JP2002048317A - Interruption method for melting furnace and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically achieve interruption of inactive gas supplied into a furnace and supply of cooling air into the furnace in response to refractory temperature, etc., and realizing maintenance work by a worker by automatically monitoring the refractory temperature and temperature in the furnace upon interrupting the melting furnace. SOLUTION: In a melting furnace where inactive gas I is supplied into a furnace to keep the inside of the furnace in reducing atmosphere, and a workpiece W to be melted that is supplied into the furnace is melted, a display lamp 17 is lighted with electric power generated by a thermoelement 16 embedded in a refractory 23 in the melting furnace to indicate that the melting furnace is running. Further, upon interruption of the melting furnace the display lamp 17 is extinguished when the refractory temperature and the temperature in the furnace are lowered to a temperature where maintenance work is ensured. Further, the refractory temperature, etc., are monitored from a current due to electric power generated by the thermoelement 16, and when the refractory temperature, etc., reach about 500 deg.C or lower upon the interruption of the melting furnace, the supply of the inactive gas I into the furnace is automatically interrupted and cooling air A is forced to enter the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation in which an inert gas such as nitrogen gas is supplied into a furnace and the furnace is operated in a reducing atmosphere, and an incinerator for municipal solid waste or industrial waste is used. Automatically monitor refractory temperature and furnace temperature when the melting furnace is shut down in a melting furnace that melts the incinerated residue and fly ash discharged using electric energy. The present invention relates to a method and an apparatus for shutting down a melting furnace in which the stopping of inert gas and the supply of cooling air to the furnace can be automatically performed according to the refractory temperature and the furnace temperature.

[0002]

2. Description of the Related Art In recent years, in order to reduce the volume and harmlessness of incineration residues and fly ash (hereinafter referred to as "melted material") discharged from incinerators such as municipal solid waste, a method of melting and solidifying the molten material has been developed. Attention has been given to practical use. This is because the volume of the material to be melted can be reduced to 1/2 to 1/3 by solidifying it, preventing the elution of harmful substances such as heavy metals, reusing molten slag, and the final landfill site. This is because the life can be extended.

[0003] In the method of melting and solidifying the material to be melted, an electric melting furnace such as a plasma melting furnace, an arc melting furnace, or an electric resistance furnace is used. A method of solidifying this by water cooling or air cooling, and using a combustion melting furnace such as a surface melting furnace, a swirling melting furnace, a coke bed furnace, etc. The method of solidifying by air cooling is often used, and when the power generation equipment is installed in the waste incineration treatment equipment, the former method using electric energy is used, and when the power generation equipment is not installed, The latter method using combustion energy has been widely adopted.

FIG. 5 shows an example of a DC arc discharge graphite electrode type plasma melting furnace juxtaposed with a conventional refuse incineration plant. In FIG. 5, reference numeral 25 denotes a melting furnace main body and 25a.
Is a molten slag outlet, 26 is a graphite main electrode, 27 is a graphite start electrode, 28 is a furnace bottom electrode, 29 is a tap hole,
0 is a hopper for the melt W, 31 is a supply device for the melt W, 32 is a thermocouple, 33 is a thermometer, 34 is a furnace bottom cooling fan, 35 is a DC power supply, 36 is an inert gas generator,
37 is an inert gas supply pipe, 38 is a combustion chamber, 39 is a cooling tower, 40 is a combustion air fan, 41 is an exhaust gas cooling fan, 42 is a bag filter, 43 is an induction ventilator, 44 is a chimney, and 45 is melting and flying. Ash conveyor, 46 is fly ash pool, 47
Is a slag water cooling tank, 48 is a slag carry-out conveyor, 49 is a slag reservoir, and 50 is a slag cooling water cooling device.

