JPS6246604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting blast furnace conditions for stably maintaining blast furnace conditions.

Conventionally, as a blast furnace operating method to maintain stable furnace conditions, the CO and CO ₂ concentrations in the furnace top gas were detected, and the gas utilization rate of the entire furnace ηCO = CO ₂ / (CO + CO ₂ ) was calculated. The CO and _CO2 concentration distribution in the radial direction of the furnace is detected directly above or above the charging material layer in the furnace, and the gas utilization rate in the radial direction ηCO=CO/(CO
+CO ₂ ) distribution, determine the furnace radial gas utilization rate distribution that maximizes the gas utilization rate of the furnace top gas,
There is a blast furnace operating method that adjusts the Ore/Coke (hereinafter referred to as O/C) distribution to achieve the gas utilization rate distribution.

However, with this conventional method, it was not possible to maintain stable furnace conditions. The reason for this is that in conventional methods, the gas distribution detected at the furnace top or upper part of the furnace is the result of the total reaction inside the furnace, and it is not possible to detect what kind of reaction is occurring at which level in the furnace height direction. It is in.

In other words, the conventional method cannot detect the situation inside the furnace in the direction of the furnace height, and operates without grasping the situation inside the furnace in the direction of the furnace height, which is closely related to the furnace condition.

The inventors have developed a vertical pipe 4 shown in FIGS.
A vertical probe 6 having a thermometer, for example, a sheathed thermocouple 5 installed inside the lower end, is attached to the upper end of the vertical probe guide pipe 2, which is provided by penetrating the top shell 1 of the blast furnace, as shown in FIGS. 1 and 2. Furnace top gas cutoff valve 9
The sonde 6 is guided by the upper vertical lifting guide device 3 and arranged to be able to be raised and lowered, and the lower end of the sonde 6 is charged to about 2 m below the stock line (hereinafter referred to as SL) 7, and then it naturally falls together with the raw material 8 in the furnace. At least, when the thermocouple 5 detects the temperature at the upper surface level of the cohesive zone, the descent is stopped, and the thermocouple 5 in the natural descent process is stopped.
The detected temperature was repeatedly recorded.
Note that the detected temperature is recorded as an electrical signal via a terminal 15 electrically connected to the thermocouple 5 shown in FIG.

In addition, the vertical sonte 6 whose lower end has reached the level of the upper surface of the cohesive zone is kept suspended until the wind of the blast furnace 10 is suspended.
Then, the wire 14, whose lower end is hooked to the hook 13 of the Sonte 6, is rolled up and extracted from the furnace. Since the thermocouple 5 of the extracted sonde 6 is damaged or the connection wire (not shown) between the thermocouple 5 and the terminal 15 is disconnected, a new sonde 6 will be used for the next measurement.
I did it using . That is, the gas temperature distribution in the furnace wall direction in the furnace height direction and the level of the top surface of the cohesive zone were detected intermittently.

In addition, in FIG. 4, 16 is an inert gas blowing pipe for purging, 17 is a gas suction pipe for sampling, and in FIGS. be.

Furthermore, FIG. 3 is a sectional view showing the detailed structure of the lifting guide device 3 shown in FIG.
is a ring-shaped packing and a collar inserted into the single tube 19, 23 is a single tube having a flange 24 at the upper end, the single tube 23 is inserted into the single tube 19, and the upper flange of the single tube 19 20 and a flange 24 are connected with bolts and nuts 25 to fix the packing 21 and collar 22. The stopper 26 of the sonde shown in FIG. 4 is in contact with the bolt nut 25 and mechanically stops the sonde from descending.

Figure 6 illustrates the measurement results of the gas temperature distribution in the furnace height direction on the furnace wall in the radial direction of the furnace using the vertical sonde device shown in Figures 1 to 5 above.
7, 28, and 29 show gas temperature distributions at different dates and times. The above gas temperature distributions 27, 28, 29 are SL
This indicates that the bottom 22, 20, and 19m positions are at the top level of the cohesive zone.

In the process of intermittently repeatedly detecting the gas temperature distribution at the upper surface level of the cohesive zone on the furnace wall and in the furnace height direction at the furnace wall, the present inventors discovered that As a result of intensive investigation into the relationship between the top surface level of the cohesive zone and the furnace conditions, the following findings were made.

