JPH01319614A - Method of operating blast furnace - Google Patents

Abstract

PURPOSE:To execute the operation of the blast furnace more efficiently than heretofore by recognizing a slip and blow by a change in the descending amt. of the charge level in the furnace and the temp. of a furnace top gas and taking an adequate action. CONSTITUTION:The furnace body of the blast furnace is circumferentially segmented to plural pieces and the level difference ( l) at the time of embedment between at least the two consecutive batch charges is detected for each of the blocks. Decision is made that the slip arises when the level difference ( l) exceeds the prescribed value (about >=0.3m) which is previously determined. The size of the slip is evaluated by the size of the level difference ( l). The blow by is decided if the temp. of the furnace top gas rises sharply or the N2 concn. in the furnace top gas changes drastically, even if the level difference ( l) is below the prescribed value. The slip and blow by in the blast furnace are detected in this way and the efficient operation is executed by the adequate action.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of operating a blast furnace, and more specifically, slip and blow-through are calculated based on the amount of fall on the surface of the contents in the furnace and the N2 in the top gas composition.
This relates to a method of operating a blast furnace that allows for the recognition of changes in concentration and top gas temperature, the evaluation of the impact of both on operations, and the ability to take appropriate action.

Conventional technology In general, in blast furnace operation, it is important to control the descending state of the charged material.
It is said that it is necessary to lower the charging material from the top of the furnace at a constant speed of 1.0 mm to maintain heat balance. In other words, inside the blast furnace, the power of charging raw materials such as iron ore charged from the top of the furnace (while descending, the temperature is gradually raised, reduced,
Each process, such as melting, is colored red to maintain the overall thermal balance.

However, if a slip or a blowout +1 occurs in the furnace, the charged raw material will fall without going through the above process, and the heat balance will be disrupted, causing a serious problem in operation.

In other words, FIG. 4 is an explanatory diagram of how slip occurs, and as shown in FIG.
When the descent of the charged material is temporarily stopped and suspended, the stagnation portion 2 blocks the rising, return and reduction, resulting in these discontinuous portions. In addition, even if the stagnation part 2 is formed, the charged raw material 4 below it continues to descend, resulting in
In the upper part of the stagnation part 2, the charge material 4 does not arrive and a cavity 3 is created.

Thereafter, the part 2 falls downward as shown by the arrow in FIG. 5 due to its own weight, and the cavity in which the cavity 3 completely disappears is shown in FIG. ), slipping will occur.

However, when a slip occurs, - the descent is temporarily interrupted and the stagnant part 2 and the charging material above it suddenly fall to the lower part of the furnace in unascented, unreduced form. This causes the thermal balance to collapse and has a serious impact on blast furnace operation.

In addition, this slip appears as an in-furnace phenomenon in the form of a sudden drop in the surface of the charging material at the top of the furnace. The difference is detected by -C.

On the other hand, even if a stagnation part is formed, if the stagnation part is not strong enough to block the upper part of the charging material and form a large cavity below, the stagnation part will be destroyed. At this time, the voids in the upper charging material layer become significantly large, and the waste concentrates in these areas and flows, causing an in-furnace phenomenon called blow-through. This will disrupt the balance.

The effect of this slip is noticeable when it occurs in the lower part of the furnace.The reason for this is that in the lower part of the furnace, FeO+C→Fe+CO
+Q, reaction occurs, whereas in the upper part of the furnace Fe, 03
+C0-rFe-1-Co21-02 reaction occurs,
The reaction heat 01 is larger than the reaction heat 02. Therefore, when a slip occurs, it is necessary to distinguish based on the location where it occurs and take appropriate measures.

Further, when blow-by occurs, the temperature at the top of the furnace rises, and the reaction efficiency of the waste in the furnace decreases. However, in order to prevent equipment from being damaged (deteriorated) due to an increase in the furnace top gas temperature, the only action that is generally taken is to lower the air flow rate to lower the furnace top gas temperature. Therefore, the reaction efficiency of the gas in the furnace decreases in both the slip and the blowout C, and even though there is little fall of the charged material, no action is taken against this, resulting in abnormal heat absorption in the furnace. A reaction takes place and the furnace heat 1/Bel drops significantly.

