JP2011202985A - Melting furnace and method for operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melting furnace which can smoothly discharge molten objects to be treated in it from its discharge port.SOLUTION: A glass melting furnace 1 includes its body 2, into which high-level radioactive liquid waste containing elements of platinum metals is poured, main electrodes 5 for charging and melting the high-level radioactive liquid waste poured into the body 2 and materials for glass and a flow-down nozzle 8, placed at the bottom of the body 2 to discharge the molten glass melted by the main electrodes 5 into a canister C. A first storage tank 17 for storing the molten glass is set up, prior toguiding the molten glass discharged from the flow-down nozzle 8 to the canister C. The first storage tank 17 has a capacity larger than that of the canister C.

Description

  The present invention relates to a melting furnace for melting an object to be treated such as a high-level radioactive waste or an industrial waste containing a metal element, and an operating method thereof.

  As a melting furnace for melting processed objects containing metal elements, it is discharged from glass melting furnaces used for solidifying high-level radioactive waste (processed objects) and incinerators such as industrial waste. 2. Description of the Related Art An ash melting furnace used for melting and solidifying ash (a material to be processed) is known.

As the glass melting furnace, for example, the one shown in FIG.
The high-level radioactive liquid waste generated after the reprocessing of spent nuclear fuel has extremely high radiation and decay heat, and is difficult to dispose of as a liquid. Therefore, it is sent into the glass melting furnace 101 and borosilicate glass. While being melted together with a glass raw material such as a glass, it is packed in a corrosion-resistant stainless steel container called canister C (storage container). Then, after being stabilized as a glass solidified body in the canister C, it is naturally cooled for a certain period and then disposed deep in the ground.

  A glass melting furnace 101 used for such vitrification includes a furnace body 102 made of refractory bricks. A bottom electrode 104 is provided at the bottom of the furnace main body 102, and a flow-down hole 103 for allowing the molten glass to flow down and discharge is formed in the bottom electrode 104. An auxiliary electrode 106 is provided above the bottom electrode 104. A pair of main electrodes 105 are provided on the side wall of the furnace body 102.

After the high-level radioactive liquid waste and the glass raw material are introduced from the inlet 107 provided on the ceiling wall of the furnace main body 102, heat from the molten glass heated to a high temperature is caused by flowing a direct current between the main electrodes 105, 105. In response, the high-level radioactive liquid waste and the glass raw material are sufficiently melted together. Further, when the amount of molten glass produced in the furnace reaches a predetermined amount, a DC current is passed through the auxiliary electrode 106 and the bottom electrode 104 located under the molten glass to melt the glass at the bottom. Then, the flow nozzle 108 extending downward from the flow hole 103 is heated by the high-frequency heating coil 109 disposed around the flow nozzle 103, and the molten glass in the furnace is flowed down into the canister C located therebelow. When a predetermined amount of molten glass is supplied into the canister C, power supply to the bottom electrode 104 and the auxiliary electrode 106 is stopped, the viscosity of the glass around the flow hole 103 is increased, and discharge of the molten glass is stopped. The molten glass accommodated in the canister C is stored as a vitrified body. In this way, the molten glass is discharged batchwise for each canister C.
On the other hand, the gas generated in the melting furnace 101 is exhausted from the exhaust port 110 as an off-gas, and the radioactive substance is completely collected and removed by a HEPA filter or the like (not shown) and then released into the atmosphere. It has become.

By the way, it is known that white metal elements such as ruthenium (Ru), palladium (Pd), and rhodium (Rh) are mixed in the high-level radioactive waste liquid supplied to the glass melting furnace 101. White metal elements are used in the production of nuclear reactor fuel rods due to their high temperature resistance and excellent spreadability. Therefore, white metal elements are mixed in the highly radioactive liquid waste obtained by cutting and melting spent fuel rods. ing.
Since the white metal element is difficult to be dispersed in the molten glass and has a specific gravity larger than that of the molten glass, it has the property of being easily deposited and deposited as metal sludge at the bottom of the glass melting furnace 101.

If such a phenomenon is left as it is, the white metal element has high electrical conductivity, and even its oxide, RuO ₂ , has high electrical conductivity. However, electrical short circuit occurs in the vicinity of the auxiliary electrode 106 and the bottom electrode 104, and Joule heat necessary for melting is not generated. As a result, it is conceivable that the glass melting time may become extremely long, or the glass cannot be melted at all and cannot be discharged from the flow down hole 103.