(1) When the relative radius of the furnace wall in the radial direction of the furnace, more specifically the furnace core, is set to 0, it can be detected from the gas temperature distribution in the furnace height direction along the furnace height direction gas flow line in the range of relative radius 0.85 to 0.95, Moreover, the furnace gas temperature t is 500
℃t≦800℃, and the gas temperature change amount dt per unit distance dh in the gas flow direction, that is, the gas temperature change rate dt/dh is dt/dh≒0, or dt/dh>0
, (dt/dh≧-20℃) The cold storage zone length, defined as the length in the furnace height direction, changes due to undetectable disturbances even if the blast furnace operating conditions (raw material charging conditions and air blowing conditions) are constant. In addition, the length of the storage zone is closely related to the stability of blast furnace operation, specifically, the number of slips and drops, wind pressure fluctuations, and % fluctuations in pig iron, and as described above, the present inventors have conducted Intermittent detection of the cold storage zone length based on the gas temperature distribution using a vertical sonde may cause a control delay in controlling the cold storage zone length to an appropriate length, resulting in problems with furnace conditions such as shelving, slippage, and fluctuations in hot metal quality. In order to maintain stable furnace conditions and operate the blast furnace without being able to resolve the malfunction, it is necessary to constantly and continuously detect the length of the cold storage zone.

(2) The cold storage zone length has a strong correlation with the gas temperature at a specific position on the furnace wall in the furnace height direction, that is, at a position of 7 to 9 m below the SL within a relative radius of 0.85 to 0.95, when the relative radius of the furnace core is 0. If the gas temperature at that location is continuously measured, the length of the cold storage zone can be continuously detected.

(3) The length of the cold storage zone can be adjusted by adjusting (manipulating) the raw material charging conditions (O/C distribution).

(4) The level of the top surface of the cohesive zone in the range of relative radius 0.85 to 0.95 is closely related to the stability of the blast furnace, and more specifically to the absolute level of [Si] in the pig iron.
At the 20m position, the absolute level of Si in the pig iron becomes stable at a low level. Under the same blast furnace operating conditions, the above cohesive zone top level does not change enough to require manipulating the raw material charging conditions (O/C distribution) in order to maintain the pig iron [Si]% at the target value. The variation of [Si]% in pig iron from the target value due to the moisture content of coke and/or ore under the same operating conditions is
The target [Si]% in pig iron can be achieved by controlling the air blowing conditions (air humidity, air temperature). Furthermore, there is a time delay of 2 to 3 days before the level of the top surface of the cohesive zone changes when the raw material charging conditions are changed.

(5) From (1) to (4) above, the level of the cohesive zone on the furnace wall can be detected when the raw material charging conditions (O/C distribution) are changed. In order to control the material to an appropriate length that maintains stability, when the raw material charging conditions are manipulated, the
If detected after a few days, it is possible to control the top surface level of the cohesive zone to control the pig iron [Si]% level to the target value. In addition, other than when changing raw material charging conditions, if the cohesive zone level is detected when the pig iron [Si]% is higher than the target value (when there is uneven cropping that can be corrected by ventilation conditions), the pig iron [Si]% can be detected. It is possible to maintain the Si]% at the target value and correct the top surface level of the cohesive zone to an appropriate level.

The present invention provides a method for detecting the furnace condition of a blast furnace using a vertical probe, in order to maintain the furnace condition stably and obtain high-quality (low Si%) hot metal, based on the findings in (1) to (4) above. It is something to do.

The present invention will be explained in detail below.

First, how to detect the length of the cold preservation zone using a vertical sonde.
The point that the length of the cold storage zone can be detected based on the detected gas temperature at the 9 m position will be explained.

The length of the cold storage zone can be detected in the following manner from the furnace gas temperature distribution in the furnace wall direction of the furnace height shown in FIG. 6 detected by the vertical sonde device shown in FIGS. 1 to 5. (1) Gas temperature distribution in Figure 6 where the horizontal axis is the gas temperature and the vertical axis is the distance below the stock line (SL) 27,2
8, 29, for example, as shown in the lower part of Figure 7, the horizontal axis is the distance h [m] in the gas flow direction, the vertical axis is the gas temperature t [℃], and the gas temperature t is 500℃≦t≦800.
This is a gas temperature distribution map in the °C region. (2) Then the seventh
Gas temperature distribution 27 at 500℃≦t≦800℃ in the lower part of the figure,
28 and 29, it is converted into a gas temperature change rate dt/dh [° C./m] in the gas flow direction, as shown in the upper part of FIG. (3) Next, the gas temperature change rate dt/dh [°C/m] is dt/dh≒0 or dt/dh>0, specifically dt/dh
The total distance in the gas flow direction where dh≧-20 [°C/m] is defined as the cold storage zone length. For example, in the gas temperature distributions 27, 28, and 29 shown in FIGS. 6 and 7, the cold storage zone lengths are 6, 3, and 1 [m], respectively.