Therefore, various methods for detecting and preventing these slips and blow-throughs have been proposed as conventional blast furnace operating methods. However, these conventional methods have not actually achieved the objective.

First, in Japanese Patent Application Laid-Open No. 55-125207, the blast furnace feeding conditions, furnace top gas composition, charging raw material composition, hot metal composition, etc. are measured, and using these s1 measured values, the carbon Calculate the consumption rate of coke consumed in the furnace from the income and expenditure, calculate the pig iron production rate from this coke consumption rate and oxygen balance, and calculate the unloading rate based on the solid volume reduction in the furnace based on this calculated rate. At the same time, calculate the actual unloading speed at the top of the furnace based on the measurement of the index finger or the amount of raw material charged, and compare these unloading speeds with the average unloading speed at a predetermined number of stages. Accordingly, a method is described in which the unloading status is determined using a predetermined formula, and the unloading of the charged raw material is adjusted based on the result.

In addition, Japanese Patent Application Laid-open No. 59-83707 (in this article, unloading abnormality is statistically determined from the unloading depth and unloading speed from the loading rod, and the number of unloading abnormalities and the unloading depth at the time of unloading abnormality) , a method is described in which the unloading status is indexed by a matrix combination and the furnace conditions such as slip are managed from this index.

In addition, JP-A No. 57-76108 describes a radial shape model of a blast furnace that shows the following parameters at each radial position (J8 ore amount, coke amount, gas flow rate, charge material particle size porosity J5, and atrium ()). A method of preventing blow-through by controlling cross-sectional average operating quantities such as ore amount/coke amount, coke base, feed 11 heavy oil injection amount, etc. so that the blow-through index at each position in the radial direction becomes a predetermined index. is listed.

In addition, JP-A-58-71340 discloses that the pressure loss is determined from the furnace top pressure and the shaft pressure in the blast furnace height direction, and the load of the charging material between the furnace top shell 1 and the pressure measurement position is described. Then, the ratio between this pressure loss and the load of the charged material at each pressure measurement position is determined. It describes how to blow air.

In addition, Japanese Patent Application Laid-Open No. 62-270712 describes the unloading speed, pressure loss, shaft pressure peak, shaft temperature, fixed sonde temperature, gas utilization rate, furnace mouth sonde temperature, etc. based on data from various sensors of the blast furnace. After creating various data showing the status of the blast furnace, such as the temperature of , Atrium +:
A method for predicting l, slip, etc. is described.

However, these methods have problems with the accuracy of the reference measurement data, and it is difficult to distinguish between slip and inflow, which indicates that the charged material flows into the center of the furnace, and it is difficult to detect abnormal furnace conditions. However, abnormalities cannot be quantitatively evaluated, and appropriate actions cannot be taken depending on the degree of abnormality.

In addition, if a slip occurs, do not take the above method (in actual operation, depending on the situation of the index finger,
The magnitude of the slip is determined by f11, and corresponding actions are taken based on this. That is, as shown in FIG. 7, when a slip occurs, the depth difference between the index fingers becomes sharper, and the extent of the slip is evaluated and detected based on its magnitude. However, when slips are detected using the index finger in this way, even things other than slips are erroneously detected as slips. That is, when detecting with the index finger, as shown in FIG. I5 is placed on the surface of the charging material 4, and as this surface descends, the weight 5
Since the weight 5 is lowered, the lowering of the charged material 4 in the furnace is detected by the lowering of the weight 5. However, even in so-called pouring, the charging material 4 in the blast furnace 1 moves to the center while descending, and as the charging material moves to the center, the weight 5 also moves to a lower center, and the weight of the index finger The movement is the same as that of a slip, and it is impossible to distinguish between a slip and a flow using only the index finger.

1. Problems to be Solved by the Invention The present invention aims to solve these problems.Specifically, in the prior art, it is not possible to distinguish between slip and flow by detecting the slip with the index finger. In addition, it is difficult to evaluate the reduction in the reaction efficiency of the in-furnace scum when blow-by occurs, and it is not possible to take appropriate actions in response to this. The purpose of this study is to solve problems such as the fact that a method of operating a blast furnace that accurately detects abnormal conditions and takes appropriate action has not yet been researched or disclosed.

