JPS60251205A - Method for controlling blast furnace operation - Google Patents

Abstract

PURPOSE:To stabilize a blast furnace operation by understanding the concn. of an alkali metal in a raceway and feeding back the detected concn. to the operation control of the blast furnace. CONSTITUTION:The relation between the emission line intensity obtd. by the spectrochemical analysis of the alkali metal vapor and the concn. of said metal is preliminarily understood with temp. as a parameter. The temp. of the raceway and the emission line intensity of the alkali metal vapor are thereupon measured in the tuyere part of the blast furnace. The concn. of the alkali metal vapor in the raceway is determined by the above-described parameter from the temp. of the raceway and the emission line intensity of the alkali metal vapor therein. The concn. of the alkali metal vapor is fed back as a control factor for the behavior or characteristic of coke in the blast furnace operation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention aims to obtain information about alkali metals from raceways formed in the blast furnace siding and use the information to control blast furnace operation. Specifically, it attempts to control information on alkali metals by relating them to the behavior and properties of coke.

[Conventional technology]

How to control blast furnace operations is one of the major concerns in the modern steel industry, and the results of research at each steel mill are enormous. In terms of direction, these studies focus on (1) technology to accurately grasp the current state of operation, and (2) control of each operational factor based on the above knowledge to obtain optimal operating conditions. It can be broadly divided into technologies for The research results mentioned above are mainly in the area of (2)!
D. In the area of (1), since the target is blast furnaces with strong black box characteristics, there is still a trial and error aspect, and it is difficult to apply all the measurement techniques known to date. is being considered. In other words, if it is possible to accurately grasp the current situation in the area of (1), the detection results can be translated into (2) with a considerable degree of freedom and expansion.
), and in order to establish the technology in (1), which can be said to be a prerequisite, that is, to understand the current situation, what kind of information can be used from what kind of phenomena and how? The current issue is how to obtain it with high precision.

[Problem that the invention seeks to solve]

If you want to understand the current status of blast furnace operations, you have traditionally focused on ore-related matters, but recently coke has also been attracting attention.For example, it is important to understand the shape of core coke and its behavior. This movement is becoming more active. Of these, the behavior of coke is attracting particular attention.
Alternatively, by applying a luminance meter or the like, the coke supply mechanism to the raceway and the combustion situation within the raceway are investigated, and the results of the investigation are fed back as control factors.

However, while the technology for utilizing survey results has been highly developed as mentioned above, the current state of affairs is that the technology for obtaining information has not yet reached a fully satisfactory state.

The present inventors particularly took this point into consideration, and as a result of examining the type of information that should be obtained from coke, they focused on the alkali metal vapor concentration within the raceway, which has not been considered in the past. In other words, considering that the alkali metal vapor in the raceway is an important factor that can accurately express the behavior and properties of the charged coke, we have established a technology that can accurately grasp this. We set this as our immediate challenge, and researched how to feed this back into blast furnace control as a control factor.

[Means for solving problems]

The gist of the present invention, which has succeeded in achieving the above object, is that the relationship between emission line intensity and concentration obtained by spectroscopic analysis of alkali metal vapor is determined in advance using temperature as a parameter.
J? ti - Determine the alkali metal vapor concentration in the raceway from the temperature of the raceway formed in the blast furnace blade and the bright line intensity of the alkali metal vapor, and feed this back as a control factor for the behavior or properties of coke during blast furnace operation. Exists at a point.

[Effect]

Iron ore and coke, which are the raw materials charged to the blast furnace, contain alkali silicates (for example, Sio, Na2S10
It is known that these substances coexist as alkaline components in blast furnace operation, and that they can be collectively understood as alkaline components during blast furnace operation.According to the investigation of samples collected from inside the blast furnace and the dismantling investigation of the blast furnace, the following is also clear. It is shown in That is, these alkaline components are partially reduced as they descend through the furnace together with the ore and coke. The alkali vapor generated here further reacts to become cyanide, but since the boiling point of these is low, such as 1530°C (NaCN) or 1625°C (KCN), in the temperature region around 1600°C Circulates in the furnace. Unreduced alkali silicate then falls into the hearth including the tuyere raceway. However, the gangue in the ore melts in the cohesive zone and becomes slag that drips to the bottom of the furnace, so the slag generally flows through the coke gap on the core side and does not flow into the tuyere raceway. That being said, if it is possible to observe the behavior of alkaline components in the raceway section, it is thought that it is based on unreduced alkali silicate in the coke ash. The brightness intensity graph (Figure 2) obtained by actually performing spectroscopic analysis of the raceway in the blast furnace siding area is shown below.
When compared with the brightness intensity graph (Fig. 3) obtained by the panel partial optical analysis measured in a vertical combustion furnace filled only with coke, a very high degree of similarity can be seen between the two.

