JPH07179917A - Method for measuring combustion temperature of blowing fuel in blast furnace and method for diagnosing combustion of fuel - Google Patents

Abstract

PURPOSE:To provide a method for measuring the combustion temp. of blowing fuel in a blast furnace, by which the combustion temp. of the blowing fuel in a blow pipe can instantaneously and continuously be measured. CONSTITUTION:A tuyere sonde 6 having a measuring hole at the tip lower part side is inserted into the blow pipe 3 from the rear side of a tuyere. An optical fiber 7 covered with a metallic pipe is inserted into the tuyere sonde 6 and the tip end part of the optical fiber 7 is faced to the measuring hole and, in the case the tip end part of the optical fiber 7 erodes, radiation beam emitted from the combustion flame 11 of the blowing fuel is detected with the tip end part of the optical fiber while gradually feeding the optical fiber 7 to the measuring hole side. Further, the combustion temp. of the fuel is continuously measured by a brightness temp. computing element 9 connected to the rear end side of the optical fiber 7 based on the radiation beam detected with the tip end part of the optical fiber 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a combustion temperature of a fuel injected into a blast furnace and a combustion state of the injected fuel in a blast furnace operation in which a large amount of fuel is injected from a tuyere to substitute a required coke. The present invention relates to a method for diagnosing combustion of injected fuel for diagnosing.

[0002]

Coke, which is used as a main fuel in a blast furnace, is generally produced from coking coal. However, coking coal has a limited production area and a higher price than steam coal used as fuel in boilers and the like. For this reason, conventionally, a method of operation has been performed in which a liquid fuel such as heavy oil or a gaseous fuel such as natural gas is blown from the tuyere as an auxiliary fuel to reduce the required amount of coke. In Japan, it is common to inject heavy oil because it is difficult to obtain natural gas.

However, in the 1980s, the injection of heavy oil became uneconomical because the oil price increased, and these auxiliary fuel injections were not carried out. Instead, a method has been implemented in which steam coal as auxiliary fuel is pulverized to a predetermined particle size, for example, a proportion of 74 μm or less to 80% and directly blown from tuyere. This method is a technology that has been practiced at steel mills where coal is easily available for a long time,
Since the 1980s, steam coal, which is easily available, can be used directly as fuel for blast furnaces, and it has become economically effective, so it has been used in many steelworks. At the same time, the coke ratio can be reduced, the load on the coke oven can be reduced, and the environmental problems associated with the operation of the coke oven can be reduced. Due to such a background, the injection of pulverized coal is directed toward the injection of a large amount, for example, 150 kg /
Pulverized coal injection of t or more (150 kg injection amount per 1 t of pig iron) is also performed.

[0004]

Generally, when trying to inject a large amount of pulverized coal, the ratio of pulverized coal / oxygen (kg / N
m ³ ) becomes large, and the combustibility of pulverized coal decreases. Therefore, the rate of replacing coke in the blast furnace, that is, the rate of replacement is reduced, and the effect of blowing pulverized coal is reduced. In addition, pulverized coal is usually blown into hot air and passes through a combustion space called a raceway at the tip of the tuyere into the blast furnace,
Since a large amount of coke is mixed in the raceway, the oxygen in the hot air rapidly decreases. Therefore, the combustible space in which oxygen exists is small, and the gas flow velocity in the tuyere is generally as high as 200 m / s. Therefore, the time during which the injected pulverized coal exists in the combustible space is very short, about 20 ms. is there. Pulverized coal that does not burn out in this combustion space is not used as a heat source in the blast furnace and accumulates in the furnace, obstructing air permeability in the furnace and making the operation of the blast furnace unstable, as well as outside the furnace. If it is discharged, the fuel cost will increase, which is not preferable.

Therefore, it is important to improve or control the combustibility in the blow pipe and the raceway that follows it, and obtain temperature information (in-furnace temperature distribution or transition) as an index representing this combustibility. , And diagnosing the combustion state based on this temperature information is extremely meaningful. However, until now, there has been no means for instantaneously and continuously measuring the fuel blown from the blow pipe following the air blowing tuyere of the blast furnace and the accurate temperature inside the furnace. To diagnose the combustion state of the fuel injected from the tuyere, insert a sonde into the blow pipe following the blast furnace tuyere from the rear of the tuyere, sample the fuel in the furnace with the sonde, and analyze it. However, there is a problem in that it takes a lot of time and effort to make a decision because it has been done.