Means for solving the problem and its operation, the method of the present invention detects abnormal situations in the furnace condition such as slips and blowouts based on the amount of descent of the charging material in the blast furnace, and At least two consecutive
The level difference at the time of embedding between two batches is measured, and when this level difference exceeds a predetermined value, it is determined to be a slip, and when the difference in level is less than the predetermined value, the furnace top scum temperature is It is characterized by determining that an atrium has occurred when there is a sudden rise, and controlling the operating conditions.

In addition, the method of the present invention predicts the occurrence intensity of slip and blow-through based on the change in the N27 concentration in the furnace top scum composition before and after the determination of slip and blow-through, and based on this predicted intensity, C
It is characterized by controlling operating conditions.

Further, in the method of the present invention, the furnace body of the blast furnace is divided into a plurality of sections in the circumferential direction, the level difference is measured for each section, and when the level difference for each section exceeds the predetermined value, It is characterized in that a slip is determined to be present when the level difference indicated by J is equal to or less than the predetermined value and the furnace top gas temperature rapidly increases, and a blowout is determined to be present, and the operating conditions are controlled.

Therefore, the effects of these means will be explained in more detail as follows.

First, the present inventors distinguished slip and inflow in the furnace using index fingers, and in order to quantify and understand this, the inventors analyzed operational data and investigated the U1 method. It was found that it was necessary to confirm the existence of (Δl).

Therefore, in order to go further and confirm that the surface level of the charged rough stone has definitely decreased, we compared the level at the time of raw material charging (1 novel at the time of embedding) for two consecutive batches and the difference ( When we calculated the difference (△l), we found that this difference (△l
), it was found that slips and inflows can be distinguished.

That is, FIG. 9(a) is an explanatory diagram of the index finger showing the case where slipping occurs, and FIG. 9(1)) is an explanatory diagram of the J-index finger showing the case of flowing. When slipping occurs, there is a level difference (△l) between the level at the time of charging unit bulk f charging and the level at the time of filling the next batch charging, and the value at which this level difference (△l) is When the level difference is higher than that, a slip occurs, and the magnitude of the slip is evaluated based on the magnitude of the level difference (Δl). On the other hand, Figure 9 (())
As shown in Figure 2, the difference in depth of the index finger is clearly noticeable, but the level difference (△l) at the time of embedding is hardly recognized between the two successive hatches. In this case, it is evaluated as inflow.

To explain in more detail, when slipping occurs, the charged material is actually falling.

For this reason, even when charging the next batch, the index finger drops significantly and the level difference (Δl) also becomes a large value. On the other hand, when pouring is occurring, even if a change appears in the index finger, the raw material force (not falling) is actually lowered, so the index finger hardly lowers when charging the next hatch, and one novel Difference (△l
) will be a small value.

In addition, in order to improve slip detection accuracy, the blast furnace body is divided into multiple sections in the circumferential direction, and each section has a level difference (△
Il) and slip can also be detected. In this way, the inside of the furnace is divided into multiple sections, and the level difference (△
l), the boundary values α, β, γ are determined as follows:
..., etc., to detect the occurrence of slip.

(1) 17 bell difference in at least two directions (△11, △
12) occurs, it is assumed that there is a slip when △It1>α and △II2>β.

(2) When there is a significant drop in only one direction and a large level difference (Δj?1) occurs, it is determined that there is a slip when ΔI11>γ.

In other words, case (1) is a case where slip and level difference occur in two or more directions, and the level difference to be compared is the level difference that should be recognized as slip and the slip. A small level difference is used to distinguish between them, and when they are satisfied at the same time, it is considered a slip.

Here, the reason why the determination level difference is set small and the comparison is made with other sections is to evaluate the influence of the amount of descent caused by slipping. In addition, since case (2) is a localized slip, the level difference that alone affects the furnace condition is set as the boundary value for slip determination. Therefore,
The boundary values have the relationship γ>αβ.

In addition, as described above, when detecting the occurrence of slip by detecting the level difference (△l) in multiple directions, the surface of the charged raw material falls, and the amount of the fall, that is, the level acid △11, △
12... occurs, there is no strong relationship between the surface drop and the decrease in furnace heat, as shown in FIG. On the other hand, when the surface drop of the charged material exceeds a certain value, the amount of change in △N2 as a partial pressure in the top gas composition before and after that can withstand the degree of decrease in furnace heat in practical terms. A strong relationship, as shown in FIG. 12, can be seen. From this point, in the method of the present invention, C evaluates the magnitude of slip based on N2%.

