JPH09194926A - Method for judging melt-down of raw material in electric furnace and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and surely judge melt-down time of charged material at the initial charging and at the additional charging into an electric furnace. SOLUTION: The judgement of the melt-down time of the raw material charged into the electric furnace 10, is executed by measuring the concn. of a prescribed component in the exhaust gas exhausted from the electric furnace 10 with a gas analyzing means 2, electric power supplied to melt the raw material with an electric power detecting means 27, the cooling water temp. of a water cooling pipe 17 arranged in the electric furnace 10 with an inlet and an outlet water thermometers 3, 4 and the temp. of a refractory arranged in the electric furnace 10 with a refractory thermometer 5. Then, values corresponding to the cooling water temp. and the refractory temp. are calculated with an arithmetic means 6, and when at least two values in the measured values and the calculated values reach each preset threshold value with a setting means 8, it is judged that the raw material is melted down with a judging means 7 and the judged result is displayed with a displaying means 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw material melting determination method and apparatus for determining the melting timing of a charging raw material initially charged and additionally charged into an electric furnace.

[0002]

2. Description of the Related Art Various metal melting furnaces are used in the process of melting various metal materials, especially special steel including stainless steel and high alloy iron. Among them, the electric furnace is mainly used as a main raw material containing various metals such as scrap, ferroalloy, ore, and mainly for smelting, slag material for slag basicity adjustment, carburizing material, and reducing material. It is used for the melting or melting of auxiliary materials, etc., and for refining. Currently used electric furnaces are arc-heated electric furnaces using an AC power supply or a DC power supply, and many of them are gradually becoming larger in size and having a large capacity. In such an electric furnace, a solid raw material containing various main and auxiliary raw materials is usually charged as described above. When electricity is supplied to the electrodes provided in the electric furnace, arc discharge starts, and the solid heat is melted or melted (hereinafter abbreviated as “melting”) by this arc heat, and various metals and alloys are melted. The melted metal melt and the slag are appropriately refined and discharged from the electric furnace body to the next step.

In the electric furnace used in this manner, the process from the charging of the solid main and auxiliary raw materials to the discharge of the molten metal is usually made into one batch, one after another. It is operated by repeating batch processing. In recent years, electric furnaces adopting such an operation form have been increased in size and capacity with particular emphasis on high efficiency, high productivity and economic efficiency. However, even if an attempt is made to charge as much raw material as possible at one time, the solid raw material is generally bulky, so it is necessary to charge all the raw materials necessary for processing one batch into the electric furnace only once. In many cases For this reason, usually, the raw material is initially charged as much as possible before the start of energization, and when this is melted by heating to some extent and the bulk thereof is reduced, the remaining necessary amount of raw material is usually added to 1
The method of additionally charging in two or three times is adopted.

As described above, in order to additionally charge the raw material into the electric furnace, or to melt the additional charged raw material to discharge the molten metal, the raw material charged into the electric furnace is almost or completely discharged. Must be dissolved in. For this purpose, it is necessary to surely grasp the melting state of the raw material inside the charged electric furnace with time and to accurately determine the melting time of the raw material. However, according to a typical conventional technique for this, the temporal understanding of the molten state of the raw material and the determination of each of the times are performed by a monitor for monitoring the inside of the furnace when the ceiling lid is opened for charging the raw material. It is done through the operator or by visualizing the inside of the furnace. Further, since the electric furnace body has openings such as a slag opening and a work opening in a part of the furnace wall, when the opening is opened, the inside of the furnace is monitored via a monitor. , Or a worker is visually inspecting the inside of the furnace.

The melting timing of the charging materials initially charged and additionally charged into the electric furnace may be determined by a predetermined constant power consumption amount. However, this predetermined power consumption is irrespective of the conditions such as the type, structure, shape, and capacity of the electric furnace itself, the charging history of the raw materials into the furnace, the energization conditions, and the raw material mixture to be charged. It is a rough product that is simply determined by multiplying the total weight of the raw materials charged by a constant electric power consumption rate empirically determined.

[0006]

In the prior art, the state of melting of the raw material can be grasped when the ceiling lid is opened at the time of charging the raw material, or the slag provided in a part of the furnace wall of the electric furnace body. It is performed only in a short time such as when opening an opening such as a mouth or a work opening. The determination method is performed by an operator visually observing a monitor screen from an in-furnace monitoring camera arranged outside the furnace, or by an operator directly visually observing the inside of the furnace.

Therefore, it is impossible to determine the melting time while continuously grasping the melting state of the raw material with time. Furthermore, since the judgment is made by the worker, there are many individual differences and mistakes in the judgment, accuracy and certainty are lacking, and stable reliability cannot be obtained. Furthermore, if the opening is frequently opened for sufficient observation, the amount of heat in the electric furnace is dissipated from the opening to the outside of the furnace each time, and the power consumption rate rises, resulting in energy-saving operation. It doesn't lead to. Furthermore, not only the dust is released in large amounts at each opening of the openings to cause environmental deterioration, but also the roof lid and the refractory layer in the electric furnace body are adversely affected by a sudden temperature change. As a result, the number of openings is limited, and as a result,
It becomes difficult to reliably determine the dissolution time. Furthermore, when the entire electric furnace is housed in the house in order to prevent the emission of dust to the outside, it is difficult for workers to observe the inside of the furnace due to the presence of the house. Even so, the observation is limited to a narrow field of view.

On the other hand, in other conventional techniques, the determination of the melting of the raw material is made by observing the inside of the furnace during the melting of the raw material,
When the power consumption reaches a certain fixed amount of electricity,
It is performed by determining that the raw material is dissolved. However, in this case, there are the following problems.

When the charging raw material is of a type and composition that are relatively soluble, or contains a liquid main raw material that is already dissolved, the raw material is completely dissolved before the power consumption reaches the set power consumption. I may end up doing it. In this case, since electric power is further supplied even after the raw material is melted, an excessive amount of electric power is supplied, resulting in a loss of the amount of melting electric power.
Further, even after the raw material is completely melted, if the current is further applied to the electrode, the arc generated from the electrode directly gives a heat load to the refractory layer on the furnace wall, so that the amount of wear of the refractory increases. Furthermore, when the raw material is almost melted in the electric furnace, expansion of slag due to rapid reaction of the raw material, so-called forming, may occur. However, in the conventional technique, it is difficult to accurately determine the melting time, and therefore it is impossible to predict the forming or the like.

When the charging raw material is of a type and composition that are relatively insoluble, even if the amount of power consumption reaches the set amount of power, the amount of power supplied will be insufficient and the charging raw material will be sufficiently dissolved. It may not be possible and may cause unmelted residue. As a result, it may not be possible to secure the target amount of tapping water, or auxiliary materials such as lime may remain in the molten metal due to insufficient refining. Further, the components of the molten metal may fluctuate and fall outside the range of the target components. Furthermore, since the additional charging is performed in a state where the raw material is not melted, that is, in the state where the space volume in the furnace is small, the additionally charged raw material does not fit in the furnace internal space and protrudes out of the furnace, and There may be a problem of so-called material filling, which makes it impossible to close.

An object of the present invention is to solve the above problems and to accurately and surely determine the melting timing of the charging raw materials initially charged and additionally charged into an electric furnace without observing the inside of the furnace. It is to provide a method and an apparatus for determining the dissolution of raw materials that can be used.

[0012]

According to the present invention, in a method for determining the melting time of a plurality of types of raw materials charged in an electric furnace, the concentration of a predetermined component in exhaust gas discharged from the electric furnace and the raw materials are determined. At least two values among the amount of electric power supplied for melting, the value corresponding to the cooling water temperature of the water cooling pipe provided in the electric furnace, and the value corresponding to the temperature of the refractory provided in the electric furnace are predetermined. It is a method for determining the dissolution of a raw material in an electric furnace, which is characterized in that the raw material is determined to be melted when each threshold value is reached. According to the present invention, the dissolution determination of the raw material charged in the electric furnace, the concentration of the predetermined component in the exhaust gas that changes corresponding to the molten state of the raw material in the electric furnace, the power amount, the The molten state of the raw material is continuously grasped without observing the inside of the furnace by the value corresponding to the cooling water temperature and the value corresponding to the refractory temperature, and at least two of these index values are It is performed by determining that the raw material is melted when each of the predetermined threshold values is reached. Therefore, the melting timing of the initially charged and additionally charged raw materials can be determined more accurately and reliably than in the conventional method which is performed in the furnace or based on a constant amount of electric power. In addition, it is possible to prevent erroneous determination due to an abnormal value, etc., as compared with the case where only one of these index values is used for determination, and the melting timing of the initially charged and additionally charged raw materials can be determined. It is possible to make a more accurate and reliable determination.

