JPH01314928A - Temperature measuring method and apparatus for melting steel - Google Patents

Abstract

PURPOSE:To reduce the measuring cost and improves the measuring accuracy by jetting out gas which is intermittently mixed with oxygen into a furnace from a temperature measuring hole, and measuring the temperature of melting steel when said gas without being mixed with oxygen is jetted out. CONSTITUTION:A temperature measuring probe 10 accommodating an optical fiber 11 thereinside is inserted into a temperature measuring hole 15. The probe 10 is provided with a condensing mechanism 22 at an end portion thereof. The other end of the optical fiber 11 accommodated within the probe 10 is connected to a radiation thermometer 1. Gas mixed with oxygen is sent with pressure from a gas suction duct 12 of the probe, passing through the space between an optical fiber support 22 and an exterior pipe 23, and jetted out from the hole 15 to be supplied into a furnace. The solidified steel produced before a tuyere 4 is removed by the oxygen. The temperature of melting steel is measured when the gas is not mixed with oxygen. Accordingly, the generation of solidified steel is prevented, and the temperature of melting steel is considerably correctly measured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for measuring the temperature of molten metal such as molten steel. More specifically, the present invention relates to a method and an apparatus for measuring the temperature of molten steel using a radiation thermometer having a temperature measuring probe (hereinafter referred to as "temperature measuring probe") installed in the siding.

(Prior art) The conventional method for measuring the temperature of extremely high-temperature molten steel, such as molten steel during blowing in a converter, is to attach a consumable thermocouple to the tip of a sublance. has been adopted.

To explain in detail the case of hot metal blowing using a converter, the main issues are controlling the molten steel components (mainly C, P, S) and molten steel temperature at the time of tapping. amount and melt
It is widely practiced to measure mL degrees by using a sublance and inserting a temperature probe into the molten steel at each degree during the middle and final stages of blowing.

This temperature measuring probe has a thermocouple installed at the tip of the sublance, but when inserted into molten steel, it melts within a few seconds, making it impossible to use it continuously or even to reuse it.

Therefore, in the past, temperatures were measured intermittently over short periods of time, such as during the middle and final stages of blowing. However, this method of intermittent molten steel temperature measurement using conventional technology is insufficient for highly accurate control of molten steel composition and temperature, and the temperature measurement probe is consumed each time it is measured, resulting in extremely high running costs. There is a problem.

In addition, as top-bottom blowing combined blowing has been adopted in recent years, it has become necessary to control the molten steel temperature at each stage of blowing.
There is a demand for continuous measurement of molten steel temperature.

Under such a background, as shown in FIG. 5, an optical fiber 41 equipped with a condensing lens at its tip 42, a built-in condensing lens and an optical fiber, and a gas surrounding the condensing lens and optical fiber are constructed. A temperature measuring probe equipped with a mechanism that blows in! ! A method has been proposed in which the heat exchanger is installed in a tuyere 44 provided on the furnace wall corresponding to the heating section of the steel furnace 43. The radiant energy of the molten steel 45 focused by a condensing lens is measured by a radiation thermometer 46 connected to an optical fiber 41 and converted into temperature.

However, with this method, the molten steel 45
is cooled, so that solidified steel 47 in the form of a pine mushroom is generated near the tuyere 44. This solidified i47 grows during blowing and comes to cover almost the entire surface of the tuyere 44 at the end of blowing. Therefore, due to the growth of the solidified steel 47, the field of view of the condensing lens is partially obstructed by the solidified steel 47, and only a portion of the field surface is visible, making it impossible to accurately measure the temperature.
In the end, measurement itself becomes impossible.

(Problem to be Solved by the Invention) Therefore, by adding oxygen to the blown gas, the formation of solidified steel, which is usually deposited in the shape of a pine mushroom, is prevented,
A method for continuously measuring the radiant energy of molten steel was proposed in JP-A-60-121628.

However, with this proposal, the interface temperature between the blown gas and molten steel changes greatly depending on the mixing degree of oxygen in the blown gas, and it is difficult to finely adjust the gas mixing ratio, so it is difficult to accurately adjust the molten steel temperature. It was difficult to make measurements.