The invention disclosed in Japanese Patent Laid-Open No. 60-24307 is to install an optical fiber in a pipe installed in a blow pipe, and send a cooling gas into the pipe so as to prevent the optical fiber from being melted and damaged. I am measuring the temperature of
Melt damage is unavoidable when measuring high temperature fields such as blown fuel, and cannot be used to measure the temperature of blown fuel.
Further, in the publication, since the optical fiber is directed in the furnace direction to measure the temperature in the furnace, there is a high possibility that the brightness in the furnace is picked up even if the temperature of the injected fuel is measured. Not suitable for measuring only the temperature of blown fuel.

Further, Japanese Patent Application Laid-Open No. 61-44113 discloses a technique relating to a method for detecting a combustion zone before the tuyere of a blast furnace. However, in the publication, an optical sensor is installed outside the tuyere peep window, and the temperature inside the furnace is measured through this tuyere peep window, so this technique is used to measure the temperature of blown fuel. Even if it does, the combustion state of the injected fuel will be measured from the rear of the fuel injection lance, and it is possible to detect the unburned state immediately after the fuel is injected or measure the brightness inside the furnace. Accurately measuring the temperature of a large, burning fuel is difficult. That is, in the conventional technology, the combustion temperature of the injected fuel is continuously detected,
The combustion state could not be diagnosed, and the development of such a technology was awaited.

The present invention has been made to solve the above problems, and in a blast furnace operation in which fuel is blown into the blast furnace from tuyere, the combustion temperature of the blown fuel in the blow pipe and the raceway and the temperature in the furnace are set. It is an object of the present invention to provide a method for measuring a combustion temperature in fuel injection into a blast furnace, which can be measured instantaneously and continuously, and a combustion diagnosis method for injected fuel using the method.

[0009]

According to the method for measuring the combustion temperature of injected fuel in a blast furnace according to the present invention, a tuyere sonde having a measurement hole at the lower end of the tip is inserted into the blow pipe from behind the tuyere, While inserting the optical fiber coated with a metal tube into the mouthsonde to expose the tip of the optical fiber to the measurement hole, when the tip of the optical fiber is melted, while sequentially feeding the optical fiber to the measurement hole side, The radiant light emitted by the combustion flame of the blown fuel is detected by the tip of the optical fiber, and based on the radiant light detected by the tip of the optical fiber, the fuel is detected by the temperature detecting device connected to the rear end of the optical fiber. The combustion temperature of is continuously measured.

In the method for diagnosing combustion of injected fuel in a blast furnace according to the present invention, a tuyere sonde having a measurement hole at the lower end of the tip is inserted into the blow pipe from behind the tuyere, and a metal pipe is attached to the tuyere sonde. The coated optical fiber is inserted so that the tip of the optical fiber faces the measurement hole, and when the tip of the optical fiber is melted, the tip of the optical fiber is sequentially fed to the measurement hole side while sequentially feeding the optical fiber to the measurement hole. The radiant light emitted by the combustion flame of the injected fuel is detected by the radiant light detected by the tip of the optical fiber, and the luminosity of the fuel is detected by the brightness / temperature detecting device connected to the rear end of the optical fiber. Alternatively, the temperature is continuously measured, and the combustibility of the fuel is diagnosed from the measured combustion brightness or temperature.

[0011]

In the present invention, when the combustion radiant light of the blown fuel in the blow pipe is detected by the optical fiber coated with the metal tube inserted in the tuyere probe, when the optical fiber is melted, the optical fibers are sequentially fed. The synchrotron radiation can be continuously detected and the temperature can be continuously measured. In addition, by continuously detecting the synchrotron radiation, it is possible to grasp the combustion state. Moreover, the combustion synchrotron radiation is detected, and the combustion state is diagnosed based on the detected synchrotron radiation. You can get it instantly.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view for explaining one embodiment of the present invention,
FIG. 2 is an enlarged view showing a part of FIG. 1 in an enlarged manner. Less than,
An embodiment of the present invention will be described with reference to FIGS. In the figure, 1 is a blast furnace furnace body, 2 is a blast branch pipe, 3 is a blow pipe following the blast branch pipe 2, 4 is a tuyere, 5 is a lance to which blown-in fuel is supplied, and 6 is inserted in the blow pipe 3. It is a hollow tuyere sonde. Reference numeral 7 denotes an optical fiber supply drum 8 to be described later, one end of which is inserted into the tuyere sonde 6 and covered with a metal tube. Brightness temperature calculator that converts
10 is a computer. Reference numeral 11 is a flame of injected fuel, 12 is a raceway, and 13 is a packed layer of coke. The optical fiber 7 and the optical fiber supply drum 8
And the brightness temperature calculator 9 constitute a radiation thermometer.