  Patent Document 1 proposes a melting furnace resistance measuring instrument for measuring the amount of metal sludge deposited as described above.

JP 2002-71891 A

However, even if the amount of deposited metal sludge can be accurately measured as in Patent Document 1, the following problem cannot be solved.
That is, since the glass melting furnace 101 discharges molten glass in a batch manner for each canister C, the molten glass is only discharged in an amount accommodated by one canister C. Therefore, all the metal sludge deposited on the bottom of the furnace is not discharged but remains deposited on the bottom of the furnace. In this case, it cannot be melted at the bottom of the furnace in the next discharging step, and a smooth molten glass discharging operation cannot be performed.

  In addition, ash melting furnaces that melt ash discharged from incinerators that incinerate industrial waste also contain metal elements with high specific gravity in industrial waste, so molten slag is removed from the discharge part at the bottom of the furnace. Similar problems occur when discharging.

  This invention is made in view of such a situation, Comprising: It aims at providing the melting furnace which can discharge | emit the molten material in a melting furnace smoothly from a discharge part, and its operating method. To do.

In order to solve the above problems, the melting furnace and the operation method thereof according to the present invention employ the following means.
That is, the melting furnace according to the present invention includes a processing container into which a processing object containing a metal element is charged, and an electric heating means for energizing and melting the processing object charged in the processing container. A melting furnace provided with a discharge unit provided at the bottom of the processing container and discharging the processed material melted by the heating means into a storage container in which the processed material is solidified and stored; Before the object to be processed discharged from the discharge unit is guided to the storage container, the molten object to be processed is stored, and a first storage tank having a larger volume than the storage container is provided. It is characterized by being.

When an object to be processed containing a metal element is melted in the processing vessel, a metal sludge such as a metal element having a large specific gravity or an oxide thereof is settled earlier than other melts. Then, metal sludge accumulates in the bottom part in which the discharge part was provided. When metal sludge accumulates in the vicinity of the discharge part, the metal element has high electrical conductivity, so even if it is energized from the electric heating means, large Joule heat is not generated, so melting in the vicinity of the discharge part will be hindered, There is a possibility that the workpiece cannot be discharged from the discharge section.
In the present invention, before the object to be processed discharged from the discharge unit is guided to the storage container, the molten object to be processed is stored and a first storage tank having a larger volume than the storage container is provided. . Thereby, it is possible to discharge more processed material than the molten processed material supplied to the storage container from the discharge unit, and it is possible to discharge the metal sludge collected near the discharge unit without staying. Thereby, since it can prevent as much as possible that metal sludge accumulates in the discharge part vicinity, the energization heating of the discharge part vicinity is not inhibited, and a molten to-be-processed object can be discharged | emitted smoothly.
Examples of the metal element include white metal elements such as ruthenium (Ru), palladium (Pd), and rhodium (Rh), and examples of the oxide include RuO ₂ .
As a melting furnace, typically, ash discharged from a glass melting furnace used when vitrifying high-level radioactive waste (processed object) or an incinerator for incineration of industrial waste (processed object) Ash melting furnace used when melted and solidified).

  Furthermore, in the melting furnace of the present invention, the first storage tank can store an amount of the object to be processed corresponding to the volume of the plurality of storage containers, and the first storage tank is stored. Distributing means for distributing the object to be processed is provided.

  In the first storage tank, it is possible to store a molten object corresponding to the volume of a plurality of storage containers. Then, the molten object to be processed is distributed to each storage container by distribution means for distributing the stored molten object to be processed to a plurality of storage containers. Thereby, compared with the case where the quantity equivalent to one preservation | save container is discharged | emitted by a batch type, the frequency | count of discharging a molten to-be-processed object from a discharge part reduces, and an operation | work becomes simple.

  Furthermore, the melting furnace of the present invention is characterized in that an auxiliary heating means that is inserted into the processing vessel and can be positioned below the electric heating means and above the discharge portion is provided.

When a large number of objects to be processed are discharged from the discharge unit, the amount of objects to be processed remaining in the processing container decreases, and the upper surface of the object to be processed may be located below the installation position of the electric heating means. In this case, since heating by the electric heating means cannot be performed, an auxiliary heating means that can be positioned below the electric heating means and above the discharge portion is inserted into the processing container. Thereby, even if the upper surface of the workpiece is positioned below the electric heating means, the workpiece can be melted.
As the auxiliary heating means, for example, an electrode for supplying electric power or an electric heater for self-heating is preferably used.

