JP2733565B2 - Blast furnace operation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a blast furnace, and more particularly, to a ventilation resistance index in a blast furnace based on a pressure loss based on a difference between a furnace top pressure and a blowing pressure or a pressure loss based on a pressure loss. Accordingly, the present invention relates to a method of operating a blast furnace with a minimum operation instruction being accurately performed by evaluating over the entire in-furnace time of a charged material.

2. Description of the Related Art In the operation of a blast furnace, if the blast furnace is enlarged and a trouble occurs during the operation, the influence on the productivity is large. Therefore, the operation management is performed so that there is no trouble.

In this operation management, in particular, the management of air permeability in the furnace is important, and if the air permeability deteriorates to a certain level or more, if that state continues, it will lead to major troubles of the blast furnace such as slip, shelf, blow-through, It suffers a major damage of reduced production.

For this reason, it is described in JP-A-52-105511, and Go-
In a blast furnace operation management system known by names such as Stop and AGOS, the permeability in the furnace is evaluated using indices such as pressure loss in the furnace and ventilating resistance index in the furnace, and these are set and managed by setting certain boundary values. Things are going on.

That is, the furnace pressure loss that changes every moment or the ventilation resistance index or the like corresponding thereto is calculated, and the calculated value is compared with a preset boundary value. Operational instructions (such as wind reduction).

However, such control of the furnace pressure loss and the ventilation resistance index is a level control, and it is not enough to control these.

For example, when the furnace pressure loss or the absolute value of the ventilation resistance index changes due to operational reasons, for example, due to changes in operating conditions such as changes in coke ratio, wind heat, moisture, enriched oxygen, or the operating conditions of the blast furnace If the fluctuations increase and the fluctuations increase, the operation manager must change the boundary value each time.

More specifically, when the operating conditions of the blast furnace change, the air permeability in the furnace cannot be evaluated unless the boundary values are sequentially changed in accordance with these changes. In other words, there is a case where an instruction is not issued when an action is to be taken, or an instruction is issued when it is not necessary, so that the operation management system becomes meaningless.

Further, even when the operating conditions of the blast furnace are not changed, there are times when the fluctuation of the ventilation is large and times when it is small. If the fluctuation increases while the boundary value is set when the fluctuation is small, an instruction for an action (such as wind reduction) is continuously issued. Such operations are safe, but at the production level, are unrealistic operating instructions.

Therefore, in order to solve the above-mentioned problem, it is necessary to change the boundary value one by one, but it is a very burdensome job for the operation manager, and it is practically difficult.

In addition, if the airflow resistance is deteriorated to a certain extent, it is not evaluated to the degree of danger such as how much slippage occurs if the airflow is deteriorated in the conventional blast furnace operation method. It just takes the action of doing.

For example, if the airflow resistance deteriorates to some extent, actions such as wind reduction are taken early, but it is not clear whether it is necessary to perform such an action to reduce production.

In addition, even when it is determined that an action such as wind reduction is unnecessary, there is often seen a case where a slip actually occurs and a trouble such as a reduction in production occurs.

In other words, according to the conventional technology, it is not possible to judge whether the increase in the airflow resistance leads to a major trouble such as slip, hanging on a shelf, or blow-by when the airflow resistance increases only by the evaluation of the air permeability.

Problems to be Solved by the Invention The present invention aims to solve these problems, specifically, as in the prior art, in blast furnace operation, the absolute value of the pressure loss in the furnace or the ventilation resistance index according to this. When assessing breathability and comparing and acting against certain thresholds,
The person in charge of operations must change the boundary value due to operational reasons or deterioration of the operating conditions, etc. Also, when the air permeability deteriorates, it is not possible to properly judge whether it is necessary to take action In addition, only by the evaluation of air permeability, to prevent the occurrence of slips, shelves, etc., the frequency of actions is increased and the production is greatly reduced, and furthermore, such blast furnace operation management methods are still studied, An object of the present invention is to propose a blast furnace operation method that solves problems such as lack of development.

