JPS5910965B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blast furnace operating method for improving the circumferential balance of a cohesive zone in a blast furnace.

Therefore, the purpose of the present invention is to reliably detect the charge level when performing scale reduction to lower the charge level, and to aim for stable scale reduction operation, and to maintain the circle of the cohesive zone even during scale reduction. After correctly detecting the circumferential balance and restoring the charge level, a uniform circumferentially balanced cohesive zone is formed in each direction to maintain stable operation over a long period of time, reduce the variation in Si in pig iron, and reduce the blast furnace fuel ratio. The aim is to provide a blast furnace operating method that achieves

Blast furnace reduced scale operation or reduced scale idle wind operation changes from normal operation.
The level of raw material charge is gradually lowered,
Conventionally, level detection of this raw material charge was performed using deep sounding.

However, during the downsizing process, phenomena such as slippage and an increase in furnace top temperature occurred, which could potentially damage the deep-insertion sounding.

If damage to the deep sounding occurs during scale reduction, the level of the raw material charge becomes unknown.

Operating the blast furnace without knowing the level of the raw material charge is undesirable for the following reasons.

(1) In the case of normal blast furnace scale reduction operation, the scale reduction level is set increasingly, and the furnace heat compensation and operating standards are determined according to the scale reduction level.

However, if the scale reduction level becomes unclear due to the above-mentioned troubles, it will be necessary to make furnace heat compensation and change operating standards, which may cause instability in the operating state due to a delay in action.

Also, if the level of raw material charge is lowered too much,
There is a possibility that operational problems such as blowouts may occur.

(2) When taking a break after downsizing, the target downsizing level is set in order to inspect the furnace walls and carry out hot spraying inside the furnace, but the level of the raw material charge is unknown. If there is a wind break, it will become impossible to repair the parts scheduled for repair, and the significance of the wind break will be halved.

Also, even if deep sounding can be used,
When the level of the raw material charge decreases, the stability of the weight due to the structure of the sounding itself, the geometric conditions of the place where the weight reaches, etc. deteriorates, and the same problem as when it breaks occurs. .

As described above, the current raw material charge detection devices such as deep sounding have various problems in detecting the level of the raw material charge during scale reduction operation.

In addition, we detect abnormalities in the furnace from the changes in various data and detect disturbances in the circumferential balance of the cohesive zone at an early stage, reduce the length of the cohesive zone to the shaft or morning glory level, and after confirming that the circumferential balance of the cohesive zone has been improved, The inventors have carried out a scale reduction operation in which the level is returned to the normal operating level and fine adjustments to the cohesive zone are made, as well as drastic adjustments to the cohesive zone.

In this scale reduction operation, by lowering the charge level, most of the detection ends that judge the uniformity of the circumferential balance of the cohesive zone are located in the cavity above the charge, and the scale is reduced. It has been extremely difficult to accurately detect the circumferential balance of the cohesive zone.

Therefore, there has been a need for an appropriate method that can accurately detect the circumferential balance of the cohesive zone even when the scale is reduced, and that can detect the timing of restoring the charge level. After considering this, we found that the information from the gas pressure sensors conventionally installed in blast furnaces is closely related to the detection of the raw material charge level, and that the way the gas pressure sensors are arranged makes it difficult to detect the cohesive zone in different directions even during scale reduction. We found that management can be done with high precision.

That is, the present invention solves the problems of detecting the raw material charge level that occur during conventional blast furnace downscaling operations and the problem of detecting the circumferential balance of the cohesive zone during conventional downscaling operations. It was developed in 2013, and its characteristics are that in blast furnace operation to improve the circumferential balance of the cohesive zone of the blast furnace, gas pressure sensors are installed at two or more locations in the circumferential direction between the blast furnace shaft and the morning glory, and gas pressure sensors are installed in the furnace. The number of installation stages is gradually increased downward, and while the signals from these gas pressure sensors are detected, scale reduction operation is performed to lower the charge level. This blast furnace operating method is characterized by increasing the amount of charge sequentially and returning to normal operation when the signal variation of the gas pressure sensor decreases, thereby improving the circumferential balance of the cohesive zone.

