JPH01319611A - Method of predicting slip in blast furnace operation - Google Patents

Abstract

PURPOSE:To greatly improve prediction accuracy and to allow adequate action by comparing the present value and past average value of the N2 concn. of a furnace top gas, cumulatively calculating the differences thereof and predicting the generation of a slip when the calculated value exceeds a set value. CONSTITUTION:The N2 concn. is detected by continuously measuring the concn. of the furnace top gas. The present N2 concn. and the average value of the N2 concn. for the past specified period before this detection are compared and the difference ( SP) thereof is determined. The difference ( SP) is cumulatively calculated when the difference ( SP) attains the prescribed or above in a positive direction. The generation of the slip is predicted and. for example, the reduction of draft by about 10-20% is executed when the cumulatively calculated value exceeds the predetermined threshold N2 value. The sure action to the slip is thus executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for predicting slip in blast furnace operation, and more specifically, the present invention relates to a method for predicting slip in blast furnace operation. The present invention relates to a method for predicting slip in blast furnace operation, which predicts slip occurring during blast furnace operation using shaft differential pressure as an index.

Conventional technology In general, during blast furnace operation, the occurrence of -C and slip suppresses a decrease in furnace heat and production volume, which has become a major problem in blast furnace operation management.

This slip occurs when the pressure loss inside the furnace is increased and the pressure inside the furnace balances the force of the downward movement of the charges. When this happens, shelving occurs, and as a result, slippage gradually occurs inside the furnace. This is a phenomenon in which a hole is generated and formed, and the charge suddenly drops to the slip hole. Furthermore, if these develop, the balance between the pressure inside the furnace and the load of the charge will be significantly disrupted, and the force of the charge (blown up, so-called blowout) will occur at the top of the furnace.

Therefore, in blast furnace operation, it is necessary to predict the occurrence of slip and prevent the occurrence of slip.If this can be properly predicted, blast furnace operation will be improved. From this point of view, various methods have been proposed to prevent slips and stairwells.
As shown in Japanese Patent No. 270712, a "°Blast Furnace Condition Detection System" has been proposed. This method predicts slippage based on the unloading speed of the contents in the furnace and the information received from the sonde. An input means and, based on this data, the unloading speed of the contents in the furnace, the pressure loss in the furnace, the shaft pressure, the shirt temperature, the temperature of the fixed sonde, the gas utilization rate, the temperature of the furnace mouth sonde, etc. a data creation means for creating various data indicating the internal situation; a means for comparing the various data with reference data to create truth/false data; a means for storing the truth/false data; and a means for storing various knowledge bases. means and
A means for predicting a blowout or a slip by making a predetermined inference based on the truth data and knowledge base of the storing means is provided.

However, in this system, first of all, the data used, for example, the unloading speed, is the data detected by lowering a measuring sensor such as an index finger to the surface of the contents in the furnace every time it is charged; It is affected by the flow of raw material near the surface of the charge or the fall of the measuring sensor, and therefore it is difficult to predict slip with high accuracy even using this data.

Furthermore, the information obtained from the sonde does not only indicate the operational status of the blast furnace, but also changes depending on the raw material charging.

In other words, for example, when charging raw materials, the temperature of the waste in the furnace decreases overall, but then it recovers over time, and the information obtained from the sonde indicates that changes in blast furnace operation and changes due to charging raw materials are observed. It is difficult to distinguish between

Generally speaking, slip holes that cause slips occur gradually. However, in the conventional example, since the occurrence of slip holes is determined at regular intervals, it is difficult to predict the occurrence of slip holes. In addition, slip holes are cavities created within the blast furnace that have an abnormally low porosity. In order to accurately estimate this, in this section, it is determined by the difference between the volume of the blast furnace contents such as ore and coke charged into the blast furnace and the volume of the molten material that has melted and dripped in the blast furnace per unit time. be. However, at present, it is not possible to estimate the amount of molten dripping in a blast furnace with a certain degree of accuracy, and from this point of view, it is difficult to estimate the occurrence and formation of slip holes by making judgments at regular intervals as in the past. It is difficult to predict.

Furthermore, since slip occurs due to the balance with the furnace pressure as described above, shaft pressure (differential pressure) can be considered as information suitable for predicting slip. However, if we look at the movement of shaft pressure, even before slipping occurs, it is not necessarily large during fluctuations. In other words, it is difficult to predict slip only by controlling the shaft pressure level.