The concentration of a predetermined component in the exhaust gas of the present invention is also
The degree of CO gas in the exhaust gas discharged from the electric furnace is
CO in combustion exhaust gas generated by combustion reaction with air_Two
It is characterized by the gas concentration. According to the present invention, one of the raw material dissolution determination indexes is
CO in combustion exhaust gas _TwoGas concentration is used. Said C
O_TwoThe gas is produced by the combustion reaction between the CO gas and air.
The above CO_TwoThe change in gas concentration depends on the CO
Changes in gas concentration can be indirectly represented. CO
The gas concentration depends on the molten state of the raw materials in the electric furnace.
Therefore, the reaction between coke and oxygen in the raw material is activated at the beginning of melting.
Although the amount of CO gas generated is large, the dissolution of the raw materials progresses.
Oxygen is consumed as you go, so if you run out of oxygen
As a result, the amount of CO gas generated peaks and then decreases. like this
In addition, the CO gas concentration changes depending on the dissolved state of the raw material.
Therefore, the CO concentration corresponding to the CO gas concentration_Twogas
Continuously grasp the melting state of the raw materials in the electric furnace by the concentration
can do. Therefore, the CO_TwoGas concentration and forecast
Accurate determination of the dissolution of raw materials based on the threshold value specified
And it can be done reliably. In addition, the exhaust gas discharged from the electric furnace contains a large amount of dust.
Since it is contained in the amount, the CO gas concentration in the exhaust gas
It is difficult to measure continuously for a long time. However
The combustion of the CO gas by reacting it with air
The dust content in exhaust gas can be significantly increased by mixing with air.
CO in combustion exhaust gas_TwoContinuous gas concentration
Can be measured for a long time. Therefore, the combustion exhaust
CO in gas_TwoGas concentration is one of the raw material dissolution determination indexes
The initial charging and the additional charging
It is possible to accurately and surely judge the dissolution of the input material.
You.

Further, the threshold value of the amount of electric power of the present invention is obtained by multiplying the weight of each kind of charging raw material by a predetermined melting power coefficient of each kind, respectively, and It is characterized in that it is set based on the total value of the multiplication values. According to the invention, the threshold value of the amount of electric power is set based on a total value obtained by adding the amount of electric power for melting obtained from the charging weight for each type of raw material to all types of charging raw materials. Therefore, it is possible to set an appropriate threshold value for the amount of electric power even if the composition of the charging raw material changes.

Further, the value corresponding to the cooling water temperature of the water cooling pipe of the present invention is characterized by a temperature difference between the outlet cooling water temperature and the inlet cooling water temperature of the water cooling pipe. According to the present invention, the temperature difference between the outlet cooling water temperature and the inlet cooling water temperature is used as one of the raw material dissolution determination indexes. The temperature difference corresponds to the melting state of the solid raw material in the electric furnace, and when the reaction of melting the solid raw material to form the molten metal is occurring, the energy given is consumed as latent heat. The increase rate of the temperature difference is small. When all the solid raw materials are melted and the reaction is completed, energy is used to raise the temperature of the molten metal itself, that is, to raise the temperature of the outlet cooling water of the water cooling pipe, and the rate of increase in the temperature difference increases. Thus, since the temperature difference of the cooling water temperature changes corresponding to the molten state of the raw material in the electric furnace, the molten state of the raw material is continuously grasped by the temperature difference, and the predetermined threshold value is set. Based on this, it is possible to accurately and surely determine the dissolution of the initially charged and additionally charged raw materials.

Further, the value corresponding to the cooling water temperature of the water cooling pipe of the present invention is characterized in that it is a time change rate of the outlet cooling water temperature of the water cooling pipe. According to the present invention, the rate of change over time of the outlet cooling water temperature in the water cooling pipe is used as one of the raw material dissolution determination indexes. The rate of change of the water temperature with time changes corresponding to the molten state of the raw material in the electric furnace, and in particular, it suddenly changes during melting, so the molten state of the raw material is continuously grasped by the rate of change with time of the water temperature, and is predetermined. It is possible to accurately and surely determine the dissolution of the initially charged and additionally charged raw materials based on the threshold value.

Further, the value corresponding to the refractory temperature of the present invention is characterized in that it is a temperature difference between the refractory temperature after the start of energization and the refractory temperature at the start of energization. According to the present invention, the temperature difference of the refractory temperature is used as one of the raw material dissolution determination indexes. Since the temperature difference of the refractory temperature changes corresponding to the molten state of the raw material in the electric furnace, the molten state of the raw material is continuously grasped by the temperature difference, and the initial charging is performed by the predetermined threshold value. Further, it is possible to accurately and surely determine the dissolution of the additionally charged raw materials.

The value corresponding to the refractory temperature of the present invention is characterized in that it is a rate of change over time of the refractory temperature. According to the present invention, the time rate of change of the refractory temperature is used as one of the raw material dissolution determination indexes. The rate of change of the refractory temperature with time changes corresponding to the molten state of the raw material in the electric furnace, and in particular, it changes abruptly during melting, so the molten state of the raw material is continuously grasped by the rate of change of the refractory temperature with time. However, it is possible to accurately and surely determine the dissolution of the initially charged and additionally charged raw materials by the predetermined threshold value.

The present invention also provides a gas analysis means for measuring the concentration of a predetermined component in the exhaust gas discharged from the electric furnace in an apparatus for determining the melting time of a plurality of kinds of raw materials charged in the electric furnace, Electric power detection means for measuring the amount of electric power supplied to the electric furnace, cooling water temperature detection means for measuring the cooling water temperature of the inlet and outlet of the water cooling pipe provided in the electric furnace,
Refractory temperature detection means for measuring the temperature of the refractory provided in the electric furnace, the temperature difference between the outlet cooling water temperature of the water cooling pipe and the inlet cooling water temperature, the time change rate of the outlet cooling water temperature of the water cooling pipe, energization Calculation means for calculating the temperature difference between the refractory temperature after the start and the refractory temperature at the start of energization and the rate of change over time of the refractory temperature, the concentration of a predetermined component in the exhaust gas, the electric energy, and the temperature of the cooling water temperature Difference, time change rate of outlet cooling water temperature, temperature difference of refractory temperature, and setting means for setting each threshold value of time change rate of refractory temperature to predetermined values, and exhaust gas measured by gas analysis means The concentration of a predetermined component therein, the amount of power measured by the power detection means, the temperature differences calculated by the calculation means, and the rate of change over time are compared with respective threshold values set to predetermined values by the setting means. And each of the above A determination unit that determines that the raw material is dissolved when at least two values out of the constant value and the calculated value reach the corresponding threshold values, and a display that displays that the raw material is dissolved in response to the output of the determination unit. And a means for determining the dissolution of a raw material in an electric furnace. According to the present invention, the apparatus for determining the dissolution of a raw material in an electric furnace measures each of the measurement values by each of the detection means, calculates each of the temperature differences and the time change rate by the calculation means, and sets each threshold value by the setting means. The value is set to a predetermined value, and each of the measured value and the calculated value is compared with each threshold value by the determination means, and at least two of the measured value and the calculated value have reached the corresponding threshold value. At this time, it can be determined that the raw material is dissolved, and the display unit can display the determination result. As a result, the dissolution determination device continuously grasps the dissolution state of the raw material by each measurement value, not by visual observation, and melts the initially charged and additionally charged raw materials based on a predetermined threshold value. Since the means for accurately and surely determining the timing is provided, the determination accuracy is better than the conventional method in which the dissolution determination of the raw material is performed by visual observation in the furnace or based on a constant amount of electric power.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram showing a simplified structure of a raw material melting determination device for an electric furnace (hereinafter, abbreviated as “melting determination device”) which is an embodiment of the present invention. . FIG. 1 shows an electric furnace 10 and a scrap preheating device 1.
9 and a system diagram of the dust collecting equipment 21 provided additionally to the electric furnace 10 are also shown. Dissolution determination device 1
Is provided in the electric furnace 10, and a gas analysis means 2 for measuring the concentration of a predetermined component in the exhaust gas discharged from the electric furnace 10, a power detection means 27 for measuring the amount of electric power supplied to the electric furnace 10. An inlet cooling water temperature detecting means 3 for measuring the temperature of the cooling water supplied to the water cooling pipe 17, an outlet cooling water temperature detecting means 4 for measuring the temperature of the cooling water discharged from the water cooling pipe 17, and an electric furnace 10. A refractory temperature detecting means 5 for measuring the temperature of the refractory, a computing means 6 for calculating a plurality of index values for determining the dissolution of the raw material, and a threshold value for each index value. The setting means 8 is set to 1., the judging means 7 for judging the dissolution of the raw material based on each threshold value set by the setting means 8, and the displaying means 9 for displaying the judgment result. The molten metal melted in the electric furnace 10 is, for example, chromium-containing hot metal used for manufacturing stainless steel.