From the above results, it was concluded that the alkali metals observed in the siding raceway correspond to the alkali metals in the coke ash.

On the other hand, when we investigated the estimated temperature (Figure 4) * Km O+NatO content (Figure 5) and pore volume (Figure 6) of the coke collected from the blast furnace siding during blast furnace body wind, we found that Power results were obtained. According to these results, there is a good inverse proportional relationship between the estimated temperature (Figure 4) and the alkali content (Figure 5) for each coke particle size, and the higher the temperature, the higher the alkali content. If the temperature is low, the alkali content will increase.
Also, when considering this and the results shown in Figure 6, it can be seen that coke with low alkali content due to high temperature has a large four-pore volume. That is, further inferring these, it can be considered that in the high-temperature area, the coke temperature rises rapidly, so the alkaline component in the ash evaporates and decreases, leaving large pores in that area.

The temperature at which alkali metals evaporate from coke ash depends on the quality of coke, but is usually 1720°C.
It is believed that the evaporation of the alkali metal does not proceed much until this critical temperature is reached, and when the critical temperature is reached, evaporation occurs rapidly. - The temperature distribution inside the blast furnace also varies depending on the operating conditions and the state inside the furnace, but according to a dismantling investigation of a certain blast furnace, the temperature of coke at the lower end of the cohesive zone was 1600℃, and this area was contaminated with cyanide as mentioned above. It seems to be cyclical.

It is thought that the temperature rises rapidly in the raceway portion, forming a high temperature of 1700° C. or more, and evaporation of the alkali metal occurs.

Based on these considerations, we found that if we could know the concentration of alkali metal vapor in the raceway, it would be possible to infer the behavior and properties of coke, and furthermore, it would be possible to use these as a control factor in blast furnace operation management. It was concluded that feedback could be provided.

The emission line intensity of alkali metal vapors depends on the concentration of alkali atoms and temperature. Therefore, we first evaporated the alkali metal at a constant temperature and determined the relationship between the amount of evaporation (measured by weight loss of the sample) and the intensity of the emission line. Since the former corresponds to the alkali vapor concentration, the above relationship can also be expressed as a calibration curve showing the correspondence between intensity and concentration. If you change the temperature conditions and create a similar calibration curve from force, the relationship between emission line intensity and concentration using temperature as a parameter will be sorted out, and this can be used as is in the following implementation. Good.

That is, in carrying out the present invention, it is necessary to actually measure the temperature of the raceway and the bright line intensity of the alkali metal vapor in the lining of the blast furnace. There are some limitations regarding the actual measurement methods for temperature and emission line intensity.
Temperature calculation may be performed by two-color temperature calculation using λ and m and λ = 650 nm). By adding correction using a blackbody furnace in advance, highly accurate temperatures can be obtained. On the other hand, since it is necessary to perform spectroscopic analysis to determine the emission line intensity of alkali metal vapor, it is necessary to select, for example, the resonance line of Na from among the wavelengths obtained in the above manner, and apply that intensity to the above-mentioned calibration curve. All you have to do is measure the metal concentration.

As described above, the concentration of alkali metal vapor measured at each tuyere of the blast furnace can be used to control the unbalance between the tuyere by knowing the unbalanced condition between the tuyeres, or to calculate the average value in the circumferential direction. It may be calculated and applied to reaction control for the overall trend.

〔Example〕

Next, a typical example of the above-mentioned control method will be listed and its outline will be explained as an example.

Regarding the coke supplied to the raceway section of the lining, the cohesive zone (root) shown in Figure 1 (single line arrows indicate coke flow, double line arrows indicate gas flow).
It is roughly divided into low-temperature coke (commonly known as dark coke) B under F and high-temperature coke (commonly known as inter-coke) A on the core side.
Until now, it has not been fully clarified which of these is primarily supplied to the raceway. However, according to the present invention, the behavior of coke around the raceway can be expressed as an index as shown in Table 1. In addition, P in FIG. 1 indicates a coke fine powder layer.

In case N[11, the raceway is at a high temperature but the alkali concentration is low. Therefore, it can be seen that the coke temperature reached 1720℃ or higher (in this example, alkali silicate evaporates rapidly above 1720℃) before being supplied to the raceway. It will be done. That is, it can be seen that coke from the core side was supplied to the raceway section. Next, in case Nn2, the raceway is at a low temperature and the alkali concentration is high, so a large amount of alkali metal vapor is generated within the raceway.In other words, the raceway is not exposed to high temperatures before reaching the raceway, It is known that the coke was not exposed to high temperatures until it reached the way, and the temperature rose to 1,720°C or higher, and such coke is considered to be dark coke. Furthermore, since Case M3 is an example in which the temperature of the raceway is low and the alkali concentration is low, it is clear that the coke cannot be burnt if the temperature exceeds 1720℃ both before and after reaching the raceway. Dark coke can be considered as coke. Cases 2 and 3 are the same in that dark coke is supplied, but the difference in the latter is that the coke is not sufficiently combusted, which is extremely useful for feedback to blast furnace operation. It is clear that it is information.