For example, as described in Japanese Patent Application Laid-Open No. 58-71310, the ratio between the pressure loss of the blast furnace and the load of the contents in the furnace is determined, and the conditions under which this ratio does not cause shelving, slipping, or blow-through are determined in advance. A blast furnace feeding method has been proposed in which air is blown so as not to satisfy this condition. However, since it is extremely difficult to increase the accuracy of measuring the load of the contents in the furnace, it is difficult to accurately predict slips and the like.

Problems to be Solved by the Invention The purpose of the present invention is to solve these problems.Specifically, the data used to predict slips, etc. in blast furnace operation is data that is easily affected by disturbances. The prediction accuracy is poor, and the prediction is insufficient and it is not possible to accurately predict slips, etc., resulting in delays in taking preventive measures or taking more measures than necessary, resulting in a decrease in furnace heat and production. The purpose of this invention is to solve the problems that there are problems such as slippage, and that methods for predicting such slips with high accuracy have not yet been sufficiently researched.

Means for solving the problem and its operation, that is, the method of the present invention detects the N2''a degree from the continuously measured furnace top gas composition, determines the current N2 concentration, and at this time, the previous past constant When the difference exceeds a predetermined value in the positive direction compared to the average N2 concentration value of the period, the difference is cumulatively calculated, and when this cumulative calculation value exceeds a predetermined N2 boundary value, It is characterized by predicting the occurrence of slip.

Hereinafter, a method of predicting the occurrence of slip, which is one of the accidents during blast furnace operation, and repairing the slip to operate the blast furnace using the method of the present invention will be described as follows.

First, the present inventors analyzed various operational data at the time of slip occurrence in blast furnace operation, and then investigated the cause of slip occurrence, which is one of the accidents in blast furnace operation. In this case, the N2 concentration in the top gas composition increased, and the ventilation resistance increased accordingly.

Going further, we analyzed the slip generation mechanism using an unsteady uniform cross-section model that is said to be close to actual blast furnace operation, and found that when a slip hole is formed at the bottom of the blast furnace, the N2 concentration in the top gas composition increases. It was found that the N2 concentration in the furnace top gas remained at a high level before the slip occurred.

Therefore, the present inventors further investigated these causes and found the following.

That is, in blast furnace operation, when slip occurs, the blowing pressure increases. This is because a cross section with high ventilation resistance is formed in the furnace, that is, in the charge, and directly below this cross section with high ventilation resistance, there is a part with high porosity, that is,
It seems that a slip ball is formed. In other words, the descending speed of the cross section with high ventilation resistance is somewhat slow, and it is thought that this is because a portion with high porosity, that is, a slip hole, is formed directly below this cross section. In other words, the cross-section with high ventilation resistance has a lower descending speed than other cross-sections, and therefore, the arrival of unreduced substances (FedX, etc.) at the lower part of this cross-section, that is, the slip hole, is reduced.

- On the other hand, although the arrival of unreduced substances is reduced, CO gas sufficiently rises from the lower part of the slip hole, and red-hot coke is also sufficiently present. Therefore, the progress of various reduction reactions shown in (1), (2), and (3) below is reduced in the slip hole, and among them, (2) and (3)
Since the reactions shown in are endothermic reactions, the reduction in these reactions results in excess heat and the formation of a superheated zone.

FeO-+-co = Fe + Co2...
(1)C0C02= 2CO・・・・・・・・・・・・
(2) FeO+ C= CO-1-Fe −・−・−
(3) In short: (1) The local reduction in the reduction reaction at the slip hole causes a decrease in the top gas composition of d5, CO+CO2i1 degree, and the N2 concentration increases accordingly.

(2) Since the above-mentioned superheated area is formed at the bottom of the cross section where the ventilation resistance is large and the descent speed is slow, the heat supply from that cross section to the top increases, and the range of the confectionery garden expands. , ventilation resistance increases significantly.

The present invention is based on the results of the above research and analysis,
In particular, by utilizing changes in N2 concentration in the top gas composition,
Predict slip occurrence.

First, in the method of the present invention, the L concentration is detected in each composition of the top gas that is continuously measured, and the current N2 concentration (hereinafter referred to as the current N2 value) and the concentration before detection are determined. That is, the difference is determined by comparing the average value of N2 degrees over a certain period of time in the past, for example, several tens of minutes or several hours (hereinafter referred to as N2 past average value). Therefore, when this difference exceeds a certain boundary value (hereinafter referred to as N2 boundary value) in the positive direction, it is predicted that the arrival of unreduced substances will decrease.