[0005] The material W to be melted such as incineration residues and fly ash is stored in the hopper 30 and continuously supplied into the melting furnace main body 25 by the supply device 31. A graphite main electrode 26 vertically and vertically inserted from the top of the furnace is inserted into the melting furnace body 25.
(− Pole) and a furnace bottom electrode 28 (+ pole) installed on the furnace bottom, and a DC power supply 35 (capacity of about 600 to 1000 kWh / T ·) applied between the electrodes 26 and 28 is provided.
An arc is generated between the two electrodes 26 and 28 by the DC voltage (200 V to 350 V) of the material to be melted, and plasma is generated by supplying an inert gas I (nitrogen gas) as a plasma gas into the arc. Thereby, the material to be melted W supplied into the melting furnace main body 25 is from 1300 ° C. to 1500 ° C.
It is heated to ℃ and becomes molten slag S.

Since the material to be melted W before melting has low conductivity, a graphite start electrode 27 is inserted into the melting furnace body 25 at the time of starting the plasma melting furnace, and is used as a positive electrode.
By energizing this and between the graphite main electrodes 26, the process waits for the melt W to melt. When the material to be melted W is melted, the conductivity of the material W is increased, so that the graphite start electrode 27 is switched to the furnace bottom electrode 28.

Further, the inside of the melting furnace main body 25 reduces the mixing of heavy metals into the molten slag S and prevents the graphite main electrode 2 from being mixed.
6 is kept in a reducing atmosphere in order to prevent oxidation, etc. Therefore, an inert gas such as nitrogen gas is supplied from an inert gas generator 36 such as a PSA nitrogen production device via an inert gas supply pipe 37. I is a graphite main electrode 26 formed in a hollow cylindrical shape
And, it is continuously supplied into the melting furnace main body 25 through the hollow hole of the graphite start electrode 27. The configuration in which the inert gas I is supplied into the melting furnace main body 25 is such that heavy metals such as Pb are easily volatilized and the quality of the slag is improved;
It is considered that when the plasma discharge region is filled with the rich inert gas I, the so-called plasma discharge properties such as generation and stability of the plasma arc are improved, and consumption of the graphite main electrode 26 and the graphite start electrode 27 is reduced. This is because it is considered to be less.

Further, the furnace bottom of the melting furnace main body 25 is air-cooled by cold air (air) from a furnace bottom cooling fan 34, thereby preventing an excessive temperature rise near the furnace bottom electrode 28. Further, the melting furnace body 25 itself is made of a refractory which can withstand high temperatures and a heat insulating material covering the same, and a water cooling jacket is provided outside the heat insulating material as necessary.

When the melting of the material to be melted W is started, volatile components present therein, carbon monoxide generated by oxidation of carbon, and the like are converted into a gas G (hereinafter referred to as exhaust gas).
Becomes The exhaust gas G (gas body) enters the combustion chamber 38 from the upper space of the molten slag outlet 25a, where the combustion air sent by the combustion air fan 40 is added, so that uncombusted air inside the combustion chamber 38 is added. The minutes were completely burned,
After being cooled by the cooling air from the cooling tower 39 and the exhaust gas cooling fan 41, the air is discharged to the chimney 44 by the induction ventilator 43 through the bag filter 42. The molten fly ash captured by the bag filter 42 is supplied to a molten fly ash conveyor 45.
Is sent to the fly ash reservoir 46.

On the other hand, metals such as iron, non-combustible components such as glass and sand contained in the material W to be melted are supplied to the heat generated by the plasma arc discharge so that their melting points (1) are reduced.
100 ° C to 1250 ° C)
The molten slag S is heated to a high temperature of 0 ° C. and becomes a liquid molten slag S having fluidity. The molten slag S continuously overflows from the molten slag outflow port 25a, and is cooled by dropping into a slag water cooling tank 47 filled with cooling water to become granulated slag. Is discharged. When the plasma melting furnace is stopped, in order to prevent the molten slag S in the melting furnace main body 25 from cooling and solidifying, the molten metal is drained from a tap hole 29 provided at the bottom level of the molten slag S. Then, the inside of the melting furnace main body 25 is emptied.

