JP2004156865A - Device and method for controlling operation of plasma arc type melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for controlling operation of a plasma arc type melting furnace reliably grasping generation of stray current of the plasma arc type melting furnace and operating with a favorable state on the basis of the grasp. <P>SOLUTION: This plasma arc type melting furnace 10 has a furnace body of which furnace inner wall made of a refractory material is coated with iron shell and generates plasma arc between electrodes inserted facing the furnace body. The furnace comprises a plasma arc detection means consisted of a first ammeter 31 for measuring current between the main electrode 11 and the furnace bottom electrode 12, an infrared camera 25 taking picture of a plasma arc generating part inside the furnace through a transmission window from outside of the furnace, and an image processor 28 analyzing plasma arc state from the images taken by the infrared camera, and a determination means 30 determining presence of stray current generated inside the melting furnace from the current measured by the current measurement means and the plasma arc state detected by the plasma arc detection means. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma arc melting furnace in which the inside of a furnace is maintained at a high temperature by a plasma arc generated between a main electrode inserted into a furnace main body and a furnace bottom electrode, and particularly to a plasma arc melting furnace. The present invention relates to an apparatus and a method for controlling operation by detecting a stray current generated in a vehicle.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a plasma arc melting furnace has been widely used as a furnace for melting and processing incineration ash and the like after incineration of waste. The plasma arc type melting furnace is one of the most useful waste treatment apparatuses because it is effective in reducing the volume and detoxification of waste, and can reuse slag after melting.
FIG. 3 shows an example of a plasma arc type melting furnace. As shown in the figure, a plasma arc type melting furnace 50 is formed by a side wall 52, a furnace bottom 54, and a furnace lid 53 formed on the inside of the furnace with a refractory material 51 having an insulating property, and a furnace shell 55 on the outside of the furnace. Main components are a coated furnace main body, and a main electrode 58 and a furnace bottom electrode 59 inserted into the furnace lid 53 and the furnace bottom 54 via an insulating sleeve 56.
[0003]
In general, an annular graphite electrode is often used in the plasma arc type melting furnace 50 having such a configuration, and a plasma arc is generated by supplying a voltage between the electrodes while supplying a plasma arc generating gas into the furnace to generate a plasma arc. The material is melt processed. The temperature in the furnace is maintained at 1000 ° C. or higher, and a slag consisting of a slag layer and a metal layer in which the material to be melted is formed in a layer at the bottom of the furnace.
In such a melting furnace, since the inside of the furnace is maintained at a high temperature, when the material to be melted contains salts having a relatively low melting point, such as incineration ash, the salts are volatilized in the gas. And adhere to the furnace inner wall. The deposits such as potassium chloride and sodium chloride thus deposited have high conductivity, and may cause stray current due to poor insulation of the furnace wall.
[0004]
There are at least two possible paths of the stray current in the furnace. As a conduction path in the furnace, when salts infiltrate into the refractory on the inner wall of the furnace and the insulation property is deteriorated, a path from the main electrode 58 to the furnace bottom electrode 59 through the refractory to the furnace bottom electrode 59 via the refractory and the inside of the furnace. When deposits made of salts or the like are deposited, there is a path from the main electrode 58 to the bottom electrode 59 through the deposits on the inner wall of the furnace.
When such a stray current occurs, the inside of the furnace cannot be maintained at an appropriate temperature, the melting state of the object to be processed deteriorates, the melting furnace does not operate normally, and an excessive load is applied to the furnace wall. There is a problem that the damage is significant.
[0005]
Therefore, in Japanese Patent Application Laid-Open No. 2000-18552 (Patent Document 1) shown in FIG. 3, an annular insulating material 57 that insulates the main electrode 58 and the furnace bottom electrode 59 is provided, and the current or the current between the two electrodes with the insulating material interposed therebetween. Measuring means such as an ammeter 60 for measuring a voltage is provided. Thereby, stray current due to insulation failure can be monitored.
In Japanese Patent Application Laid-Open No. Hei 6-331278 (Patent Document 2), a voltage between a furnace bottom electrode and a furnace bottom steel shell isolated by an insulator is measured, and a current flowing from the furnace bottom electrode to a grounding resistor is measured. By measuring and determining the abnormal voltage of the furnace bottom electrode portion based on these measured values, damage to the furnace shell due to stray current is prevented beforehand.
[0006]
[Patent Document 1]
JP 2000-18552 [Patent Document 2]
JP-A-6-331278
[Problems to be solved by the invention]
However, a method of monitoring the stray current by measuring the current or voltage of the steel shell as in these conventional techniques, or a method of detecting the stray current by detecting an abnormal voltage of the hearth steel shell is a very effective method. However, as described above, it is impossible to detect a stray current generated in a part other than the conduction path through the furnace shell, and it is impossible to completely grasp a stray current generated in the melting furnace.
