JPH03291315A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To improve productivity and to lower fuel ratio by using highly accurate coke temp. at raceway part in a blast furnace as information of furnace heat, combining it with the theoretical combustion temp. and rapidly executing operation under blasting condition for adjusting the furnace heat. CONSTITUTION:The coke temp. Tc at the raceway part in the blast furnace is detected from the tuyere part and also the ratio Tc/Tf of Tc to the theoretical combustion temp. Tf is calculated, and Tf and/or fine powdered coal quantity blown from the tuyere part are adjusted beforehand so that this ratio is in the set range. Tc can be detected under good accuracy by arranging a radiation thermometer at peeping hole part in the tuyere to measure the coke surface temp. and Tf is obtd. with the prescribed equation. At the time of maintaining Tc to the constant by adjusting Tf and the fine powdered coal quantity blown from the tuyere part, Si content in molten iron as the representative index for the furnace heat in the blast furnace, can be maintained to the constant and the furnace heat is stabilized. When Tc/Tf is not the constant only by maintaining Tc to the constant, as Tc can not be maintained to the constant, it is necessary to adjust both of Tc and Tc/Tf.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention stabilizes the furnace heat of the blast furnace by maintaining a constant coke temperature in the blast furnace raceway, thereby improving productivity and reducing the fuel ratio. Regarding blast furnace operation method.

[Prior art] During blast furnace operation, the inside of the raceway is observed with the naked eye through the tuyere peephole, the furnace heat of the blast furnace is judged, and the ratio of ore and coke charged from the top of the furnace (0/ (abbreviated as C), ventilation conditions (
The temperature of the hot metal flowing out from the tap hole and the silicon content in the hot metal are maintained constant by adjusting the feeding temperature, oxygen amount, steam amount, and pulverized coal amount.

Instead of observing with the naked eye, some cameras are installed in the peepholes to observe the inside of the raceway.

The criteria for determining the furnace heat of a blast furnace based on these observations are the swirling speed of coke in the raceway, the brightness (brightness) of coke, etc., and are largely subjective to the observer.

[Problems to be Solved by the Invention] In conventional blast furnace operations, the inside of the raceway is observed to determine the furnace heat by either a person looking directly through a peephole, or a person looking through an image taken by a camera. The criteria for judgment differs depending on the person observing, and it is practically impossible to observe continuously, so the information is fragmentary. Therefore, the accuracy of furnace heat information is low.

For this purpose, the temperature of the hot metal flowing out from the taphole and the silicon content in the hot metal are measured before the furnace heat adjustment is performed. It takes one to two hours for the hot metal to flow out, and the temperature of the hot metal can be measured immediately, but it takes an additional hour to analyze the silicon content in the hot metal, so information is available after a two to three hour delay. As a result, there was a delay in the operation to maintain a constant furnace heat, a decrease in productivity due to fluctuating furnace heat, and an increase in the fuel ratio, which limited the ability to improve blast furnace operational performance.

Therefore, the present invention aims to improve productivity and reduce the fuel ratio by accurately detecting information on the furnace heat in the raceway and quickly controlling the air blowing conditions to adjust the furnace heat. do.

[Means and effects for solving the problem] In order to achieve the object, the blast furnace operating method of the present invention detects the coke temperature in the blast furnace raceway part from the tuyere part, and also detects the coke temperature and the theoretical combustion temperature. The method is characterized in that the theoretical combustion temperature and/or the amount of pulverized coal injected from the tuyeres are adjusted so that the coke temperature and the ratio fall within a preset range.

The coke temperature (referred to as Tc) in the blast furnace raceway can be detected by installing a radiation thermometer in the tuyere peephole and measuring the coke surface temperature. Also, the theoretical combustion temperature (T
(referred to as f) can be obtained by equation (1).

Tf-155! ]i, 839・Tb-8,033・Hb
◆4972・Ω, -3.01[1・PC...(1) Here, Tb is the blowing temperature (℃), Hb is the amount of steam added during blowing (g/Nm"-AIR), and 02 is Amount of oxygen added during blowing (Nm'/Nm'-AIR) PC is the amount of pulverized coal (g/Nm3-AIR) blown in from the tuyere.Equation (1) is・The theoretical combustion temperature obtained by calculating the mass balance is Tb,
Hb, 02. This is statistically arranged as a linear equation of PC.

The inventors discovered through operational tests that Tc is a highly accurate index representing the furnace heat of a blast furnace. In Figure 3, T
The relationship between c and the silicon content in the hot metal flowing out from the taphole after 1 to 2 hours (a typical index of blast furnace heat) is shown.

According to this figure, there is a clear positive correlation between the two.

It can be seen that the heating state of the coke in the blast furnace raceway section determines the heating state of the hot metal slag dripping into the coke packed bed, that is, the furnace heat of the blast furnace.

The inventors also found that Tc changes depending on Tf. FIG. 4 shows the relationship between Tc and Tf. According to this figure, there is a clear positive correlation between the two, and
is approximately 0.75 times as large as Tf. It can be seen that the temperature of the gas flowing into the blast furnace raceway determines the heating state of coke in the blast furnace raceway.