[0011]

In the plasma melting furnace described above, a carbon-based refractory (carbon brick, etc.) is used as a refractory in order to reduce the amount of burnout. In a plasma melting furnace using this carbon-based refractory, when air flows into the furnace, oxidative consumption of the refractory becomes severe. Therefore, it is necessary to operate the furnace in a reducing atmosphere. Further, even when the plasma melting furnace is shut down, it is necessary to keep the inside of the furnace in a reducing atmosphere without allowing air to flow into the furnace until the temperature of the refractory and the temperature in the furnace become 500 ° C. or less. Therefore, in the conventional plasma melting furnace, an inert gas I such as nitrogen gas is supplied into the furnace to operate the furnace in a reducing atmosphere. When the plasma melting furnace is shut down, the temperature of the refractory and the temperature in the furnace are reduced. After confirming that the temperature has dropped below 500 ° C,
The supply of the inert gas I is stopped, and forced air cooling by blowing cooling air or the ventilation system is stopped to allow natural cooling.

However, in the conventional plasma melting furnace, when the plasma melting furnace is shut down, an operator operates the thermocouple 32.
In addition, the refractory temperature and the furnace temperature must be monitored one by one with the thermometer 33, and there is a problem that workability and handleability are poor. Of course, in order to monitor the temperature of the refractory and the temperature in the furnace with the thermocouple 32, it is necessary to make a hole for installing the thermocouple 32 on the refractory when constructing the plasma melting furnace. There is also a problem. Further, in the conventional plasma melting furnace, when the plasma melting furnace is shut down, an operator manually stops inert gas I such as nitrogen gas supplied to the furnace, so that the refractory Even when the temperature and the furnace temperature are already 500 ° C. or less, an inert gas I such as nitrogen gas may be supplied into the furnace. as a result,
There is a problem that the use amount of the inert gas I such as nitrogen gas which is expensive increases, and the running cost rises.
Further, in the conventional plasma melting furnace, high-temperature heat is generated due to melting of the material to be melted W, but several tens of the heat is lost due to heat radiation. Further, in the conventional plasma melting furnace, since the refractory forming the melting furnace body 25 has reached several hundred degrees, it is possible to use this heat, but most of the heat is wasted. It is currently not used. In addition, in conventional plasma melting furnaces, even when the operation of the plasma melting furnace is stopped during maintenance work (for example, inspection work or maintenance work), the temperature of the refractory and the temperature inside the furnace are kept high. The operator may accidentally open the inspection port or manhole at this time, and this poses a problem of poor safety.

The present invention has been made in view of the above problems, and has as its object to automatically monitor the temperature of a refractory and the temperature in a furnace when the melting furnace is shut down and supply the temperature to the furnace. In addition to automatically stopping the inert gas such as nitrogen gas and supplying cooling air to the furnace according to the temperature of the refractory and the furnace, melting is performed so that maintenance work by workers can be performed safely. It is an object of the present invention to provide a method for shutting down a furnace and a device therefor.

[0014]

In order to achieve the above object, an invention according to claim 1 of the present invention is to supply an inert gas into a furnace to maintain the inside of the furnace in a reducing atmosphere, In the melting furnace where the material to be melted supplied is melted by electric energy, the indicator light is turned on by the electric power generated by the thermoelectric element that converts the heat energy embedded in the refractory of the melting furnace into electric energy and melts. In addition to indicating that the furnace is in operation, when the melting furnace is shut down, the indicator lamp is turned off when the temperature of the refractory and the temperature in the furnace have fallen to a temperature at which maintenance work of the melting furnace can be performed. The refractory temperature and the furnace temperature are monitored from the current value generated by the power generated by the element, and when the refractory temperature and the furnace temperature fall to about 500 ° C or less when the melting furnace is shut down, inert gas is introduced into the furnace. Automatically stop supply Rutotomoni, is characterized in that by introducing the cooling air into the furnace was set to be air-cooled.

