JPS61262644A - Method for estimating configuration of softened fused strip in shaft furnace - Google Patents

Abstract

PURPOSE:To estimate the configuration of a fused strip in a shaft furnace with good accuracy, by such a simple method that the measured temp. values of the upper and lower parts of the shaft part of the shaft furnace are compared with the average furnace wall temp. obtained from actual operation results and the temp. index of a furnace body is calculated from a specific formula. CONSTITUTION:The temp. of the furnace wall of a shaft furnace is measured at a plurality of arbitrary points in the height direction of said furnace while the average furnace wall temp. at said temp. measuring points is preliminarily calculated from the actual operation results of the shaft furnace. The temp. index S of the furnace body is calculated from an upper side furnace wall temp. TS, a lower side furnace wall temp. TB and an actual average furnace wall temp. Tav according to formula. That is, it is estimated that the configuration of a softened fused strip is an inverted V-shape at the time of S<0, and L-shape at the time of S>0 and TB<=Tav and a W-shape at the time of S<0 and TB<Tav. By this method, the configuration of the softened fused strip can be estimated only from the measured results of the furnace outside temps. without extracting data for calculation from the interior of the shaft furnace.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for accurately estimating the shape of a softened cohesive zone in a blast furnace using a simple method. This invention relates to a method that can instantly estimate the shape of a softened cohesive zone during blast furnace operation based on temperature results.

[Prior art] As is well known, in blast furnace operation, iron ore raw material and coke are alternately charged from the top of the furnace, hot air is sent through the bottom lining, and the iron ore is reduced by the reducing gas rising inside the furnace. will be carried out. Ore that has undergone a compositional change due to reduction exhibits a softening and melting temperature unique to each ore, but since the temperature inside the blast furnace is high at the bottom, the ore on its way down will eventually reach the same level as the softening and melting temperature. temperature range. In this case, normal iron ore does not change from lumpy to molten all at once, but undergoes a process of softening, melting, and then dripping over a certain temperature range to form hot metal and slag.

That is, a softened and fused ore layer exists in a certain part of the furnace, and this is generally called a softened and fused zone (hereinafter sometimes simply referred to as a fused zone).

In the past, the shape of the cohesive zone was only a matter of speculation, but recent blast furnace dismantling surveys conducted by various companies have gradually led to a more or less accurate understanding of its appearance, and even more Various methods have been attempted to detect the shape of the cohesive zone inside. According to these studies, it has been found that the shape of the cohesive zone in the furnace exhibits a large distribution in the height direction and horizontal direction of the blast furnace, and that these distributions are closely related to the conditions inside the furnace. Although it is known that various patterns are shown depending on the conditions of the blast furnace, the most standard pattern is shown schematically in FIG. That is, in Fig. 1, 1 is a blast furnace, and ore 3 (regardless of the distinction between pellets and sintered ore) and coke 4 are charged alternately from the top 1a of the furnace, and then solidified. 6 is such a blocky band that continues to descend sequentially while maintaining its shape. A cohesive zone 7 is formed in layers and in the shape of a mountain from the shaft portion 1b downward.
Hot metal and slag drip through the voids in the encapsulated core coke layer 5, while hot air is blown from the tuyere 2 and rises as shown by the arrow. Since it has extremely low porosity, it has extremely poor ventilation and acts as a resistance plate for rising gas inside the furnace.

Therefore, the reducing gas that has passed through the core coke layer 5 and ascended is distributed in the height direction and horizontal direction when it reaches the cohesive zone 7, as shown by the arrows in FIG. 1, and the upward gas is fused. Gas rising in the core coke layer 5 along the layer of the band 7 and moving in the horizontal direction passes through the coke slit 7' sandwiched between the cohesive zones 7 and exits to the lump band 6 side. That is, cohesive zone 7
indicates the distribution function of rising gas, and the degree of dispersion of the gas in the furnace is greatly influenced by its formation state, especially its distribution. When the shape is W-shaped), the gas flow at the top of the furnace is mainly a peripheral flow, and when the cohesive zone 7 is biased toward the furnace wall, the gas flow mainly forms a center flow. When a peripheral flow is formed, the reduction in the lumpy zone 6 is nine-dimensional at the periphery, while when a central flow is formed, the opposite is true, but these directly influence the formation of the next cohesive zone. Not only that, but it is also the main controlling factor for the reduction process in the entire furnace.