The exhaust gas containing dust discharged from the electric furnace 10 is treated as follows. The exhaust gas is discharged from the dust collecting elbow 12 provided on the ceiling lid 13 of the electric furnace 10 to the outside of the furnace, and inside the first dust collecting duct 14a provided facing the dust collecting elbow 12 and spaced apart. Then, it is sucked by the attracting fan 16 of the dust collecting equipment 21. The suction force of the attraction fan 16 not only sucks the exhaust gas, but also draws air from the air intake port 15 formed in the gap between the dust collecting elbow 12 and the first dust collecting duct 14a into the first dust collecting duct. Aspirate into 14a. The exhaust gas and the air sucked into the first dust collecting duct 14a are guided to the combustion tower 11 where the exhaust gas reacts with the air and burns. Since the exhaust gas contains a large amount of unburned CO gas, it reacts with the air and burns in the first dust collection duct 14a and the combustion tower 11. Most of the combustion exhaust gas that has become high temperature due to the combustion reaction is guided to the scrap preheating device 19 through the second dust collecting duct 14b provided on the outlet side of the combustion tower 11 and charged into the basket 20. Preheat the scraps that are present. The exhaust gas from which the scrap has been preheated is guided to the fourth dust collecting duct 14d on the outlet side of the scrap preheating device 19.

A part of the exhaust gas discharged from the combustion tower 11 does not pass through the scrap preheating device 19 and passes through a third dust collecting duct 14c provided at the lower exit side of the combustion tower 11 to pass the fourth dust collecting. It is guided to the duct 14d. A sample probe 23 for collecting the combustion exhaust gas discharged from the combustion tower 11 is provided in the third dust collecting duct 14c. The exhaust gas containing dust guided to the fourth dust collecting duct 14d is cooled by the gas cooler 25, removed by the bag filter in the dust collector 26, and discharged to the outside by the attraction fan 16 provided on the downstream side of the dust collector 26. It

FIG. 2 is a front sectional view showing a simplified structure of the electric furnace shown in FIG. The electric furnace 10 includes a ceiling lid 13 to which an electrode 28 is attached and a furnace body 29. The furnace body 29 includes a substantially cylindrical furnace wall 30 and a bowl-shaped furnace floor 3.
1 and 1. A refractory layer 33 is provided on the inner wall of the furnace wall 30 and the hearth 31 with which the molten metal 32 of the furnace body 29 contacts and the furnace body 2 that does not directly contact the molten metal 32 and the like.
On the inner wall of 9 and the inner wall of the ceiling lid 13, a water cooling furnace wall 18 constituted by a water cooling pipe 17 through which cooling water is passed is provided. On one side of the furnace body 29, a working port 35 for removing slag 34 and the like generated when the raw material is melted and refined is provided, and at a position facing the working port 35,
A tap hole 36 and a tap trough 36 for tapping the molten metal 32
a is attached. Furthermore, at the bottom of the furnace body 29, a blowing nozzle 37 for blowing a gas for stirring the molten metal 32, such as nitrogen gas, is provided.

There is a gap between the raw material such as scrap charged in the furnace body 29 of the electric furnace 10 and the tip of the electrode 28 provided on the ceiling lid 13,
When a current whose voltage is adjusted by the transformer is applied to the electrode 28, an arc is generated between the electrode 28 and the raw material, and the raw material is melted by the heat generated at this time. The molten metal 32 and the slag 34 produced by melting the raw materials are stored inside the furnace body 29.

FIG. 3 is a plan view showing a simplified structure of the ceiling lid of the electric furnace shown in FIG. The ceiling lid 13 is composed of a water cooling wall 18a and a small ceiling 13a, and water cooling pipes 17a are continuously and densely arranged in the circumferential direction on the water cooling wall 18a. Three vertically movable electrodes 28 (28a, 28b, 28c) are inserted through the small ceiling 13a.
The book electrodes 28 are arranged at equal intervals in the circumferential direction.

FIG. 4 is a perspective view showing a simplified structure of the water cooling furnace wall of the electric furnace shown in FIG. The water-cooled furnace wall 18 provided in the furnace body 29 of the electric furnace 10 is divided into a plurality of blocks, for example, eight blocks (BL1 to BL8) in the circumferential direction, and the water-cooled pipe 17 is densely arranged in each block. It is located in. At the inlet side and the outlet side of each water cooling pipe 17, an inlet water temperature gauge 3 which is an inlet cooling water temperature detecting means composed of a thermocouple and an outlet water temperature gauge 4 which is an outlet cooling water temperature detecting means are respectively arranged. The cooling water temperature during operation can be continuously measured. Note that FIG.
The cooling water supplied to the water cooling pipes 17 and 17a shown in FIG. 4 circulates in the closed path, and the water cooling furnace walls 18 and 1
The cooling water that has passed through 8a and has been heated is cooled by a cooling facility and is supplied again as inlet cooling water. Therefore, the temperature of the inlet cooling water is almost constant, for example, 12 to 20.
It is kept at ° C.

FIG. 5 is a sectional view showing a simplified structure of the outlet cooling water temperature detecting means shown in FIG. The outlet water thermometer 4 includes a thermocouple 4a, a temperature sensing portion 4b thereof, and a protection tube 4c.
And the temperature sensing part 4b is installed so as to be arranged on the central axis 17b of the water cooling pipe 17. The inlet water temperature gauge 3
The configuration of is exactly the same as that of the outlet water thermometer 4.

FIG. 6 is a cross-sectional view of the electric furnace taken along the section line VI-VI in FIG. The refractory layer 33 formed on the furnace wall 30 of the furnace body 29 of the electric furnace 10 includes a consumable brick layer 33a in contact with the molten metal 32 and a permanent brick layer 33b provided on the outer side of the consumable brick layer 33a. . A plurality of refractory thermometers 5 (5a to 5f) as refractory temperature detecting means, for example, six refractory temperature detectors 5 (5a to 5f) are installed between them. The six refractory thermometers 5 (5a-5f) are
Near the three electrodes 28, three refractory thermometers 5a, 5c, 5e are arranged at three so-called hot spots, which are easily subjected to the heat load of the electrodes 28. 3 so-called cold spots that are difficult
Three refractory thermometers 5b, 5d, 5f are installed. The refractory temperature detecting means 5 is composed of a thermocouple or the like, and can continuously measure the refractory temperature during operation.

FIG. 7 is a system diagram showing a simplified structure of the gas analysis means. Gas analyzer 2 which is a gas analysis means
Is a filter 39, a suction pump 40, and a solenoid valve 41.
And a CO / CO ₂ concentration meter 42 and an O ₂ concentration meter 43, which are connected to the sample probe 23. The exhaust gas collected by the sample probe 23 is sucked by the suction pump 40 of the gas analyzer 2, and dust of 0.2 μm or more is removed by the two filters 39 provided on the upstream side of the suction pump 40, O ₂ densitometer 43 and CO arranged in series
/ CO ₂ concentration meter 42 is introduced in this order, and after exhaust gas component concentration analysis, it is discharged to the outside. Each densitometer 42,43
The exhaust gas is introduced into the chamber by opening and closing the solenoid valve 41. The CO / CO ₂ densitometer 42 is an infrared absorption densitometer, and can measure the CO gas and CO ₂ gas concentrations in the exhaust gas simultaneously and continuously. O ₂ concentration meter 4
3 is a magnetic flow ratio densitometer, which is capable of continuously measuring the O ₂ gas concentration in the exhaust gas.