Next, the fuel combustion temperature measuring method according to the present invention will be described. First, the tuyere sonde 6 from the rear of the blow pipe 3 into the flame 11 generated by the combustion of fuel.
And insert the optical fiber 7 inserted through the tuyere probe 6 into the flame 11 through the measurement hole provided at the tip of the tuyere probe 6.
Radiant light emitted by the flame 11 is detected by sending the flame 11 into the inside. Since the temperature of the flame 11 is 2000 to 2500 ° C., the optical fiber 7 sent into the flame 11 is
Although it melts instantly together with the coated metal tube, it has a very high response speed, and therefore radiates light emitted from the flame 11 during the period from being sent into the flame 11 until melting. The incident radiant light is guided to the brightness temperature calculator 9 through the optical fiber 7, converted into an electric signal, and then converted into a temperature,
The computer 10 performs indexing and data processing. If the optical fiber 7 is continuously fed by the optical fiber supply drum 8, continuous temperature measurement can be performed.

Since the flow of fuel in the blow pipe 3 is very fast, it is necessary to use a detector having a very fast response speed and a limited field of view in order to accurately detect the temperature of this fuel. This is because in the case of a detector having a slow response speed and a wide field of view, the measurement target becomes too large, the change in combustion cannot be detected, and only averaged information can be obtained. Further, the temperature of the fuel in the blow pipe becomes extremely high, and it is necessary to take measures against it. For the above reasons,
Thermocouples, which are commonly used for temperature measurement, have a slow response speed and are melted at high temperatures, so they are not suitable for the measurement of the present application. Therefore, the optical fiber 7 used in this example is a GI50 / 125 fiber made of quartz having corrosion resistance,
For example, a metal tube coating (or an ultraviolet curing resin coating) such as stainless steel is used, and the brightness temperature calculator 9 has two elements if the detection element is Si (wavelength 0.9 μm or there are a plurality of measurement targets and the area ratio thereof affects. (Color thermometer), and the measurement temperature range is 200 to 3000 ° C. Further, the response speed is 0.5 msec or less, and the field of view is NA = 0.2, which is suitable for measuring the temperature of a high-temperature high-speed fluid.

Further, the characteristics of the present invention are as follows.
This means that the temperature of a radiant object (gas, liquid, solid) can be measured without contact. Moreover, since the optical fiber 7 according to the present invention has a large strength due to the metal tube coating, it can be stably fed from the rear of the tuyere 4 without damaging the optical fiber itself. Moreover, since the optical fiber 7 having a length sufficient for several tens of measurements can be accommodated in the optical fiber supply drum 8 outside the furnace, continuous measurement is possible, and new optical fibers 7 are successively added from the water-cooled tuyere probe 6. Therefore, it is not necessary to consider durability under high temperature atmosphere for a long time.

The tuyere probe 6 will be described in more detail with reference to FIG. 2. A measurement hole 14 for feeding the optical fiber 7 is provided on the lower side of the tip of the tuyere probe 6.
This measurement hole 14 is for preventing the measurement hole 14 from being blocked by small coke, coke powder, unburned fuel, etc. when the tuyere sonde 6 is inserted into the raceway 12 and the coke packed layer 13 and in the furnace. Without being affected by synchrotron radiation,
The opening is formed at a right angle to the axial direction of the tuyere sonde 6 in order to detect only the radiant light emitted by the combustion flame of the blown fuel. In addition, in order to prevent blockage due to molten pig iron dropping from above, it is preferable to open downward.

In order to demonstrate the effect of the present invention, the following combustion temperature measurement test was carried out in an actual furnace. Hot air is flowing from the upstream direction of the blow pipe 3 in FIG. 1, the gas flow velocity in the blow pipe 3 is 105 m / s, and the tuyere 4
The gas flow velocity at the tip of is 200 m / s. Other conditions are shown in Table 1. In addition, in this test, the measurement hole 14 was moved from the tip of the blowing lance 5 to the downstream side by 90 degrees.
The tuyere probe 6 is inserted so as to be placed at a position of 0 mm. Then, the optical fiber 7 is fed into the tuyere sonde 6, and the temperature is measured by capturing the emitted light of the burning fuel until the optical fiber 7 is melted.