According to a second aspect of the present invention, there is provided a thermoelectric element for converting thermal energy buried in a refractory of a melting furnace into electric energy, an indicator light which is turned on by the power generated by the thermoelectric element, and A control valve interposed in an inert gas supply pipe for supplying active gas, a cooling air supply pipe for supplying cooling air into the melting furnace, and a cooling air fan connected to the cooling air supply pipe. , A control valve and a controller for controlling the cooling air fan. The indicator light is turned on or off according to the amount of power generated by the thermoelectric element, and is controlled by the controller based on the current value generated by the power generated by the thermoelectric element. It is characterized in that the valve and the cooling air fan are controlled.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a melting apparatus for a melting furnace according to an embodiment of the present invention, which is installed in a plasma melting furnace of a DC arc discharge graphite electrode type operated in a reducing atmosphere. In FIG. Furnace body 2, melt supply port 3, melt slag outlet 4, graphite main electrode 5,
Is a graphite start electrode, 6 is a furnace bottom electrode, 7 is a tap hole, 8 is a hopper for the melt W, 9 is a supply device for the melt W, 10 is a furnace bottom cooling fan, 11 is a DC power supply, 12
Is an inert gas generator, 13 is an inert gas supply pipe, 1
4 is a combustion chamber, 15 is a melting furnace lowering device, 16 is a thermoelectric element, 17 is an indicator light, 18 is a control valve, 19 is a cooling air supply pipe, 20 is a cooling air fan, and 21 is a control valve 18. A controller 22 is a controller for the cooling air fan 20.

The melting furnace body 1 includes a steel plate casing (not shown) and a refractory 23 having excellent corrosion resistance and heat resistance.
(For example, a carbon-based refractory such as a carbon brick) and the like, each of which is formed of a peripheral wall 1a, a ceiling wall 1b, and a furnace bottom 1c, and has a circular cross-sectional shape.
Further, on the peripheral wall 1a of the melting furnace main body 1, a melted material supply port 2 for supplying a melted material W such as incineration residues and fly ash into the furnace is formed. A supply device 9 for the melt W, such as a screw feeder, is connected to the melt supply port 2 so that the melt W can be continuously and quantitatively supplied into the furnace. Further, a molten slag outlet 3 is formed on the peripheral wall 1a of the melting furnace main body 1 at a position facing the melt supply port 2 in the diameter direction. The molten slag outflow port 3 is connected to the molten slag S in the furnace and the high-temperature flue gas G.
And is connected to a slag treatment system such as a slag water-cooled layer (not shown) and an exhaust gas treatment system such as the combustion chamber 14 in communication with each other.

The melting furnace body 1 is provided with a graphite main electrode 4, a graphite start electrode 5, and a furnace bottom electrode 6 for generating a plasma arc in the furnace. That is, the graphite main electrode 4 is inserted and supported in the center of the ceiling wall 1b of the melting furnace main body 1 so as to be able to move up and down, and is moved up and down so as to keep a constant distance from the molten slag S. . The graphite main electrode 4 is connected to the cathode of the DC power supply 11. The graphite start electrode 5 is inserted and supported on the outer peripheral edge of the ceiling wall 1b of the melting furnace main body 1 so as to be movable forward and backward with an inclined posture. The ascent / descent operation is performed over a discharge action position protruding into the furnace in a state of being close to the tip of the graphite main electrode 4. This graphite start electrode 5
Connected to the anode of DC power supply 11. Further, the furnace bottom electrode 6 is provided on the furnace bottom 1c of the melting furnace body 1,
Connected to the anode of DC power supply 11.

The graphite main electrode 4 and the graphite start electrode 5
Are formed in a cylindrical shape, and an inert gas I such as nitrogen gas necessary for maintaining the inside of the furnace in a reducing atmosphere is supplied from an inert gas generator 12 through an inert gas supply pipe 13. The gas is supplied into the furnace through the hollow holes of the electrodes 4 and 5.

The plasma melting furnace lowering device 15 according to the embodiment of the present invention converts thermal energy buried in the refractory 23 of the plasma melting furnace (the refractory 23 of the melting furnace body 1) into electric energy. Thermoelectric element 16 and thermoelectric element 1
6, an indicator lamp 17 which is turned on by the generated power, and an inert gas supply pipe 1 for supplying an inert gas I such as nitrogen gas into the furnace.
3, a cooling air supply pipe 19 for supplying cooling air A into the furnace, a cooling air fan 20 connected to the cooling air supply pipe 19, and a control valve 18.
, A controller 22 for controlling the cooling air fan 20, and the like. The indicator lamp 17 is turned on or off according to the amount of power generated by the thermoelectric element 16 embedded in the refractory 23. At the same time, the controllers 21 and 22 control the control valve 1 based on the current value of the power generated by the thermoelectric element 16.
8 and the cooling air fan 20 are respectively controlled.