Means for Solving the Problems and Their Actions In other words, the method of the present invention is based on the pressure loss based on the difference between the furnace top pressure and the blast pressure, or the ventilation index corresponding to this pressure loss. Over the entire furnace time, evaluate the air permeability in the furnace, when operating the blast furnace based on this air permeability evaluation, sampling pressure loss in the furnace or a ventilation resistance index equivalent thereto as measurement data in a short cycle, The average value of the measured data for each predetermined judgment cycle within the period excluding within 30 minutes from the raw material supply during the in-furnace time is taken as the long-term rising air permeability, while 30 minutes after the raw material supply during the in-furnace time. The average value of the measurement data for each judgment cycle within the short-term rising air permeability, and then the average value of the measurement data of the latest judgment cycle when the judgment should be made as the latest air permeability, The difference with long-term ventilation While the difference between the maximum value of the measured data in the latest judgment cycle and the short-term rising permeability is calculated as the furnace condition fluctuation value of the short-term rising permeability, the difference between the short-term rising permeability and the furnace condition fluctuation value is calculated. In addition to monitoring each reactor condition fluctuation value of short-term rising permeability, judgment of reactor condition abnormality is based on each reactor condition fluctuation value based on each boundary value set for each period corresponding to long-term and short-term rising permeability. And controlling the operation of the blast furnace.

Therefore, the configuration as the means of the present invention and its operation will be described more specifically as follows.

The present inventors conducted research on the current state of blast furnace operation in order to evaluate the permeability in the furnace in the operation of the blast furnace in a maintenance-free manner and in conformity with the actual operation of the blast furnace. Evaluation conditions are required.

(1) The air permeability is evaluated by a relative value. That is, it is divided into a short-term air permeability increase and a long-term air permeability increase, and the short-term and long-term air permeability are evaluated based on their relative values.

(2) Depending on the magnitude of the change in the air permeability, 2
Set a boundary value for the relative values of the two fluctuations and take action.

(3) When the N ₂ gas in the furnace top gas changes at a high level and the airflow resistance increases, slip holes are formed even though the degree is still small, and slip, shelf hanging or blow-through occurs. The possibility of developing into trouble is great. In this case, an action is taken when the airflow resistance slightly deteriorates, rather than taking an action by evaluating the air permeability as in (1) and (2).

(4) When the shaft differential pressure changes at a high level and continues at a high level for a long time, a slip hole is formed even if the degree is small. At this time, it is determined that there is a high possibility of developing into a big trouble. In this case, an action is taken when the airflow resistance is slightly worse than an action is taken by the air permeability evaluation.

In this way, the conditions for evaluating the permeability of the blast furnace are examined, and the operation method of the blast furnace is performed based on the evaluation of the permeability.

(A) First, data for a certain period is collected for the evaluation of the air permeability in the furnace.

That is, in order to evaluate the ventilation resistance in the furnace, for example, within a short period such as 30 seconds or less, as a ventilation resistance value from the furnace, the pressure loss based on the difference between the furnace top pressure and the blowing pressure, The ventilation resistance index corresponding to the pressure loss is sampled as measurement data for calculation, and the ventilation resistance value in that period is calculated, and is set as the ventilation resistance value in that period.

The data collection period is not necessarily shorter than 30 seconds, and may be determined as desired, but may be longer than 30 seconds. However, shorter than 30 seconds is preferable because accuracy is improved.

As described above, the ventilation resistance values are collected within a period of 30 seconds or less, and a determination cycle of, for example, 5 minutes is taken. Therefore, each ventilation resistance value in the determination period is averaged, and the average value is defined as a ventilation resistance value for each determination period of, for example, about 5 minutes (hereinafter, simply referred to as a ventilation resistance value in the determination period), and this is used. It is determined and filed for at least 8 hours or more (because this time indicates the furnace life from the time of charging the blast furnace to the time of tapping).

In addition, this judgment cycle is determined from the detection accuracy of the abnormality,
The judgment period does not necessarily have to be 5 minutes, and for example, the judgment period can be determined according to the collection period such as 30 seconds.

In addition, a shorter judgment cycle can be taken if the calculation function used for processing sensor information is allowed.

(B) As described above, the air permeability is evaluated separately for a long-term increase and a short-term increase based on the airflow resistance value obtained as an average value within a predetermined judgment cycle.

First, of the furnace time from when the raw material is supplied into the furnace for more than 30 minutes to when it is discharged through the furnace, for example, except for one hour before the judgment, for example, hand,
From the past 1 hour to 8 hours, the airflow resistance value is determined as the average value of the measured data in each judgment cycle, and this is defined as the long-term rising air permeability. The average value of the airflow resistance value in the judgment cycle such as 5 minutes in the long-term rising air permeability is compared with the airflow resistance value in the judgment cycle such as 5 minutes corresponding to the latest at the time of the judgment, and the airflow is calculated based on the difference from the air permeability at the judgment time. Monitor the long-term rise of sex,
Thus, the fluctuations in the reactor conditions are observed.