[0018]

[Table 1]

FIG. 3 shows the results of combustion temperature measurement under the test condition (A) shown in Table 1. The vertical axis of FIG. 3 represents the temperature (° C.), and the horizontal axis represents the length (cm) of the chart paper. For the sake of easy understanding of the response of the measurement signal, the rise of the temperature peak is real time, the fall is the response delayed by 1 second, and the chart speed is set to 60 cm / min. As can be seen from FIG. 3, according to the present invention, continuous temperature measurement is possible even in a high temperature field exceeding 2000 ° C. such as a fuel combustion field, and the measurement result can be obtained instantly.

Next, the position of the measuring hole 14 is blown into the blowing lance 5.
The temperature was measured at a plurality of positions by moving it from the tip to the downstream side. FIG. 4 shows the results, in which the vertical axis shows the temperature (° C.) and the horizontal axis shows the distance (mm) from the tip of the lance 5 of the measuring hole 14, respectively. Further, (A) and (B) in FIG. 4 respectively show the test conditions (A) (when fuel is injected) in Table 1 and the test conditions (B) (when fuel is not injected) in Table 1 as well. ing. As a result of the test, as shown in FIG. 4, as compared with the case where the fuel was not injected (B), the temperature inside the furnace when the fuel was injected (A) was 900 mm at the tuyere tip due to the solution loss reaction of the pulverized coal. A decrease was observed. Further, it was found that the temperature decreased in the coke packed layer 13 at the inner side of the raceway, and it was confirmed that the present invention can measure the temperature distribution in the furnace at the time of fuel injection. Needless to say, when the fuel is not blown in, the furnace temperature can be measured by the same method as described above.

Next, a combustion diagnosis method for diagnosing the combustion state of the fuel based on the measurement result measured by the above-mentioned method for measuring the combustion temperature of the injected fuel will be described. In this embodiment, the measurement hole 1 is placed at a position 300 mm from the tip of the lance.
The tuyere sonde 6 was inserted so that 4 came, and the combustion temperature was measured. The measured temperature is based on the highest temperature value,
It is indexed as an average value or a difference between measured values at intervals of several milliseconds, and the flammability is judged from the index. When the combustion state of the fuel is good, the combustion temperature is high and the average index is large.
Further, in this case, since the high temperature is maintained, the difference index is small. On the other hand, when the combustion state is not good, the combustion temperature detected successively is low and the measured value rarely becomes high in temperature, so the average index is small and the difference index is large. In the present invention, the burning rate of fuel is defined as follows using the above-mentioned index. Combustion rate index (%) = exponential average value (α) / exponential maximum value (β) * 100 Information on this combustion rate index is fed back to adjust the operating conditions to maintain or improve the state of good combustibility. is there.

In the above description, the brightness of the radiant light detected by the optical fiber 7 is converted into temperature. However, the burning rate index is calculated by the above formula based on the brightness measured without being converted into temperature. (%) May be obtained. The relationship between the intensity of synchrotron radiation and the combustion state of fuel is, for example, Onuma (Combustion Research, (1979) .vo150.P26).
Well-studied in the field of combustion engineering as seen in the literature, and the correlation has been confirmed.

In order to demonstrate the effect of the present invention, first, a combustion temperature measurement experiment was conducted. The conditions of this experiment are shown in Table 2.
As shown in.

[0024]

[Table 2]

FIG. 5 is a graph showing the combustion temperature measurement results under the experimental conditions shown in Table 2. Case (A) in Table 2 is a condition in normal operation, and case (B) is a condition when oxygen enrichment is performed to increase the combustion rate of fuel. As shown in FIG. 5, in the case of high oxygen concentration (B), the measured index is larger and the time variation is smaller. From this, in case (B),
It can be seen that the combustion state of the fuel is good and that state is persistent.

Table 3 shows the combustion rate index obtained by the above experiment and the combustion rate (analytical value) calculated based on the result of chemical analysis of the sampled fuel.