  Furthermore, in the melting furnace of the present invention, a return path is provided between the first storage tank and the processing container to return the object to be processed melted in the first storage tank to the processing container. It is characterized by.

  The molten material to be processed stored in the first storage tank was returned to the processing container and circulated. As a result, the molten material to be processed is supplied into the processing container and the storage amount of the molten material to be processed in the processing container is ensured, so that heating by electric heating means is possible, and the processed material in the processing container is melted. The state can be maintained. In addition, since the molten state in the processing container can be maintained in this way, a large amount of molten object can be discharged from the discharge part, and the metal sludge deposited near the discharge part can be discharged together with the molten object. it can.

  Furthermore, in the melting furnace of the present invention, the first storage tank can store an amount of the processing object corresponding to the processing object that can be held in the processing container.

  By using the first storage tank in which an amount of the object to be processed that can be held in the processing container can be stored, almost all of the molten object to be processed in the processing container is discharged from the discharge unit. Can do. Thereby, almost the whole amount of metal sludge such as metal elements and oxides deposited near the discharge part can be discharged. Moreover, the metal sludge deposited on the bottom can be washed away with the molten glass at the top by discharging the entire amount of the molten material.

  Furthermore, in the melting furnace of the present invention, a second storage tank in which the melted workpiece is stored is provided in the middle of the return path.

  In the middle of the return path, a second storage tank is provided to temporarily store the molten material. Thereby, the quantity of the melted material to be returned to the processing container can be adjusted, and the molten state in the processing container can be appropriately controlled.

  Furthermore, the melting furnace of the present invention is characterized in that a melting point depressant feeding means for feeding a melting point depressant that lowers the melting point of the melted workpiece is provided.

When the molten object to be processed is circulated, components that raise the melting point may be concentrated and the melting point of the object to be processed may increase. In view of this, a melting point depressant feeding means for curing the melting point of the object to be melted is provided. Thereby, melting | fusing point of a to-be-processed object does not rise, but the malfunction that melting | fusing of a to-be-processed object becomes inadequate can be avoided.
The position at which the melting point depressant introduction means is provided may be provided in the processing container or in the second storage tank.
As the melting point depressant, for example, fluorite (calcium fluoride) or borax is preferably used.

  The operation method of the melting furnace of the present invention includes a processing container into which a processing object containing a metal element is charged, and electric heating for energizing and melting the processing object charged into the processing container. And a discharge section provided at the bottom of the processing container and discharging the processed object melted by the heating means into a storage container in which the processed object is solidified and stored In the operation method, the amount of the object to be processed discharged from the discharge unit is larger than the volume of the storage container with respect to the first storage tank that stores the object to be processed before being guided to the storage container. The object to be treated is discharged.

  An amount of the processing object larger than the volume of the storage container is discharged to the first storage tank that stores the processing object before the processing object discharged from the discharge unit is guided to the storage container. Thereby, it is possible to discharge more processed material than the molten processed material supplied to the storage container from the discharge unit, and it is possible to discharge the metal sludge collected near the discharge unit without staying. Thereby, since it can prevent as much as possible that metal sludge accumulates in the discharge part vicinity, the energization heating of the discharge part vicinity is not inhibited, and a molten to-be-processed object can be discharged | emitted smoothly.

The present invention has the following effects.
Since it was decided to discharge a larger amount of the object to be processed than the volume of the storage container, more objects to be processed than the molten object to be supplied to the storage container can be discharged from the discharge part. Collected metal sludge can be discharged without staying. Thereby, since it can prevent as much as possible that metal sludge accumulates in the discharge part vicinity, the energization heating of the discharge part vicinity is not inhibited, and a molten to-be-processed object can be discharged | emitted smoothly.