Here, the reason why the level detection means for the raw material charge was limited to the above information will be described below.

The pressure drop of the pressure gauge varies greatly depending on the level of the raw material charge.

In other words, if the level of the raw material charge is between two pressure gauges, it will always indicate a certain pressure drop value due to the pressure loss of the gas flow flowing between the raw material charges. When the raw material charge is below the level of the pressure gauge, the pressure drop of the gas flow flowing between the pressure gauges becomes only the resistance between the gas flow at the furnace wall and the furnace wall, and becomes an extremely small value.

Therefore, the point in time when the pressure drop of the pressure gauge becomes almost zero can be regarded as the point in time when the raw material charge passes through the pressure gauge below the pressure gauge.

Next, we will discuss the reason why the installation of gas pressure sensors was limited to each direction and height in order to accurately detect the circumferential balance of the cohesive zone even during reduced scale operation.

If the circumferential balance of cohesive zones at the same height level in different directions is completely uniform, the amount of gas flowing through that portion should be exactly the same, and as a result, the same gas pressure value should be exhibited.

Therefore, by providing multiple stages of gas pressure sensors in at least two locations in the circumferential direction, cohesive zone management in each direction during normal operation can be performed.

However, when the scale is reduced, most of the gas pressure sensors that are normally installed are located in the cavity above the charge, and the few gas pressure sensors below the charge have good accuracy in cohesive zone circumferential balance. Management is not expected.

In addition, the detection of the charge level during scale reduction as mentioned earlier is also possible.
The closer you go to the bottom of the furnace, the more important it becomes. Therefore, as shown in Figure 1, gas pressure sensors are arranged in multiple stages at at least two locations in the circumferential direction from the shaft to the morning glory. Therefore, it is necessary to increase the number of installed stages.

The preferred method of arranging gas pressure sensors is to arrange them at four locations in the circumferential direction, with a pitch of 2 m from the upper shaft to the middle of the shaft, a pitch of 1 m from the middle of the shaft to the lower shaft, and a pitch of 0.5 m from the lower shaft to the morning glory. As a result, it can be effectively used for both charge level control during scale reduction and cohesive zone circumferential balance control during scale reduction.

At this time, in order to further improve the control accuracy of the charge level, the pitch of the gas pressure sensors provided in multiple stages may be narrowed in only one direction.

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

Figure 2 is an example showing the installation status of the gas pressure sensor and the position of the raw material charge, and Figure 3 shows the implementation of level detection of the raw material charge using pressure information from the gas pressure sensor. This is an example.

As described above, the present invention accurately detects the level of the raw material charge from the pressure loss value obtained from the pressure information of the gas pressure sensor,
The aim is to implement stable blast furnace scale reduction operations.

That is, as shown in Figures 2 and 3, when the raw material charge falls from the state between pressure gauges A and B to pressure gauge B, the pressure values indicated by pressure gauges A and B will change. will show almost the same pressure value, and the pressure loss between A and B will be almost zero.

Therefore, it can be considered that the raw material charge has passed through point B at this point.

Based on the same idea, as shown in FIG. 3, it is possible to accurately detect the charge level.

In this way, while detecting the level of the charge, reduction is performed to successively lower the level of the charge.

In addition, the shaft pressure sensors are arranged at four locations in the circumferential direction, with a distance of 2 m from the upper shaft to the middle shaft.
By setting the pitch to 1m from the middle of the shaft to the bottom of the shaft, and 0.5m from the bottom of the shaft to the morning glory, it is possible to control the charge level when reducing the length, and to adjust the circumference of the cohesive band when reducing the length. You can be satisfied with both aspects of balance management.

