wall is detected by a thermometer, and the above-described measures for suppressing the temperature rise are taken for this portion.

The operating parameters used for the calculation are shown in Table 1, and the model shape at the tuyere level is shown in FIG.

[0040]

[Table 1]

The calculation was performed under the conditions shown in Table 2. Case 1
Is the tuyere No. 1 to No. In both cases, air blowing and PC blowing were performed under the same conditions, and this was used as a base. In cases 2 to 5, the tuyere immediately above the site where the furnace bottom side wall temperature increased was No. 4. 1 and No. No. 2 is assumed.
1 and No. In this case, the amount of air blown from the tuyere 2 is reduced compared to the amount of air blown from other tuyeres, and the blowing of PC is stopped.

In cases 2 to 5, as the amount of air blow decreases,
No. 1 and No. It is estimated that the unloading speed of the charge immediately above the tuyere 2 decreases and the cohesive zone on the side wall rises. Then, steam was blown in Cases 3 to 5 in order to suppress an increase in the temperature of the dropping hot metal due to the rise of the cohesive zone.

Table 2 also shows the calculation results.

[0044]

[Table 2]

As is clear from these results, Cases 2 to
In No. 5, the dropping amount of the hot metal was reduced to about 70 as compared to the case where Case 1 was set to 10, but the dropping hot metal temperature increased by 48 ° C. in Case 2 where steam was not blown, as compared to Case 1. This is because N
o. 1 and No. It is presumed that the speed of unloading the charged material immediately above the tuyere 2 was reduced, and the cohesive zone was raised due to a decrease in the heat flow ratio.

Case 3 is a case where steam is blown at a rate of 20 g / min to suppress the rise in the temperature of the dropping hot metal in Case 2.
It could be kept at 7 ° C. The effect was even greater in Case 4 in which the steam was blown in at a rate of 40 g / min, and the hot metal temperature was lower by 10 ° C. than in Case 1.

However, the amount of steam blown was 60 g / m
In the case of “in” (case 5), although the dropping hot metal temperature further decreased, unreduced FeO was present in the raceway, which was not preferable. However, the evaluation of the upper limit changed by changing the operation specifications.

When the effect of lowering the dropping hot metal temperature was evaluated based on the calculation results of the above three-dimensional mathematical model of the blast furnace, “case 4> case 3> case 2” was obtained, and the effect of steam injection was confirmed. However, if the blowing amount is too large, the above-mentioned adverse effects occur, which is not preferable.

Note that the above calculation example corresponds to No. 1 and N
o. It is assumed that the furnace bottom wall temperature in the lower part of the tuyere 2 rises. In the same manner as above, the effect of water vapor blowing when the remaining brick thickness is thinner than other portions can be confirmed.

(2) Actual furnace test example An actual furnace (furnace volume: 4800) based on the above model calculation results
(m ³ blast furnace), the effect of the method of the present invention was investigated.

The temperature of each part of the furnace bottom side wall was monitored by a plurality of thermometers installed on the furnace bottom side wall, and one of the following measures was taken when the measured temperature exceeded the control value. Note that the measure C is the method of the present invention.

A) A titanium source (solel flux, lutel, iron sand, etc.) is blown from the tuyere.

B) The amount of air blown from the tuyere located above the temperature rising portion is reduced to half.

C) The amount of air blown from the tuyere located above the temperature rising portion is reduced to １ ／, and steam is blown from this tuyere (the steam blow is lower than the theoretical combustion temperature at other tuyeres). And the amount of blowing was determined each time).

Then, the number of days (the number of days until the measured temperature exceeding the control value returns to the control value or less) until the effect of each of the above measures appears was determined, and the average number of days was compared.

FIG. 3 shows the investigation results. From this result, it is understood that the effects of the measures A and C appear faster than the measures B. However, in the case of the measure A, since the Ti source is expensive, the measure C can be said to be the most immediate and economical means for suppressing the rise in the furnace bottom wall temperature.