Based on the above measurement results using a large number of vertical sondes, the present inventors have determined that, as illustrated in FIG.
Low-temperature storage zone length and specific position in the furnace height direction, that is, the furnace wall
It was found that there is a strong correlation between the gas temperature at a position of 7 to 9 m below the SL.

This specific position was determined as follows. With the vertical sonde device shown in Figures 1 to 5,
The gas temperature distribution in the furnace wall direction in the furnace height direction as shown in Figure 6 is determined, and based on this temperature distribution, the low temperature storage length is determined by the above means, and the gas temperature at a specific point within the low temperature storage zone and the low temperature storage are determined. The correlation with the band length was determined using specific points as parameters, and the specific point with the highest correlation was selected.

Figure 8 shows that there is a strong correlation between the gas temperature 8 m below the stock line of the furnace wall and the length of the cold storage zone. It was also confirmed that the gas temperature at

Therefore, the length of the cold storage zone can be determined by positioning the vertical sonde so that the thermometer on the vertical sonde is 7 to 9 meters below the stock line and continuously detecting the gas temperature detected by this thermometer. ,the above
The length of the cold storage zone can be continuously detected using a correlation diagram or a correlation equation between the gas temperature 7 to 9 meters below the SL and the length of the cold storage zone.

Next, the relationship between the cold storage zone length and furnace conditions will be explained.

Figures 9 and 10 show the relationship between the gas temperature, wind pressure fluctuations, and pig iron [Si] fluctuations in the 8 m lower part of the SL, which have a strong correlation with the length of the cold storage zone as shown in Figure 8. 9th and 10th
The figure shows that when the gas temperature at the bottom 8 m of the furnace wall in the furnace height direction decreases and the length of the cold storage zone increases as shown in Figure 8, indirect reduction at the top of the furnace does not proceed.
This indicates that a large amount of unreduced ore falls to the lower part of the furnace, increasing wind pressure fluctuations and hot metal quality fluctuations.

The relationship between the cold storage zone length and furnace condition fluctuations can be explained as follows based on fluctuations in the contents distribution in the furnace. That is, when the O/C in the entire radial direction of the blast furnace or at a specific position is changed, the heat flow ratio in the entire radial direction or at a specific position changes, and the temperature distribution in the furnace height direction changes. When the heat flow ratio is low, the length of the cold storage zone is short, but when the O/C increases overall in the radial direction by lowering the fuel ratio, and by adjusting the charge distribution, the O/C at a specific position in the radial direction increases. When /C is increased, the heat flow ratio increases when O/C is increased.

As a result, the gas temperature at the top of the shaft decreases,
The cold storage zone length increases. In the low-temperature storage zone, indirect reduction hardly occurs, so if the low-temperature storage rate is long, the ore reaches the lower part of the shaft without progressing to reduction. Since most of the reduction of ore in the lower part of the shaft is direct reduction, the amount of direct reduction increases in this case.

As mentioned above, if the O/C in the entire radial direction or at a specific position rises intentionally or due to disturbance,
In the entire radial direction or in specific locations, the cold storage zone is lengthened to increase the direct reduction in the lower part of the shaft.

Direct reduction is an endothermic reaction, so if it occurs in large quantities, the heat retained in the lower part of the furnace will decrease, causing unfavorable phenomena for blast furnace operation such as enlargement of the fused material and poor fluidity of hot metal and slag, leading to problems such as shelves, slips, etc. Unloading fluctuations such as
Increases hot metal quality variation. For example, in Figure 11,
This figure shows the relationship between the length of the cold storage zone and the number of drops and slips.

As is clear from the above, if the length of the cold storage zone is detected continuously, that is, if the vertical sonde is used, the thermometer of the sonde will be 7 to 9 degrees below the stock line.
If the gas temperature at this position is continuously detected, and the length of the cold storage zone is continuously detected based on the correlation between this gas temperature and the cold storage zone length, the raw material storage The length of the cold storage zone can be controlled without time lag by adjusting the input conditions (O/C distribution), and the blast furnace condition can be maintained stably.