Further, in order to prevent an increase in interface temperature, a method of blowing only an inert gas through the tuyere was proposed in JP-A-62-52423 and JP-A-60-61633. However,
As mentioned earlier, in these methods, a pine mushroom-like solidified steel is formed in front of the siding due to the cooling effect of gas injection, resulting in the field of view of the condensing lens being cut off, etc., making it difficult to make high-precision measurements. could not be done.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional technology and provide a method and apparatus for measuring molten steel temperature with high accuracy, thereby reducing measurement costs and improving measurement accuracy. That is.

(Means for Solving the Problems) The present inventors have conducted various studies to solve the above problems, and as a result 1) In order to prevent the formation of solidified steel in front of the temperature measurement probe, it is necessary to In other words, it is effective to mix an appropriate amount of oxygen into the gas ejected from the temperature measurement hole, but if oxygen is constantly mixed into the gas, the molten steel that is about to be oxidized and burns, so it is not possible to accurately measure the amount of molten steel. Temperature measurement will no longer be possible. Therefore, the temperature of molten steel is measured by mixing oxygen intermittently with the gas and measuring the temperature of molten steel when no oxygen is mixed.2) Protecting the inner wall of the temperature measurement hole through which the gas mixed with oxygen intermittently flows with oxide-based refractories. The present invention was completed based on the finding that abnormal melting of the tuyeres caused by the reaction between oxygen gas and refractory bricks can be prevented and the formation of solidified steel can be reliably prevented.

In other words, the gist of the present invention is to provide a tuyere on the bottom or wall of the furnace corresponding to the sump of a steelmaking furnace, and install a temperature measurement probe containing a built-in optical fiber with a condensing mechanism at its tip. In a molten steel temperature measurement method, a temperature measurement hole and a gas blowing hole are installed in the tuyere, and the temperature of molten steel in the furnace is measured by a radiation thermometer connected to the optical fiber,
This molten steel temperature measuring method is characterized in that a gas intermittently mixed with oxygen is ejected into the furnace from the temperature measurement hole, and the temperature of the molten steel is measured while the gas without oxygen is ejected.

From another perspective, the bottom of the furnace, which is equivalent to the sump of a steelmaking furnace, has an optical fiber with a light condensing mechanism at its tip for temperature measurement, a temperature measurement hole with a probe installed, and a gas injection hole. Alternatively, a molten steel temperature measuring device includes a slat provided in a furnace wall, a first gas supply device for blowing gas into the gas blowing hole, and a radiation thermometer connected to the optical fiber, and a gas flow path whose interior is made of an oxide refractory that has poor wettability with slag and is located within the temperature measurement hole and installed around and/or inside the temperature measurement probe; and the gas flow path. This is a molten steel temperature measurement device that includes a second gas supply device that blows gas into the gas flow path, and an oxygen gas supply device that intermittently supplies oxygen gas to the gas flow path.

Temperature-measuring holes whose interiors are made of oxide-based refractories have poor wettability with slag and molten steel, so they are fireproof with oxygen and can prevent reactions with gas. An example of the material for the refractory is stabilized zirconia.

The principle of the temperature measurement method itself is the same as the known conventional method. That is, the radiant energy from the molten steel collected by a condensing mechanism provided at the tip of the optical fiber is transmitted to a radiation thermometer via the optical fiber and converted into the temperature of the molten steel.

In addition, the tuyere structure has a multi-hole nozzle structure with many gas blowing holes arranged around the temperature measurement hole, which is suitable from the viewpoint of gas blowing, but it also functions as a gas flow path, that is, it can blow gas into the furnace. It goes without saying that there is no particular restriction as long as the tube has a triple tube tuyere (that is, the center tube is a temperature measuring hole and the outer circumference is a gas blowing hole).

Furthermore, the gas mixed with oxygen and supplied into the furnace through the temperature measurement hole or the gas supplied alone into the furnace through the gas blowing hole is A.
Although inert gases such as r and Nz are preferable, they are not necessarily limited to inert gases; for example, gases such as CO□ can also be used. However, in the case of gas mixed with oxygen and supplied into the furnace, the mixing ratio of oxygen and gas that can prevent abnormal melting of the tuyeres and reliably remove solidified steel depends on the type of gas with which the oxygen is mixed. Needless to say, it changes depending on C.
If O2 is used, it will act mainly as an inert gas before the tuyere in the early stages of hot metal refining, and as a weakly oxidizing gas in the final stage, so the oxygen mixing ratio will naturally need to be changed during the blowing period. I understand. Further, when Ar gas is used, oxygen is required to be at least 10% by volume or more in order to prevent a temperature drop due to mixed gas injection.

