JPH0417607A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To improve the productivity and to reduce fuel ratio by directly detecting charged material descendent velocity and temp. in a furnace at lower part of the furnace and using these to execute distribution control of the charged material. CONSTITUTION:At near the working position (within about 5cm from the furnace wall) in the lower part (bosh part from belly part) in the blast furnace, heat resistant alloy-made protecting tube 3 is inserted and a thermocouple 5 is inserted from outer part through this protecting tube 3 and tip part of the protecting tube 3 is positioned to the (a) part. With this thermocouple 5, the temp. at near the working position ((a) part) is detected and the charged material descendent velocity is calculated from periodical change of the detected temp. and the ratio of ore and coke at circumferential part in the furnace charged from the furnace top is adjusted so that the temp. and the charging material descendent velocity come in the set range. By this method, the blast furnace is stably operated, the productivity is improved, the fuel ratio is reduced, and the molten iron can stably be supplied.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention detects the temperature near the operating surface from the belly part of the blast furnace to the morning glory part, and adjusts the top charge distribution of the blast furnace. This paper relates to a blast furnace operating method that improves performance and reduces fuel ratio.

(Prior art) In blast furnace operation, by adjusting the radial distribution of the ratio of ore and coke (abbreviated as 0/C) charged from the top of the furnace, the ventilation of the blast furnace is ensured and productivity is increased. In addition, the fuel ratio is lowered to improve gas reduction efficiency.

In adjusting the burden distribution, it is very important to detect the rate of descent of the charge in the furnace, and in particular, the rate of descent of the charge in the periphery of the blast furnace almost determines the permeability and reduction efficiency of the blast furnace. Therefore, detection methods have been developed and put into practical use.

For example, Japanese Patent Publication No. 57-031104 discloses a method of detecting the rate of descent of a charge using two wooden sondes, which utilizes the difference in electrical resistance between iron ore and coke.

Furthermore, it has long been known that the temperature of the furnace wall of a blast furnace is an important indicator of the furnace heat of the blast furnace.
No. 46419 discloses a blast furnace operating method using stave cooler temperature as the temperature of the furnace wall.

(Problem to be solved by the invention) By the way, in conventional blast furnace operation,
The measurement position of the detection methods that have been developed and put into practical use, including the method for detecting the rate of descent of the charge disclosed in Japanese Patent No. 104, is limited to a low-temperature region up to about 5 m from the surface of the figure made at the top of the furnace. The reason for this is that in the high-temperature region of the lower part of the furnace, detection using the difference in electrical resistance loses the difference in resistance between iron ore and coke, making it impossible to detect in principle, and the sonde equipped with the sensor There is a limit to heat resistance,
This is due to the inability to operate stably over the long term. However, it is important to detect the rate of descent of the burden at the bottom of the furnace, and there is a time lag of 5 to 6 hours between estimating the rate of descent of the burden at the bottom of the furnace from the rate of descent of the burden at the top of the furnace. In addition, the iron ore and coke charged around the top of the furnace do not necessarily descend down the furnace wall with the piston flow, resulting in poor detection accuracy, which makes it difficult to improve productivity by controlling the burden distribution. However, there was a limit to the reduction in fuel ratio.

In addition, the temperature at the wall of the blast furnace is indirectly measured by thermocouples embedded in stave coolers and bricks, so although it is the temperature at the bottom of the furnace, the detection accuracy is not sufficient, and it is There was a limit to productivity improvement and fuel ratio reduction by the charge distribution control used.

In this way, in conventional blast furnace operations, when trying to improve productivity and reduce the fuel ratio, there is no accurate measurement means to detect the lower part of the furnace, so charge distribution control technology is not effectively utilized. .

Therefore, the present invention aims to improve productivity and reduce the fuel ratio by directly detecting the rate of descent of the charge in the lower part of the furnace and the temperature inside the furnace, and using this to control the distribution of the charge. 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 temperature near the operating surface from the belly part of the blast furnace to the morning glory part, and periodically changes the temperature. The method is characterized by calculating the rate of descent of the burden, and adjusting the ratio of ore and coke in the area around the furnace charged from the top of the furnace so that the temperature and rate of descent of the burden fall within a preset range. do.