Therefore, in the present invention, a vertical sonde is positioned so that the sonde's thermometer is located 7 to 9 meters below the stock line, and the length of the cold storage zone is continuously detected based on the gas temperature detected by this thermometer. It is something.

Next, the relationship between the upper surface level of the cohesive zone on the furnace wall, which can be detected by a vertical sonde, and the furnace condition, that is, the absolute level of [Si]% in hot metal, will be explained.

Figure 12 shows the temperature distribution in the furnace height direction using the vertical sonde device shown in Figures 1 to 5 above.
SL where the temperature rises rapidly in the range from ℃ to 1100℃
This figure shows the relationship between the upper surface level of the cohesive zone detected as the lower specific position and the [Si]% in the hot metal. Incidentally, the % Si in pig iron on the vertical axis in FIG. 12 shows the average value for two days before and after the measurement of the top surface level of the cohesive zone, that is, the average value for four days.

As is clear from Fig. 12, the furnace wall and cohesive zone top surface levels are closely related to the absolute level of [Si]% in the pig iron. The absolute level of middle [Si]% is stable at a low level. Also, according to the research results of the present inventors,
Under the same blast furnace operating conditions, the top level of the cohesive zone is
In order to maintain the pig iron [Si]% at the target value, the feedstock charging conditions (O/C distribution) do not change enough to require manipulation, and the coke and/or ore content under the same operating conditions. Fluctuations in the pig iron [Si]% from the target value due to moisture fluctuations can be absorbed by manipulating the air blowing conditions (air humidity, air temperature). Furthermore, there is a time lag of 2 to 3 days before the level of the top surface of the cohesive zone changes after changing the raw material charging conditions (O/C distribution).

Therefore, in order to maintain stable furnace conditions, two to three days after adjusting the O/C distribution by changing the raw material charging conditions,
When the top surface level of the cohesive zone is detected, that is, the sonde that detects the length of the cryogenic storage zone is allowed to naturally descend together with the raw material in the furnace, and based on the gas temperature detected by the thermometer during this descent process, the temperature of the furnace wall is lowered. If the top level of the cohesive zone is detected, the length of the cryopreservation zone immediately before the detection of the cohesive zone level is detected. If it is short within the appropriate range, increase the length of the cold storage zone within the appropriate range and lower the top level of the cohesive zone in order to lower the [Si]% level in the pig iron, i.e., the raw material charging conditions. (O/C distribution) changes can be made. As a result, hot metal with a low [Si] level can be obtained while maintaining stable furnace conditions.

Therefore, in the present invention, when changing raw material charging conditions,
The thermometer inside the sonde is 7 to 9 meters below the stock line.
The sonde in the position is allowed to fall naturally together with the raw materials in the furnace, and the level of the upper surface of the cohesive zone on the furnace wall is detected based on the gas temperature detected by the thermometer during this descent process.

In addition, we continuously detect the furnace condition after changing the raw material charging conditions, or after detecting the top surface level of the cohesive zone, the furnace condition (cold storage zone length) without changing the charging conditions. In order to extend the service life, in the present invention, after detecting the level of the upper surface of the cohesive zone, the vertical probe is pulled up and the thermometer is returned to a position of 7 to 9 meters below the stock line.

EMBODIMENT OF THE INVENTION Hereinafter, the method of detecting the condition of a blast furnace using a vertical sonde according to the present invention will be explained in detail based on an example of a vertical sonde apparatus shown in FIGS. 1 to 5.

The vertical sonde 6 shown in FIGS. 4 and 5 is suspended and held by the wire 14 shown in FIG. 1, the lower end of the sonde is inserted into the lifting guide device 3 shown in FIG. Open the valve 9, lower the inside of the guide pipe 2, and position the lower end of the sonde on the SL7 surface.

Next, insert the lower end of the sonde to about 1 to 2 m below the SL7 surface. Then, the vertical sonde 6 is naturally lowered together with the raw material 8 in the furnace, and the thermocouple 5 of the sonde 6
When a specific position, for example 8 m, is reached, 7 to 9 m below the SL, the wire 14 is tightened to hang and hold the sonde 6 at that position.