On the other hand, among the raw materials in the furnace time, the ventilation resistance value, which is the average value of the measured data in the determination cycle corresponding to within 30 minutes before the determination, is defined as the short-term rising permeability, and this short-term rising permeability is determined. This difference is compared with the maximum value among the ventilation resistance values (for example, 30 seconds) of each measurement data detected within the immediately following judgment cycle (for example, 5 minutes), and the difference between the reactor condition fluctuation for monitoring a short-term increase in the permeability. I do.

(C) A boundary value is set for each of the long-term rise and the short-term rise air permeability.

That is, the boundary value that determines the ventilation resistance of the short-term rise and the long-term rise is a management value for furnace condition monitoring that is determined in advance for each furnace from the substance of past troubles and the like. The boundary value is set in accordance with the level of fluctuation described later. When the fluctuation level is high, the boundary value level is set high, and when the fluctuation level is low, the boundary value level is set low.

Fluctuation levels refer to: Using the airflow resistance value for each judgment cycle, σ is calculated based on the elapsed time in which the change of the blast furnace operating conditions and the like are reflected in the furnace condition, for example, the variation between 1 and 2 hours, and this is calculated as the variation in air permeability. Level. Since the elapsed time varies depending on the capacity of the furnace and the like, it is determined and determined for each furnace.

The fluctuation level of the reactor condition at this time indicates the reactor condition given by the latest change in the blast furnace operating conditions, etc.
It can be regarded as a furnace condition fluctuation in the judgment cycle. Further, even if there is no change in the operating conditions, it can be used as an indication of the fluctuations in the reactor conditions that occurred during this period. In addition, it is not preferable to take a long elapsed time because it includes the previous fluctuation.

(D) Compare the air permeability of the long-term rise and the short-term rise with their respective boundary values and take action accordingly.

That is, actions (wind heat reduction, wind reduction, coke ratio increase, etc.) are determined according to the degree of deterioration of the air permeability or in consideration of other blast furnace operating conditions, for example, the relationship with the thermal state. Take these actions.

As described above, according to the method of the present invention, (1) the ventilation resistance value for each judgment cycle is calculated separately for each short-term rise and long-term rise ventilation resistance. (2) Then, each short-term rise and long-term rise ventilation resistance is calculated. (3) The average value of the ventilation resistance values obtained in (1) and the maximum value in the latest judgment cycle are compared with each of these boundary values. (4) Instruct a predetermined action based on the result of the comparison.

By adopting the above method, it is possible to sequentially change the boundary value according to the operation state of the blast furnace, and to issue a realistic operation instruction.

The following is a more detailed description of the time flowchart shown in FIG.

First, in FIG. 1, (A) shows a case where air permeability is stable, and (B) shows a case where air permeability is unstable. Therefore, in the case of (A), since the ventilation is stable (the fluctuation is small), the boundary value is set lower than in the case of (B) where the ventilation is unstable.

For this reason, in the stable state of (A), an action instruction (wind reduction) is issued regardless of (relatively) small deterioration of the air permeability, that is, any of a long-term rise and a short-term rise. On the other hand, when the state becomes unstable in (B), it is not possible to change and set the boundary value to a large value in consideration of the large fluctuation level, and to instruct an action until the ventilation deteriorates to some extent. Instead, an action is instructed only when the changed boundary value is exceeded, and excessive action can be prevented.

When the blast furnace is operated by evaluating the air permeability as described above, the blast furnace can be operated by predicting the occurrence of a slip hole in combination with the change in the N ₂ concentration from the furnace top gas.

That is, where the present inventors have analyzed studied blast furnace operation data, before slip generation, when detected by the N ₂ concentration N ₂ amount as partial pressure in the furnace top gas composition, changes N ₂ concentration is high I do. At this time, the degree of increase in the ventilation resistance such as the ventilation resistance index is small, and furthermore, the shaft differential pressure obtained by measuring the furnace pressure at intervals in the height direction of the blast furnace continues at a high level for a long time. It turns out that it is changing.

