JPS585242B2 - Blast furnace operation method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a blast furnace operating method.

Therefore, the purpose of the present invention is to drastically improve the circumferential imbalance of the cohesive zone in the blast furnace, and to reduce the decrease in the fuel ratio of the blast furnace and the variation in the iron medium (Si:) over a long period of time. The purpose of this project is to provide a method for operating a blast furnace that allows for efficient operation of blast furnaces.

The cohesive zone consists of a cohesive layer and a coke layer, and the cohesive layer is rock-like as a result of blast furnace disassembly, making it difficult for gas to pass through.

On the other hand, the coke layer has a certain porosity, so gas can pass through it very easily.

Therefore, it can be said that the cohesive layer in the cohesive zone plays the role of a gas rectifier.

In extreme terms, it can be said that the shape of the cohesive zone determines the gas production capacity of the blast furnace and controls the blast furnace fuel ratio, which is a representative index of blast furnace operation performance.

It is no exaggeration to say that those involved in blast furnace operations are taking various actions in pursuit of an ideal cohesive zone shape with uniform circumference and balance.

However, as will be explained later, there are various factors that disturb the circumferential balance of the cohesive zone during blast furnace operation, making it difficult to maintain a uniform circumferentially balanced cohesive zone over a long period of time. .

Such a disruption of the circumferential balance of the cohesive zone not only directly means a decrease in gas reduction efficiency and an increase in the fuel ratio, but also induces fluctuations in the blast furnace furnace conditions, resulting in large variations in the Si content in the pig iron.
It becomes difficult to supply good hot metal.

Furthermore, until now there has been no method for fundamentally adjusting the shape of the cohesive zone, and it has been common for the above-mentioned furnace conditions to be prolonged.

The cause of such a disturbance in the circumferential balance of the cohesive zone is when the charging amount in each direction is different due to a defect in the top charging device such as uneven wear of the large bell when charging the blast furnace raw material from the top of the furnace. , ore bones are formed when the inner surface profile inside the blast furnace becomes uneven due to damage to the bricks or the formation of deposits directly under the hardware, and a mixed layer (layer of mixed coke and ore) is formed directly under the damaged area or deposits, or This may occur due to changes in furnace conditions, such as a temporary one-sided depletion phenomenon (a phenomenon in which unloading is different depending on the direction), or an imbalance in the air volume from the tuyeres. This causes a decrease in the CO2 in the top gas (ηCO=□ CO$ in the top gas) (CO$ in the top gas) and the variation in the pig iron (St). Enlarge.

In addition, due to the steady flow of gas due to an imbalance in the circumference, deposits are formed on the side of the gas drift, the heat load on the furnace body becomes abnormally high, and the charge material temporarily descends irregularly (hereinafter referred to as This causes a problem called irregular unloading, and is a major factor in the increase in the blast furnace fuel ratio.

Therefore, in order to equalize the circumferential balance of the cohesive zone, ■ restore the original functions of equipment and the furnace body (repair and adjust the furnace top charging device, etc., smooth the furnace profile by removing deposits, etc.) ■ Adjustment of charge distribution (4-way adjustment of movable armor, change of charging pattern, change of material charge level height, etc.) ■ Adjustment of gas flow in the lower part of the furnace Adjustment of tuyere diameter for each tube, for each tube Adjustments were made to the amount of heavy oil injected.

However, even if a slight imbalance in the circumference of the cohesive zone could be corrected, the existing cohesive zone still existed and it was not possible to make a drastic correction.

The inventors of the present invention have considered this situation and have noticed that all previous cohesive zone adjustments are based on the existence of an existing cohesive zone. We found a method to reconstruct the cohesive zone.

In other words, the present invention was developed to solve the conventional problem that the cohesive zone cannot be fundamentally adjusted. By capturing the timing when differences in top gas concentration and/or differences in shaft pressure occur, a reduced wind operation is performed to lower the charge level below the level of the top of the existing cohesive zone, and then normal operation is resumed and the cohesive zone is removed. This is a blast furnace operating method characterized by improving the circumferential balance of the blast furnace.

Furthermore, the present invention captures the timing at which differences in gas temperature and/or gas composition occur between the charges at various points in the circumferential direction of the same radius at a specific height position in the blast furnace, and adjusts the charge level to the existing melting rate. This is a blast furnace operating method characterized by performing a reduced wind rest operation in which the wind is lowered to below the level of the top of the cohesive zone, and then shifting to normal operation to improve the circumferential balance of the cohesive zone.

The reason for limiting the above management elements will be described below.

If the cohesive zone is ideally balanced and uniform in circumference, it can be said that the gas temperature and gas concentration at each point in the circumferential direction of the same radius at each height position in the furnace are the same.