Next, the difference is compared with the N2 boundary value to predict the occurrence of slip, and when the difference exceeds the boundary value in the positive direction, the difference is cumulatively calculated from that point on, and the unreduced material to the slip ball is calculated. Find the amount of decrease in the arrival of . In other words, as described above, by predicting the occurrence of slip and cumulatively calculating the difference since the prediction, it is possible to concretely understand the size of the formed slip ball and its duration, and to check the formation of slip in the furnace. The extent of the damage was determined, and specific measures were taken to repair the slipholes.

In addition, after predicting the slip in this way, the difference is cumulatively reduced, and in conjunction with this, for example, by reducing the amount of air flow and controlling the operating conditions, the slip ball is repaired, and the unreduced material is removed from the slip hole. Eliminate the decline in arrivals. The timing of completion of this repair can be accurately determined as when the difference falls below the N2 boundary value, and at this time, the cumulative calculation of the difference is stopped.

Further, the N2 boundary value to be compared is determined in advance by actually measuring whether slip occurs or not, taking into consideration the capacity of the blast furnace and the area of the hearth. For example, in a 4000 m3 class blast furnace, 0
．． If a constant value of about 2% is taken, slip can be accurately predicted.

In addition to the N2 waterfall level of the furnace top gas, we also take into account the pressure drop and ventilation resistance index of the blast furnace, making it possible to predict slip more accurately. In other words, when a slip hole is formed in the furnace, the ventilation resistance increases, and the pressure drop and ventilation resistance index are calculated using this ventilation resistance value as a fallout, and these are combined with the average of the past ventilation resistance values. The difference between the two values is calculated, and this difference is compared with the air permeability boundary value in the same way as above to predict slippage.

If this prediction method based on ventilation resistance value is used in combination with the prediction method based on N2 concentration, slip lf can be predicted more accurately. To explain in more detail, if slip is predicted only based on changes in N2 concentration, Li
1 degree rises. Therefore, when slip prediction is performed in combination with the furnace ventilation resistance value, the prediction accuracy is improved.

Further, as described above, the detection factors used in prediction will be explained in more detail as follows.

(1) Top gas N2 (a) From the composition of the top gas that is continuously measured,
Li1 degree is detected at a fixed period, for example, every 5 minutes.

A5: If conditions such as air humidity and oxygen enrichment rate are changed during the process, the gas amount will change due to moisture decomposition, and the charging N211 will change.
N21i1 degree changes due to changes in i, etc. This change was theoretically examined and N2i! The degree is corrected to make the reference state and the article f4 equivalent.

(1)) Difference between current N2 value and past N2 value during operation (△
N21 is determined by h4 calculation.

(C) When the difference (ΔN2) exceeds the N2 boundary value of, for example, 0.2%, the difference is cumulatively calculated (■・ΔN2
)do.

(d) When the difference (ΔN2) becomes less than the N2 boundary value of, for example, 0.2%, the cumulative calculation is stopped and set to zero.

Here, the reason why it is set to zero is that it can be determined that the growth of the slip ball has stopped and that it has been resolved.

(e) The cumulative division value (T·ΔN2) is also set to the D·N2 boundary value.

In addition to setting this ■・N2 boundary value to the value immediately before slip is expected, this value can be divided into large and small values and boundary values for each stage are set for blast furnaces that suppress slip. It becomes possible to adopt the operating method.

Calculate the cumulative calculation value (1・ΔN2) every fixed period,
■・Compare with N2 boundary value.

The above operations are performed at regular intervals.

(2) Air permeability The air permeability index is used as an index to indicate air permeability, and this index is divided into long-term and short-term based on data collected at regular intervals as follows: Predict slips.

(a) Collection of furnace data for calculating the ventilation resistance index In order to evaluate the ventilation resistance in the furnace, data for calculating the ventilation resistance index over a fixed period, such as every 5 minutes, such as furnace top pressure and blowing pressure. Find the pressure loss etc. obtained as the difference between.

Next, the ventilation resistance index for each cycle was maintained for at least 8 hours (this time corresponds to the time the lunatic raw material was in the blast furnace).

) or more.