Therefore, in the method of the present invention, the slip is predicted by managing these as an index, and the ventilation is evaluated in consideration of the slip prediction. In other words, there is a high possibility that slip holes will be formed and slips and shelves will develop, and when the furnace condition is determined to be abnormal, the action on the blast furnace operation should be taken even if the ventilation resistance is slightly deteriorated in response to the abnormality. It is a method that can be implemented. In other words, when forming a slip hole, the boundary value for the increase in the ventilation resistance is set to 50% to 80% of the boundary value in the normal stable operation, and is set to a small value. Detects this and issues an action instruction early. In this way, the operation of the blast furnace is stable,
Moreover, it is possible to perform maintenance-free ventilation management without relying on manual operations of the operator.

As described above, in the method of the present invention, the evaluation of the permeability in the furnace is divided into a long-term rise and a short-term rise, and these are compared with a boundary value. It is set or changed in response to the situation.

Therefore, setting or changing of the boundary value will be described in more detail as follows.

First, the boundary value (increase width) for each long-term and short-term rise in ventilation resistance without slip prediction is defined as boundary value 1.
And This boundary value 1 is determined according to the level of fluctuation of blast furnace ventilation. At this time, it can be determined from the results of past troubles or changes in the ventilation chart.

Next, when slip prediction is performed, assuming that a boundary value (a rise width) for each of a long-term and a short-term rise of the ventilation resistance is a boundary value 2, the boundary value 2 is determined as follows.

That is, due to a furnace condition abnormality in which the formation of a slip hole is predicted in advance, a boundary value 2 is determined as follows below a boundary value 1 under an unpredictable condition in order to increase the detection level of a change in ventilation resistance, as follows. Increase detection sensitivity.

0.5 × Boundary value 1 <Boundary value 2 <0.8 × Boundary value 1 The reason is that if the boundary value 1 is less than 0.5, disturbance is apt to occur, and if the coefficient exceeds 0.8, the detection of abnormality becomes insufficient.

Moreover, in practice, to assess the breathability by such boundary values, along with being divided into a short and long term for the ventilation resistance value to evaluate the rise time of determination, obtains the N ₂ concentration from in the top gas Then, a cumulative calculation is performed by adding a difference from the reference boundary value, and the cumulative value is set to (T · ΔN ₂ ), thereby performing a slip evaluation.

FIG. 2 is a flow sheet when the blast furnace is operated by evaluating the ventilation resistance in addition to the slip prediction according to the method of the present invention. In FIG. Y indicates Yes and N indicates No. First, the operation is started, the slip is predicted, “Yes”, and if the ventilation resistance exceeds the set threshold value, it becomes “Yes”, and action 1 (wind reduction 5%) is instructed earlier than usual. Be executed. On the other hand, if it is within the boundary value, "N
o ", action 2 is instructed, and if there is no thermal problem, the blast temperature is reduced.

When there is no slip prediction, the state becomes "No". At this time, the boundary value is compared with a boundary value higher than the boundary value when there is slip prediction ("Yes" state) and exceeds the boundary value. Time ("Yes"), action 3
(10% wind reduction) is instructed and taken. Also, action 4 (wind reduction 5%) can be instructed according to the degree of increase in ventilation resistance.
Operate without taking any measures.

In addition, the flow chart of FIG. 2 may be determined not only by the presence or absence of slip prediction but also by the magnitude of the prediction, and the airflow resistance may be determined for each long-term / short-term change. The good thing is, of course.

Note that the size of the slip prediction may be distinguished by dividing by the size of the N ₂ concentration or shaft differential pressure.

FIG. 3 shows an example of a time flowchart when the blast furnace is operated as shown in FIG.

In FIG. 3, in all three cases a, b, and c, an increase in airflow resistance is observed. In case a, no slip hole is formed, and an increase in airflow resistance is small, and it is not necessary to take action.

In case b, the rise in ventilation resistance is small (case a
(Same level as above) was predicted to form a slip hole, indicating a similar change in airflow resistance, but an action of 5% wind reduction was taken.

In case c, no slip hole was formed, but the airflow resistance was significantly increased, so that the wind was reduced by 5%.

There was no trouble in any case, and the operation continued stably.

In addition, slip prediction is based on N ₂
It can be performed as a predictor of N ₂ concentrations by detecting the amount of gas as a partial pressure by as detected by the shaft differential pressure.