Similarly, if the shaft pressure values are at the same height, the amount of gas in front of the shaft pressure gauge will be constant, so it should show exactly the same value.

Conversely, if the circumferential balance of the cohesive zone is disrupted and the gas flow is disrupted, the gas temperature and gas concentration at each point in the circumferential direction of the same radius at each height position in the furnace will be different. Moreover, the shaft pressure values are also different.

As described above, the top gas concentration distribution and inter-burden gas concentration are
A shaft pressure gauge was selected as the instrument for selecting the gas temperature between the charges and the uniformity of the longitudinal cross section, and the above management elements were selected for the purpose of three-dimensionally controlling the circumferential balance of the cohesive zone. limited.

Note that the reason why the inventors did not limit the top temperature distribution as a control factor is that water spraying on the charge has recently been strengthened to prevent dust, and as a result, the top gas concentration distribution becomes sharp. This is based on my experience that when the moisture in the charge evaporates, heat is transferred, so the temperature distribution at the top of the furnace tends to be flat and cannot be said to accurately reflect the gas flow in the cohesive zone. be.

From the above, it can be said that the top gas concentration, shaft pressure gauge, gas concentration between charges, and gas temperature are extremely important instruments for detecting the circumferential balance of the cohesive zone.

The present invention has the following effects.

■ Drastic adjustment of the circumferential balance of the cohesive zone By reducing the length of the existing cohesive zone to the lower part of the shaft and the morning glory, a uniform cohesive zone that is completely different from the existing cohesive zone with an unbalanced circumference can be created. Rebuilt.

Therefore, the conventional gas drift is eliminated and ηco is significantly improved.

2. Reduced variation in Si and L in the pig iron. Since the circumferential balance of the cohesive zone becomes uniform, the melting level of the cohesive layer in each direction becomes uniform, and the hot metal components are stable and good hot metal can be supplied.

Furthermore, since the dispersion in the pig iron [Si] can be reduced, it is possible to lower the pig iron [Si].

3. Reducing the heat load on the furnace body By preventing gas drift due to an imbalance in the circumference of the cohesive zone, the heat load on the furnace body is reduced, and the heat dissipated from the furnace body is also reduced.

As a result, it becomes possible to maintain the original furnace function for a long period of time, and the heat output of the blast furnace is reduced due to the heat dissipation of the furnace body.

4. Removal of deposits During the process of reducing the size of the charge material or in the process of returning to the normal level, even small deposits are removed due to the effect of colliding the charge material with the deposits and the thermal shock caused by the downtime of the size reduction. It can be completely removed.

Therefore, after the wind down is reduced, unloading will be smooth and the furnace condition will be stable.

5 More than a decrease in fuel ratio 1, 2, 3, 4. Together, these effects can significantly reduce the fuel ratio.

Next, the present invention will be explained in detail with reference to embodiments shown in the drawings.

The examples shown in FIGS. 1 to 4 are all examples in which it is determined that the circumferential balance of the cohesive zone has been significantly disrupted.

In other words, Fig. 1 shows that the furnace top gas concentration ηco differs greatly in the circumferential direction (north-south direction) of the same radius, and Fig. 2 shows that the shaft pressure in the circumferential direction of the same radius at the height position in the furnace differs greatly. Figure 3 shows that there is a difference in the blast furnace gas concentration ηco between shaft charges in the circumferential direction of the same radius at a specific height position in the furnace. Figure 4 also shows that there is a difference in gas temperature between the charges.

When one or more of the above-mentioned management factors occur, the present invention reduces the raw material charge level to the existing cohesive zone level at the lower part of the shaft, the furnace belly, or the morning glory, and regenerates the cohesive zone. It aims to build on this.

That is, as shown in FIG. 5, by lowering the charge material to the lower part of the shaft or morning glory at the level of the existing cohesive zone, the volume of the cohesive zone after reduction becomes less than 50% of the volume of the existing cohesive zone.

Therefore, it can be said that the cohesive zone formed during the reduced wind rest period was completely different from the cohesive zone that was out of balance.

When the air starts to blow, the air volume should be increased to the limit that does not cause slippage (1.2 N m3/min per internal volume is a guideline), and in order to stabilize the wind pressure at the start of the air, the air volume should be increased to a level that does not cause slippage (1.2 N m3/min per internal volume). Start when the speed reaches 1.0 N m/min.

When the air blows up after the conventional reduced-scale air suspension, it causes slip tuyere blockage due to large deposits falling off, etc., forcing operation at a low air volume, and heavy oil injection may not start until 8 to 10 hours after air blowing. It was always.