That is, the lowering device 15 turns on the indicator lamp 17 by the power generated by the thermoelectric element 16 embedded in the refractory 23 of the melting furnace main body 1 to indicate that the plasma melting furnace is operating, When the plasma melting furnace is shut down, the indicator lamp 17 is turned off when the temperature of the refractory and the temperature in the furnace decrease to a temperature at which maintenance work (inspection work, maintenance work, repair work, etc.) of the plasma melting furnace can be performed,
Also, the refractory temperature and the furnace temperature are automatically monitored from the current value generated by the power generated by the thermoelectric element 16, and the controller is controlled when the refractory temperature and the furnace temperature fall to about 500 ° C. or less when the plasma melting furnace is shut down. The control valve 18 is closed by 21 to automatically stop the supply of the inert gas I into the furnace.
2, the cooling air fan 20 is operated so that the cooling air A flows into the furnace.

As shown in FIGS. 2 and 3, for example, the thermoelectric element 16 is made of iron silicide (FeSi ₂ ) containing Mn, Al, C
P-type thermoelectric material 16 to which at least one of r is added
a and (Fe _0.9 Mn _0.1 Si ₂ molar ratio, etc.), also iron silicide (FeSi ₂₎ to Co, B, P, at least one added comprising N-type thermoelectric material 16b of Ni (Fe _{0. 95}
(Co _0.05 Si ₂ molar composition ratio, etc.) in a substantially U-shape. The thermoelectric element 16 has a joint portion 1 between a P-type thermoelectric material 16a and an N-type thermoelectric material 16b.
When 6c is heated and a temperature difference is applied between the joint 16c and both ends 16d of the thermoelectric element 16, an electromotive force is generated and current flows. Such a thermoelectric element 1
The magnitude of the electromotive force 6 is determined by the temperature difference between the junction 16c of the thermoelectric element 16 on the high-temperature side and the both ends 16d of the thermoelectric element 16 on the low-temperature side.

The thermoelectric element 16 is embedded and fixed in a refractory 23 (carbon brick) constituting the peripheral wall 1a and the ceiling wall 1b of the melting furnace main body 1 as shown in FIGS. Both end portions 16d on the sides are exposed to the outside of the refractory 23. The thermoelectric element 16 is embedded in the refractory 23 when forming the refractory 23 having a predetermined shape. And the refractory 23 in which the thermoelectric element 16 is embedded
Is set so that the joining portion 16c of the thermoelectric element 16 faces the inside of the furnace (the right side in FIG. 2), and both ends 16d of the thermoelectric element 16
Is fitted to the furnace wall of the plasma melting furnace so as to face the outside of the furnace (left side in FIG. 2). Therefore, in the thermoelectric element 16 buried in the refractory 23 of the plasma melting furnace, the effect of the heat of the refractory 23 and the joining portion 16c on the high-temperature portion side which is affected by the heat of the refractory 23 whose temperature has increased is very small. An electromotive force is generated due to a temperature difference between both ends 16d on the low-temperature side, which is not affected, and a current flows through the lead wire 24 connected to both ends 16d of the thermoelectric element 16.