First, a method of making a prediction based on the N ₂ concentration will be described as follows.

(1) the top gas N ₂ concentration measurement in 1) N ₂ concentration determined period of furnace top gas (for example, 5 minutes) is measured for each.

If conditions such as blast moisture and oxygen enrichment are changed on the way, the N ₂ concentration changes due to a change in the amount of gas due to the decomposition of water, a change in the amount of N ₂ charged, and the like. This change on the theoretical examination, by correcting the N ₂ concentration, to equalize the reference states and conditions.

2) Calculate the difference (ΔN ₂ ) between the current value of the N ₂ concentration and the conventional value (for example, the average value of the past 1 to 8 hours).

3) A certain level of difference (ΔN ₂ ) (for example, 0.2%)
If it is above, the cumulative value (TN ₂ ) is additionally obtained.

4) If ΔN ₂ is below a certain level (0.2%), it is determined that the furnace condition abnormality has been resolved and no accumulated value is obtained.

 5) The above operation is performed for each judgment cycle.

(2) Breathability Similar to the above-described breathability, short-term rise, long-term rise, and breathability are calculated for each judgment cycle.

(3) Boundary value A boundary value is set for each of the cumulative calculated value (TN ₂ ) and the air permeability. Note that the boundary value of air permeability is set to 50, which is the value set here.
Set to a value of ~ 80%.

Also, an action (wind heat down, wind reduction, etc.) is determined for each combination of levels.

(4) The cumulative value (TN ₂ ), the short-term rise, and the long-term rise air permeability are calculated for each judgment cycle, and each boundary value is compared.

(5) Based on the result of the above comparison, an action is determined according to each variation according to the flow shown in FIG. Flow of the fourth diagram shows the respective determination flow by dividing the accumulated value of the N ₂ concentration variation in small and large. The actions corresponding to the respective fluctuations are as shown in Table 1, and the action numbers in the table correspond to those in FIG. In Table 1, the action 1 indicates that both slip prediction and ventilation increase are large. Therefore, the most significant wind reduction action is set to eliminate the slip.
Although there is slip prediction, since there is no change in ventilation resistance, an action of only wind heat down is set.

Hereinafter, similarly, a predetermined action is adopted after the determination of the furnace condition abnormality, and the control for the blast furnace operation is started.

FIG. 5 shows an example of a time flowchart of the operation when the blast furnace is operated as shown in FIG. 4 as described above.

As shown in FIG. 5, at the timings a and b, the N ₂ concentration in the top gas composition changed at a higher level than the average value in the past. The cumulative value was obtained by adding the difference from the average value, but the cumulative value did not increase so much at the timing of a. On the other hand, at the timing b, it gradually increased and exceeded the preset boundary value. At this time, the ventilation resistance rise index value was also large and already exceeded the set value. For this reason, in this case, wind reduction was instructed as control for the blast furnace operation, and although the index finger was coarse and dense, there was no slip and continued stable operation.

Next, a method of predicting a slip by a shaft differential pressure will be described as follows.

(1) First, the furnace pressure is measured at predetermined intervals in the height direction of the blast furnace, and the shaft differential pressure data is processed at regular intervals (for example, every 5 minutes).

The difference (ΔSP) between the current value and the past average level (for example, 1 hour to 9 hours ago) is obtained.

If the difference (ΔSP) is larger than a predetermined value, the difference is added to the cumulative value (TΔSP). If the difference (ΔSP) between the accumulated values becomes smaller than a predetermined constant value, the accumulated value TΔSP is set to 0.

The calculation of shaft differential pressure is performed for each measurement point.
Each boundary value is determined and calculated.

(2) Judgment At regular intervals, it is determined whether the accumulated value (TΔSP) is larger than a certain value. A judgment is made for each measurement point.
If the cumulative value (TΔSP) becomes larger than a certain level, the occurrence of slip is predicted, and an action instruction (wind reduction)
10-20%).

The above-described cumulative calculation allows not only the determination of the level of the shaft differential pressure but also the duration at a high level to be taken into account, greatly improving the slip prediction accuracy.

Therefore, an example of a time flowchart in the case of slip prediction based on the shaft differential pressure as described above will be described.
As shown in the figure.