Accordingly, the present invention has been made in view of the problems of the related art, and it is possible to reliably grasp occurrence of stray current in a plasma arc type melting furnace, and to operate a melting furnace in a suitable state based on the current. An object of the present invention is to provide a melting furnace operation control device and a method thereof.
[0008]
[Means for Solving the Problems]
Therefore, the present invention, in order to solve such a problem,
It has a furnace body in which the furnace inner wall formed of an insulating refractory is covered with an iron shell, and generates a plasma arc between a main electrode and a furnace bottom electrode inserted opposite to the furnace body to raise the temperature in the furnace to a high temperature. In the operation control device of the plasma arc type melting furnace holding,
Current measuring means for measuring a current value between the main electrode and the furnace bottom electrode,
An infrared camera that captures an image of the plasma arc generator in the furnace from outside the furnace via a transmission window, and an image processing device that analyzes a plasma arc state from an image captured by the infrared camera, a plasma arc detection unit including: With
It is characterized in that the presence or absence of a stray current generated in the melting furnace is determined from the current value measured by the current measuring means and the plasma arc state analysis result obtained by the plasma arc detecting means.
[0009]
The plasma arc generated in the melting furnace has a specific emissivity, and the amount of infrared radiation varies depending on the emissivity and the temperature. Therefore, the plasma arc detecting means takes in an infrared image signal captured by the infrared camera into the image processing device, and generates a grayscale image using the amount of infrared radiation as a luminance value from the infrared image signal by the image processing device. It is configured to analyze the plasma arc state such as the plasma arc shape and temperature distribution based on the data.
[0010]
As a preferred control method using such a device,
It has a furnace body in which the furnace inner wall formed of an insulating refractory is covered with an iron shell, and generates a plasma arc between a main electrode and a furnace bottom electrode inserted opposite to the furnace body to raise the temperature in the furnace to a high temperature. In the operation control method of the plasma arc type melting furnace holding,
While measuring the current value between the main electrode and the furnace bottom electrode,
An image of the plasma arc generating section is taken by an infrared camera installed outside the furnace, and a plasma arc state is analyzed from the taken image,
It is characterized in that the presence or absence of a stray current generated in the melting furnace is determined based on the analysis result of the current value and the plasma arc state.
[0011]
As described above, since the presence or absence of the stray current is determined based on the analysis result and the inter-electrode current value, not only the stray current flowing through the steel skin as in the related art, but also the current whose path is unknown is reliably detected. It becomes possible. In addition, since an infrared camera is used for image recognition of the plasma arc, the plasma arc can be accurately identified even if the inside of the furnace is not visible due to the dust atmosphere.
In addition, since the determination is made based on the inter-electrode current value in addition to the analysis result of the plasma arc, it can be clearly distinguished from a plasma arc abnormality due to another factor such as a failure of the electrode, and the occurrence of the stray current can be accurately determined. Can be grasped.
[0012]
Furthermore, it is preferable that the operation control device of the plasma arc type melting furnace is provided with a control means for controlling power supply to the melting furnace based on the presence or absence of the determined stray current.
According to this, since the operation of the melting furnace is not continued in a state where the stray current is generated, it is possible to appropriately maintain the melting state of the processing object without applying an unnecessary load to the melting furnace. it can.
[0013]
Further, a second current measuring means for detecting a leakage current between the furnace lid side and the furnace bottom side of the steel shell is provided by sandwiching an insulator disposed on the furnace wall so as to insulate the electrodes, and It has a double detection structure.
As described above, the stray current generated in the melting furnace can be reduced by the double detection structure including the stray current detection means based on the inter-electrode current value and the result of the plasma arc analysis, and the leak current detection means of the steel shell. The detection can be performed reliably, and the location where the stray current occurs can be easily grasped.
[0014]
Furthermore, as a method using the control device, when the measured current value is equal to or more than a threshold value capable of steady operation and the analysis result of the plasma arc shows an abnormality, there is generation of a stray current in the melting furnace. It is preferable to control so as to stop the power supply to the melting furnace.
Further, a second current measuring means for detecting a leakage current between the furnace lid side and the furnace bottom side of the steel shell is provided with an insulator provided on the furnace wall so as to insulate the electrodes therebetween, and When a current value larger than the allowable limit current value based on the insulation state of the skin is detected by the second current measuring means for a predetermined time or more, the power supplied to the melting furnace is stopped, and If it is small, it is preferable to determine the presence or absence of the stray current according to claim 4.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Not just.
FIG. 1 is an overall configuration diagram of an operation control device for a plasma arc melting furnace according to the present embodiment, and FIG. 2 is a flowchart of an operation control method according to the embodiment of the present invention.