[0027]

[Table 3]

The burn rate by analysis is defined by the following equation and means the weight loss rate of the heatable content under the assumption that the ash content (Ash) in the fuel is constant before and after combustion. Burning rate (%) = 100 * [1- [100-Ash (fuel)] *
Ash (raw fuel)] / [100-Ash (raw fuel)] * As
h (Fuel) As shown in Table 3, the result (analytical value) by the chemical analysis and the result of the above-mentioned embodiment correspond well, and from this fact, the combustibility of the fuel can be measured by the present invention. confirmed.

FIG. 6 is a graph of an operation test result in which the burning rate index was measured by the above-described embodiment and the operation was performed based on the measurement result. The ventilation resistance index used here is an index related to the pressure loss of the blast furnace and is used as an operation index. The following can be seen from the graph of FIG. That is, the injection amount of fuel is 200 kg / t.
However, as shown in case (a) in the figure, the fuel combustion rate index continues to be low, and the amount of unburned fuel produced increases, which accumulates in the furnace and the ventilation resistance in the furnace increases. It got bigger. Therefore, when oxygen enrichment was performed so that the burning rate index increased, the ventilation resistance in the furnace decreased as shown in case (b) in the figure, and the operation became stable.

[0030]

As described above, according to the present invention, when the combustion radiant light of the blown fuel in the blow pipe is detected by the optical fiber covered with the metal tube inserted in the tuyere probe, the optical fiber is melted Since the optical fiber is sequentially fed, the combustion radiant light of the fuel can be continuously detected, and the combustion temperature can be continuously measured.

Further, since the emitted light is continuously detected and the combustion state is diagnosed on the basis of the detected emitted light, the diagnosis result can be obtained accurately and instantaneously. Further, by controlling the operating conditions based on the result of this diagnosis, it is possible to easily realize the blast furnace operation in which the ventilation resistance is not increased.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an embodiment of the present invention.

FIG. 2 is an enlarged view showing a part of FIG. 1 in an enlarged manner.

FIG. 3 is a graph showing a combustion temperature measurement result in an example.

FIG. 4 is a graph showing a measurement result of combustion temperature in another example.

FIG. 5 is a graph showing the measurement results of combustion temperature under the experimental conditions of Table 1.

FIG. 6 is a graph of an operation test result in which a combustion rate index is measured according to the present example and an operation is performed based on the measurement result.

[Explanation of symbols]

 1 Blast furnace main body 2 Blower branch pipe 3 Blow pipe 4 Tuyere 5 Lance 6 Tuyere sonde 7 Optical fiber 8 Optical fiber supply drum 9 Brightness temperature calculator 10 Computer 14 Measuring hole

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tsutomu Kawamura 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Yoshiro Yamada 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Date Inside the Steel Pipe Co., Ltd. (72) Inventor Yoshiyoshi Yamanaka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Steel Pipe Co., Ltd.

Claims (2)

[Claims] 1. A tuyere probe having a measurement hole at the lower end of the tip is inserted into the blow pipe from the rear of the tuyere, and an optical fiber coated with a metal tube is inserted into the tuyere probe to attach the tip of the optical fiber to the tip. While facing the measurement hole, when the tip of the optical fiber is melted, while sequentially feeding the optical fiber to the measurement hole side, the radiant light emitted by the combustion flame of the blown fuel is detected by the tip of the optical fiber, Based on the radiant light detected by the tip of the optical fiber, the combustion temperature of the fuel is continuously measured by a temperature detecting device connected to the rear end of the optical fiber. Combustion temperature measurement method. 2. A combustion diagnosis method for diagnosing a combustion state of injected fuel in a blow pipe following a tuyere of a blast furnace, wherein a tuyere sonde having a measurement hole at a lower end of the tip is provided in the blow pipe from behind the tuyere. And insert a metal tube-coated optical fiber into the tuyere probe to expose the tip of the optical fiber to the measurement hole, and if the tip of the optical fiber is melted, measure the optical fiber sequentially. While feeding to the hole side, the radiant light emitted by the combustion flame of the blown fuel is detected by the tip of the optical fiber, and based on the radiant light detected by the tip of the optical fiber, it is connected to the rear end side of the optical fiber. Continuously measuring the combustion brightness or temperature of the fuel with the brightness / temperature detection device, and diagnosing the combustibility of the fuel from the measured combustion brightness or temperature. A method for diagnosing combustion of blown fuel, comprising: