JP2001303120A - Method for measuring temperature on surface in inside of refining vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for restraining the adverse effect due to a high temperature on a wall refractory in a furnace to the minimum limit in a refining method by controlling the surface temperature of the refractory and/or the temperature in a space part for preventing the sticking of skull. SOLUTION: A material 1 having high heat conductivity is buried into the refractory for the furnace wall, and further, according to the temperature and/or rising/lowering speed of the temperature measured with a thermocouple 3 disposed in the inner part of this material 1, the secondary combustion ratio in the furnace or the firing power of a fuel burner is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring the temperature on the inner surface of a smelting vessel such as a converter.

[0002]

2. Description of the Related Art In the refining process of molten iron using a refining vessel such as a converter or a vacuum degassing device, the molten iron is scattered (= spitting) due to the energy of a top blown gas, a bottom blown gas, and a gas generated by a degassing reaction. ) Occurs, the metal is adhered to the inner wall of the furnace, and the yield is deteriorated, the operation is impaired, and the molten metal is contaminated by the metal.

[0003] Therefore, for the purpose of preventing adhesion and melting of the metal, a method of preventing the adhesion and melting of the metal by increasing the temperature in the furnace by secondary combustion of CO gas or a fuel burner has been disclosed ( For example, JP-A-3-240912, JP-A-6-248323, JP-A-6-7334
No. 32 publication). In these methods, it is possible to prevent adhesion and melting of metal, but on the other hand, if the secondary combustion rate or fuel burner becomes excessive, the furnace wall refractories are exposed to high temperatures for a long time, It has adverse effects such as shortening of furnace life due to melting of the material.

[0004]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for preventing the adhesion of ingots and the above-mentioned problems in the melting method. It is intended to provide a measuring method.

[0005]

The gist of the present invention resides in the following method. (1) A material having a high thermal conductivity of 10 W / m · k or more is buried in the refractory on the furnace wall side with the refractory disposed on the furnace wall side.
From the temperature measured by a thermocouple installed at least at one position inside the material and / or the rate of temperature rise / fall, the temperature of the inside surface of the refractory and / or the temperature of the inside surface of the metal adhered to the surface of the refractory A method for measuring the temperature of the inner surface of a smelting vessel, characterized by estimating the temperature (2) The method for measuring the temperature of the inner surface of a smelting vessel according to (1), wherein the boundary between the material having a high thermal conductivity of 10 W / m · k or more and the refractory on the furnace wall is covered with a heat insulating material. . (3) As a material having a high thermal conductivity of 10 W / m · k or more, one or a combination of two or more of Fe, Mo, W, and Cu is used (1) or (2). The method for measuring the temperature of the inner surface of a smelting vessel as described in the above.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a metal refining vessel, a material having a low thermal conductivity is generally used for the furnace wall refractory to prevent heat dissipation. Therefore, the responsiveness to a temperature change in the furnace or a change in the thickness of the metal adhered to the furnace inner wall is low, and it is not easy to detect a thermal load on the refractory on the furnace inner wall. Therefore, in the method of raising the temperature inside the furnace by secondary combustion of CO gas or a fuel burner to prevent adhesion and melting of the metal, the heat load on the furnace wall refractory becomes excessive, and the furnace wall refractory becomes Exposure to high temperature for a long time tends to cause adverse effects such as shortening of furnace life due to melting of refractories.

An embodiment of the present invention will be described with reference to FIG. According to the present invention, a furnace wall refractory made of a wear brick 5 and a perm brick 6 whose surface is covered with a steel shell 7 has a resistance of 10 W / m ·
A material 1 having a high thermal conductivity of not less than k (hereinafter referred to as a high thermal conductor) is embedded, and the temperature and / or the temperature rise / fall rate measured by the thermocouple 3 installed inside the material 1 Provides a method for measuring the internal surface temperature of a smelting vessel. By controlling the secondary combustion rate or the fuel burner thermal power in the furnace according to the measured surface temperature, it is possible to minimize the adverse effect on the furnace wall refractories. As an example of the method of estimating the inner surface temperature from the measured value of the thermocouple 3, there is, for example, a method of obtaining the temperature from an unsteady heat transfer analysis based on the following equation (1). ∂t / ∂τ = α (∂ ² t / ∂x ² ) (1) where t: temperature (K), τ: time (sec), α: temperature conductivity (m ² / sec) x : Distance (m) An appropriate value is used for the temperature conductivity depending on the material, and where heat transfer occurs, the heat transfer concerned is considered. Equation (1) is an equation taking into account one-dimensional heat conduction. However, if more precise measurement is required depending on the application, it is desirable to consider two-dimensional or more heat transfer. In the case of this transient heat transfer analysis, the value obtained from the temperature change at a certain time has higher reliability than the value obtained from the temperature measured at a certain time.

The thermal conductivity of the high thermal conductor is 10 W / m ·
If it is less than k, the responsiveness to a change in the furnace temperature or a change in the thickness of the metal adhered to the furnace inner wall is low, which is not preferable for measuring the surface temperature. The higher the thermal conductivity, the better, but it is desirable to select a material according to the operating temperature range and the required response speed.