FIG. 4 shows a method of detecting the temperature in the vicinity of the working surface of the blast furnace from the belly part to the morning glory part in the present invention. In Fig. 4, 1 is a blast furnace shell, 2 is a brick, 3 is a heat-resistant alloy protective tube, 4 is a driven sonde, 5 is a thermocouple, and 6 is a shutoff valve. A method is shown in which a thermocouple inserted into an alloy protection tube is inserted into the furnace from the outside, and the tip of the protection tube is positioned near the operating surface. This example shows how to insert the probe (built-in) and position the tip of the probe near the operating surface when making measurements.

As shown in Fig. 4, the method of the present invention involves inserting a thermocouple inserted into a heat-resistant alloy protective tube into the furnace from the outside near the working surface of the lower part of the furnace (from the furnace belly to the morning glory part). There is a method of positioning the tip of the protective tube near the operating surface (see part a), and a method of inserting a driven sonde (with built-in thermocouple) through the opening from the belly of the blast furnace to the morning glory section to make measurements. How to position the tip of the sonde near the operating surface (see part b)
by.

In the present invention, the operating surface refers to this range since the tip of the thermocouple is inserted within 5 cm from the furnace wall for measurement.

When the temperature near the working surface of the belly of a blast furnace was measured using these methods, for example, in the case of a certain blast furnace, the measurement results shown in FIG. 1 were obtained. In FIG. 1, the horizontal axis shows the elapsed time, and the vertical axis shows the temperature near the working surface of the reactor belly. This temperature changes periodically, and t indicates the time between the troughs of this period.

The temperature near the operating surface of the lower part of the blast furnace (from the furnace belly to the morning glory part) is a very accurate indicator of furnace heat because the temperature of the gas flowing in this area is directly measured. Also the first
As shown in the figure, this temperature (temperature at the bottom of the furnace in this case) changes periodically, and among the iron ore and coke charged in layers from the top of the furnace, only the iron ore softens and melts in the lower part of the furnace. As a result, the permeability of this area deteriorates and the temperature decreases, with periodicity following the alternating descent of iron ore and coke. The time t (m
in), and the rate of charge descent can be calculated using equation (1).

(Charge descending speed, m/m1n) = (Coke charging amount, ton/time) x (Coke compression ratio,
! ¥)/looo/((Blast furnace cross-sectional area at sensor installation location, m2) x (Coke bulk density, ton/m3) xt)
(1) A coke compression ratio of 80% is normally used. The charge descending speed determined in this way is highly accurate because it is based on data directly measured in the lower part of the reactor.

To maintain the temperature near the operating surface of the lower part of the furnace and the rate of descent of the charge within a certain range by controlling the charge distribution, the following steps are taken. In other words, when the temperature near the operating surface is high and the rate of descent of the charge is slow, the O/C around the furnace is reduced, and when the temperature and rate of descent are outside a certain range, O around the furnace
The action direction of /C is shown in Table 1.

In the present invention, the furnace periphery refers to the area within 1.0 m from the furnace wall.

$1 table The inventors measured the temperature near the operating surface of the lower part of the blast furnace (from the furnace belly to the morning glory part), and based on the periodic changes in temperature (1)
Calculate the charge descending speed according to the formula, and
Operational tests were conducted to increase and decrease 7C to track the relationship between temperature and charge fall rate and the furnace periphery 07C. The present invention is a method obtained as a result of those tests.
As shown in the figure, using the relationship between the amount of change from the standard value and the amount of change in the furnace peripheral area 0/C to return to the standard value, the temperature near the operating surface of the lower part of the blast furnace (from the furnace belly to the morning glory part) By adjusting the furnace peripheral area 07C so that the charge descending speed is constant, the blast furnace operation can be stabilized, productivity can be improved, and the fuel ratio can be reduced.