In FIG. 6, the cases of a and b have the same level of the shaft differential pressure, but have different durations.
Slip occurs only in In the conventional example, case a
And b both predict slip, but the method of the present invention clarified the distinction between case a and case b, and was able to determine only case b where slip actually occurred.

<Effects of the Invention> As described above, the method of the present invention uses the pressure loss based on the difference between the furnace top pressure and the blowing pressure or the ventilation resistance index according to the pressure loss to determine the entire furnace time during which the charged material passes through the blast furnace. The furnace air permeability was evaluated over a period of time, and when operating the blast furnace based on this air permeability evaluation, the pressure loss in the furnace or the airflow resistance index equivalent thereto was collected as measurement data in a short cycle, and the The average value of the measured data for each predetermined judgment cycle within the period excluding within 30 minutes from the supply of the raw material shall be the long-term rising air permeability, while the determination shall be made within 30 minutes after the supply of the raw material in the furnace time The average value of the measured data for each cycle is the short-term rising air permeability, and the average value of the measurement data of the latest judgment cycle when the judgment should be made is the latest air permeability. The difference between the long-term air permeability and the furnace On the other hand, the difference between the maximum value of the measured data in the latest judgment cycle and the short-term rising permeability is determined as the furnace condition fluctuation value of the short-term rising permeability, and the long-term rising permeability and the short-term rising permeability are determined as the fluctuation values. Controls blast furnace operation by monitoring furnace condition fluctuations and judging furnace condition abnormalities based on each furnace condition fluctuation value based on each boundary value set for each period corresponding to long-term and short-term rising air permeability. It is characterized by doing.

Therefore, in the operation of the blast furnace, the air permeability was evaluated as a relative value, and the boundary value for the air permeability was set according to the level of the air fluctuation during the operation, and the action was taken. This eliminates the need for maintenance, allows operation with peace of mind, and reduces the load.

In addition, the operation can be performed with the same feeling as the operation action at the site, there is no sense of incongruity, it can be fully utilized at the site, and there is no variation among operators, and stable operation can be performed.

When the ventilation resistance deteriorates, the necessary action is determined by examining not only the change of the ventilation resistance but also whether the deterioration of the ventilation resistance leads to a bigger trouble such as a slip or a shelf.

As a result, timely, necessary, and effective actions can be accurately performed with respect to the deterioration of the ventilation resistance.

In addition, we will prevent production reduction due to excessive operation and production shortage due to insufficient action volume,
In addition, slip prevention has become possible, and stable blast furnace operation can be maintained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of a time flow chart when the method of the present invention is carried out, FIG. 2 is a flow sheet of an example when a blast furnace is operated by the method of the present invention, and FIG. 3 shows the operation of another embodiment. FIG. 4 is an explanatory diagram of an example of a time flow chart, FIG. 4 is a flow sheet of another example when a blast furnace is operated by the method of the present invention, and FIGS. 5 and 6 are time charts of the flow sheet shown in FIG. FIG. 9 is an explanatory diagram showing a time flowchart illustrating the operation of another example.

Claims (1)

(57) [Claims] A pressure loss based on a difference between a furnace top pressure and a blowing pressure or an air permeability index corresponding to the pressure loss is used to evaluate the air permeability in the furnace over the entire furnace time in which the charged material passes through the blast furnace. When operating the blast furnace based on this permeability evaluation, the pressure loss in the furnace or the ventilation resistance index equivalent thereto is sampled as measurement data in a short cycle, and the raw material supply during the furnace time is measured. While the average value of the measurement data for each predetermined judgment cycle within the period excluding within 30 minutes is taken as the long-term rising air permeability, from after the raw material supply during the furnace time
The average value of the measurement data for each judgment cycle within 30 minutes is a short-term rising air permeability, and then, the average value of the measurement data of the latest judgment cycle when the judgment should be made is the latest air permeability, While determining the difference between the latest permeability and the long-term rising permeability as a furnace condition fluctuation value of the long-term rising permeability, the difference between the maximum value of the measurement data in the latest judgment cycle and the short-term rising permeability is determined. Obtain the short-term rising air permeability as a furnace condition fluctuation value, monitor the long-term rising air permeability and the short-term rising air permeability each furnace condition fluctuation value, and correspond each furnace condition fluctuation value to the long-term and short-term rising air permeability. A method for operating a blast furnace, characterized in that a furnace condition abnormality is determined based on each boundary value determined for each period and the blast furnace operation is controlled.