1 is a longitudinal sectional view showing a glass melting furnace according to a first embodiment of the present invention. It is the longitudinal cross-sectional view which showed the glass fusing furnace concerning 2nd Embodiment of this invention. It is the longitudinal cross-sectional view which showed the conventional glass melting furnace.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a glass melting furnace 1 used when vitrifying a high-level radioactive liquid waste (object to be processed) D generated after reprocessing of spent nuclear fuel.
The glass melting furnace 1 includes a furnace body (processing vessel) 2 made of refractory bricks. The furnace body 2 is formed with a processing space S for processing the high-level radioactive waste liquid D together with the glass raw material (object to be processed) G. The upper area of the processing space S is an upper area having a certain cross-sectional shape (for example, a quadrangle), and the lower area of the processing space S is a lower area of a cone shape (for example, a quadrangular pyramid) whose cross-sectional area gradually decreases downward. It has become. On the side wall of the furnace main body 2, main electrodes (electric heating means) 5 and 5 are provided at a position corresponding to the upper region of the processing space S so as to face each other. By flowing a direct current between the main electrodes 5 and 5, the high-level radioactive waste liquid that is the object to be processed and the glass raw material are melted to obtain molten glass. A cooling water W for cooling the electrodes is circulated through the main electrodes 5 and 5.

From the upper part of the furnace body 2, a high-level radioactive waste liquid D and a glass raw material G such as borosilicate glass are introduced. The high-level radioactive liquid waste D and the glass raw material G may be charged continuously or batchwise.
The upper wall of the furnace body 2 is provided with an exhaust port 10 for exhausting gas generated in the processing space S as off-gas. The off-gas exhausted from the exhaust port 10 is discharged into the atmosphere after the radioactive material is completely collected and removed by a HEPA filter or the like and rendered harmless.
Further, an indirect heating device 12 that indirectly heats the inside of the processing space S is provided on the upper wall of the furnace body 2. The indirect heating device 12 is an infrared heater, for example, and supplements heat radiation from the upper surface of the molten glass.

A bottom electrode 4 is provided on the bottom of the furnace body 2 at a position corresponding to the lower end of the processing space S. The bottom electrode 4 is formed with a flow-down hole (discharge portion) 3 for flowing the molten glass down and discharging it. A direct current is passed through the bottom electrode 4 and is energized in accordance with the timing of discharging the molten glass downward.
On the side wall on the bottom side of the furnace body 2, auxiliary electrodes 6 and 6 are provided above the bottom electrode 4 and at a position corresponding to the lower region of the processing space S. By flowing a direct current between these auxiliary electrodes 6 and 6, the highly viscous molten glass located at the bottom of the processing space S is heated and fluidized. Cooling water W for cooling the electrodes is circulated through the auxiliary electrodes 6 and 6.

  Furthermore, an insertion auxiliary electrode (auxiliary heating means) 14 that can be moved up and down to the same height as the auxiliary electrodes 6 and 6 is provided. By flowing a direct current between the insertion auxiliary electrode 14 and the auxiliary electrodes 6 and 6, the highly viscous molten glass located at the bottom is heated and fluidized. The insertion auxiliary electrode 14 is advantageously used when it is difficult to melt the object to be processed only by the auxiliary electrodes 6 and 6. The insertion auxiliary electrode 14 is inserted vertically downward from above the furnace body 2.

  A falling nozzle 8 is connected below the bottom electrode 4. The falling nozzle 8 is provided with a high-frequency heating coil 9. The high frequency heating coil 9 is energized in accordance with the timing of discharging the molten glass downward.

A first storage tank 17 that stores the molten glass before the molten glass is guided to the canister (storage container) C is provided below the flow-down nozzle 8. The volume of the 1st storage tank 17 shall be larger than the volume for one canister C, for example, is the volume for four canisters C. The volume of the first storage tank 17 is preferably equal to or larger than the volume corresponding to the region S1 in the processing space S where the deposition of white metal particles (metal sludge) derived from the white metal element is remarkable.
The first storage tank 17 is provided with distribution means 19 for extracting the molten glass stored inside and distributing the molten glass to each canister C.

Next, an operation method of the glass melting furnace 1 having the above configuration will be described.
First, a high level radioactive waste liquid D and a glass raw material G are introduced from the upper part of the furnace body 2, and then a direct current is passed between the main electrodes 5 and 5. As a result, the high-level radioactive liquid waste and the glass raw material are sufficiently melted together by being heated to a high temperature by Joule heat and receiving heat from the molten glass. At this time, the white metal element present in the high-level radioactive waste liquid D becomes white metal particles, settles downward, and deposits below the processing space S. In this embodiment, the area S1 in which a large amount of white metal particles is deposited as described above has a volume corresponding to, for example, four canisters C. The total amount of molten glass in the processing space S is, for example, ten canisters C.