The certain range in which the temperature and charge descending rate should be controlled shall be determined for each furnace, with reference to when the blast furnace is in good operating condition. The amount of change in O/C around the furnace shall also be determined for each furnace by conducting operational tests of the furnace.

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

Example 1 A thermocouple inserted into a heat-resistant alloy protection tube is placed near the operating surface of the bosh section, and the time (t, m1n) for passing through the valleys of periodic temperature changes is measured. The value was 5 to 15 minutes. In equation (1), coke charging amount = 25 tons/time, coke compression rate = 80%, blast furnace cross-sectional area at sensor installation position = 135 m', coke bulk density = 0.5
Substituting ton/m3 to calculate the rate of descent of the charge, we get:
The speed was 0.059 to 0.020 m/min. The temperature also varied between 105°C and 114°C. The temperature was set at 1080 to 11 as the control range determined in advance through operational tests.
20t, charge descent speed 0.030-0.050m
/min, and the O/C around the furnace was operating at 4.0.

When the temperature exceeds the upper limit of 1140℃ and +2o'e,
According to Figure 2, the O/C around the furnace should be adjusted from 4.0 to 5.
．． 0 and +1.0 increase, and after 8 hours, it becomes 1120℃
The O/C around the furnace was restored to its original condition. Also, when the temperature is 1050'C, which is -30°C below the lower limit, the O/C around the furnace is reduced by -1.5 from 4.0 to 2.5 for 9 hours according to Figure 2. After 108
Since the temperature returned to 0t, the 0/C around the furnace was returned to its original value.

The lower limit of the charge descending speed is 0.020 m/min -0,
0.010 m/min, the O/C around the furnace was increased by +1.3 from 4.0 to 5.3 according to Figure 3, and after 8 hours it returned to 0.030 m/min. Therefore, the O/C around the furnace was returned to its original state. In addition, the charge descending speed is Q, 059 m/min, and the upper limit is +0.009
m/min, reduce the 07C around the furnace by -1.1 from 4.0 to 2.9 according to Figure 3.
After 7 hours, the speed returned to 0.050 m/min, so the O/C around the furnace was returned to its original value.

If both the temperature and the charge descending rate are out of range, first adjust the O/O around the furnace to bring the charge descending rate within the control range.
After that, the O/C around the furnace was adjusted so that the temperature was within the control range.

Example 2 A driven sonde (with a built-in thermocouple) was installed near the operating surface of the reactor abdomen, and the time (t) for passing through the valleys of periodic temperature changes was measured.
, m1n), the values ranged from 4 to 12 minutes. (
1) Coke charging amount: 25 tons/time, coke compression ratio = 80%, blast furnace cross-sectional area at sensor installation position = 14
5m' Coke bulk density = 0.5) When calculating the rate of descent of the charge by substituting ton/m3, it is 0.069 to 0.0.
The speed was 23m/min. Also, the temperature is 960-1050
It varied between ℃.

The temperature is set as the control range determined in advance through operational tests.
980-1020℃, charge descent rate 0.030-1020℃
It is set at 0.055m/min, and the O/
C was running on 4.1.

When the temperature exceeds the upper limit by 30°C (1050°C), the second
According to the diagram, increase the O/C around the furnace from 4.1 to 5.6.
The temperature increased by +1.5, and after 9 hours, the temperature returned to 1020°C, so the 0/C around the furnace was returned to the original value. Also, when the temperature is 960℃, -20℃ below the lower limit, the second
According to the diagram, change the 0/C around the furnace from 4.1 to 3.1.
The temperature decreased by -1.0 and returned to 980°C after 7 hours, so the 07C around the furnace was returned to its original value.

The lower limit of the charge descending speed is 0.023 m/min -0,
0.007m/min, increase the O/C around the furnace from 4.1 to 4.9 (÷0.8) according to Figure 3, and return to 0.030m/min after 7 hours. Therefore, the O/C around the furnace was returned to its original state. In addition, the charge descending speed is 0.069 m/min, which increases the upper limit by +0.014 m/min.
m/min, reduce the O/C around the furnace by -1.7 from 4.1 to 2.4 according to Figure 3.
After 10 hours, the speed returned to 0.055 m/min, so the O/C around the furnace was returned to its original value.