Furthermore, the inventors found that even when Tf is constant, Tc changes and the ratio between the coke temperature in the blast furnace raceway and the theoretical combustion temperature (referred to as Tc/Tf) changes, so the ratio can be kept constant depending on the amount of pulverized coal. We found that it is possible to maintain FIG. 5 shows the relationship between Tc/f and the variation width of the amount of pulverized coal in a range where Tf is approximately constant. According to this figure, there is a clear positive correlation between the two, and it can be seen that when Tf is constant, TC/Tf changes depending on the amount of pulverized coal. This is because when the amount of pulverized coal is increased, the rate of descent of the coke that descends into the blast furnace raceway section is slowed down, and the coke is sufficiently heated above the tuyeres.On the other hand, when the amount of pulverized coal is decreased, the blast furnace This is because the coke that descends into the sway portion becomes faster and the coke is not heated sufficiently above the tuyere.

If Tf is determined from Figure 4, Tc is determined, and from Figure 3 T
It can be seen that once c is determined, the silicon content in hot metal, which is a typical index for blast furnaces, is determined. Also, in Figure 4, the same -Tf
When Tc changes (that is, Tc/Tf changes), but as shown in Fig. 5, by changing the amount of pulverized coal injected from the tuyere, Tc/Tf becomes constant (that is, Tc/Tf changes).
Therefore, it can be seen from FIG. 3 that if Tc is determined, the silicon content in the hot metal, which is a typical index of the furnace heat of the blast furnace, is determined.

In other words, if Tc is maintained constant by adjusting Tf and the amount of pulverized coal injected from the tuyere, the silicon content in hot metal, which is a typical indicator of blast furnace furnace heat, can be maintained constant, and the furnace heat can be maintained constant. It will become stable. By simply keeping Tc constant, T
When c/Tf is not constant, the charge descending speed is not stable, so Tc gradually fluctuates, and Tc
cannot be maintained constant, and the silicon content in the hot metal becomes unstable. Therefore, it is necessary to adjust both Tc and Tc/Tf.

If the furnace heat is stabilized during blast furnace operation, the fuel ratio can be lowered, productivity will improve, and desirable operating conditions will be achieved. In order to stabilize the furnace heat, it is sufficient to maintain the silicon content in hot metal, which is a typical index of the furnace heat of a blast furnace, constant.

By the blast furnace operating method of the present invention, the coke temperature (Tc) in the blast furnace raceway is maintained at 1600±20°C, and the ratio of the coke temperature in the blast furnace raceway to the theoretical combustion temperature (Tc/Tf) is 0. 75±0.02, the target silicon content in hot metal can be set to ±0.
It can be adjusted to 0.5% by weight, stabilizes the furnace heat of the blast furnace, lowers the fuel ratio, and improves productivity. The operating criteria at that time will be explained using Figure N1 and Figure 2. Figure 1 shows the difference (change width) in the Tc value measured at the tuyere with respect to the preset Tc reference value (1600°C), and the manipulated amount of Tf (change width) to make the Tc change width zero. For example, if the Tc value measured at the tuyere is 1625°C
If so, the range of change is +25°C, so it is sufficient to operate Tf by -35°C in N1 diagram C. The N2 diagram shows the difference in the ratio Tc/Tf of Tc and Tf measured at the tuyere with respect to the preset standard value of Tc/Tf (0,75).
(variation width) and the manipulated variable (change i) of the amount of pulverized coal injected from the tuyere portion to make the variation width of Tc/Tf zero. For example, if the value of the ratio e/f of Tc and Tf measured at the tuyere is 0.775, the range of change is +0.0
25, the amount of pulverized coal injected from the tuyeres in FIG. 2 can be adjusted to 1750 kg/h.

The relationships shown in FIGS. 1 and 2 can be determined by analysis of stable blast furnace operating conditions or by operational tests.

The radiation thermometer is installed mainly in the upper part of the taphole, and the number of tuyere installed is preferably at least twice the number of tapholes for measurement accuracy.

In addition, in order to adjust the theoretical combustion temperature (Tf), as shown in equation (1), the 4a of blowing temperature, steam amount, oxygen amount, and pulverized coal amount
can be changed, so one type or two or more types of 4fi can be selected depending on the operating state of the blast furnace at that time.

[Example] The features of the present invention will be specifically explained below with reference to Examples.

As shown in Table 1, in Example 1, in a blast furnace equipped with four tapholes, there are two tuyere peep holes at the top of the taphole (eight in total).
A radiation thermometer was installed at
The ratio of the coke temperature in the blast furnace raceway to the theoretical combustion temperature (Tc/Tf) varied between 0.716 and 0.767 (the theoretical combustion temperature was 2150 t). Ta). Using Figures 1 and 2, set Tc/T so that Tc is between 1600±20°C.
This is an example of operation in which the theoretical combustion temperature (Tf) and the amount of pulverized coal injected from the tuyere were adjusted so that f was between 0.75±0.02. The target silicon content in hot metal is 0.
It was 30%. To adjust Tf, send J! The I temperature, the amount of steam added during ventilation, the amount of oxygen added during ventilation, and the amount of pulverized coal blown in from the tuyere were individually changed. J! l Temperature, amount of pulverized coal blown in from the tuyere, and amount of oxygen added during blowing: 2f!
At the same time, I performed a change operation.