(Function) First, the measuring method according to the present invention will be specifically explained together with a measuring device as an embodiment thereof. Note that this is just one embodiment of the present invention, and the present invention is not unduly limited thereby.

In this example, a porous nozzle is used as the tuyeres, but as mentioned above, the use thereof is not limited to porous nozzles, but any type that has a function as a gas flow path may be used. Of course, triple pipe tuyere etc. can also be used.

FIG. 1 is a sectional view of a molten steel temperature measuring device according to an embodiment of the present invention. A refractory filler 5 is filled in the gap between the wall of a tuyere 4 provided in a refractory brick 3 on the furnace wall of a steelmaking furnace and the porous nozzle 1. A metal vibro is connected in an airtight manner to the rear part of the porous nozzle 1, and the metal vibro extends to the outside through a through hole provided in the iron skin 7 covering the refractory brick 3. The gap between the refractory bricks 3 is filled with another refractory filler 8.

Furthermore, a temperature measurement hole 15 penetrates through the center of the multi-hole nozzle 1, and the temperature measurement hole 15 has an optical fiber 11 equipped with a condensing mechanism 22 at its tip as shown in FIG. A temperature measuring probe 10 is inserted.

The other end of the optical fiber 11 built into the temperature measuring probe 10 is guided outside the furnace and connected to the radiation thermometer 2 outside the furnace. Furthermore, the gas tit can be set to a desired value for the temperature measuring probe 10 and the metal vibro through the gas blowing duct 2 for the temperature measuring probe and the gas blowing duct 13 for the porous nozzle, respectively. An oxygen gas supply device (not shown), a temperature probe gas supply device (not shown), and a porous nozzle gas supply device (not shown) are connected. The structure is such that the oxygen supplied from the oxygen gas supply device is intermittently mixed with the gas supplied from the temperature measuring probe gas supply device and supplied into the furnace. For example, if a three-way valve is provided in the middle of the gas supply pipe, the oxygen gas supply pipe may be connected to the three-way valve, but since such a structure is already known, further explanation will be omitted.

Similar to the furnace wall of a steelmaking furnace, the porous nozzle 1 is made of, for example, an Mg0-C refractory brick 14 in this embodiment, and the temperature measurement hole 15 into which the temperature measurement probe 10 described above is inserted is In the illustrated embodiment, it is a through hole with a diameter of 5 mm provided on the center line of the tuyere 4, and as shown in FIG. 2, the inner wall is protected by an outer tube 23 made of stabilized zirconia. An optical fiber support 21 containing an optical fiber 11 is fixed in the center of the temperature measurement hole 15 by a fixing member 24 that supports the optical fiber support 21 and the outer tube 23. The fixing member 24 does not completely cover the space around the optical fiber support 21, but partially joins the two at several points in the circumferential direction to allow gas to flow through the space.

The optical fiber support 21 constitutes the outer skin of the temperature measuring probe 10, and has a light condensing mechanism 22 at its tip. A gas mixed with oxygen is pumped through the temperature measuring probe gas blowing duct 12, passes through the space between the optical fiber support 21 and the outer tube 23, is ejected from the temperature measuring hole 15, is supplied into the furnace, and is supplied to the tuyere 4. The solidified steel 47 produced before this step is removed by oxygen. In this embodiment, the space between the optical fiber support 21 and the outer tube 23 is used as the flow path for the gas that mixes oxygen, but the space is not limited to this space. For example, the optical fiber support 21
An appropriate ventilation hole may be provided inside the optical fiber support 21 to serve as a flow path for the gas that mixes oxygen, or the tip of the optical fiber support 21 may be provided as a flow path for the gas that mixes oxygen. A gas mixed with oxygen may be ejected from. In any case, what is important in the measurement method according to the present invention is to supply a gas intermittently mixed with oxygen into the furnace through the temperature measurement hole.

In order to completely prevent the formation of solidified steel, it is effective to blow the gas mixed with oxygen into two times, at the beginning and end of the rinsing period. In addition, as mentioned earlier, the mixing ratio of oxygen changes depending on the type of gas used, so the specific conditions should be checked in the actual converter and set appropriately, but it is important to note that the mixing ratio of oxygen varies from room temperature to molten steel temperature. The amount must be such that the heat of reaction is greater than the sensible heat that increases the temperature.

On the other hand, if too much oxygen is mixed, the temperature in front of the nozzle will rise too much and the tuyere will melt abnormally.