[0016]
As shown in FIG. 1, a plasma arc melting furnace 10 according to the present embodiment has a furnace body 17 in which a furnace cover 17, a furnace side wall 18, and a furnace bottom 19 formed of an insulating refractory 15 are covered with an iron shell 16. 14, a main electrode 11 inserted into the furnace lid 17 with an insulator 20 interposed therebetween, and a furnace bottom electrode 12 arranged on the furnace bottom 19, and the main electrode 11 is connected to the main electrode 11 by a DC power supply 13. A DC voltage is applied between the furnace bottom electrode 12 to generate a plasma arc 23 to melt the slag, such as incineration ash, which has been charged into the melting furnace. A slag layer 21 and a metal layer 22 are formed at the bottom of the melting furnace by the melted workpiece.
[0017]
The material to be melted by the plasma arc high-temperature gas flow generated by the plasma arc 23 contains a large amount of low-melting salts, which are vaporized as vapor and adhere to the furnace inner wall. , Penetrate.
Most of the furnace body 14 is formed of an insulating refractory such as silica brick, alumina castable, or the like. However, the adhesion of the volatiles such as the salts causes insulation failure, or the volatiles infiltrate the insulation. Or decrease the quality. In order to prevent stray currents induced by these factors, a ring insulator 20 is provided on the refractory 15.
[0018]
In the present embodiment, a first ammeter 31 is connected between the main electrode 11 and the furnace bottom electrode 12 in series with the DC power supply 13. The first ammeter 31 has a function of measuring a current value of electric power supplied into the furnace to generate a plasma arc, and the measured current value is transmitted to a stray current determination device 30 described later. You.
Further, a through hole 27 is provided above the furnace side wall 18, and a transmission window 26 is provided so as to seal the through hole 27. The transmission window 26 is formed of a material that can transmit infrared rays, and the infrared camera 25 is installed at a position where an image of the plasma arc generator can be taken from outside the furnace via the transmission window 26. The wavelength of the infrared camera 25 can be 3 μm or more, but preferably 8 μm or more.
Furthermore, an image processing device 28 is connected to the infrared camera 25, and image data captured by the infrared camera 25 is transmitted.
[0019]
The plasma arc 23 generated in the melting furnace has a specific emissivity, and the amount of infrared radiation varies depending on the emissivity and the temperature. The infrared camera 25 takes in the captured infrared image signal into the image processing device 28, generates a grayscale image using the amount of infrared radiation as a luminance value from the infrared image signal by the image processing device 28, and generates a plasma arc based on the image data. Analyze the plasma arc state such as shape and temperature distribution.
At this time, it is possible to analyze the plasma arc shape such as the plasma arc length by determining the mounting angle of the infrared camera 25 and the position of the main electrode, and thereby it is possible to accurately grasp the plasma arc generation state. .
[0020]
Further, a second ammeter 32 for measuring a current between the furnace lid side and the furnace bottom side of the steel shell 16 is provided with the insulator 20 interposed between the furnace walls. The second ammeter 32 measures a leakage current value flowing through the steel shell 16 and transmits the measured value to the determination device 30.
Furthermore, it is connected to the first ammeter 31, the image processing device 28, and the second ammeter 32, and the inter-electrode current value from the first ammeter 31, the plasma state analysis result from the image processing device 28, and the second A stray current judging means 30 for judging the presence or absence of a stray current from the iron current value from the ammeter 32 is provided.
Then, the DC power supply 13 is controlled by the DC power supply control device 29 based on the determination result of the determination means 30.
[0021]
An example of a flow of a control method using the operation control device will be described with reference to FIG. Electric power is supplied to the plasma arc type melting furnace 10 of the present embodiment to maintain the inside of the furnace at a high temperature and perform a steady operation (S1), and at a predetermined time interval, the iron current is measured by the second ammeter 32. (S2). At this time, if the measured current value is equal to or more than the allowable current value at which a leakage current is recognized, the presence of a stray current is detected in the steel shell, and operation is stopped to perform maintenance. On the other hand, if the current is not more than the allowable current value, the first ammeter 31 measures the current between the main electrode 11 and the furnace bottom electrode 12 (S4).
[0022]
A threshold value, which is a current value at which a plasma arc is normally generated and a normal operation is possible, is set in advance, and the measured current value is compared with the threshold value (S5). Assuming that the current is not flowing normally, the operation of the melting furnace is stopped and maintenance is performed. On the other hand, when the current is larger than the threshold value, the plasma arc is analyzed by the image processing device 28 (S6). Then, when a plasma arc abnormality such as a break of the plasma arc is recognized by the analysis for a predetermined time or more, it is determined that a stray current whose path is unknown is generated, and the power supply to the furnace is stopped by the DC power supply control device 29. In addition, when the said plasma arc abnormality is not recognized, steady operation is continued.