FIG. 4 shows that the refractory 23 in which four types of thermoelectric elements 16 are embedded is fitted into the furnace wall of the plasma melting furnace, and the refractory 23 and the inside of the furnace are heated from room temperature to about 900 ° C. 3 is a graph showing the relationship between the output of the thermoelectric element 16 and the temperature of the refractory and the furnace. As is clear from this graph, the refractory temperature and the furnace temperature can be known from the magnitude of the output of the thermoelectric element 16 embedded in the refractory 23. Therefore, when the plasma melting furnace is operated or shut down, it is possible to monitor the refractory temperature and the furnace temperature at that time by examining the change in the current value due to the power generated by the thermoelectric element 16 embedded in the refractory 23. Becomes

The indicator lamp 17 is turned on during the operation of the plasma melting furnace to notify an operator that the plasma melting furnace is operating, and is turned off when the plasma melting furnace is shut down to turn off the refractory temperature and the furnace temperature. The operator is notified that the internal temperature has dropped to a temperature at which maintenance work (inspection work, maintenance work, repair work, etc.) can be performed. That is, the indicator light 1
Numeral 7 is connected to the thermoelectric element 16 via a lead wire 24, and is turned on by the power generated by the thermoelectric element 16 during operation of the plasma melting furnace. It is configured to turn off the light when the internal temperature decreases and the temperature becomes lower than the current value generated when the temperature reaches a temperature at which maintenance work can be performed. In addition, a conventionally known patrol light is used for the indicator light 17.

The control valve 18 is connected to the inert gas generator 1
Inert gas supply pipe 1 that connects 2 to the inside of the melting furnace body 1
3 and an inert gas I such as nitrogen gas is introduced into the furnace.
Or the inert gas I supplied to the furnace is stopped. The control valve 18 is an electric on-off valve.

The controller 21 of the control valve 18 is connected to the thermoelectric element 16 via a lead wire 24. When the plasma melting furnace is shut down, the refractory temperature and the furnace temperature are lower than a predetermined temperature (about 500). The control valve 18 is controlled so as to close when the temperature becomes equal to or lower than (° C.). In this controller 21, a current value or the like generated when the refractory temperature and the furnace temperature are about 500 ° C. is input in advance as a set value, and is compared with the detected value to determine when it is necessary. Control valve 18
Is to be closed. That is, the controller 21 automatically detects the refractory temperature and the furnace temperature from the current value generated by the power generated by the thermoelectric element 16, and the refractory temperature and the furnace temperature decrease when the plasma melting furnace is shut down. The control valve 18 is configured to be closed when the temperature becomes lower than the current value generated when the temperature becomes lower than about 500 ° C. Thereby, the supply of the inert gas I into the furnace is automatically stopped.

The cooling air supply pipe 19 is connected to the melting furnace main body 1 so as to communicate with the inside of the furnace, and allows the cooling air A to flow into the furnace when the plasma melting furnace is shut down. The cooling air supply pipe 19 has a cooling air fan 2 for forcibly sending cooling air A into the furnace.
0 is connected.

The controller 22 of the cooling air fan 20
Is connected to the thermoelectric element 16 through the lead wire 24, and when the temperature of the refractory and the temperature in the furnace become lower than a predetermined temperature (about 500 ° C. or lower) when the plasma melting furnace is shut down, cooling air is supplied. This controls the fan 20 to operate. In the controller 22, a current value or the like generated when the refractory temperature and the furnace temperature are 500 ° C. is input in advance as a set value. The cooling fan is operated. That is, the controller 22 automatically detects the refractory temperature and the furnace temperature from the current value generated by the power generated by the thermoelectric element 16, and the refractory temperature and the furnace temperature decrease when the plasma melting furnace is shut down. The cooling fan is operated when the temperature becomes lower than a current value generated when the temperature becomes lower than about 500 ° C. Thereby, the cooling air A is sent into the furnace, and the refractory and the inside of the furnace are forcibly air-cooled.

During the operation of the plasma melting furnace provided with the above-mentioned lowering device 15, the melted material such as incineration residue and fly ash supplied into the melting furnace body 1 by the supply device 9 is provided. W is heated to a temperature exceeding a melting point (1100 ° C. to 1250 ° C.) by thermal energy due to plasma arc discharge generated between the graphite main electrode 4 and the furnace bottom electrode 6, and is heated to a high temperature of 1300 ° C. to 1500 ° C. It becomes a liquid molten slag S. The molten slag S overflows and is discharged from the molten slag outlet 3 to the slag processing system sequentially. The high-temperature combustion exhaust gas G generated in the melting furnace body 1 is discharged from the molten slag outlet 3 to the exhaust gas treatment system. During operation of the plasma melting furnace, the indicator lamp 17 is turned on by the power generated by the thermoelectric element 16 embedded in the refractory 23,
Indicates that the plasma melting furnace is operating. This allows the operator to easily and reliably confirm that the plasma melting furnace is in operation, and does not erroneously operate the plasma melting furnace.