Further, as the temperature measuring means, a radiation thermometer 2 is used that measures radiant energy from the surface of the molten steel.

Furthermore, the temperature measuring probe 10 is prevented from coming into contact with the molten steel by blowing gas from the tuyere 4 through the temperature measuring probe 10 and the porous nozzle around it at a sufficient flow rate so that the tips of the tuyere do not become clogged. It is cooled to prevent it from melting due to the radiant heat from the molten steel, and also prevents molten steel from flowing in.

The temperature of molten steel is measured when no oxygen is mixed with the gas. This is because, as mentioned above, when oxygen is mixed with the gas, the molten steel in front of the tuyeres is oxidized and burned, making it impossible to accurately measure the temperature of the molten steel.

In other words, by injecting gas mixed with oxygen intermittently into the furnace from the temperature measurement hole and measuring the temperature of the molten steel when no oxygen is being mixed, the temperature of the molten steel can be measured extremely accurately while preventing the formation of solidified steel. It can be done.

Next, a detailed description of the device according to the present invention will be given in conjunction with the description of the device described above.

Noro and! Magnesia stabilized zirconia is used as the oxide refractory for the outer tube 23! ! [Also, since it has poor wettability and is resistant to thermal shock, only the outer tube 23 will not be damaged or damaged even if used for a long period of time. This is to prevent direct contact between 14 and oxygen and to prevent abnormal melting and damage of the tuyere. Therefore, the temperature measuring hole 15 can maintain a stable pipe shape even though gas mixed with oxygen is intermittently blown into the pipe, and the solidified steel 47 formed before the tuyere 4 can be effectively removed by oxygen. This makes it possible. In this embodiment, a zirconia tube having the same outer diameter as the inner diameter of the temperature measurement hole 15 was used as the sleeve structure, but the sleeve structure is not limited to this, and the inner wall of the temperature measurement hole may be protected with an oxide refractory. Any structure that does so is fine.

FIG. 3 is a front view of the multi-hole nozzle 1 seen from the direction AA' in FIG. The above-mentioned temperature measuring hole 15 is provided in the center, and around it are holes each having a diameter of 2 mm in a mesh shape of 10 mm on each side.
A large number of square gas blowing holes 31 of ms are provided. A large number of gas blowing holes 31 each pass through the refractory brick 14 and are connected to the duct 13 at the outer end of the furnace, and gas is circulated through the duct 13 by a gas blowing device for a multi-hole nozzle, and into the furnace. It is configured to blow out.

In this example, when a porous nozzle with a diameter of 100 mm was used, the gas blown into the temperature probe had a flow rate of 15 mm.
01/min Ar gas, flow rate 6 for porous nozzle
00 j! /min Ar gas was used.

In this way, by flowing the blowing gas for the temperature measurement probe, the optical fiber 11 is cooled, and at the same time, molten steel is prevented from entering from the tip of the tuyere 4 during blowing, and the blowing gas for the porous nozzle is Flowing promotes stirring of molten steel.

Now, the radiant energy from the molten steel surface is the temperature measurement probe 10.
The light is collected by a light collecting mechanism 22 located inside the , and guided to the radiation thermometer 2 via the optical fiber 11 .

As the condensing mechanism used here, a convex lens or the like may be used, and its focal length may be set according to the distance between the molten steel to be measured and the lens, but it is not particularly limited to a convex lens. Since such a light condensing mechanism is already known, further explanation will be omitted.

It is desirable to use the radiation thermometer 2 in a wavelength range in which only thermal radiation from molten steel is observed and measure the radiant energy, so here we set the dominant wavelength to 0.9 μm, where there is no absorption by the blown gas. Set.

The radiant energy guided to the radiation thermometer 2 is photoelectrically converted there, and after being converted into electrical energy according to the amount of light,
Converted to temperature value.

Stream 4] 50j for temperature measurement probe! /win Ar gas, for porous nozzle, flow rate 5QQ 12 /min A
An example in which the temperature of molten steel during blowing was measured by the temperature measuring method based on this example under the condition of supplying r gas is shown by a broken line in FIG. 4. In FIG. 4, the molten steel temperature measured with an immersion thermometer is also indicated by a white circle. Looking at this figure 4, although the measured values of the two always almost correspond, there is a certain deviation between the fixed values on both sides, and the measured value of this example is lower than the measured value of the conventional immersion type thermometer. You can see that it is happening.

