JPH0627281B2 - Blast furnace operation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for operating a blast furnace, and more particularly to an operation method for controlling the position and distribution of the upper end of a thermochemical storage zone in a blast furnace.

(Prior Art) In the operation of a blast furnace, it is important for the raw materials to be charged to be properly lowered and to be stably heated and reduced and melted. Therefore, it is important to accurately grasp the conditions inside the furnace.

As a typical example of this, it has been proposed to use an embedded vertical probe as disclosed in JP-A-59-16917.

Further, by using these sondes, Japanese Patent Laid-Open No. 243702/1987.
As shown in the publication, the position and distribution of the cohesive zone in the furnace is detected, and the heights of the top layer, the middle part and the root of the cohesive zone with respect to the height from the tuyere center to the stock line in the blast furnace. It has been proposed to control the heat level by manipulating the fuel ratio or blast conditions, etc. so that none of them fall below 40%, 15% and 20%, respectively, and some of them have significantly reduced the effect. .

(Problem to be solved by the invention) However, in the method of detecting the cohesive zone in the blast furnace and controlling the heat level of the distribution in an appropriate range, the cohesive zone of the blast furnace is generally formed in the downward direction. Even if the cohesive zone is detected abnormally and treated, it is difficult to recover sensitively and it is difficult to normalize the furnace condition.

Also, the fluctuation pattern of the cohesive zone of the blast furnace does not always reflect the furnace conditions sufficiently.

FIG. 6 shows changes in the cohesive zone (1100 ° C.) level, the thermochemical preservation zone (ηco30%) level, the fluctuation of the shaft pressure and the unloading index. When the thermochemical storage zone level is lowered, the schaft pressure fluctuation and the unloading index are increased, but the cohesive zone level is delayed by about 2 to 3 days after the thermochemical storage zone level is started to decrease.

That is, at the cohesive zone level, it is difficult to grasp the change in the situation inside the furnace at an early stage.

The present invention enables early detection of abnormalities and sensitive measures against abnormalities, which are the drawbacks of these conventional techniques, and performs proper heat level control by detecting abnormalities in the furnace that cannot be detected by the cohesive zone. It is to provide a method of operating a blast furnace capable of performing the above.

(Means for Solving the Problem) The present invention is based on the finding that the upper end of the thermochemical preservation zone formed in the upper layer portion of the cohesive zone of the blast furnace shows a follow-up change extremely close to the fluctuation of the furnace condition of the blast furnace. It was done.

That is, the present invention detects at least the position and distribution of the upper end of the thermochemical storage zone of the blast furnace and performs control so that the upper end position of the thermochemical storage zone has a predetermined distribution. Measured at three points in the middle part and the peripheral part, the average level of the upper end of the thermochemical preservation zone and the level of the peripheral part at the measurement points are 50 to 60% with respect to the height from the tuyere center to the stock line, respectively. A blast furnace operating method is characterized in that the heat level is controlled by any one of a fuel ratio, a charge distribution, and a blast condition or a combination thereof so as to be maintained at 45 to 55%.

First, FIG. 5 shows the cohesive zone (1100 ° C.) level and the unloading index of the blast furnace. When the cohesive zone level decreases, a similar downward tendency is shown until a certain point, but conversely in the low region, the unloading index. Rises, and cannot always be used as a reactor condition judgment index.

However, as shown in Fig. 1, the upper edge of the thermochemical preservation zone (ηco3
(0% level) and the unloading index have a strong correlation, and are optimal as reactor condition indicators.

That is, by controlling the upper end of the thermochemical preservation zone at an appropriate position, the unloading can be controlled in the smaller stable state of the furnace condition.

Further, since the upper end of the thermochemical preservation zone is formed in the upper part of the furnace, the anomaly can be detected at an early stage, and the action can be taken early so that the sensitive recovery can be achieved.

The upper end of the thermochemical preservation zone, which is advantageous for the operation management of this blast furnace, exists at point A shown in FIG.

That is, the figure shows ηco in the height direction using one vertical probe.
It shows the result of measuring (a) and temperature (b).
The line corresponding to% is the thermochemical preservation zone, the point A is the upper end, and the present invention measures and manages this point A.

Furthermore, when obtaining the above-mentioned point A, at least three points in the central portion, the intermediate portion, and the peripheral portion are measured in the radial direction from the center of the furnace, and as shown in FIG. 3, a constant ηco diagram of ηco30% is obtained.

The furnace condition of the blast furnace can be judged by the overall level and distribution of this iso ηco diagram.

In the present invention, as shown in Table 1, this thermochemical preservation zone (ηco
30%) The upper end is controlled at the average level and the peripheral level, and is maintained at 50 to 60% and 45 to 55% with respect to the height from the tuyere center to the stock line, respectively.