(i)) Long-term rising ventilation resistance index When determining the occurrence of slip, calculate the average of the ventilation resistance index for each period stored as described above over the past period, for example, 8 hours, and use this average value for the latest cycle at the time of judgment. and the ventilation resistance index, and the difference is taken as the long-term rising ventilation resistance index.

(C) Short-term rising airflow resistance index During operation, at a cycle such as every 5 minutes, 3 times before the time of the judgment.
The maximum value of the ventilation resistance index for a period shorter than 0 seconds is compared with the average value of the ventilation resistance index for the past 30 minutes, for example, from that time, and the difference is taken as the short-term rising ventilation resistance index.

(d) As per the air permeability boundary value, divide the difference in air resistance index into long-term and short-term, calculate short-term increase and long-term increase air resistance index, and compare these indices with the preset air permeability boundary value. do.

In this comparison, the occurrence of slipping is predicted when each upper back index exceeds the air permeability boundary value.

In addition, in the above section, the ventilation resistance index is adopted as an index showing the permeability, but instead of this, in the blast furnace, the internal pressure (hereinafter referred to as shaft differential pressure Slip can also be predicted by measuring the shaft pressure difference at each measurement location.

First, the present inventors investigated in detail the changes in shaft differential pressure between when a slip occurs and during normal operation, and found that when a slip occurs, the shaft differential pressure is at a higher level than during normal operation. It was found that the change lasted for a long time.

Next, in order to use the change in shaft differential pressure to predict slip, the shaft differential pressure is determined at each measurement location in the blast furnace at regular intervals, such as every 5 minutes, or every moment.
The current shaft differential pressure (hereinafter referred to as the current differential pressure value) and the average shaft differential pressure over the past 8 hours since then, for example 11
1I (hereinafter referred to as past average differential pressure) to determine the difference. This difference is cumulatively calculated, and when the cumulatively calculated value exceeds a predetermined differential pressure boundary value, the occurrence of slip is predicted. By cumulatively dividing this difference, the magnitude and duration of the shaft differential pressure can be concretely grasped, and the occurrence of slip can be predicted.

Furthermore, after slip prediction, the slip hole is repaired by reducing the wind.

More specifically, the shaft differential pressure data is processed at regular intervals, such as every 5 minutes, and the difference (ΔSP) between the current differential pressure value and the past average differential pressure value (for example, from 1 hour to 9 hours ago) is calculated.
), perform cumulative calculation for this difference (△SP), and when the difference (△SP) becomes smaller than the past average value of differential pressure, stop the cumulative calculation and calculate the cumulative calculation value (■・△SP).
) to zero.

Such shaft differential pressure processing is performed at each measurement point by predetermining a differential pressure boundary value.

Next, after starting the cumulative calculation, it is determined individually for each measurement point of the blast furnace whether the cumulative calculated value (■・ΔSP) is larger than a predetermined differential pressure boundary value.

In this judgment, if the cumulative calculated value (■・△SP) for at least one measurement point 1 becomes larger than the differential pressure boundary value, then the occurrence of slip is predicted, and for example 10~
Reduce the wind by 20%, etc.

Examples Example 1 First, during operation of a blast furnace with a capacity of 4000 m' class, the N2 concentration is detected from the top gas composition that is continuously measured. ), the difference is accumulated and N2
The cumulative calculation value (T·ΔN2) was determined.

Next, as shown in Figure 1, the N2 cumulative calculation value (■・ΔN2
) is divided into large and small, and this is correlated with changes in the ventilation resistance in the furnace (ventilation resistance index taken) to predict slip.
The operating conditions of the blast furnace were adjusted.

In other words, when the N2 cumulative calculation value (■・ΔN2) is large and the ventilation resistance is large, action 1 shown in Table 1 is applied.
was selected and the slip was repaired by performing maximum 7i wind.

In addition, if the increase in ventilation resistance was small even when the N2 cumulative calculated value (T·ΔN2) was for humans, action 2 was selected, and the air reduction amount was slightly lower than action 1, which had the maximum air reduction amount. In this way, in each case, by selecting each action shown in Table 1, automation of blast furnace operation could be achieved in response to slip prediction.

Table 1 However,! The air volume decreases in the order of AI>A2>A3>A4, and the amount of decrease in the air volume also decreases in the order of B1>82.