Based on the outputs of the inlet water temperature gauge 3, the outlet water temperature gauge 4 and the refractory thermometer 5, the calculating means 6 outputs the outlet cooling water temperature and the inlet temperature of the water cooling pipe 17 provided in the water cooling furnace wall 18. The temperature difference from the cooling water temperature, the time change rate of the outlet cooling water temperature of the water cooling pipe 17, the temperature difference between the refractory temperature after the start of energization and the refractory temperature at the start of energization, and the time change rate of the refractory temperature are shown. Calculate each. These calculated values were charged into the electric furnace 10 together with the concentrations of predetermined components in the exhaust gas measured by the gas analyzer 2 and the energized electric energy measured by the electric power meter 27 as the electric power detection means. It is used as an index value for determining the dissolution of raw materials.

The setting means 8 sets the threshold value of each index value to a predetermined value from a keyboard or the like. Each threshold value is set as will be described later by previously grasping the value of each index value corresponding to the melting time of the charging raw materials initially charged and additionally charged into the electric furnace 10 from the operation results and the like. To be done.

The judging means 7 compares the respective index values with the respective threshold values, and when at least two index values among the respective index values reach the corresponding threshold values, initial charging and It is determined that the additionally charged raw materials have melted.

In response to the output of the determination means 7, the display means 9 has melted the initially charged and additionally charged raw materials by visual display such as a red blinking indicator light or acoustic display such as a buzzer. Is displayed.

Since the dissolution determination device 1 of the present embodiment is constructed as described above, it comprises the gas analyzer 2, power meter 27, inlet water temperature meter 3, outlet water temperature meter 4 and refractory thermometer 5. The concentration of a predetermined component in the exhaust gas, the amount of energizing power, the inlet cooling water temperature, the outlet cooling water temperature, and the refractory temperature are measured, respectively, and the temperature difference between the cooling water temperature and the refractory temperature is calculated by the calculating means 6 by the calculating means 6. , The outlet cooling water temperature time change rate, the refractory temperature difference and refractory temperature time change rate are calculated, respectively, these calculated values, the concentration of the measurement component in the exhaust gas and the measured value of the amount of energized electricity Is used as an index value for determining the dissolution of the charging raw material, the threshold value of each index value is set to a predetermined value by the setting means 8, and the index value is set to each threshold value by the determination means 7. value In contrast to each other, when at least two index values among the index values reach the corresponding threshold values, it is determined that the initially charged and additionally charged raw materials are melted, and the display means 9 is used. The judgment result can be displayed.

As described above, the melting determination device 1 indicates that the initially charged and additionally charged raw materials have melted,
Since it is provided with a means capable of making an accurate and reliable determination, the dissolution determination accuracy is much superior to the conventional method in which the dissolution determination of the raw material is performed by visual observation in the furnace or based on a certain amount of electric power. In addition, by accurately determining the melting time of the raw material, excessive power input is eliminated and the heat load on the furnace wall is reduced, so the amount of refractory wear on the furnace wall is greatly reduced and the life of the furnace wall is greatly reduced. Be extended.

The threshold value of each index value is the electric furnace 1
The values of the respective index values corresponding to the melting time of the initially charged and additionally charged raw materials at 0 are set in the following manner by grasping in advance from the operation results and the like.

FIG. 8 is a schematic diagram showing, in a time series, changes in the component concentration of the combustion exhaust gas discharged from the combustion tower during the melting of the raw materials of the electric furnace. At time t1, the raw material is charged into the electric furnace 10 for the first time, that is, the initial charging is performed, and the energization is started. As the melting of the raw material progresses, a carbon source such as coke in the raw material reacts with oxides in the raw material and oxygen in the furnace to generate CO gas. Although the amount of CO gas generated is high in the reaction at the initial stage of dissolution, oxygen is consumed as the raw materials are dissolved, and therefore the amount of CO gas generated peaks and decreases due to lack of oxygen. The CO gas in the exhaust gas discharged from the electric furnace 10 reacts with air and burns in the combustion tower 11 to generate CO ₂ gas. Therefore, the CO ₂ gas concentration in the combustion exhaust gas discharged from the combustion tower 11 changes corresponding to the CO gas concentration, and exhibits the same temporal transition as the transition of the CO gas concentration. Further, the O ₂ gas concentration in the combustion exhaust gas shows a temporal transition that increases and decreases, contrary to the transition of the CO ₂ gas concentration.

As described above, since the CO gas concentration changes in accordance with the melting state of the raw material in the electric furnace 10, the CO ₂ gas concentration also corresponds to the melting state of the raw material in the electric furnace 10. And change. Thus, it is possible to grasp the dissolved state of the raw material by the CO ₂ gas concentration, the concentration of the predetermined component in the exhaust gas of the present embodiment, it is preferable to use the CO ₂ gas concentration. The CO gas is not used as the concentration of the predetermined component in the exhaust gas because the exhaust gas discharged from the electric furnace 10 contains a large amount of dust and the CO gas concentration in the exhaust gas is high. This is because it is difficult to measure continuously for a long time. On the other hand, since the dust content in the combustion exhaust gas is significantly reduced by mixing with air, the CO ₂ gas concentration in the combustion exhaust gas can be continuously measured for a long time.

At time t2, the concentration of CO ₂ gas in the combustion exhaust gas decreases and reaches a predetermined threshold value L1.
The threshold value L1 is a threshold value of the CO ₂ gas concentration at which it is determined that the initially charged raw material is melted to a dissolution rate at which additional charging is possible. Predetermined. The raw material dissolution rate is the ratio of the raw material dissolution amount to the total amount of the raw material charged.

In actual operation, CO _{2 in} combustion exhaust gas
The gas concentration may fluctuate, and it may be unclear when the CO ₂ gas concentration becomes less than the threshold value L1. Therefore, the criteria for determining that the initially charged raw material has dissolved to a dissolution rate that allows additional charging is:
When the CO ₂ gas concentration is less than the threshold value L1 continuously for 3 minutes or more, or
It is preferable to sample the ₂ gas concentrations every 1 second and select one when the moving average value for 3 minutes is less than the threshold value L1. The dissolution rate that can be additionally charged is preferably about 80%. This is because if the melting rate exceeds 80%, the heat loss increases and the heat load on the refractory increases, so the amount of wear of the refractory increases, and if the melting rate is less than 80%, Since the space volume of is small and the volume for charging the additional charging material cannot be ensured, the additionally charged raw material does not fit in the furnace internal space and protrudes outside the furnace, and the ceiling lid 13 does not close. This is because there is a possibility that a heap may occur.

At time t3, the second charging of raw materials, that is, additional charging is performed. The temporal changes in the CO ₂ gas concentration and the O ₂ gas concentration in the combustion exhaust gas after the additional charging of the raw materials are the same as in the case of the initial charging. Generally, since the second charging amount of the raw material is equal to or less than the first charging amount, the CO ₂ gas concentration level and the peak height are lower than those in the initial charging. At time t4, the CO ₂ gas concentration in the combustion exhaust gas decreases and reaches a predetermined threshold value L2. The threshold value L2 is a threshold value of the CO ₂ gas concentration at which it is determined that the additionally charged raw material has been dissolved up to 80% which is a dissolution rate at which the additional charging can be performed again. It is determined in advance from a large number of operation performance values. The criteria for the actual operation are the same as those for the threshold value L1. As described above, the additional charging of the raw material is performed at a charging amount equal to or less than the initial charging amount, and the level of the CO ₂ gas concentration after the additional charging is lower than that after the initial charging. The threshold value L2 is set to be equal to or less than the threshold value L1. Therefore, it is possible to accurately and surely determine the dissolution of the additionally charged raw material.

At time t5, the third charging of the raw material, that is, the additional charging is performed. The temporal transitions of the CO ₂ gas concentration and the O ₂ gas concentration in the combustion exhaust gas after the third charging are the same as in the case of the additional charging. Since the re-additional charging is performed with a charging amount equal to or less than the additional charging amount, the level of the CO ₂ gas concentration becomes lower than that in the case of the additional charging.
At time t6, the CO ₂ gas concentration in the combustion exhaust gas decreases and reaches a predetermined threshold value L3. Threshold L3
Is a threshold value of the CO ₂ concentration at which it is judged that the raw material recharged again is completely dissolved.
Is determined in advance from a large number of actual operation values in. In addition,
The judgment criteria in the actual operation are the same as in the case of the threshold value L1. After it is determined that the raw materials are completely melted, the temperature of the molten metal is adjusted, the refining and refining of the chromium oxide in the slag, and further oxygen blowing as necessary are performed, and tapping is performed at time t7.