Next, the method of the present invention was carried out when there was a portion where the remaining thickness of the brick on the bottom wall of the furnace bottom was locally reduced.

At the time of implementation, the data of the furnace bottom side wall temperature from the time of burning is summarized in time series for each part, and the furnace internal temperature is calculated based on the maximum temperature shown in the past and the thermal conductivity of the brick existing in the radial direction of the part. The temperature distribution in the radial direction is determined, and the line at 1150 ° C. is the maximum erosion line (FIG. 1).
The remaining thickness of the brick was calculated.

As a result, it was found that the remaining thickness was partially reduced. Therefore, the present invention in which the inner diameters of the two tuyeres above the portion where the remaining thickness is reduced is reduced to suppress the blowing amount to about 1/2 and to blow 40 g / min steam from the tuyeres. The method was carried out for 30 days and the furnace bottom side wall temperature was 80
The number of times exceeding% was investigated.

Table 3 shows the test results. In Table 3, the conditions are when the above-described method of the present invention was carried out. The condition is a case where blowing is performed under the condition using a hot air control valve, which is also the method of the present invention. The condition is the case where the operation is performed under the normal blowing condition, and the condition is the case where the blowing amount is suppressed to about に without performing the steam blowing. The test days were all 30 days.

As is clear from the results in Table 3, the number of days when the furnace bottom side wall temperature exceeded 80% of the past maximum temperature was as follows:
In the case of ordinary blowing conditions (conditions) or the case where only the blowing amount was reduced to about 1/2 (conditions), the number was relatively large, but in the method (conditions and) of the present invention, it was 0. Note that the conditions are excellent in that they have the flexibility of easily changing the air flow.

[0062]

[Table 3]

[0063]

According to the method for operating a blast furnace of the present invention, the amount of hot metal dropped and the temperature of hot metal in the vicinity of a brick worn portion on the bottom wall of the furnace can be accurately controlled while ensuring stable operation. By this, the site where the local erosion of the brick of the furnace bottom side wall is predicted, and further, the site where the residual thickness of the refractory brick has already been locally reduced due to wear by hot metal,
Wear of the brick at the site can be suppressed immediately and effectively for a long period of time, and the life of the blast furnace can be extended.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a state of a lower part of a blast furnace during operation.

FIG. 2 is a diagram illustrating a model shape at a tuyere level in a blast furnace integrated simulator.

FIG. 3 is a diagram comparing the effects of each measure in an actual furnace test.

[Explanation of symbols]

 1: Iron skin 2: Carbon brick 3: Chamotte brick 4: Tuyere 5: Lance for PC injection 6: Dropping hot metal 7: Tap hole 8: Furnace bottom side wall 9: Erosion part 10: Maximum erosion line

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoru Wakabayashi 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd.

Claims (3)

[Claims] 1. A method for reducing the amount of air blown from a tuyere located above a blast furnace bottom side wall portion where brick erosion is predicted, and blowing water or steam from the tuyere. And controlling the amount and temperature of hot metal dropped on the furnace bottom at this location, whereby the blast furnace operation method for suppressing erosion of bricks on the blast furnace bottom wall. 2. The furnace bottom wall temperature is measured by a plurality of thermometers installed on the blast furnace bottom wall, and when the measured temperature exceeds a control value, the amount of air blown from a tuyere located above the temperature rising point. The erosion of bricks on the side wall of the blast furnace bottom is controlled by controlling the amount and temperature of hot metal dropped on the furnace bottom at this location by blowing water or steam from the tuyere. Operating method of blast furnace. 3. A method for reducing the amount of air blown from a tuyere located above a part where a brick thickness is locally small on a bottom wall portion of a blast furnace bottom and blowing water or steam from the tuyere. And controlling the amount and temperature of hot metal dropped on the furnace bottom at this location, whereby the blast furnace operation method for suppressing erosion of bricks on the blast furnace bottom wall.