  The molten glass produced in the furnace is discharged by a batch method. In the discharging step, a high-viscosity molten glass located at the bottom of the processing space S is heated and fluidized by passing a direct current through the main electrodes 5 and 5 and the auxiliary electrodes 6 and 6 or the bottom electrode 4. Then, by supplying power to the high-frequency heating coil 9 of the downflow nozzle 8 located below the downflow hole 3, the first storage located below the molten glass in the furnace from the downflow hole 3 via the downflow nozzle 8. It flows down into the tank 17. An amount of molten glass corresponding to the area S <b> 1 in the processing space S in which the accumulation of white metal particles is remarkable is caused to flow into the first storage tank 17. When a predetermined amount of molten glass is supplied to the first storage tank 17, power supply to the bottom electrode 4 and the auxiliary electrode 6 is stopped, the viscosity of the glass around the flow-down hole 3 is increased, and discharge of the molten glass is stopped. In this way, most of the white metal particles deposited below the processing space S are discharged from the furnace.

  The molten glass stored in the first storage tank 17 is distributed to each canister C by the distribution means 19. The molten glass accommodated in the canister C is stored as a vitrified body.

When the molten glass is discharged from the processing space S to the first storage tank 17 and the liquid level of the molten glass in the processing space S becomes lower than the height position of the main electrode 5, heating by the main electrode 5 is performed. Since it cannot do, the molten glass located below is heated using the insertion auxiliary electrode 14.
In addition, when the melting in the region S1 in the processing space S where the accumulation of white metal particles is remarkable does not proceed, the insertion auxiliary electrode 14 may be used to increase the heating amount.

As described above, according to the present embodiment, the following operational effects are obtained.
Before the molten glass discharged from the flow-down hole 3 is guided to the canister C, the molten glass is stored and the first storage tank 17 having a larger volume than the canister C is provided. Thereby, more molten glass than the molten glass supplied to the canister C can be discharged | emitted from the process space S, and the white metal particle which gathers in the flowing-down nozzle 8 vicinity can be discharged | emitted, without staying. As a result, it is possible to prevent white metal particles from being deposited in the vicinity of the flow-down nozzle 8 as much as possible, so that energization heating in the vicinity of the flow-down nozzle 8 is not hindered.

  The molten glass is distributed to each canister C by the distribution means 19 that distributes the molten glass stored in the first storage tank 17 to the plurality of canisters C. Thereby, compared with the case where the quantity equivalent to one canister C is discharged | emitted from the falling nozzle 8 by a batch type, the frequency | count of discharging | emitting molten glass from the flowing nozzle 8 decreases, and an operation | work becomes simple.

When a large amount of molten glass is discharged from the processing space S, the molten glass left in the processing space S decreases, and the liquid level of the molten glass may be located below the installation position of the main electrode 5. In this case, since the heating by the main electrode 5 cannot be performed, the insertion auxiliary electrode 14 that can be positioned below the main electrode 5 and above the flow-down nozzle 8 is inserted into the processing space S. Thereby, even if the liquid level of a molten glass will be located under the main electrode 5, a molten glass can be heated and fluidized.
As the insertion auxiliary electrode 14, for example, an electrode for supplying electric power or an electric heater for self-heating is preferably used.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
Unlike the first embodiment, the present embodiment is configured to circulate molten glass. Therefore, it differs from the first embodiment in that the configuration of the first storage tank is different and the second storage tank 20 is provided. However, since the structure with respect to the furnace main body 2 and its attachment is common, those description is attached | subjected and the description is abbreviate | omitted.

As FIG. 2 shows, the 1st storage tank 18 arrange | positioned under the flow-down nozzle 8 has a larger volume than the 1st storage tank 17 of 1st Embodiment. Preferably, the first storage tank 18 of the present embodiment has a volume that can store the molten glass together with the second storage tank 20 described later when the entire amount of the molten glass stored in the processing space S is discharged. (For example, if the total amount of molten glass accommodated in the processing space S is the volume of 10 canisters C, the volume is equal to or more than 10).
The first storage tank 18 is provided with a stirrer 21 and a heater 23. Thereby, the molten glass in the 1st storage tank 18 is cooled and it is not solidified. The first storage tank 18 is provided with distribution means 19, and the molten glass in the first storage tank 18 is supplied to each canister C by the distribution means 19.