If the average level from the tuyere center to the upper end of the thermochemical storage zone is 50% or less of the height from the tuyere to the stock line, shaft pressure fluctuations or load fluctuations may occur due to temperature rise or insufficient reduction of the charge. When the down index increases and exceeds 60%, a thermal surplus state occurs and stable operation cannot be achieved.

Even if the average level at the upper end of the thermochemical preservation zone is within the control range, if the peripheral level is 45% or less, the temperature rise and reduction of the peripheral charge will be insufficient, and eventually the root of the cohesive zone will be stable. It is not formed, and the loading and unloading becomes irregular. On the other hand, if it is 55% or more, the reducing gas becomes excessive in the peripheral portion, and the temperature rise / reduction of the charged material in the middle portion or the central portion of the furnace is delayed, and efficient blast furnace operation becomes impossible.

Therefore, if it is out of this range, the fuel ratio, charge distribution, air flow rate, etc. are controlled as shown in Table 1 to be maintained in an appropriate range.

The average level in the present invention is an area load average value of the central portion, the intermediate portion, and the outer peripheral portion when the furnace center is divided into approximately three in the outer peripheral direction, and the peripheral level is the outer peripheral portion. The actions shown in Table 1 above are carried out both when these are combined and when each is independent.

Further, the temperature of 700 to 800 ° C. shown in FIG. 1 may be similarly controlled without being limited to the level of ηco ₂ 30%, and substantially the same effect can be obtained as long as it is at the upper end of the thermochemical storage zone. To be

(Example) FIG. 4 shows a case where the operation management of the present invention is applied to an actual blast furnace.

Fig. 4 shows that the outer peripheral direction is divided into three parts from the center of the furnace,
A total of 6 points of each 2 points were measured as an outer peripheral portion, and an equivalent ηco diagram of ηco30% was obtained, and a typical pattern is shown as a situation.

In case 1, the average level at the upper end of the thermochemical preservation zone is within the control range, but the peripheral level is too high. Central part,
The middle part drooped and the surrounding gas flow was promoted.

On the other hand, as a result of the ore being shaken out to suppress the gas flow around it, the sagging of the central part and the intermediate part was recovered after 3 days.

Case 2 is a case where both the average and the peripheral level at the upper end of the thermochemical preservation zone are outside the lower limit. Since the root of the cohesive zone formed below the thermochemical preservation zone was not stable, the unloading became abnormal and the peripheral flow became unstable. On the other hand, as a result of increasing the fuel ratio, it recovered to an appropriate level after 3 days.

Case 3 is a case where the average level at the upper end of the thermochemical storage zone is too high. The level of the central part and the middle part is high, and the gas flow in the peripheral part is unstable because it is close to the furnace wall side.

On the other hand, as a result of reducing the fuel ratio, the average level recovered to an appropriate level after one week.

Thus, in the present invention, by accurately grasping the unloading situation that is difficult to detect in the cohesive zone and detecting an abnormality in the upper region of the furnace, it is possible to achieve stable operation of the blast furnace by accurate action and early action, and to improve the fuel ratio. Energy saving can be achieved through optimization, and the tap ratio can be increased.

(Effects of the Invention) As described above, by using the blast furnace operating method of the present invention, the furnace condition in the blast furnace can be grasped quickly and accurately. Further, it is possible to stabilize the operation of the blast furnace by appropriate treatment at an early stage, and to optimize the fuel ratio and increase the tap ratio through the operation.

[Brief description of drawings]

Figure 1 shows the 30% level of ηco and the unloading index in the reactor, and Figures 2 (a) and (b) show η when measured using a vertical sonde.
Fig. 3 (a) and (b) are diagrams showing the co%, the height from the stock line, the position of the thermochemical preservation zone, and the upper surface position, and Fig. 3 (a) (b) is an ηco diagram of ηco30% in the radial direction from the center of the furnace FIG. 4 is a diagram showing a method of obtaining the above, and FIG. 4 is a diagram showing an embodiment of the present invention. Fig. 5 shows the conventional cohesive zone and the unloading index in the furnace. Fig. 6 (a) (b) (c) (d) shows ηco30% level, 1
It is a figure which shows the transition of a 100 degreeC line, a shaft pressure change, and a unloading index.

Claims (1)

[Claims] 1. When detecting the position and distribution of the upper end of the thermochemical storage zone of the blast furnace and controlling the upper end position of the thermochemical storage zone to have a predetermined distribution, at least the central portion in the radial direction of the furnace from the center of the furnace.・ Measure at three points in the middle part and the peripheral part, and the average level at the upper end of the thermochemical preservation zone and the level at the peripheral part at the measuring points are 50 to 60 with respect to the height from the tuyere center to the stock line. %, 45 to 55%, the heat level is controlled by any one of the fuel ratio, the charge distribution, the blast condition, or a combination thereof to operate the blast furnace.