Of course, N2% indicates the temperature as N2 partial pressure in the gas composition of the furnace top scum. The reason for this is that when slip occurs in the lower part of the furnace, FeO+ Go−J Fe 4− Co2Co, +C→
2GO FeO+ Q-+ Fe + G.

As a result of the rapid reaction, the N2% in the top gas composition decreases.

Therefore, when evaluating the influence of slip on the furnace condition using the N2% in the furnace top scum, which is an index of the reaction in the lower part of the furnace, the magnitude of the slip can be determined by the magnitude of the N2% decrease before and after the occurrence of the slip. It can be evaluated. In other words, N2 itself does not contribute to the reaction inside the blast furnace, and therefore it is difficult to evaluate the magnitude of slip using the absolute value of the amount of N2.

However, when slipping occurs, as mentioned above, N2%
changes, and therefore, the degree of slip can be evaluated by the amount of change in N2% in the top gas before and after slip occurs.
Preferably, the following N2% change amount is used. When the amount of change in N2 in the furnace top gas (ΔN2) is shown over time, it changes as shown in FIG. In FIG. 11, a slip occurs at the time indicated by ↓, and a significant decrease in N2% is observed after the slip occurs, indicating that it is suitable for use in slip evaluation. During this change in N2% in the furnace top scum, if the difference between the maximum value immediately before slippage and the minimum value after slipping is used as the amount of change in N2% for slip evaluation, the furnace condition before slipping can be evaluated. This allows evaluation including abnormalities, making quantitative evaluation of the degree of slip more accurate.

J5, 11.12 in the figure indicates the most recent time before and after the occurrence of slip, respectively, tl is 10 to 50 minutes, 1
2 is about 60 minutes. Furthermore, analysis of furnace top gas can be performed continuously, and N2% can be determined with high accuracy. In addition, the maximum and minimum values of N2% can be automatically determined by a computer from the rate of change of N2%. can.

Furthermore, even if the amount of descent of the charging material surface is small, a sudden rise in the furnace top gas temperature and a large change in the N2 concentration in the furnace negative gas may occur. Here, this is defined as an atrium, but
At this time, it was found that blow-through could be evaluated using the index of the change in N2% as in the evaluation of the furnace top scum temperature rise and the slip described above.

Therefore, preferred examples of operating the blast furnace as described above are as follows.

1. Recognition of slip △Z1 ＞α Gatsu △12>β・・・・・・(1) △11
＞γ ・・・・・・・・・・・・・・・・・・(
When the relationship 2) is established, it is recognized that there is a slip.

Here, a-0.6 to 1.2 m (average 0.9 m) β-
For 0.3~0.8 (average 0.(3m) γ-1.5~2.
5m (average 2.0m126 Slips are classified into human, medium, and small based on the degree of influence on furnace heat.

a) When △N2 < 81, the formula shown in (1) or (2) is established, and when △11 < +), the slip is small and the influence on the furnace heat is small.

b) a, < ΔN2 < a2 and (1) or (
When the formula shown in 2) holds true and Δ11<bl, the slip is moderate and the influence on the furnace heat is moderate.

C) When △N2 > a2, the equation (1) or (2) is established, and when △11>b, the slip is large and the influence on the furnace heat is significant.

Here, al<a.

△l value that can distinguish b1 Nislip Furthermore, during the process, the law 1 moisture, oxygen enrichment rate, etc., row cropping force (if changed, due to changes in the amount of waste due to decomposition of water, changes in the amount of charged N2, etc.) The N2'lfA degree changes.This change is theoretically examined, and the N2) seismic intensity is corrected to make the conditions equivalent to the -C5 reference state.

Here, the amount that should be recognized as slip is β (well, 0.3 m or more. The reason for this is that if it is less than C0.3 m, it cannot be distinguished from the flowing J method, so it is preferable (well, β (well, if it is 0.6 m or more) Make a clear distinction.

In addition, C1γ is defined as an amount that can be evaluated as having a large influence on the furnace due to locally generated slip, and is classified by setting it to at least 1.5 m or more, preferably 2 m or more.