On the other hand, if the melting furnace is shut down (operation of the melting furnace is stopped) during maintenance work (inspection work, maintenance work, repair work, etc.) of the plasma melting furnace, the temperature of the refractory and the temperature in the furnace decrease sequentially. Go. At this time, in the lowering device 15, the refractory temperature and the furnace temperature are automatically detected from the current value generated by the thermoelectric element 16 embedded in the refractory 23, and the refractory temperature and the furnace temperature are detected. Temperature is about 500 ℃
When the current value becomes equal to or less than the current value generated at
1, the control valve 18 is automatically closed to stop the supply of the inert gas I into the furnace, and the cooling air fan 20 is operated by the controller 22 to flow the cooling air A into the furnace. Air cooling. As a result, the plasma melting furnace does not need to manually stop the inert gas I and supply the cooling air A, and is excellent in workability and handling. In addition, a costly inert gas I such as nitrogen gas is not unnecessarily supplied into the furnace, and the amount of the inert gas I used is reduced, so that the running cost can be reduced. Further, the time when the cooling air A is blown into the furnace becomes optimal, and the oxidative consumption of the carbon-based refractory 23 can be prevented.

When the temperature of the refractory and the temperature in the furnace decrease to a temperature at which maintenance work can be performed, the power generated by the thermoelectric element 16 embedded in the refractory 23 also decreases, and the indicator lamp 17
Is turned off, and the operator is notified that the temperature of the refractory and the temperature in the furnace have decreased to a temperature at which maintenance work can be performed.
Thereby, the operator can determine that the temperature of the plasma melting furnace has dropped to a temperature at which the maintenance work can be performed, and can provide a guide to the maintenance work. As a result, the worker can safely perform maintenance work without erroneously opening an inspection port, a manhole, or the like of the plasma melting furnace in which the refractory temperature and the furnace temperature are maintained at high temperatures.

In the above embodiment, the melting furnace is a plasma melting furnace, but the present invention can of course be applied to an arc melting furnace, an electric resistance melting furnace and the like.

In the above embodiment, iron silicide is used as the material of the thermoelectric element 16, but in other embodiments, iron silicide is used as the material of the thermoelectric element 16. Besides BiTe, Bi ₂ Te ₃ , Bi ₂ Sb ₈ Te ₁₅ , P
bTe, GeTe (Bi), AgSbTe ₂ , InAs
(P), Si-Ge, Si-Ge (GaP), CrSi
₂ , MnSi _1.73 , CoSi or the like may be used.

Further, in the above embodiment, the controller 21 for controlling the control valve 18 and the controller 22 for controlling the cooling air fan 20 are provided separately. In this case, the control valve 18 and the cooling air fan 20 may be controlled by one controller (not shown).

[0036]