FIG. 9 is a transition diagram showing, in a time series, changes in the component concentration of the combustion exhaust gas discharged from the combustion tower in the actual operation of the electric furnace. FIG. 9 also shows the time-series transition of the undissolved rate of the raw material, which is determined by opening the ceiling lid 13 of the electric furnace 10 and visually observing the inside of the furnace. The undissolved rate of the raw material is the ratio of the undissolved raw material to the total amount of the charged raw materials. A transition line G1 in FIG. 9 shows a time series change of the CO ₂ gas concentration in the combustion exhaust gas, and a transition line G2 shows a time series change of the O ₂ gas concentration in the combustion exhaust gas.

At time t11, the raw material is initially charged into the electric furnace 10, and at time t12, energization is started. As the heating and melting of the raw materials progress, the CO ₂ gas concentration in the combustion exhaust gas discharged from the combustion tower 11 increases, and then decreases after reaching the upper limit peak. The O ₂ gas concentration in the combustion exhaust gas decreases, contrary to the CO ₂ gas concentration, and increases through the lower limit peak. The undissolved rate of the raw materials gradually decreases. Time t1
In No. 3, the undissolved rate of the raw material reaches 20%, that is, the dissolved rate of 80% at which the additional charging is possible reaches. Since the CO ₂ gas concentration at time t13 is less than 5%, the threshold value L1 is set to 5%, for example. Time t1
In step 4, additional charging is performed, and at time t15, energization is started again. The time series transitions of the CO ₂ gas concentration and the O ₂ gas concentration after time t15 are from time t16 to time t.
Except for the trouble period of stopping the energization in 17, the tendency is the same as the transition from the time t12 to the time t13. At time t18, the undissolved rate of the raw material reaches 20%. In this operation, re-additional charging is not performed, but if necessary, re-additional charging can be performed at time t18. Since the CO ₂ gas concentration at time t18 is less than 3%, the threshold value L2 is set to 3%, for example. In the main operation, since the energization is continued after the time t18, the undissolved rate is further reduced.

At time t19, the undissolved rate reaches almost 0%, and the raw material is almost completely dissolved. Since the CO ₂ gas concentration at time t19 is less than 2%, the threshold value L3 is set to 2%, for example. At time t20, the molten metal is discharged, and the operation of the electric furnace 10 for one charge is completed.

Thus, the CO ₂ gas concentration and the O ₂
The time-series transition of the gas concentration corresponds to the molten state of the raw material, so that the molten state of the raw material can be continuously grasped. Further, the CO ₂ gas concentration threshold values L1 and L
By setting 2 and L3 as described above, it is possible to accurately determine the melting timing of the initially charged and additionally charged raw materials without observing the inside of the furnace. Therefore, it is possible to reduce power loss and save energy. Furthermore, since it is not necessary to observe the inside of the furnace, it is not necessary to open the opening of the electric furnace 10, and a large amount of dust is diffused from the opening, so that there is no risk of deteriorating the environment. Furthermore, since the molten state of the raw material can be continuously grasped, the expansion of the slag 34 due to the rapid reaction of the raw material occurring at the raw material melting time, so-called forming, can be predicted in advance. Although the O ₂ gas concentration is not directly used for determining the dissolution timing of the raw material, it is continuously measured as a component concentration that backs up the CO ₂ gas concentration.

The threshold value of the energized power amount is set as follows. The weight of each type of plural (n) types of raw materials charged in the electric furnace 10, such as scrap or lime, is Mi (i = 1 to n), and the melting power coefficient of each type is ci (i = 1 to n), the melting power amount E for all kinds of charging raw materials is obtained by the equation (1).

[0048]

[Equation 1]

The melting power coefficient ci is a coefficient representing the amount of melting power per unit weight for each type of raw material, and is determined according to the type of raw material charged, the number of times the raw material is charged, the amount of molten metal discharged, and the like. It is determined in advance from past operation performance values. The coefficient c
i takes a large value for a raw material of a type that is difficult to dissolve, and conversely takes a negative value for a raw material that promotes dissolution of a solid charging raw material such as a raw material in a molten state. Also,
The coefficient ci depends on the temperature of the charging raw material and is small when the temperature of the charging raw material is high, and increases when the temperature is low. The melting power amount E is a value corresponding to the melting of the raw material, and thus is preferably used as the threshold value of the power amount.

In this way, the melting power amount E corresponding to the degree of easiness of melting different for each kind of raw material and the increase or decrease of the blending amount for each kind of raw material is determined as the threshold value of the energizing power amount. Therefore, even if the type and composition of the initially charged and additionally charged raw materials are changed, it is possible to accurately and surely determine the melting time of the raw materials. Also,
The melting electric energy E is the initial loading period after the initial charging of raw materials,
It is preferable to calculate for each charging period of the electric furnace operation such as the additional charging period. However, the total melting power amount E per charge may be calculated, and the melting power amount for each period may be calculated and distributed according to the weight of the raw material charged in each charging period.

FIG. 10 is a transition diagram showing the change over time of the cooling water temperature of the water cooling pipe provided on the water cooling furnace wall of the electric furnace shown in FIG. The transition line W1 is a transition line showing the cooling water temperature measured by the outlet water thermometer 4 of the block BL1 of the water cooling furnace wall 18 located in the hot spot portion of the electrode 28a shown in FIG. 4, and the transition lines W2 and W3 are , The block B of the water-cooled furnace wall 18 located at the hot spots of the electrodes 28b, 28c
It is a transition line showing outlet cooling water temperature of L4 and BL7, respectively. Water cooling pipe 1 provided on the water cooling furnace wall 18 of the electric furnace 10.
Since the temperature of the outlet cooling water of 7 is easily affected by the heat load due to the arc and the temperature change of the molten metal itself, the temperature change during operation is large, and the change depends on the molten state of the raw material, that is, the solid raw material. Corresponds to the proportion of liquid melt.

When power supply to the electrode 28 is started from time t21, heating and melting of the raw material is started. In the early stage of melting indicated by arrow A1, the solid material is filled in the entire space in the furnace, and in order to cut off the arc toward the water-cooled furnace wall 18, the water-cooled furnace wall 18
Is not directly subjected to the heat load of the arc, and when the raw materials are melted, most of the applied heat energy is consumed as latent heat for melting the solid raw materials, so the water-cooled furnace walls located at each hot spot The cooling water temperature measured at the outlet side of the water cooling pipe 17 of 18 does not rise and change significantly. However, in the latter stage of melting indicated by arrow B1, most of the raw material is melted, the ratio of the raw material occupying in the furnace space becomes very small, the water-cooled furnace wall 18 is directly subjected to the heat load of the arc, and most of the raw material is melted. Since most of the thermal energy given by doing so is used to raise the temperature of the molten metal itself, the outlet cooling water temperature measured at each hot spot portion greatly rises, and the rate of change of water temperature with time also increases. When the ceiling lid 13 is opened for additional charging at time t22, the heat in the furnace is dissipated and the temperature in the furnace is lowered, so that the outlet cooling water temperature is also lowered.
When the additional charging is finished at time t23 and the energization of the electrode 28 is restarted, the outlet cooling water temperature exhibits the same behavior as the temperature change before the additional charging, and greatly increases in the early period of melting shown by the arrow A2. However, the temperature greatly increases in the latter stage of melting indicated by arrow B2, and the rate of change in water temperature with time also increases. At time t24, the ceiling lid 13 is opened for tapping, so the outlet cooling water temperature decreases. As described above, since the inlet cooling water temperature is kept substantially constant, the transition of the outlet cooling water temperature substantially coincides with the transition of the temperature difference between the outlet cooling water temperature and the inlet cooling water temperature.

FIG. 11 shows the frequency of occurrence of the material heap and the material dissolution rate of 80% or more with respect to the temperature difference between the outlet cooling water temperature of the water-cooled furnace wall and the inlet cooling water temperature between the initial charging and the additional charging. It is a characteristic view showing the relationship of. The raw material dissolution rate of 80% is a dissolution rate at which the raw material can be additionally charged as described above. It can be seen from FIG. 11 that the temperature difference of the cooling water temperature and the melting state of the raw material correspond to each other, and the melting of the raw material progresses as the temperature difference increases, and the occurrence frequency of the material heap decreases. . That is, in the range where the temperature difference is less than 15 ° C., the melting rate of raw materials is low, which corresponds to the initial stage of melting, and as the temperature difference increases, the melting rate sharply increases and the occurrence frequency of material puddle sharply decreases. There is.
When the temperature difference is 15 ° C. or more, the dissolution rate of the raw material is high, which corresponds to the stage where the dissolution of the raw material has progressed considerably, and the occurrence frequency of the material heap is almost 0%. Is possible. Therefore, the threshold value of the temperature difference of the cooling water temperature is preferably selected to be 15 ° C. Also,
This makes it possible to accurately and surely determine the time when the dissolution rate of the initially charged raw material reaches the dissolution rate at which additional charging is possible. In addition, when the temperature difference is 30 ° C. or more,
Since the raw materials are almost completely dissolved, it is not desirable as the time for additional charging, and excessive power input causes an increase in power consumption.