Note that since α and β are the amounts of decline when evaluated in combination, α takes the intermediate value between both β and γ. In other words, it is not the small amount of precipitation that causes localized slip (I, in this case, γ), but rather the impact on the reactor (in this case, medium-scale, in which case it is difficult to distinguish between slip and slip). A slip can be detected under the condition that it can be evaluated and under conditions are occurring in other parts as well.

In addition, evaluation of the size of slip etc. is performed as follows.

The amount of change in N2 concentration after recognition of slip is divided into necessary divisions, that is, into the number desired to be evaluated, and the slip strength is determined based on the magnitude of the N2'tlA degree.

In addition, the slip strength can be determined by combining the amount of descent at the time of slip recognition with the amount of change of human, intermediate, and scale (N2 i11 degrees) as described above.

In other words, (1) When a slip occurs, the change in N21 degrees occurs by 0.5% or more in cases where the difference is at least 0.2% or more, and reaches 7% or more in large-scale cases. . This 41 can be measured by detecting the N2-It degree difference (ΔN2) using the method of the present invention.

Therefore, by dividing the N2 concentration difference (△N2) from 0.2 to 7% (amount exceeding 7% is acceptable) into necessary categories, and setting the slip strength for each of the divided stages, slip can be reduced. The size can be evaluated by dividing it into each stage. For example, if formula (1) or (2) is satisfied, N
If the two-way difference (△N2) is divided into 0.2 to 7%,
(1) Divided into stages and each division 8. , a2...
...Displayed as al-1. )1) △N2<0.2%
...Slip strength 1 (al) 2) 0.2%...△N2<a,...Slip strength? (al) 3)a2 te△N2〈a3...Slip strength 34) a fn-+) <△N2<a,,...
・The blast furnace operation action to be taken corresponding to each slip strength (2) can be set in advance.

(2) By combining the scale of slip occurrence, the difference in N2 concentration, and the classification of ΔN2, the following slip strengths can be classified. Here, if the slip size is small, medium or medium, and the number of people is 111 and C2, then formula (1) or (2) is satisfied, ■△N2 <8
1 △1 mouth<1] 1...Slip strength small ■ai
<△N, <a,, △ln<111 ... Slip strength medium (hang △N2>a2 △l n> l] 1...
...If the slip strength is large, only cases with large slips are subdivided into ■△13ko・1〕1 △12>β...
...Slip strength 1■△L>l)2 △l,>β・
・・Slip strength 2■a2 <△N2〈a3・・・・
- Slip strength 3■△N2>al-1... It can be evaluated as slip strength n, and )) may be determined with the accuracy required for blast furnace operation.

In addition, the determination of open space is performed as follows.

Blow-through is determined by a sudden change in the furnace top gas temperature. Atrium (
The distinction between the two groups is determined by the maximum value of the most recent waste temperature, and the occurrence of blow-through can be detected when the temperature is at least 300'C or higher.Preferably, when the temperature exceeds 400 degrees For example, it is possible to detect atriums that have an effect on the furnace.

This can also be evaluated for each strength based on ΔN2. For example, )...Intensity 1■ Atrium does not occur a2<△N2<a3...Intensity 2■Atrium does not occur △N2>ah...Intensity 11 Each of the above An example is shown in which the action amount for CY operation is determined according to slip strength and blowout strength.

Here, BV indicates the air flow rate, expressed as the air reduction rate, CR
It shows the coke ratio and shows the rise value (g load).Blank means no ore charging and does not show the number of charges.

In addition, this table can also be used for each atrium or slip.
If the results are similar for evaluation purposes, it can be prepared as one table. In addition, since each intensity is a quantitative evaluation of the impact without affecting the furnace condition, it is easy to set actions.

Note that the action amount determined from this table is compared with past action recall, and the final action is determined based on the past action recall.

Examples Example 1 During blast furnace operation, as shown in FIG. 1, level differences △11 and △12 were observed between successive hatch charges. Ten slips occurred at time t1.

However, the evaluation of ΔN2 at this time was "small slip" and no action was taken.Thereafter, there was no change in the furnace top temperature or ΔN, no action was taken, and the furnace condition became stable.