There are three typical patterns of the cohesive zone shape during actual blast furnace operation, as shown in Fig. 2: the so-called inverted V-shaped pattern indicated by the symbol Δ, the L-shaped pattern indicated by the symbol Δ, and the W-shaped pattern indicated by the symbol W. It has been empirically confirmed that the cohesive zone can be divided into two types, and among these, the L-type is thought to be the shape of the cohesive zone when the smoothest and most efficient furnace operation is maintained.

From the above points, in order to maintain smooth operation of the blast furnace and ensure high productivity, it is necessary to properly maintain the shape of the cohesive zone inside the furnace. It is necessary to understand the current shape of the cohesive zone as accurately as possible.

In order to meet these demands, various methods have been proposed, such as (a) a mathematical simulation method and (b) an actual measurement method using sensors. In other words, method (a) above measures the temperature and gas composition in the upper part of the blast furnace laminated material at multiple locations in the radial direction of the blast furnace using a sonde, etc. 12 estimated from this estimation model.
This is a method of estimating the external shape of the cohesive zone based on the 00"0 isotherm. In addition, the method (b) above involves inserting a sensor into the furnace belly or the top of the furnace to actually measure the temperature at multiple locations inside the furnace. This is a method to confirm the shape of the cohesive zone.

[Problems to be solved by the invention] However, all of the above methods are batch-type and cannot continuously measure the shape of the cohesive zone, and furthermore, the measuring equipment including sensors etc. is extremely expensive. Therefore, it is not possible to constantly grasp the situation inside the reactor using these methods.Furthermore, method (a) above is a method of predicting based on various estimated values including theoretical calculations, so it is not accurate in terms of accuracy. There's a problem.

Under these circumstances, the present invention is capable of estimating the shape of the cohesive zone in a blast furnace with high accuracy using a relatively simple method, and also makes it possible to continuously perform the estimation operation in the actual operation process. This is an attempt to provide a possible method.

[Means for Solving the Problems] The method for estimating the cohesive zone shape according to the present invention that achieves the above object is to measure the furnace wall temperature at arbitrary plural points different in the height direction of the blast furnace. , is a method in which the average furnace wall temperature in the temperature measurement area is determined from the operational history of the blast furnace, and the shape of the softened cohesive zone in the blast furnace is estimated based on these temperatures, and the upper furnace wall temperature: Ts , find the furnace body temperature index: S from the lower furnace wall temperature: TB and the actual average furnace wall temperature: Tav using the following formula, (Ts - Tav) @ (TB - Tav) > 0 (
7) When 5 = Te / Ts - [1] (Ts - Tav) * (Te - Tav) < 0, then 5 = - TB / T s ... [II] The S
Based on the values, the shape of the softened cohesive zone when S is 0 is an inverted V-shape, and the shape of the softened cohesive zone when S>0 and T[I≦Ta is L-shaped.

When S>O and TB<Tav, the shape of the softened cohesive zone is W
The gist lies in the fact that we recognize that each type is a type.

[Function] Based on the knowledge that the rising condition of hot air changes considerably depending on the shape of the cohesive zone in the blast furnace, and the temperature distribution of the furnace wall changes accordingly, the present inventors I thought that there might be a certain correlation between the temperature distribution and the shape of the cohesive zone, and I have been conducting various experiments along this line. As a result, we measure the temperature at arbitrary multiple points that differ in the height direction of the blast furnace, such as the upper and lower parts of the blast furnace shaft, and calculate this as the average furnace wall temperature in the above temperature measurement area determined from the operating history of the blast furnace. By comparison, the furnace body temperature index (S) is calculated using the formula below, and if this value is compared and observed with the above-mentioned actually measured furnace wall temperature and actual average furnace wall temperature, the cohesive zone shape at that time will be the same as that of the previous three types. I learned that it is possible to accurately estimate which pattern it falls under.