Table 1 As can be understood from the above explanation, in the case where Nn4 is to be affected (i.e., the raceway is at a high temperature and the concentration of alkali metal vapor is also high), it has already been heated to a high temperature by the time it reaches the raceway. We agree with the case that alkali metal vapor was generated at once during combustion in the raceway because the generation of alkali metal vapor was incomplete due to the feed force (therefore, while light coke was being supplied).
Theoretically, this is difficult to imagine. Therefore, it is not listed in Table 1. However, since complex factors are intertwined with each other in blast furnace operation, a situation that applies only to any of the above three cases is not formed in every case. In other words, in actual blast furnaces, intermediate-level conditions in each case are often detected, so it is only necessary to judge the situation and provide feedback to operational management while taking into account other operating factors in the blast furnace, the type of raw coke, etc. It turns out. For example, the cohesive zone shape,
The core coke shape, raceway shape, etc. are considered to be the controlling factors, but the particularly important factor is the cohesive zone shape on the furnace wall side (the shape of the cohesive zone root), which affects the fall rate of dark coke. Depends on it. Therefore, by measuring the supply ratio of light and dark coke, the shape of the root of the cohesive zone can be estimated, and this can be fed back to the operational control of the blast furnace.

Furthermore, the temperature of the coke supplied to the raceway section is considered to have a significant influence on the temperature of the gas generated immediately, and to control the heat level of the blast furnace. This pre-button information is used to estimate the temperature of the coke supplied to the raceway section from the brightness/darkness of the coke, and is used to measure the temperature of the hot metal that is actually tapped [S1 ] It makes it possible to estimate the furnace heat before measurement, and it also plays an important role in controlling the operation.

Next, the use of coke for quality evaluation will be explained.

The causes of deterioration of coke charged into a blast furnace include impact fracture when the charge falls, abrasion between coke grains during descent into the furnace, deterioration due to reaction with CO2 in the 900-1100℃ range, and deterioration in the xioo'c or higher range. Various types of deterioration (C
Examples include deterioration due to reaction with O, thermal deterioration, deterioration due to alkali attack) and combustion powdering in the tuyere raceway. Among these, deterioration on the high temperature side C (especially above 1100℃) has a large impact on the ventilation and furnace heat in the lower part of the furnace, so quality control is carried out by adding hot properties to the conventional coke evaluation criteria. It becomes necessary. On the other hand, the alkali metal vapor contained in the furnace gas enters into the cracks of the coke and condenses, causing the coke to become powder. Furthermore, the alkali metals that adhere and condense on the surface of the coke penetrate into the graphite crystals and form interlayer compounds, causing surface peeling and cracking of the coke. FIG. 7 is a graph showing the influence of alkali on the gasification of coke, and the influence of alkali metals on reactivity is difficult to ignore. However, the currently widely used coke reactivity test method (JIS K2/115B
(1977)) did not take into account the influence of alkali metals. If the present invention reveals the alkali metal vapor concentration in the raceway under such circumstances, it will be possible to define a method for evaluating the hot properties of coke under conditions similar to those in the furnace, and improve blast furnace operation control. In particular, it becomes possible to provide feedback for quality control of coke.

〔Effect of the invention〕

We determined the alkali metal concentration in the raceway and fed this information back to blast furnace operation control.
For example, it has become possible to understand the feeding behavior of coke to the raceway and the hot properties of coke, which can contribute to stabilizing blast furnace operations.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the situation of the raceway section, Figure 2 is the spectroscopic analysis result of the blast furnace wall section, Figure 3 is the spectroscopic analysis result of the vertical combustion furnace, and Figure 4 is a graph showing the estimated temperature of coke. ,
FIG. 5 is a graph showing the behavior of the alkali component, FIG. 6 is a graph showing the micropore volume, and FIG. 7 is a graph showing the relationship between the gasification rate of coke and the apparent density after reaction. Applicant: Kobe Steel Co., Ltd. (Q) (%) O”?N+0”M

Claims (1)

[Claims] The relationship between the emission line intensity and concentration obtained by spectroscopic analysis of alkali metal vapor is determined in advance by using temperature as a parameter, and from the raceway temperature actually measured at the blast furnace siding and the emission line intensity of alkali metal vapor, A method for controlling blast furnace operation, characterized in that the concentration of alkali metal vapor in the blast furnace is fed back as a control factor for the behavior or properties of coke during blast furnace operation.