As the variation in gas pressure values at the same height level in each direction increased and the gas reduction efficiency in the furnace decreased, it was determined that the circumferential balance of the cohesive zone in the furnace was slightly disturbed, and the scale was reduced to the middle stage of the shaft. Figure 4 shows the shaft pressure values at the same height and in the same direction at the lower shaft A and the morning glory opening.

As can be seen from this figure, the variation in shaft pressure values at the same height and in the same direction after scale reduction is reduced.

Therefore, it was determined that the circumferential balance of the cohesive zone had been improved, and the charge was restored to the normal operating level.

In this way, the present invention provides charge level management during scale reduction,
Alternatively, this is an extremely effective blast furnace operating method for controlling the circumferential balance of the cohesive zone during scale reduction.

Next, examples of the present invention will be described.

Example 1 In blast furnace A with a height of 730 m', the average number of slips over the past two months has increased by 3 times/day or more for two consecutive months, and the gas pressure values of morning glories at the same height level in different directions (at the same height in different directions) have increased. The daily average gas pressure in the direction showing the maximum pressure value of the level - the monthly average value of the daily pressure average value in the direction showing the minimum pressure value) is 350 g/cri in the upper row of morning glories, and 300 g in the lower row of morning glories. /d, it was determined that the circumferential balance of the cohesive zone had collapsed, and it was decided to reduce the length to the lower part of the shaft.

After 4 hours of scale reduction, the gas pressure value at 8 m below the SL matched the furnace top pressure, and after 10 hours of scale reduction, the gas pressure value at 15 m below the SL matched the furnace top pressure. The charge level after hours was determined to be 8m and 15m below SL, respectively, and 6 at the reduced level at the bottom of the shaft at 15m below SL.
After holding for a certain period of time, the variation in the gas pressure value in the upper stage of morning glory decreased to 100 g/d, and the variation in the gas pressure value in the lower stage of morning glory decreased to 120 g/cril.

As a result, it was determined that the circumferential balance of the cohesive zone had been improved.
The charges were gradually restored to normal operating levels.

At the time of returning to normal operation, the variation in gas pressure values at the same height in different directions was greatly reduced to a maximum of 115 g/i, so it can be said that the circumferential balance of the cohesive zone was greatly improved.

As a result, the slip disappeared from the next month, and the fuel ratio was 5.5k.
g/t-p also decreased significantly, and a favorable fuel ratio was maintained from then on.

In this way, the present invention makes it possible to accurately detect the charge level during scale reduction operations, and to detect the circumferential balance of the cohesive zone in each direction during the scale reduction process, thereby making it possible to accurately detect the charge level during normal operation. It can be said that it is an important method for making judgments to recover.

Therefore, the present invention makes it possible to perform reduced scale operation under stable conditions, form a cohesive zone with a uniform circumference balance in each direction, maintain stable operation over a long period of time, reduce the variation in Si in iron, and improve the blast furnace fuel ratio. This can have extremely beneficial effects on blast furnace operation.

[Brief explanation of the drawing]

Figure 1 shows the arrangement of gas pressure sensors, Figure 2
The figure shows the gas pressure sensor and raw material charge level, Figure 3 shows the method of detecting the raw material charge level, and Figure 4 A shows gas pressure values at the same height level in each direction. FIG. ■、■、■・・・・・・Charge level, A, B, C, D
, E...- Gas pressure sensor, a... Before scale reduction, b... After scale reduction.

Claims (1)

[Claims] 1 In blast furnace operation to improve the circumferential balance of the cohesive zone of the blast furnace, gas pressure sensors are installed at two or more locations in the circumferential direction between the blast furnace shaft and the morning glory, and the number of installation stages is increased sequentially toward the bottom of the furnace. When the signal from the gas pressure sensor is detected and the charge level is reduced, and the signal variation of the gas pressure sensors at the same height and in the same direction decreases after the reduction, the installation A blast furnace operating method characterized by gradually increasing the amount of charge and returning to normal operation to improve the circumferential balance of the cohesive zone.