As described above, in the present embodiment, the double detection structure of the stray current detecting means based on the current value between the skin and the stray current detecting means based on the analysis result of the plasma arc state and the current between the electrodes is adopted. Can detect a stray current that could not be detected.
[0023]
【The invention's effect】
As described above, according to the present invention, the presence or absence of a stray current is determined based on the analysis result and the inter-electrode current value. It is possible to reliably detect. In addition, since an infrared camera is used for image recognition of the plasma arc, the plasma arc can be accurately identified even if the inside of the furnace is not visible due to the dust atmosphere.
In addition, since the determination is made based on the inter-electrode current value in addition to the analysis result of the plasma arc, it can be clearly distinguished from a plasma arc abnormality due to another factor such as a failure of the electrode, and the occurrence of the stray current can be accurately determined. Can be grasped.
Furthermore, the stray current generated in the melting furnace can be reliably detected by adopting a double detection structure including a stray current detecting means based on a current value between the electrodes and a plasma arc analysis result and a leak current detecting means between the steel shells. At the same time, and the location of the stray current occurrence can be easily grasped.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an operation control device of a plasma arc type melting furnace according to the present embodiment.
FIG. 2 is a flowchart of an operation control method according to the embodiment of the present invention.
FIG. 3 is a schematic sectional view of a melting furnace provided with a conventional stray current prevention device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Plasma arc melting furnace 11 Main electrode 12 Furnace bottom electrode 13 DC power supply 15 Refractory 16 Iron shell 20 Insulator 23 Plasma arc 25 Infrared camera 26 Transmission window 27 Through hole 28 Image processing device 29 DC power supply control device 30 Stray current judgment Device 31 First ammeter 32 Second ammeter

Claims (6)

It has a furnace body in which the furnace inner wall formed of an insulating refractory is covered with an iron shell, and generates a plasma arc between a main electrode and a furnace bottom electrode inserted opposite to the furnace body to raise the temperature in the furnace to a high temperature. In the operation control device of the plasma arc type melting furnace holding,
Current measuring means for measuring a current value between the main electrode and the furnace bottom electrode,
An infrared camera that captures an image of the plasma arc generator in the furnace from outside the furnace via a transmission window, and an image processing device that analyzes a plasma arc state from an image captured by the infrared camera, a plasma arc detection unit including: With
The operation of the plasma arc type melting furnace, wherein the presence or absence of a stray current generated in the melting furnace is determined from the current value measured by the current measuring means and the plasma arc state analysis result obtained by the plasma arc detecting means. Control device. 2. The operation control device for a plasma arc melting furnace according to claim 1, further comprising control means for controlling power supply to the melting furnace based on the presence or absence of the determined stray current. A second current measuring means for detecting a leakage current between the furnace lid side and the furnace bottom side of the steel shell is provided by sandwiching an insulator arranged on the furnace wall so as to insulate the electrodes, and a double stray current is provided. The operation control device for a plasma arc type melting furnace according to claim 1, wherein the operation control device has a detection structure. It has a furnace body in which the furnace inner wall formed of an insulating refractory is covered with an iron shell, and generates a plasma arc between a main electrode and a furnace bottom electrode inserted opposite to the furnace body to raise the temperature in the furnace to a high temperature. In the operation control method of the plasma arc type melting furnace holding,
While measuring the current value between the main electrode and the furnace bottom electrode,
An image of the plasma arc generating section is taken by an infrared camera installed outside the furnace, and a plasma arc state is analyzed from the taken image,
An operation control method for a plasma arc type melting furnace, characterized by determining whether there is a stray current generated in the melting furnace based on the analysis result of the current value and the plasma arc state. When the measured current value is equal to or greater than a threshold value at which steady operation is possible, and when the analysis result of the plasma arc shows an abnormality, it is determined that stray current has occurred in the melting furnace, and power supply to the melting furnace is stopped. The operation control method for a plasma arc type melting furnace according to claim 4, wherein the control is performed so as to perform the operation. A second current measuring means for detecting a leakage current between a furnace lid side and a furnace bottom side of the steel shell is provided with an insulator provided on a furnace wall so as to insulate the electrodes therebetween, and When a current value larger than the allowable limit current value based on the insulation state is detected by the second current measuring means for a predetermined time or more, the power supplied to the melting furnace is stopped, and the current value is smaller than the allowable limit current value. The method for controlling the operation of a plasma arc type melting furnace according to claim 4, wherein the presence or absence of the stray current according to claim 4 is determined in some cases.

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