This is caused by the gas it blown from the temperature probe lO.
This is thought to be because the molten steel interface at the tip of the tuyere 4 is being cooled.

In addition, since solidified steel was formed during the rinsing period and the measured value rapidly decreased, the effect of mixing oxygen with 25% by volume Ar gas and injecting it for 7 seconds is also shown by the broken line in Figure 4.
It can also be seen that the temperature at the front of the temperature measuring probe rose rapidly due to the effect of oxygen injection, melting the solidified steel and making the temperature readings reasonable.

Furthermore, it is possible to correct the measured temperature by using the amount of temperature reduction of the molten steel caused by the blown gas as a function of the flow rate of the temperature measuring probe gas.

Flow rate 50β of Ar gas for temperature measurement probe in this example
The amount of temperature decrease corresponding to /min was measured in advance with a radiation thermometer as a correction amount, and the temperature of the molten steel was measured, and the results are shown in the dashed line in the fourth measurement. The measured values after correction are in excellent agreement with the measured values of the immersion thermometer, and it can be seen that the measurement of molten steel temperature by the method and apparatus of the present invention achieves sufficient accuracy.

Thus, the molten steel temperature measuring device according to the present invention can measure the temperature of molten steel extremely accurately.

In this example, a porous nozzle with pores arranged in a mesh pattern was used, but the arrangement of the pores does not necessarily have to be in a mesh pattern, and may be arranged concentrically or completely irregularly.

Additionally, in this example, Mg0-C firebricks were used as the gas injection tuyere to prevent the molten steel from solidifying, but the invention is not limited to this, and any material that does not react with oxygen may be used. Needless to say.

(Effects of the Invention) As described above in detail, according to the present invention, there is no need to wear out the parts unlike the conventional temperature measurement method using a thermocouple, and it is possible to perform highly accurate temperature measurement. can.

Therefore, the method and device for measuring molten steel temperature of the present invention are extremely useful.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a molten steel temperature measuring device in an embodiment of the present invention; Fig. 2 is a cross-sectional view of a probe in an embodiment of the present invention; Fig. 3 is a cross-sectional view of a porous nozzle tip in an embodiment of the present invention. A front view; FIG. 4 is a graph showing the measurement results of the molten W4 temperature by the measuring method according to the present invention; and FIG. 5 is a cross-sectional view of a conventional steelmaking furnace. 1: Porous nozzle 2.467 radiation thermometer 3, 14
: Firebrick 4.44 : Tuyere 5.8 = Fireproof filling 6 : Metal pipe 7 : Iron shell
10: Temperature measurement probe IL 41: Optical fiber 12: Gas injection duct for temperature measurement probe 13; Gas injection duct for porous nozzle 15: Temperature measurement hole 21: Optical fiber support 22:
Light collecting mechanism 23: Outer tube (zirconia tube) 24: Fixing member 31: Gas blowing hole 42: Tip 43:
Steelmaking furnace 45: Molten H47: 4[[

Claims (2)

[Claims] (1) A tuyere is installed on the bottom of the furnace or the furnace wall, which corresponds to the sump of a steelmaking furnace, and a temperature measurement hole and gas blowing hole are installed with a temperature measurement probe containing a built-in optical fiber with a condensing mechanism at the tip. In the molten steel temperature measuring method, in which the temperature of molten steel in the furnace is measured by a radiation thermometer installed in the tuyere and connected to the optical fiber, a gas mixed with oxygen intermittently is introduced into the furnace through the temperature measurement hole. A method for measuring the temperature of molten steel characterized by measuring the temperature of molten steel while ejecting gas that is not mixed with oxygen. (2) Equipped with a temperature measurement hole equipped with a temperature measurement probe containing an optical fiber with a light condensing mechanism at the tip and a gas injection hole, the bottom or wall of the furnace corresponds to the sump of a steelmaking furnace. A molten steel temperature measuring device having a tuyere provided, a first gas supply device for blowing gas into the gas blowing hole, and a radiation thermometer connected to the optical fiber, wherein the temperature measuring hole is connected to the molten steel and slag. The interior is made of an oxide refractory with poor wettability, and the gas flow path is located in the temperature measurement hole and installed around and/or inside the temperature measurement probe, and the gas flow path is provided with a gas flow path. A molten steel temperature measuring device comprising a second blowing gas supply device and an oxygen gas supply device intermittently supplying oxygen gas to the gas flow path.