Example 2 is a blast furnace equipped with four tapholes. Radiation thermometers are installed in the three tuyere peepholes (12 in total) at the top of the taphole, and the coke temperature (Tc) in the blast furnace raceway is measured. When measured, the average value of 12 samples was 1570℃ to 1655℃
The ratio of the coke temperature in the blast furnace raceway section to the theoretical combustion temperature (Tc/Tf) varies between 0.730 and 0.
．． (the theoretical combustion temperature was 2150°C).

Tc/Tf is 0.75: t: 0.02+7) Using the notes in Figure 1, Tc is 1600±20°C.
This is an example of operation in which the theoretical combustion temperature (Tf) is adjusted so that it falls between Target silicon content in hot metal is 0.3
It was 5%. To adjust Tf, simultaneously change the amount of oxygen added during blowing and the amount of pulverized coal blown in from the tuyere, and the amount of steam added during blowing and the amount of pulverized coal blown in from the tuyere. In addition, the air blowing temperature, the amount of steam added during air blowing, the amount of pulverized coal blown in from the tuyeres, the amount of steam added during air blowing, the amount of oxygen added during air blowing, and the amount of pulverized coal blown in from the tuyeres. No. 3
We performed an operation to change the species at the same time.

In Example 3, in a blast furnace equipped with four tapholes, radiant temperature needles were installed in two tuyere peepholes (total of 8 pieces) at the top of the taphole, and the coke temperature (Tc) in the blast furnace raceway was measured. When measured, the average value of the 8 wood fluctuates between 1595°C and 1620t, and the ratio of coke temperature to theoretical combustion temperature (Tc/Tf) in the blast furnace raceway section ranges from 0.725 to 0.
736 (7) k (theoretical combustion temperature is 2200
t), and Tc is within 1800°C ± 20°C, so using Figure 2, Tc/Tf is set to 0.75 ± 0.
．． This is an example of an 8I operation in which the amount of pulverized coal injected from the tuyere was adjusted so that it fell between 02 and 7. The target silicon content in hot metal was 0.40%.

In either case, when compared to the comparative example, the target silicon content in the hot metal falls within the range of ±O, OS%, and the amount of pig iron tapped is large and the fuel cost is low.

In the comparative example, the inside of the raceway was observed with the naked eye through the tuyere peephole, the furnace heat of the blast furnace was determined, and the temperature of the hot metal flowing out from the tap hole and the silicon content in the hot metal were measured. ,
This is an example of operation in which furnace heat adjustment was performed. The target silicon content in hot metal was 0.40%. Examples 1-3
Compared to , the target silicon content in hot metal is ±0.
05, the amount of iron output is low and fuel costs are high.

[Effects of the Invention] As explained above, in the present invention, the highly accurate coke temperature in the blast furnace raceway is used as information on the furnace heat in the raceway, and in combination with the theoretical combustion temperature, the furnace heat adjustment is performed. Therefore, by quickly controlling the air blowing conditions, the furnace heat of the blast furnace can be stabilized, productivity can be improved, the fuel ratio can be lowered, and a stable supply of hot metal can be achieved.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the range of change in coke temperature in the blast furnace raceway section relative to the standard value and the range of change in the theoretical combustion temperature required for operation. Figure 2 shows the relationship between the coke temperature in the blast furnace raceway section and the theoretical combustion temperature. FIG. 2 is a diagram showing the relationship between the range of change in temperature ratio with respect to a reference value and the range of change in the amount of pulverized coal required for operation. Figure 3 shows the coke temperature in the blast furnace raceway and 1 to 2.
Figure 4 shows the relationship between the silicon content in the hot metal flowing out from the taphole after hours, Figure 4 shows the relationship between the coke temperature in the blast furnace raceway and the theoretical combustion temperature, and Figure 5 shows the relationship between the coke temperature in the blast furnace raceway and the theoretical combustion temperature. FIG. 2 is a diagram showing the relationship between the ratio of the coke temperature and the theoretical combustion temperature and the range of change in the amount of pulverized coal. Change width of pulverized coal amount (△PC) (kg/hl Change width of theoretical combustion temperature (△Tf) (''C) Coke temperature in blast furnace raceway (Tc) ('C) Silicon content in hot metal II (%)

Claims (1)

[Claims] 1. Detect the coke temperature from the tuyere section to the blast furnace raceway section, calculate the ratio between the coke temperature and the theoretical combustion temperature, and set the theoretical combustion temperature so that the coke temperature and the ratio fall within a preset range. and/or a blast furnace operating method characterized by adjusting the amount of pulverized coal injected from the tuyere.