(Ts - Tav) * (TB - Tav) When > O, 5 = TB/Ts (Ts - Tav) m (TB - Tav) <0 (7
) when S = -Te/Ts where Ts: Furnace wall temperature in the upper part of the blast furnace τB = Furnace wall temperature in the lower part of the blast furnace Tav: Actual average furnace wall temperature in the temperature measurement area S: Furnace body temperature index, that is, also clear in the examples below As can be seen, when the furnace body temperature index 1) determined by the above formula shows a negative value, the cohesive zone shape exhibits an inverted V shape without exception. On the other hand, the above (
When the S) value shows a positive value, the cohesive zone shape will be L-shaped or W-shaped depending on whether (TO) is on the high temperature side or low temperature side with respect to the above (Ta) value, and TB≦ It has become clear that the shape of the cohesive zone when Ta is present is L-shaped without exception, and the shape of the cohesive zone when TB>Tav is W-shaped without exception. These estimation results were confirmed by comparing them with the actual measurement results of the cohesive zone using a vertical and horizontal sonde, and after all, according to the present invention, (Tav) can be determined from the blast furnace operation results. Furnace wall temperature (Ts) at each time.

TB), it is possible to accurately estimate which of the three types the cohesive zone shape corresponds to, and these estimates can be made continuously by continuously measuring the furnace wall temperature. It is possible to implement it. That is, according to the present invention, the shape of the cohesive zone can be estimated based on the measurement results of the temperature outside the furnace without extracting calculation data from inside the blast furnace, so the estimation operation is not only extremely simple but also There is no need for particularly expensive equipment, and it is possible to continue operation while constantly grasping the cohesive zone shape during blast furnace operation.To be more precise, the above three types of cohesive zone patterns can be further subdivided and quantified. However, in actual blast furnace operation, it is necessary to identify the three types of cohesive zone patterns and ensure the L-shaped cohesive zone shape that provides the best blast furnace operating efficiency. By controlling operating conditions, the original management objectives of blast furnace operation can be fully achieved.

[Example] In order to investigate the correlation between the cohesive zone shape and the furnace wall temperature during blast furnace operation, a blast furnace (inner volume 3850 Oboro 3
) Multiple thermometers were installed on the furnace wall from the shaft part of 1 to the furnace wall, and the shape of the fused material and the furnace wall temperature distribution were investigated using vertical and horizontal sondes. The results shown in Figure 4 were obtained. Ta in the obtained diagram 0 is the average furnace wall temperature between the temperature measurement points 55 and B1, which is determined from the operational history of the blast furnace.This temperature is determined as a temperature unique to each blast furnace, but it is The TB temperature in the blast furnace used for Upper side (S5.

S4.33) temperature (Ts ) and the lower side of the shaft (3
2, 51, 82), when the cohesive zone shape is L-shaped, both Ts and Ta are lower than the TB ma, and the cohesive zone shape is inverted V-shape. In this case, Ts is lower than that of TB, and TB is higher than that of TB, and when the cohesive zone shape is W-shaped, both Ts and TB are higher than that of TB.

As is clear from these figures, the shape of the cohesive zone in the blast furnace can be determined fairly accurately by determining the relative values of each furnace wall temperature at the upper and lower sides of the shaft and the actual average furnace wall temperature TB. It turns out that it can be estimated. However, it is not comfortable to calculate the temperature distribution of the furnace wall each time and visualize it to estimate the shape of the cohesive zone, and it is not desirable from the viewpoint of continuous estimation. We thought that it would be possible to immediately know the shape of the cohesive zone by converting it into an index, so we proceeded with further research.

As a result, the furnace body temperature index S is calculated from the above [I] and [11 equations] based on the temperature measurement results and the actual average furnace wall temperature, and the fusion bond is calculated from the S value and the relative value of the TB and TB I learned that the band shape can be immediately determined. That is, when the cohesive zone shape is an inverted V shape, the S value becomes negative. Also, when the cohesive zone shape is L-shaped, the S value is positive and TB≦Tav, and when the cohesive zone shape is W-shaped, the S value is positive and TB>
It has been confirmed that there are almost no exceptions to these relationships. By the way, Figure 5 shows an internal volume of 3850
The wind pressure index in Figure 0, which is a graph that aggregates and organizes the data obtained from 7 months of actual operation using a blast furnace, indicates the ventilation status inside the blast furnace during operation. When the shape of the cohesive zone was actually measured using a vertical and horizontal sonde, the shape of the cohesive zone at the time of measurement surrounded by zone ■ was an inverted V shape.