If both the temperature and the charge descending rate are out of range, first adjust the O/O around the furnace to bring the charge descending rate within the control range.
After that, the O/C around the furnace was adjusted so that the temperature was within the control range.

Example 3 A thermocouple inserted into a heat-resistant alloy protective tube was installed near the operating surface of the morning glory section, and a driven sonde (
When we installed a thermocouple (with built-in thermocouple) and measured the time (t, win) to pass through the troughs of periodic temperature changes, the values were 5 to 14 minutes for the morning glory and 4 to 11 minutes for the furnace belly, respectively. . (
1) Equation Nikoke charging amount = 25 tons/time, coke compression rate = 80%, sensor installation position = blast furnace cross-sectional area = 13
5 m2 (morning glory section), 145 m2 (furnace belly), coke bulk density = 0.5) tons/m3 to calculate the charge descent rate, the morning glory section 0.059 to (1,02
1m/min, furnace belly 0.069-0.025m/m
intona)ta.

Further, the temperature varied between 1100 to 1200°C for the morning glory part and 990 to 1110°C for the furnace part. As the control range determined in the preliminary operation test, the temperature was set at 1130 to
1170°C, furnace belly 1030-1070°C, charge descending speed 0.030-0.050 m/min in morning glory part,
The furnace was set at 0.035 to 0.055 m/win, and the 07C around the furnace was operated at 3.9. The O/C around the furnace, similar to those in Examples 1 and 2, was first adjusted so that the temperature in the furnace belly and the rate of descent of the charge fell within the control range determined in advance through operational tests, and then the O/C in the morning glory area was adjusted. The temperature and rate of charge descent were adjusted so that they fell within the control range determined in advance through operational tests.

In any case, as shown in Table 2, compared to the comparative example, the amount of pig iron tapped was large and the fuel ratio was low.

In the comparative example, when the temperature was measured using a thermocouple embedded in the bricks in the furnace belly, the temperature varied between 100 and 200°C. As a control range determined in advance through operational tests, the temperature was adjusted to 0/C around the furnace to maintain the temperature at 150±20°C.
This is an example of an operation in which adjustments were made. As shown in Table 2, compared to Examples 1 to 3, the amount of pig iron tapped is small and the fuel ratio is high.

Table 2 (Effects of the Invention) As explained above, in the present invention, the blast furnace
By adjusting the top charge distribution so that the temperature near the operating surface and the rate of charge descent from the top to the morning glory section remain constant, the blast furnace operates stably, improving productivity and reducing the fuel ratio. This enables stable supply of hot metal.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of periodic changes in the temperature of the blast furnace belly area, which is used in the blast furnace operating method of the present invention, and FIG. 2 is a diagram showing the vicinity of the operating surface of the blast furnace belly portion, which is used in the blast furnace operating method of the present invention. Figure 3 is a diagram showing the relationship between the range of change in the temperature of the furnace relative to the standard value and the range of change in the furnace peripheral area 07C. FIG. 4 shows a temperature measuring device near the operating surface from the furnace belly to the morning glory section in the longitudinal section of the blast furnace, which is used in the blast furnace operating method of the present invention. 1... Blast furnace shell 2... Brick 3... Alloy protection tube 4... Drive type sonde 5... Thermocouple
6...Shutoff valve Fig. 2 Fig. 1 Range of change in temperature near the working surface of the reactor abdomen relative to the reference value (''C) Fig. 3 Elapsed time (minutes) Range of variation relative to the reference value (s/minl)

Claims (1)

[Claims] 1. Detect the temperature near the working surface of the blast furnace from the belly to the morning glory section, calculate the rate of descent of the charge from periodic changes in temperature, and make sure that the temperature and rate of descent of the charge fall within a preset range. A blast furnace operating method characterized by adjusting the ratio of ore and coke in the periphery of the furnace, which are charged from the top of the furnace.