[0009] Even if the temperature distribution of only the refractory is measured without using a high thermal conductor, the response speed is extremely slow and not practical. It is possible to make a precise estimation from the temperature distribution inside the sensor and its change with time, which is sensitive to the above.

[0010] By accurately measuring the inner surface temperature of the refining vessel in this way, the heat on the furnace wall refractories, such as the furnace temperature rises too much, the thickness of the deposited metal becomes too thin, etc. When the load becomes excessive, it responds sensitively to detect an excessive thermal load on the furnace wall refractory.

The number of thermocouples to be installed is at least one. However, in order to more accurately measure the heat load condition on the inner wall surface of the furnace under unsteady heat transfer conditions, the thermocouples are installed at a plurality of locations. It is desirable. When the furnace is installed at only one place, it is desirable to estimate the temperature of the furnace inner wall surface from the temperature change over time, that is, the temperature rise / fall speed.
In FIG. 2, a plurality (three in FIG. 2) of high thermal conductors 11 are embedded in the inclined portion of the furnace opening of the converter 16 which is a smelting vessel when the prevention and melting of the metal are performed by the secondary combustion of the CO gas. This shows an example in which the temperature of the furnace wall surface is measured to minimize the adverse effect on the furnace wall.

Further, by covering the boundary of the high thermal conductor with the heat insulating material 2, the influence of noise due to heat transfer in a direction perpendicular to the heat transfer direction from the inside of the furnace to the outside of the furnace can be reduced. Here, the boundary refers to the boundary between the high thermal conductor and the refractory. However, it is not preferable to provide a heat insulating material between the inside of the furnace of the high thermal conductor and the refractory at this boundary, since heat conduction from the inside of the furnace to the high thermal conductor is prevented. If the boundary is not covered with heat insulating material, the amount of heat transfer between the refractory inside the furnace wall and the material with high thermal conductivity embedded in it will increase, and it will be possible to grasp the heat load condition on the surface of the furnace inner wall. It will be difficult.

It is desirable to use Fe, Mo, W, and Cu as materials having a high thermal conductivity of 10 W / m · k or more. This is because these materials have characteristics of higher melting point and higher thermal conductivity than other materials. Further, depending on the operating temperature range, two or more of these materials may be used in combination due to restrictions such as a melting point.

In addition, if the surface temperature of the metal or refractory can be measured using an optical fiber or the like,
It is also possible to estimate the thickness of the metal from the temperature gradient of the high thermal conductor embedded inside the refractory. If the metal thickness can be accurately estimated, energy can be saved without unnecessary metal removal, and if the temperature is increased using secondary combustion, the recovered gas Can also be prevented from lowering the CO concentration.

[0015]

EXAMPLE 1 First, using the apparatus shown in FIG. 3, the relationship between the change in the temperature distribution of the high thermal conductor, the surface temperature and the thickness of the metal was examined. The high thermal conductor used was 99% pure Mo.
Is a cylinder having a diameter of 50 mmφ and a length of 300 mmφ. The thermal conductivity of this cylinder is uniformly -3.5 × 10 ⁻² × T + 1.
The evaluation was performed at 35 W / m · k (where T is a temperature (° C.) from 500 ° C. to 1700 ° C.). As a result, as shown in FIG. 4, it was confirmed that the high thermal conductor had a high follow-up property with respect to the metal surface temperature and the metal thickness. Based on the measurement results, a simple program A for estimating the surface temperature and the metal thickness from the temperature distribution at two or more points in the high thermal conductor using an unsteady heat transfer model was constructed. Further, a simple program B for estimating the surface temperature and the metal thickness from one or more temperature rising and falling speeds using an unsteady heat transfer model was constructed.
In the following examples, these programs were used for estimating the surface temperature and the metal thickness.

(Example 2-1) Next, a test was conducted in a 6t scale top and bottom blown converter. The upper blowing lance uses a 12φ 4-hole lance, and the oxygen supply rate is 1800-3600.
Nm ³ / hr. The bottom blow was performed using a double tube tuyere of oxygen and propane gas for cooling, and oxygen was supplied at about 100 Nm ³ / hr.
The surface temperature of the refractory was measured by transmitting light in the furnace to a radiation thermometer using an optical fiber for observation in the furnace. The same high thermal conductor as that used in Example 1 was used for the high thermal conductor embedded in the refractory. 3 from the refractory surface as in FIG.
Embed so that the tip of the Mo bar is located at 0 mm,
Thermocouples were set at 0 mm, 100 mm, and 200 mm from the end of the Mo bar. A nozzle incorporated in the upper lance is used to control the refractory surface temperature. Natural gas (10 to 20 Nm ³ / hr) and oxygen (50 to 75 Nm ³ / hr) are supplied as a burner during heating, and nitrogen is used during cooling. 100-3 gas
00Nm ³ / hr.