In addition, when operating as described in 1, as shown in Figure 2, in each period (a) and (b), the N211f1 degree in the top gas composition was higher than the past average value of N2. It remained at the level. Therefore, in each period (a) and (I]), the difference between the current N2 value and the past average N2 value was calculated, and this difference was cumulatively calculated. However, in the (a) period, the cumulative calculation 4111 (T・ΔN2 ) did not become very large, but in the (1)) period, the cumulative reduction value (■・ΔN2 ) gradually increased and reached the preset TN2 boundary value. (2,0
%). For this reason, when the air flow rate was reduced by approximately 20% after reaching this point, coarseness and density were observed in the index finger, but no slipping occurred and stable operation could be continued.

Example 2゜ First, the blast furnace was operated in the same manner as in Example 1, and during the period (C) and (d) shown in Fig. 3, the current value of the differential pressure was larger than the past average value of the differential pressure. became. The difference in these rainy periods is the same novel, but the duration is different, and the cumulative calculated value of the difference (T・△SP) was greater than the differential pressure boundary value in period (d), which was reduced by 10%. When air was applied, the cumulative calculated value (T・Δ51)) decreased below the differential pressure boundary value, and the slip ball was repaired.

<Effects of the Invention> As explained above, the method of the present invention determines the N21 lit degree from the continuously measured furnace top gas composition, and
The ventilation resistance value in the furnace such as 1°C or ventilation resistance index is used as an index, and when determining a slip, the current index value is compared with the average value obtained by averaging the index values over a certain period of time in the past, and the difference is calculated as a predetermined value. In this case, the difference is accumulated and the accumulated calculated value is compared with a predetermined boundary value to predict the occurrence of a slip. In addition, the shaft differential pressure is compared with the past average value of the differential pressure to the shirt 1, and if it is higher than a predetermined value, the difference is accumulated, a boundary value corresponding to the cumulative gi value is determined, and this boundary value is This is used to judge whether there is an abnormality in the furnace condition based on the value.

Therefore, according to the method of the present invention, the accuracy of predicting the occurrence of a slip is greatly improved, so it is possible to take appropriate action, and it is also possible to take corrective action only when a slip is likely to occur. Now all slip-related problems can be solved.

[Brief explanation of the drawing]

Fig. 1 is a flow diagram showing an example of actions when carrying out the method of the present invention, Fig. 2 is an operation time flow diagram of the example shown in Fig. 1, and Fig. 3 is an operation time flow diagram of another embodiment. be.

Claims (1)

[Claims] 1) Detecting the N_2 concentration from the continuously measured furnace top gas composition, determining the current N_2 concentration, and comparing it with the average value of the N_2 concentration over a certain period in the past, The blast furnace is characterized in that the difference is cumulatively calculated when the difference exceeds a predetermined value in a positive direction, and occurrence of slip is predicted when this cumulatively calculated value exceeds a predetermined N_2 boundary value. A method for predicting slips in operations. 2) Detect the N_2 concentration from the continuously measured furnace top gas composition, and at the same time detect the ventilation resistance value including the pressure drop or ventilation resistance index, and calculate the current N_2 concentration from the N_2 concentration for a certain period of time in the past. When the difference exceeds a predetermined value in the positive direction compared to the average concentration value, the difference is cumulatively calculated, and when this cumulative calculation value exceeds a predetermined N_2 boundary value, , the current air permeability is compared with the average value of the air resistance values over a certain period in the past, the difference is calculated, and this difference is also taken into consideration to predict the occurrence of slip in blast furnace operation. Prediction method. 3) Among the ventilation resistance values obtained for each predetermined cycle, the difference between the ventilation resistance value of the latest cycle and the average value averaged over the time corresponding to the time in the furnace of the previously charged raw material at that time, 3. The method for predicting slip in blast furnace operation according to claim 2, characterized in that it is determined as a long-term increased ventilation resistance value. 4) The difference between the ventilation resistance value within a period shorter than 30 seconds before determining whether or not slipping has occurred and the average value obtained by averaging the ventilation resistance values over the past 30 minutes prior to the determination is defined as the short-term increased ventilation resistance value. The method for predicting slip in blast furnace operation according to claim 2. 5) Compare the shaft differential pressure detected at each measurement point formed in the blast furnace at a predetermined interval in the height direction with the average value obtained by averaging the shaft differential pressure over a certain period of time before this measurement. , in a blast furnace operation characterized in that, when the shaft differential pressure is higher than a predetermined value, the difference is cumulatively calculated, and this cumulatively calculated value is compared with a predetermined differential pressure boundary value to predict slip. Slip prediction method.