FIG. 12 is a characteristic diagram showing the relationship between the temperature of the outlet cooling water of the water-cooled furnace wall and the temperature of the inlet cooling water between the initial charging and the additional charging with respect to the unit power consumption of the initially charged raw material. Is. The unit power consumption of the initially charged raw material is the amount of consumed electric power consumed for melting the initially charged raw material divided by the total weight of the initially charged raw material. From FIG. 12, it can be seen that there is a correlation between the temperature difference of the cooling water temperature and the basic unit of melting power, and the temperature difference increases due to the load of melting power. Further, zero, which is the reference value of the unit power consumption of melting, is a unit power consumption of melting when the above-mentioned conventional technique is used, and the temperature difference of the cooling water temperature at this time is in the range of approximately 25 to 30 ° C. Shows. Therefore, when the temperature difference of the cooling water temperature at the time of additional charging exceeds 30 ° C., it is understood that the melting power becomes excessive.

Furthermore, when the temperature difference of the cooling water temperature at the time of additional charging is less than 15 ° C., which is below the threshold value, the power consumption rate is significantly reduced,
Since the raw materials are not sufficiently melted, not only the frequency of occurrence of the material puddle increases, but also the raw material having a low temperature is additionally charged while the temperature of the molten metal does not rise sufficiently. For this reason, the temperature of the molten metal is further lowered, and in particular, when the raw material deposited on the inclined portion of the hearth 31 of the electric furnace 10 is not melted and the current is terminated and remains in the furnace even after the molten metal is discharged. There is.
This lowers the melt yield and causes variations in the melt components. Therefore, it is preferable that the threshold value of the temperature difference of the cooling water temperature is 15 ° C. at which the raw materials charged as described above are sufficiently melted and the excessive input of the melting power does not occur. It is preferable that the difference is 30 ° C. or less and additional charging is performed.

FIG. 13 is a characteristic diagram showing the relationship between the rate of change of the outlet cooling water temperature of the water-cooled furnace wall between the initial charging and the additional charging and the frequency of occurrence of the material heap and the frequency of the material dissolution rate of 80% or more. Is. From FIG. 13, the rate of change of the outlet cooling water temperature with time corresponds to the melting state of the raw material, and as the rate of change with time increases, the melting of the raw material progresses and the frequency of occurrence of material piles decreases. I understand. That is, in the range where the rate of change with time is less than 3 ° C./minute, the rate of dissolution of the raw material is low, which corresponds to the initial stage of dissolution, and the rate of change increases as the rate of change with time increases, and the frequency of occurrence of material piles increases. Is decreasing sharply. The rate of change with time is 3 ° C /
Above the minute, the rate of dissolution of the raw material is high, which corresponds to the stage where the dissolution of the raw material has progressed considerably, and the occurrence frequency of the material heap is almost 0%, so that additional charging of the raw material is possible.
Therefore, the threshold value of the time change rate is preferably selected to be 3 ° C./minute. Further, by this, it is possible to accurately and surely determine the time when the dissolution rate of the initially charged raw material reaches the dissolution rate at which additional charging is possible.

FIG. 14 is a characteristic diagram showing the relationship of the dissolution rate of the raw material with respect to the temperature difference between the outlet cooling water temperature of the water-cooled furnace wall and the inlet cooling water temperature between the additional charging and the hot water discharge. FIG.
It can be seen from 4 that the temperature difference corresponds to the dissolution rate of the raw material, and the larger the temperature difference, the more the raw material is dissolved. That is, in the range where the temperature difference is less than 20 ° C., the dissolution rate of the raw material is low, which corresponds to the stage where the undissolved raw material remains, and the dissolution rate rapidly increases as the temperature difference increases. When the temperature difference is 20 ° C. or more, it corresponds to the stage where the raw materials are completely dissolved. Therefore, it is preferable that the threshold value of the temperature difference is selected to be 20 ° C. Further, by this, it is possible to accurately and surely determine that the additionally charged raw material is completely dissolved.
Although the molten metal can be discharged after the raw materials have been completely melted, in actual operation, the molten metal should be discharged after adjusting the temperature of the molten metal and reducing and refining the chromium oxide in the slag. There are many.

FIG. 15 is a characteristic diagram showing the relationship between the rate of change of the outlet cooling water temperature of the water-cooled furnace wall with respect to time and the rate of dissolution of the raw material between the additional charging and the tapping. It can be seen from FIG. 15 that the rate of change of the outlet cooling water temperature with time corresponds to the rate of dissolution of the raw material, and the higher the rate of time variation, the more the dissolution of the raw material progresses. That is, the time change rate is 3
Within the range of less than ° C / min, the dissolution rate of the raw material is low, which corresponds to the stage where the undissolved raw material remains, and the dissolution rate increases sharply as the rate of change with time increases. When the rate of change with time is 3 ° C./minute or more, it corresponds to the stage where the raw materials are completely dissolved. Therefore, the threshold value of the time change rate is preferably selected to be 3 ° C./minute. Further, by this, it is possible to accurately and surely determine that the additionally charged raw material is completely dissolved.

FIG. 16 shows the frequency of occurrence of material heap and the rate of material dissolution of 80% or more with respect to the temperature difference between the refractory temperature after the start of energization and the refractory temperature at the start of energization between the initial charging and the additional charging. It is a characteristic diagram showing the relationship of the frequency of. It can be seen from FIG. 16 that the temperature difference of the refractory temperature and the melting state of the raw material correspond to each other, and the melting of the raw material progresses as the temperature difference increases, and the frequency of occurrence of the material heap decreases. . That is, in the range where the temperature difference is less than 40 ° C., it corresponds to the initial stage of dissolution in which the raw material dissolution rate is low,
As the temperature difference increases, the dissolution rate sharply increases, and the frequency of material swelling sharply decreases. When the temperature difference is 40 ° C. or more, the melting rate of the raw material is high, which corresponds to the stage where the raw material is considerably melted, and the occurrence frequency of the material heap is almost 0%. Is possible. Therefore, the threshold value of the temperature difference is preferably selected to be 40 ° C. Further, by this, it is possible to accurately and surely determine the time when the dissolution rate of the initially charged raw material reaches the dissolution rate at which additional charging is possible. When the temperature difference is 50 ° C. or higher, the raw materials are almost completely dissolved.
It is not preferable as the time for additional charging, and excessive power input causes an increase in the power consumption rate.

FIG. 17 is a characteristic diagram showing the relationship between the rate of change in the refractory temperature with time from the initial charging to the additional charging and the frequency of occurrence of the material heap and the frequency of the material dissolution rate of 80% or more. It can be seen from FIG. 17 that the rate of change of the refractory temperature with time corresponds to the melting state of the raw material, and that the larger the rate of time change, the more the melting of the raw material progresses and the lower the frequency of occurrence of material heap. I understand. That is, in the range where the rate of change of the refractory temperature with time is less than 5 ° C./minute, it corresponds to the initial stage of melting in which the rate of dissolution of the raw material is low, and as the rate of change with time increases, the rate of dissolution increases sharply. The frequency of swells is sharply decreasing. If the rate of change with time is 5 ° C./minute or more, the raw material dissolution rate is high, which corresponds to the stage where the raw material is considerably dissolved, and the occurrence frequency of the material pile is almost 0%.
Therefore, additional charging of raw materials is possible. For this reason,
The threshold value of the rate of change with time is preferably selected to be a value of 5 ° C./minute. Also, by this, the time when the dissolution rate of the initially charged raw material reaches the dissolution rate that can be additionally charged,
It can be accurately and surely determined.

FIG. 18 is a characteristic diagram showing the relationship of the raw material dissolution rate with respect to the temperature difference between the refractory temperature after the start of energization and the refractory temperature at the start of energization between the additional charging and the tapping.
It can be seen from FIG. 18 that the temperature difference between the refractory temperatures and the raw material dissolution rate correspond to each other, and the melting of the raw material progresses as the temperature difference increases. That is, the temperature difference is 4
In the range below 0 ° C., the dissolution rate of the raw material is low, which corresponds to the stage where the undissolved raw material remains, and the dissolution rate rapidly increases as the temperature difference increases. The temperature difference is 40 ° C
The above corresponds to the stage where the raw materials are completely dissolved. Therefore, the threshold value of the temperature difference is preferably selected to be 40 ° C. Further, by this, it can be accurately and surely determined that the additionally charged raw material is completely dissolved. The treatment after the determination of complete dissolution of the raw material is as described above.