The shape of the cohesive zone during measurement surrounded by zone ■ is L-shaped, and the shape of the cohesive zone during measurement surrounded by zone ■ is W-shaped, indicating that the estimation method of the present invention has high accuracy. confirmed.

Figures 6 to 8 show the results of investigating the relationship between the wind pressure index, corrected fuel ratio, and hot metal temperature, which are typical indicators of the quality of blast furnace operating conditions, and the cohesive zone pattern estimated by the above method. It is something. It is generally said that the best blast furnace operability is obtained when the cohesive zone shape is L-shaped.
It can be confirmed that a similar tendency exists in any of the results shown in FIGS. 6 to 8. In other words, Figure 6 shows the relationship with the wind pressure index, and it can be confirmed that the lower this index is, the less the wind pressure fluctuations are and the more stable the furnace condition is. It can be seen that the value is stable and lower than that of other cohesive zone shapes. In addition, Figure 7 shows the relationship with the corrected fuel ratio, and the lower this value is, the lower the fuel consumption per unit production of hot metal can be, but it is clear that the L type has the lowest fuel consumption. It can be confirmed. Furthermore, Fig. 8 shows the relationship with hot metal temperature, and the higher and more stable this temperature is, the better the thermal efficiency inside the furnace is, which is also advantageous for preliminary treatment after tapping, etc. L
In the case of molds, it can be confirmed that the temperature of the hot metal is also stable on the high temperature side.

However, the above wind pressure index and corrected fuel ratio were determined by the following method.

(However, ΔPi indicates the difference between the actual values of the blowing pressures measured.) Corrected fuel ratio> Corrected fuel ratio = Calculated coke ratio (kg/1-p) + Calculated blown fuel ratio (kg /1-p)+0-1x (blow temperature-1
100) -0,2X [Calculated slag ratio (kg/1-P
)-3001-0,7X [Blow humidity (g/Nm3)-
151-10X [:I-Ash content ($)-111-
0.15 It was now possible to accurately estimate the shape of the cohesive zone inside the furnace by using the extremely simple method of determining . Moreover, all the data that serve as estimation elements can be obtained by measuring the temperature of the furnace wall, so estimation can be made continuously, and changes in the shape of the cohesive zone can be made by simply installing an automatic temperature measurement device and a simple calculation/display mechanism. can be automatically detected and displayed, and even if the shape of the cohesive zone has deteriorated, it can be immediately known. Therefore, it is possible to quickly respond to poor furnace conditions, which can significantly contribute to improving the efficiency of blast furnace operation.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the internal situation during blast furnace operation, Figure 2 is a schematic diagram showing a typical pattern of cohesive zone shape, and Figure 3 is a schematic diagram showing the internal situation during blast furnace operation.
．． Figure 4 is an explanatory diagram showing an example of furnace wall temperature measurement in the present invention;
The figure is a graph of experimental results showing the correlation between the estimated value according to the present invention and the actually measured cohesive zone shape. It is a graph showing the relationship with the shape of the belt.

Claims (1)

[Scope of Claims] While the furnace wall temperature is measured at arbitrary plural points different in the height direction of the blast furnace, the average furnace wall temperature in the temperature measurement area is determined from the operational history of the blast furnace, and these temperatures are A method for estimating the shape of a softened cohesive zone in a blast furnace based on
From the upper furnace wall temperature: T_s, the lower furnace wall temperature: T_B, and the actual average furnace wall temperature: Tav, the furnace body temperature index: S is determined by the following formula, and (T_s-Tav)・(T_B-Tav)>0. Toki S
=T_B/T_s (T_s-Tav)・(T_B-Tav)<0 when S
=-T_B/T_s Based on the S value, when S<0, the shape of the softened cohesive zone is an inverted V-shape; when S>0 and T_B≦Tav, the shape of the softened cohesive zone is L-shaped, and when S>0 and the shape of the softened cohesive zone when T_B<Tav is W-shaped. A method for estimating the shape of the softened cohesive zone in a blast furnace.