However, in the reduced wind downtime operation of the present invention, reduced wind downtime is carried out as a regular operation based on the management factors described above, before large deposits are generated, so there is no possibility that they will occur in the conventional downsized wind downtime. There are almost no problems, and the air can be started up under stable operation.

Therefore, it is possible to inject a high air volume without causing slippage, and by injecting heavy oil at the beginning of the start-up of the air, the raceway in front of the tuyere is enlarged and the air volume reaches the center of the furnace, allowing for more stable operation by early injection of heavy oil. It is said that the role of heavy oil in the raceway is to reduce the consumption rate of coke involved in combustion, thereby preventing the coke in the vicinity of the raceway from becoming pulverized, expanding the raceway, and improving ventilation. ) From the above, it is possible to start up operations extremely stably after wind reduction and wind suspension.

In addition, since a high air volume can be stably supplied after the air blast starts, it is now possible to reconstruct a cohesive zone with a uniform circumferential balance, which is completely different from the existing cohesive zone with an unbalanced circumference.

Next, examples of the present invention will be described.

Example 1 In a blast furnace A with a furnace capacity of 1,730 m, the phenomenon shown in Figures 1 to 4 was detected, and the circumferential balance of the cohesive zone became uneven, so a reduced-scale downsized operation was immediately implemented. did.

The scale reduction level was defined as the furnace belly level.

After observing the inside of the reactor, localized deposits were found to have formed at the middle level of the south shaft, and most of them fell off due to thermal shock during the downtime.

As shown in Figure 6, heavy oil was injected 1 hour and 30 minutes after the start of air blowing, and things went very smoothly.

As a result, the shaft pressure values at each point in the circumferential direction with the same radius are almost the same, and the gas concentration distribution at the top of the furnace, the gas temperature distribution between the charges, and the gas concentration distribution between the charges are all at each point in the circumferential direction with the same radius. The difference has been resolved.

As a result, ηco increased by 0.9% and the fuel ratio was 5.5k
g/tp decreased.

Example 2 In a B blast furnace having a furnace capacity of 1150 m, the shaft pressure values differed in the circumferential direction of each same radius in the furnace height direction, as shown in FIG.

Although there are no particular problems with other management factors, as the overall ηco has been trending slightly downward, we have implemented reduced wind rest operation down to the lower part of the shaft.

The rise of the reduced wind rest is extremely stable, as shown in Figure 8.
The shaft pressure values in the circumferential direction of each same radius in the height direction of the furnace are almost the same, resulting in a uniform circumferentially balanced cohesive zone, ηco increases by 0.7%, and the fuel ratio is 4 or 5 k.
g/tp decreased.

As described above, by carrying out the present invention, it is possible to fundamentally and all at once improve the disturbance in the circumferential balance of the cohesive zone, and by preventing gas drift, not only ηco is improved, but also the furnace condition of the blast furnace is improved. The fuel ratio drops significantly.

Furthermore, since it is possible to prevent the gas from flowing around the surrounding area, it is possible to maintain a healthy furnace body over a long period of time, making it an extremely useful blast furnace operating method.

[Brief explanation of drawings]

Figure 1 is a diagram showing the top gas concentration ηco distribution in the circumferential direction (northwest direction), Figure 2 is a shaft pressure distribution diagram in the circumferential direction of each same radius in the blast furnace height direction, and Figure 3 is a diagram showing the shaft pressure distribution in the blast furnace height direction. The blast furnace gas concentration ηco distribution diagram between the shaft charges in the circumferential direction of the same radius at a specific height position, Figure 4 is a diagram showing the gas temperature between the charges, and Figure 5 is a diagram showing the gas temperature between the charges. Figure 6 is a diagram showing the reduced wind resting operation status in Example 1, Figures 7 and 8 are circles with the same radius in the height direction inside the blast furnace in Example 2. FIG. 3 is a shaft pressure distribution diagram in the circumferential direction.

Claims (1)

[Claims] 1. By capturing the timing at which differences in top gas concentration and/or differences in shaft pressure occur at each point in the circumferential direction of the same radius at a specific height position in the blast furnace, A blast furnace operating method characterized by performing a reduced wind rest operation in which the wind is lowered to below the level of the top of the cohesive zone, and then shifting to normal operation to improve the circumferential balance of the cohesive zone. 2 By capturing the timing at which a difference in gas temperature and/or gas composition occurs between the charges at each point in the circumferential direction of the same radius at a specific height position in the blast furnace, the charge level is adjusted to the level of the top of the existing cohesive zone. We will carry out reduced wind down operations to the following levels:
A blast furnace operating method characterized in that the circumferential balance of the cohesive zone is improved by then shifting to normal operation.