FIG. 19 is a characteristic diagram showing the relationship of the raw material dissolution rate with respect to the time change rate of the refractory temperature between the additional charging and the hot water discharge. From FIG. 19, it can be seen that the rate of change of the refractory temperature with time corresponds to the rate of dissolution of the raw material, and the melting of the raw material progresses as the rate of change with time increases. That is, when the time change rate is less than 5 ° C./minute, the dissolution rate of the raw material is low, which corresponds to the stage where the undissolved raw material remains. The larger the time change rate, the more rapidly the dissolution rate increases. When the rate of change with time is 5 ° C./minute or more, it corresponds to the stage where the raw materials are completely dissolved. Therefore, it is preferable that the threshold value of the rate of change with time is selected to be a value of 5 ° C./minute. Further, by this, it is possible to accurately and surely determine that the additionally charged raw material is completely dissolved.

FIG. 20 is a flow chart for explaining the raw material melting determination method by the raw material melting determination apparatus for the electric furnace shown in FIG. In step s1, the electric furnace 10 is initially charged with the raw material of stainless steel. As the charging raw material, stainless steel scrap, ferrochrome, ferronickel, coke and lime are mainly used. In step s2, the electric power supply to the electric furnace 10 is started,
The refractory temperature T1 at the start of energization is measured by the refractory thermometer 5. After the start of energization, CO gas is generated as the raw material is heated and melted, and the outlet cooling water temperature TW2 and the refractory temperature T2 rise. The CO gas discharged from the electric furnace 10 is introduced into the combustion tower 11, reacts with air and burns, and CO ₂ gas is produced as a combustible organism.

In step s3, the threshold values of the respective index values for judging the dissolution of the initially charged raw materials are set to predetermined values. As mentioned above, as the index value,
CO ₂ gas concentration GA1 in the combustion exhaust gas discharged from the combustion tower 11, energizing power amount E1, the temperature difference between the outlet coolant temperature TW2 and the inlet coolant temperature TW1 (TW2-TW1), refractory temperature after the start of energization T2 and refractory temperature T at the start of energization
1, a temperature difference (T2-T1), a time change rate RW1 of the outlet cooling water temperature TW2 and a time change rate R1 of the refractory temperature T2 are used, and the threshold value is 5% in the same order, EL 1kWh, 15 ℃, 40 ℃, 3 ℃ / min, 5 ℃
/ Minute is set respectively. The threshold value EL1 of the energized electric energy E1 is calculated from the weight of each kind of the initially charged raw material using the above equation (1).

At step s4, the CO ₂ gas concentration G
A1, energization power amount E1, inlet cooling water temperature TW1, outlet cooling water temperature TW2 and refractory temperature T2 are measured by the gas analyzer 2, power meter 27, inlet water thermometer 3, outlet water thermometer 4 and refractory thermometer 5. Each is measured. Steps
In 5, the temperature difference (TW2-TW1), the time change rate RW1, the temperature difference (T2-T1), and the time change rate R1 are calculated by the calculation means 6. As described above, the inlet water thermometer 3 and the outlet water thermometer 4 are provided in the circumferential direction of the water cooling furnace wall 18, respectively, and the refractory thermometer 5
Since six are provided in the circumferential direction of the furnace wall 30, the temperature difference (TW2-TW1) and the time change rate RW1.
For eight, eight sets of calculated values are calculated, and the temperature difference (T
2-T1) and the time change rate R1, six sets of calculated values are calculated.

In step s6, it is judged whether or not the values of at least two of the six index values have reached the respective threshold values. Of the six index values used for this determination, the temperature difference (TW2-TW1),
For (T2-T1) and the time change rates RW1 and R1, the minimum value of the calculated plurality of calculated values is used. This is because the dissolution of the raw material is rate-determined at the positions corresponding to the outlet water thermometer 4 and the refractory thermometer 5 which show the minimum value, which can prevent the raw material from locally remaining unmelted. If the determination in step s6 is negative, it is determined that the dissolution rate of the initially charged raw material has not reached the dissolution rate at which additional charging is possible, the process returns to step s4, and steps s4 to s6 are performed again. The process of is repeated. This repetitive process is repeated until the determination in step s6 becomes affirmative. If the determination in step s6 is affirmative, it is determined that the dissolution rate of the raw material has reached the dissolution rate at which additional charging is possible, the power supply is stopped, and the process proceeds to step s7.

In step s7, additional charging of raw materials is performed. The processing from step s7 to step s12 is
Since this is a process for the additionally charged raw material and is basically the same as the process from step s3 to step s6, duplicate description will be omitted. In step s9, the threshold value of each index value for determining the dissolution of the additionally charged raw material is set to a predetermined value. The respective index values and their threshold values are such that the CO ₂ gas concentration GA2 is 3
%, The energization power amount E2 is EL2 kWh, the temperature difference (TW4-TW3) between the outlet cooling water temperature TW4 and the inlet cooling water temperature TW3 is 20 ° C., and the refractory temperature T4 and energization start after the energization start Temperature difference with the refractory T3 (T4
-T3) is 40 ° C., the outlet cooling water temperature TW4 has a time change rate RW2 of 3 ° C./min, and the refractory temperature T4 has a time change rate R2 of 5 ° C./min. If the determination in step s12 is negative, it is determined that the additionally charged raw material is not completely dissolved, the process returns to step s10, and the processes from step s10 to step s12 are repeated again. This repeating process is repeated until the determination in step s12 becomes affirmative. If the determination in step s12 is affirmative, step s13
Proceed to. In step s13, it is determined that the additionally charged raw material is completely melted, the temperature of the molten metal is adjusted, the refining and refining of chromium oxide in the slag is performed, and the tapping is performed in step s14.

As described above, in the present embodiment, the determination of the melting of the raw material is made by continuously grasping the molten state of the raw material by the respective index values which change corresponding to the molten state of the raw material in the electric furnace 10. It is performed by determining that the raw material is dissolved when at least two of these index values reach the respective threshold values set to predetermined values. For this reason, it is possible to determine the melting timing of the initially charged and additionally charged raw materials more accurately and reliably than in the conventional method in which observation is performed in the furnace or based on a constant amount of electric power. In addition, since the dissolution determination is performed based on at least two index values among the respective index values, erroneous determination due to an abnormal value or the like can be made as compared with the case where the dissolution determination is performed based on only one index value among the respective index values. This can be prevented, and the time of dissolution of the raw material can be determined more accurately and surely. Furthermore, since the melting time can be shortened and the power loss can be reduced by accurately determining the melting time of the raw material, the power consumption rate can be reduced and energy can be saved. Furthermore, since the undissolved raw materials can be prevented, the molten metal yield is improved and the variation of the molten metal components is reduced.

[0069]

EXAMPLE A 90-ton electric furnace 10 shown in FIG. 2 was used to melt a chromium-containing hot metal used for melting stainless steel. Table 1 shows the main raw material composition in the case of smelting chromium-containing molten pig iron for SUS304 series stainless steel, and Table 2 shows the smelting result. In the examples of the present invention, the dissolution determination apparatus 1 shown in FIG. 1 was used to determine the dissolution of the initially charged and additionally charged raw materials by the dissolution determination method shown in FIG. Regarding the comparative example of the conventional technique, the dissolution determination of the charging raw material was performed based on a certain amount of power consumption.

It can be seen from Table 2 that the Examples can accurately and surely determine the dissolution of the initially charged and additionally charged raw materials, as compared with the Comparative Examples, so that the raw material dissolution time can be shortened. , The electric power consumption is significantly reduced, and the arc heat to the refractory layers of the water-cooled furnace wall 18 and the furnace wall 30 is reduced, so that the life of the water-cooled furnace wall 18 is greatly extended and the refractory repair is performed. It can be seen that the cost is significantly reduced, and the material pile does not occur at the time of additional charging.