As is apparent from the above description, according to the method of the present invention, the refractory temperature and the furnace temperature are automatically monitored from the current value generated by the thermoelectric element buried in the refractory, and the melting temperature is determined. Refractory temperature and furnace temperature are about 5 when the furnace is shut down.
When the temperature becomes lower than 00 ° C., the supply of the inert gas into the furnace is automatically stopped, and cooling air is caused to flow into the furnace to cool the furnace. As a result, there is no need for the worker to monitor the refractory temperature and the furnace temperature one by one when the melting furnace is shut down, or to manually stop the inert gas or supply the cooling air. And excellent handleability. In addition, a costly inert gas such as nitrogen gas is not unnecessarily supplied into the furnace, and the amount of the inert gas used is reduced, so that the running cost can be reduced. Furthermore, the time when the cooling air is blown into the furnace becomes optimal, and the oxidation and consumption of the carbon-based refractory can be prevented. Of course, the thermoelectric element is buried in the refractory in advance when molding the refractory, so there is no need to make a hole for installing the thermocouple in the refractory at the time of construction of the melting furnace like a thermocouple, which saves trouble. Will be. Further, according to the method of the present invention, the indicator light is turned on by the generated power of the thermoelectric element embedded in the refractory to indicate that the melting furnace is operating, and the refractory temperature and the temperature when the melting furnace is shut down. The indicator light is turned off when the temperature in the furnace falls to a temperature at which maintenance work of the melting furnace can be performed. As a result, the operator can easily and reliably determine that the melting furnace is in operation by checking the lighting of the indicator lamp, and does not say that the melting furnace is erroneously operated. In addition, the worker can confirm that the temperature of the melting furnace has dropped to a temperature at which maintenance work can be performed by confirming that the indicator lamp is turned off, and this can be used as a guide for maintenance work. The maintenance work can be performed safely without inadvertently opening the inspection port or manhole of the maintained melting furnace.

According to the apparatus of the present invention, the above-described method can be suitably performed. Of course, in the apparatus of the present invention, the heat energy of the melting furnace is converted into electric energy by the thermoelectric element, and the indicator light is turned on by the electric energy, so that the heat of the melting furnace is effectively used. In addition to this, it is not necessary to newly provide a power supply for turning on the indicator lamp.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a plasma melting furnace in which a method of the present invention is carried out, and which is provided with a lowering device.

FIG. 2 is a schematic enlarged sectional view showing a part of a furnace wall of the plasma melting furnace.

Fig. 3 Refractory with embedded thermoelectric element (carbon brick)
It is a perspective view of.

FIG. 4 is a graph showing a thermoelectric characteristic of a thermoelectric element and showing a relationship between a temperature and an output.

FIG. 5 is a schematic vertical sectional view of a conventional plasma melting furnace.

[Explanation of symbols]

13 is an inert gas supply pipe, 15 is a falling device, 16 is a thermoelectric element, 17 is an indicator light, 18 is a control valve, 19 is a cooling air supply pipe, 20 is a cooling air fan, and 21 is a control valve. , 22 is a controller of a cooling air fan, 23 is a refractory, A is cooling air, I is an inert gas, and W is a material to be melted.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F27D 1/00 F27D 19/00 A 4K063 11/08 21/00 G 19/00 21/04 21/00 G01K 1/14 H 21/04 7/02 A G01K 1/14 B09B 3/00 ZAB 7/02 303L (72) Inventor Masaaki Kurata 2-33 Kingara-cho, Amagasaki-shi, Hyogo F-term in Takuma Co., Ltd. (Ref.)

Claims (2)

[Claims] In a melting furnace, an inert gas is supplied into the furnace to maintain the inside of the furnace in a reducing atmosphere, and the melt supplied into the furnace is melted by electric energy. The indicator light is turned on by the generated power of the thermoelectric element that converts the thermal energy buried in the refractory of the furnace into electric energy to indicate that the melting furnace is operating,
When the melting furnace is shut down, the indicator lamp is turned off when the temperature of the refractory and the temperature in the furnace are reduced to a temperature at which maintenance work of the melting furnace can be performed. Monitor the furnace temperature and automatically stop the supply of inert gas into the furnace when the refractory temperature and furnace temperature fall below about 500 ° C when the melting furnace is shut down. A method for shutting down a melting furnace, wherein air is cooled by flowing cooling air. 2. A thermoelectric element for converting thermal energy buried in a refractory of a melting furnace into electric energy, an indicator light turned on by electric power generated by the thermoelectric element, and an inert gas for supplying an inert gas into the furnace. A control valve interposed in the supply pipe, a cooling air supply pipe for supplying cooling air into the melting furnace,
A cooling air fan connected to the cooling air supply pipe,
A control valve and a controller for controlling the cooling air fan.The indicator light is turned on or off according to the amount of power generated by the thermoelectric element, and the control valve is controlled by the controller based on a current value generated by the power generated by the thermoelectric element. And a cooling air fan for controlling a cooling furnace.