From the start of blowing, oxygen and natural gas were blown from the heating / cooling nozzle for metal removal for about 5 minutes. During this time, the temperature estimated by the present invention was evaluated based on the result of measuring the surface temperature of the refractory with a radiation thermometer using an optical fiber. When the surface temperature is estimated by the program A from the three temperature distributions, the error is almost 5%.
Met. When the temperature distribution was measured at only two points by the same program, the error was 8%. In addition, when the surface temperature was estimated by the program B from the three temperature rise and fall speeds, the error was within 5%. In addition, the error is 7% in the estimation from the temperature rise and fall speeds at two points, and 12% at one point.
It became. Thereafter, the surface temperature of the refractory was estimated based on the temperature rise and fall speeds at three points. Five minutes later, the surface temperature of the base metal reached 1600 ° C., so the supply of the heating gas was stopped.
Thereafter, the temperature of the refractory surface gradually increased, and when it reached 1650 ° C. three minutes before stopping the blowing, nitrogen for cooling was blown. As a result, the average refractory surface temperature from the furnace body narrowed portion to the furnace mouth portion could be controlled in the range of 1400 ° C. to 1700 ° C., the amount of deposited metal was extremely small (average 8 mm), and there was no refractory erosion.

EXAMPLE 2-2 A ceramic fiber heat insulating material (density: 128 kg / m ^3, thermal conductivity: 0.1 W / m · k at 500 ° C.) was applied to the boundary between Mo and the refractory in the same manner as in FIG. A similar test was performed using the same apparatus as in Example 2-1 except for disposing. In the estimation using the program A from the three temperature distributions, the error was reduced to 4% by using the heat insulating material.

(Example 2-3) As a high thermal conductor, Fe
(0.1% carbon steel, thermal conductivity 50, 800 at 400 ° C)
A similar test was performed using the same apparatus as in Example 2-1 except that 30 W / m · k at 30 ° C. was used. In the estimation using the program A from the three temperature distributions, the error was 10%. It is considered that the thermal conductivity was lower than that of Mo, so that the thermal responsiveness was deteriorated.

(Example 2-4) Inside the furnace 5 of a high thermal conductor
A similar test was performed using the same apparatus as in Example 2-1 except that three thirds was Mo and two-fifths of the furnace outside were Fe. In the estimation using the program A from the three temperature distributions, the error is 6
%Became. Although the accuracy is lower than the case of Mo,
Material costs are low.

[0021]

According to the present invention, it is possible to detect an excessive thermal load on the furnace wall refractory since the responsiveness to a change in the furnace temperature and a change in the thickness of the metal adhered to the furnace inner wall is high. In addition, the control of the secondary combustion rate in the furnace or the control of the fuel burner power is improved by preventing the adhesion of the metal and melting.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a method of burying a material having high thermal conductivity in a furnace wall refractory and measuring a heat load on a furnace inner wall surface.

FIG. 2 shows a method of measuring the temperature of a furnace wall surface by embedding a plurality of high thermal conductors in a furnace port inclined part when preventing and melting metal ingot by secondary combustion of CO gas. The figure which shows the outline of the method of minimizing an adverse effect.

FIG. 3 is a view showing a test apparatus for examining the relationship between the surface temperature and the metal thickness and the temperature distribution of the high thermal conductor.

FIG. 4 is a diagram showing a relationship between a surface temperature, a metal thickness, and a temperature distribution of a high thermal conductor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 high heat conductor 2 heat insulating material 3 thermocouple 4 ingot 5 wear brick 6 perm brick 7 iron skin 8 simulated ingot 9 refractory 10 burner 11 high heat conductor for temperature measurement 12 lance for preventing adhesion of ingot 13 heating / cooling Nozzle 14 Heating / cooling gas 15 Lance for blowing acid (Main lance) 16 Converter

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shinya Kitamura 20-1 Shintomi, Futtsu-shi, Chiba F-term in the Technology Development Division, Nippon Steel Corporation 4K002 AF04 CA01 4K013 CE08 FA01

Claims (3)

[Claims] In a refining vessel made of metal, a material having a high thermal conductivity of 10 W / m · k or more at a use temperature is buried in a refractory of a furnace wall by arranging the refractory on a furnace inner wall side. From the temperature measured by a thermocouple installed at at least one position inside the material and / or the temperature rise / fall speed, the furnace inner surface temperature of the refractory and / or the furnace inner surface temperature of the metal adhering to the refractory surface is determined. Characterized by estimating,
A method for measuring the temperature of the inner surface of a smelting vessel. 2. The temperature of the inner surface of the refining vessel according to claim 1, wherein a boundary between the material having a high thermal conductivity of 10 W / m · k or more and the refractory of the furnace wall is covered with a heat insulating material. Measuring method. 3. A material having a high thermal conductivity of 10 W / m · k or more, wherein one or a combination of two or more of Fe, Mo, W, and Cu is used. The method for measuring the temperature of the inner surface of a smelting vessel as described in the above.