[0071]

[Table 1]

[0072]

[Table 2]

[0073]

As described above, according to the present invention, it is possible to continuously grasp the melting state of a plurality of types of raw materials charged in an electric furnace without performing visual observation in the furnace, and Since it is possible to accurately and surely determine the melting time of the raw material, it is possible to reliably melt the charged raw material without excessively supplying electric power. Therefore, the dissolution time is shortened. Further, since the loss of electric power is reduced, the unit consumption of electric power is reduced and energy can be saved. Furthermore,
Excessive power input is eliminated, and the heat load on the furnace wall is reduced, so that the amount of refractory material worn on the furnace wall is greatly reduced, and the life of the furnace wall is greatly extended. Furthermore, since the undissolved raw materials can be prevented, the melt yield is improved and the variation of the melt components is reduced. Furthermore, since the additional charging of raw materials will not be performed in a state where the raw materials are not melted, the additionally charged raw materials will not fit in the furnace internal space and will protrude outside the furnace, making it impossible to close the ceiling lid. Is prevented from occurring.
Furthermore, since it is not necessary to visually observe the inside of the furnace, it is not necessary to open the opening of the electric furnace, and there is no possibility that a large amount of dust will be emitted from the opening to cause environmental deterioration.
Furthermore, since the molten state of the raw material can be continuously grasped, expansion of slag due to a rapid reaction of the raw material generated at the time of melting the raw material, so-called forming, can be predicted in advance.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a simplified configuration of a raw material melting determination device for an electric furnace according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view seen from the front, showing a simplified configuration of the electric furnace shown in FIG.

FIG. 3 is a plan view showing a simplified configuration of a ceiling lid of the electric furnace shown in FIG.

FIG. 4 is a perspective view showing a simplified structure of a water cooling furnace wall of the electric furnace shown in FIG.

5 is a sectional view showing a simplified configuration of the outlet cooling water temperature detecting means shown in FIG.

FIG. 6 is a transverse cross-sectional view of the electric furnace taken along the section line VI-VI in FIG.

FIG. 7 is a system diagram showing a simplified configuration of a gas analysis unit.

FIG. 8 is a schematic diagram showing, in a time-series manner, a change in component concentration of combustion exhaust gas discharged from a combustion tower during melting of raw materials of an electric furnace.

FIG. 9 is a time-series transition diagram showing changes in component concentration of combustion exhaust gas discharged from a combustion tower in actual operation of an electric furnace.

FIG. 10 is a transition diagram showing a change over time in the cooling water temperature of a water cooling tube provided on a water cooling furnace wall of the electric furnace shown in FIG.

FIG. 11 shows the relationship between the outlet cooling water temperature of the water-cooled furnace wall from the initial charging to the additional charging and the temperature difference between the inlet cooling water temperature and the frequency of occurrence of material puddle and the frequency of material dissolution rate of 80% or more. It is a characteristic view to show.

FIG. 12 is a characteristic diagram showing a relationship between a temperature difference between an outlet cooling water temperature of a water-cooled furnace wall and an inlet cooling water temperature between initial charging and additional charging with respect to a basic unit of dissolved power of an initial charging raw material.

FIG. 13 is a characteristic diagram showing a relationship between the time rate of change of the outlet cooling water temperature of the water-cooled furnace wall between the initial charging and the additional charging, the frequency of occurrence of the material heap, and the frequency of the material dissolution rate of 80% or more. .

FIG. 14 is a characteristic diagram showing a relationship of a dissolution rate of a raw material with respect to a temperature difference between an outlet cooling water temperature of a water-cooled furnace wall and an inlet cooling water temperature between additional charging and tapping.

FIG. 15 is a characteristic diagram showing the relationship between the rate of change of the outlet cooling water temperature of the water-cooled furnace wall with respect to time and the dissolution rate of the raw material between the additional charging and the hot water discharge.

FIG. 16: Frequency of occurrence of material heap and raw material dissolution rate of 80% with respect to temperature difference between refractory temperature after start of energization and refractory temperature at start of energization between initial charging and additional charging
It is a characteristic view which shows the relationship of the above frequencies.

FIG. 17 is a characteristic diagram showing the relationship between the rate of change in the refractory temperature with time from the initial charging to the additional charging, the frequency of occurrence of the material heap, and the frequency of the material dissolution rate of 80% or more.

FIG. 18 is a characteristic diagram showing the relationship of the raw material dissolution rate with respect to the temperature difference between the refractory temperature after the start of energization and the refractory temperature at the start of energization between additional charging and tapping.

FIG. 19 is a characteristic diagram showing a relationship of a raw material dissolution rate with respect to a temporal change rate of refractory temperature between additional charging and tapping.

FIG. 20 is a flow chart for explaining a method for determining the dissolution of a raw material by the raw material dissolution determination apparatus for the electric furnace shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Raw material dissolution determination device for an electric furnace 2 Gas analysis means 3 Inlet cooling water temperature detection means 4 Outlet cooling water temperature detection means 5 Refractory temperature detection means 6 Calculation means 7 Judging means 8 Setting means 9 Display means 10 Electric furnace 11 Combustion tower 15 Air Intake Port 17 Water Cooling Tube 18 Water Cooling Furnace Wall 27 Power Detection Means 42 CO / CO ₂ Concentration Meter 43 O ₂ Concentration Meter

Claims (8)

[Claims] 1. A method for determining a melting time of a plurality of kinds of raw materials charged in an electric furnace, the concentration of a predetermined component in exhaust gas discharged from the electric furnace, and an electric power supplied for melting the raw materials. When at least two of the quantity, the value corresponding to the cooling water temperature of the water cooling pipe installed in the electric furnace, and the value corresponding to the temperature of the refractory material installed in the electric furnace have reached predetermined threshold values. A method for determining dissolution of a raw material in an electric furnace, characterized by determining that the raw material is melted. 2. The concentration of a predetermined component in the exhaust gas is a CO ₂ gas concentration in a combustion exhaust gas generated by a combustion reaction between CO gas in the exhaust gas discharged from the electric furnace and air. The method for determining dissolution of a raw material in an electric furnace according to claim 1. 3. The threshold value of the amount of electric power is obtained by multiplying the weight of each type of charging raw material by a predetermined melting power coefficient of each type, and multiplying each value with respect to all types of charging raw material. The method for determining dissolution of a raw material in an electric furnace according to claim 1 or 2, wherein the method is set based on a total value of 4. The value corresponding to the cooling water temperature of the water cooling pipe is a temperature difference between the outlet cooling water temperature and the inlet cooling water temperature of the water cooling pipe. A method for determining dissolution of a raw material in an electric furnace according to claim 2. 5. The electric furnace according to claim 1, wherein the value corresponding to the cooling water temperature of the water cooling pipe is a time change rate of the outlet cooling water temperature of the water cooling pipe. Method for determining dissolution of raw materials. 6. The value corresponding to the refractory temperature is a temperature difference between the refractory temperature after the start of energization and the refractory temperature at the start of energization. The method for determining the dissolution of a raw material in an electric furnace as set forth in. 7. The value corresponding to the refractory temperature is a rate of change of the refractory temperature with time.
The method for determining dissolution of a raw material in an electric furnace according to any one of 1. 8. An apparatus for determining a melting time of a plurality of kinds of raw materials charged in an electric furnace, comprising: a gas analysis means for measuring a concentration of a predetermined component in exhaust gas discharged from the electric furnace; The electric power detection means for measuring the amount of electric power supplied, the cooling water temperature detection means for measuring the cooling water temperature at the inlet and outlet of the water cooling pipe provided in the electric furnace, and the temperature of the refractory material provided in the electric furnace Refractory temperature detection means to measure, the temperature difference between the outlet cooling water temperature of the water cooling pipe and the inlet cooling water temperature,
Outlet cooling water temperature change rate of the water cooling pipe, a calculation means for calculating the time change rate of the refractory temperature at the start of energization and the refractory temperature at the start of energization and the time change rate of the refractory temperature, in the exhaust gas Set the threshold values of the concentration of predetermined component, electric energy, temperature difference of cooling water temperature, time change rate of outlet cooling water temperature, temperature difference of refractory temperature, and time change rate of refractory temperature to predetermined values. Setting means, the concentration of a predetermined component in the exhaust gas measured by the gas analysis means, the amount of electric power measured by the electric power detection means, the temperature differences calculated by the calculation means, and the time change rate are predetermined by the setting means. Judging means for judging that the raw material is dissolved when at least two values among the measured values and the calculated values are compared with respective threshold values set to the respective values and the corresponding threshold values are reached. , In response to an output of the determining means, dissolution determination device of the raw material in an electric furnace, characterized in that it comprises a display means for displaying that the material was dissolved.