Example 2 As in Example 1, the level differences △11 and △12 were observed as shown in FIG. In this case, time t]
A slip occurred. The evaluation at the 11th point was that it was a "small slip" and no action was taken.
The coke ratio was lowered from 3/nl in to 560 ON m3/min, the coke ratio was increased by 20 klJ/, and one charge of blank charge was introduced. Furthermore, at time point 13, ΔN2
further decreased, and "slip strength 5" was detected. At this time, the wind was reduced by 200ONm3/min, and the coke ratio was 5.
0 kg bar, it corresponds to the blank charge 3 charge action, but what about the action that has already been performed? i1i correct, sending J! Ill amount is 500ON n13/nl! nM■
Further, the coke ratio was increased by 30 l<a/t, and two blank charges were carried out.

Example 3 As in Example 1, the level differences △11 and △12 were observed in Figure 3 (as shown in Figure 3). The top temperature increases and Δ
N2 also decreased, and "blow-out strength 2" was detected.Therefore, the air flow rate was changed from 700ONm3/min to 56ONm3/min.
Reduce the coke ratio to 0ON m3/min and reduce the coke ratio to 20 kg.
/t J2, 1 charge of blank charge was charged. Furthermore, at the 12th point, △N2 decreased, and the strength of the atrium was 3.
” was detected and learned. For this reason, the action that has already been taken is corrected and the air flow rate is increased to 500ON lll3/m i I'
The coke ratio was increased by 10 kg/l, and one A7-tube blank charge was charged.

<Effects of the Invention> As explained above, the method of the present invention detects abnormal furnace conditions such as slips and blowouts based on the amount of descent of the charging material in the blast furnace, and operates the blast furnace. In this case, the level difference at the time of embedding is measured between at least two consecutive batches, and when this one-novel difference exceeds a predetermined value, it is determined that a slip has occurred, and the level difference is less than or equal to the predetermined value. J-1 is characterized in that when the furnace top scum temperature rises at the core, it is determined that blow-through has occurred, and the operating conditions are controlled.

Therefore, according to the method of the present invention, it is possible to differentiate between slip and inflow, and between slip and blow-through in blast furnace operation, so it is possible to take action to respond to these abnormal furnace conditions, compared to the conventional method. Operations can be carried out efficiently.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are explanatory diagrams that do not show the time flow of each embodiment of the method of the present invention, and Figure 4 is an explanation of the occurrence of stagnation in the charging material of the blast furnace. Figure 5 is an explanatory diagram of the occurrence of slip from the stagnation part shown in Figure 4,
Figure 6 is an explanatory diagram of changes in the level of charged raw material when slip occurs, Figure 7 is an explanatory diagram for distinguishing the occurrence of slip in the present invention, and Figure 8 is a method for detecting the level of charged raw material using an index finger. Figures 9(a) and (b) are explanatory diagrams showing the level changes of the charging material in the case of slipping and pouring, respectively, and Figure 10 shows the amount of level change of the charging material and its furnace. Figure 11 is a graph showing the relationship between the effect on heat and the effect on furnace heat.
Figure 2 is a graph showing the relationship between ΔN2 and its influence on heat. Code 1: Blast furnace 2: Stagnant part 3: Cavity 4: Charge 5: Weight

Claims (1)

[Scope of Claims] 1) Based on the amount of descent of the charged material in the blast furnace, abnormal situations such as slip and blow-through are detected, and at least two successive batches are processed when operating the blast furnace. The level difference at the time of embedding is measured at the entrance, and when this level difference exceeds a predetermined value, it is determined to be a slip, and when the level difference is less than the predetermined value and the furnace top gas temperature rises rapidly, a blow-through is detected. A method of operating a blast furnace characterized by determining that the operating conditions are controlled. 2) A claim characterized in that the intensity of occurrence of slip and blow-through is predicted based on the change in N_2 concentration in the top gas composition before and after the judgment of slip and blow-through, and the operating conditions are controlled based on this predicted intensity. The method of operating a blast furnace according to item 1. 3) Divide the furnace body of the blast furnace into a plurality of sections in the circumferential direction, measure the level difference in each section, and determine a slip when the level difference in each section exceeds the predetermined value. 3. The blast furnace operating method according to claim 1, wherein when the level difference is equal to or less than the predetermined value and the furnace top gas temperature rises rapidly, it is determined that blow-through occurs and the operating conditions are controlled.