Then, through the terminal 15 of the sonde 6, the output signal of the thermocouple 5 corresponding to the gas temperature in the furnace is continuously measured and recorded, and the length of the cold storage zone is continuously measured and recorded based on the detected gas temperature.

When the O/C distribution is adjusted by changing the raw material charging conditions, two to three days after the change, the tension on the wire 14 is released and the sonde 6 is allowed to fall naturally together with the raw material 8 in the furnace. During the process, via terminal 15 of sonde 6, SL lower 8
Continuously measure the output signal of the thermocouple 5 corresponding to the furnace gas temperature at each position below m and record it on a chart. , wire 14 to winch 12
Wind it up and pull up Sonde 6. Then, the thermocouple 5 of the sonde 6 is returned to the position 8 m below the SL.

When the sonde 6 returns to the upward position, continuous measurement and recording of the length of the cryogenic storage zone is resumed. The level of the top surface of the cohesive zone on the furnace wall can be detected using, for example, a chart that records the gas temperature distribution, and measures the temperature of sonde 6 (pipe 4) up to the point at which the above-mentioned rapid temperature rise was observed.
Detection is performed based on the amount of fall.

As described in detail above, the present invention is capable of substantially continuously detecting the length of the cold storage zone, which is closely related to the furnace condition, at low cost, using a single vertical sonde, and also detecting the raw material charging conditions. The top surface level of the cohesive zone, which is closely related to hot metal quality, can be detected when changing raw material charging conditions, allowing stable furnace conditions to be maintained and high quality (low [Si] level) hot metal to be obtained. It is extremely useful for blast furnace operation.

[Brief explanation of the drawing]

FIG. 1 is an overall explanatory diagram of the present invention, FIG. 2 is a partial explanatory diagram of FIG. 1, FIG. 3 is an explanatory diagram of another part of FIG. 1, and FIG. 4 is an explanatory diagram of a vertical sonde device for a blast furnace. Figure 5 is a cross-sectional view of Figure 4, Figure 6 is a chart showing an example of the measurement results of the gas temperature distribution in the furnace height direction using a vertical sonde, Figure 7 is a diagram of the gas temperature distribution in the furnace height direction, and Figure 8 is a diagram showing the gas temperature distribution in the furnace height direction.
Figure 9 is a graph showing the correlation between the gas temperature 8m below the stock line and the length of the cold storage zone. Figure 9 is a graph showing the gas temperature and wind pressure fluctuations 8m below the stock line.
Figure 0 is a diagram explaining the relationship with the molten [Si]% variation, Figure 11 is a diagram explaining the relationship between the length of the cold storage zone and the number of drops and slips, and Figure 12 is the top level of the cohesive zone on the furnace wall. It is an explanatory chart of the relationship between and pig iron [Si]%. 1: Blast furnace top shell, 2: Guide pipe, 3: Vertical sonde lifting guide device, 4: Vertical pipe, 5: Thermocouple, 6: Vertical sonde, 7: Stock line (SL), 8: Raw material in the furnace, 9: Furnace top gas cutoff valve, 1
0: Blast furnace, 11: Blast furnace turret, 12: Winch, 1
3: Hook, 14: Wire, 15: Terminal, 16: Inert gas blowing pipe for purging, 17: Gas suction pipe for sampling, 18: Raw material intrusion prevention material, 19: Single pipe, 20: Flange, 21: Ring shape Patsukin, 22: Color, 23: Single tube, 24:
Flange, 25: Bolt/Nut, 26: Stopper, 27, 28, 29: Furnace height direction gas temperature distribution.

Claims (1)

[Claims] 1. A vertical sonde with a thermometer inscribed inside the lower end of the vertical pipe is arranged so as to be able to move up and down inside the furnace in the radial direction of the furnace wall by penetrating the top shell of the blast furnace. The gas temperature at a position of 7 to 9 meters below the stock line is detected, and the length of the cold storage zone of the lumpy zone on the furnace wall is continuously detected.When the raw material charging conditions are changed, the above-mentioned sonde is used together with the raw material charged in the furnace. Let it fall naturally, and detect the upper surface level of the cohesive zone on the furnace wall based on the gas temperature detected by the thermometer during this descent process. After detection, pull up the vertical sonde and place the thermometer at a position of 7 to 9 m below the stock line. A method for detecting the condition of a blast furnace using a vertical sonde, which comprises continuously detecting the length of the low-temperature preservation zone after returning to the normal state.