A second storage tank 20 is provided above the first storage tank 18 and above the furnace body 2. The second storage tank 20 is provided with a stirrer 25 and a heater 27. Thereby, the molten glass in the 2nd storage tank 20 is cooled and it is not solidified. In addition, an arrow B indicates that by stirring the molten glass with the stirrer 25, the region A in which the white metal particles are circulated and concentrated is moved upward and becomes uniform.
The second storage tank 20 is provided with a melting point depressant feeding means 29 for feeding a melting point depressant that lowers the melting point of the molten glass. This is because a component that raises the melting point by circulating the molten glass (for example, white metal particles) may be concentrated to increase the melting point of the molten glass. As the melting point depressant, for example, fluorite (calcium fluoride) or borax is preferably used.

The second storage tank 20 and the first storage tank 17 are connected by a circulation pipe (return path) 30. By depressurizing the upper space of the second storage tank 20 by a decompression pump (not shown), the molten glass in the first storage tank 17 is guided to the second storage tank 20 through the circulation pipe 30.
The second storage tank 20 and the processing space S of the furnace body 2 are connected by a retransmission pipe (return path) 32. By arranging the second storage tank 20 at a position higher than the processing space S and utilizing the head difference, the molten glass in the second storage tank 20 is guided to the processing space S through the retransmission pipe 32. It has become.

Next, an operation method of the glass melting furnace 1 having the above configuration will be described.
First, a high level radioactive waste liquid D and a glass raw material G are introduced from the upper part of the furnace body 2, and then a direct current is passed between the main electrodes 5 and 5. As a result, the high-level radioactive liquid waste and the glass raw material are sufficiently melted together by being heated to a high temperature by Joule heat and receiving heat from the molten glass.

  The molten glass produced in the furnace is discharged by a batch method. In the discharging step, a direct current is passed through the auxiliary electrodes 6 and 6 and the bottom electrode 4 to melt the glass at the bottom of the processing space S. Then, by supplying power to the high-frequency heating coil 9 of the downflow nozzle 8 located below the downflow hole 3, the first storage located below the molten glass in the furnace from the downflow hole 3 via the downflow nozzle 8. It flows down into the tank 18. The entire amount of molten glass in the processing space S is caused to flow down into the first storage tank 18. Thereafter, power supply to the bottom electrode 4 and the auxiliary electrode 6 is stopped. In this way, the entire amount of molten glass in the processing space S is discharged from the furnace.

A portion of the molten glass stored in the first storage tank 18 is distributed to each canister C by the distribution means 19. The molten glass accommodated in the canister C is stored as a vitrified body.
On the other hand, the molten glass stored in the first storage tank 18 is guided to the second storage tank 20 through the circulation pipe 30. The molten glass guided to the second storage tank 20 is supplied with the melting point depressant from the melting point depressant feeding means 29 to lower the melting point, and then returned to the processing space S through the retransmission pipe 32. . In this way, a part of the molten glass discharged from the processing space S to the first storage tank 18 is guided to the canister C, but the remaining amount is returned to the processing space S via the second storage tank 20. It is circulated to.

As described above, according to the present embodiment, the following operational effects are obtained.
Since the entire amount of the molten glass in the processing space S is discharged, almost the entire amount of the white metal particles deposited in the vicinity of the flow nozzle 8 can be discharged. Further, by discharging the entire amount of the molten glass, the white metal particles deposited on the bottom can be washed away with the molten glass on the top.
Since the molten glass is circulated, the molten glass is supplied to the processing space S and the liquid surface position of the molten glass in the processing space S is ensured, so that heating by the main electrode 5 is possible, and the molten glass is melted. Can be suitably maintained.

In the present embodiment, the second storage tank 20 is provided and the molten glass is circulated. However, the present invention is not limited to this, and the second storage tank 20 is omitted and the first storage tank 18 is provided. The molten glass may be returned directly to the processing space S. In this case, the molten glass is drawn from the first storage tank 18 by depressurizing the upper space of the processing space S.
Although the melting point depressant introduction means 29 is provided in the second storage tank 20, the present invention is not limited to this, and the melting point depressant may be introduced into the processing space S.

  In the first embodiment and the second embodiment described above, the glass melting furnace used when vitrifying the high-level radioactive waste has been described. However, the present invention is not limited to this, and the metal element The present invention can be applied to a melting furnace that melts an object to be processed, for example, an ash melting furnace that is used when melting and solidifying ash discharged from an incinerator.

1 Glass melting furnace (melting furnace)
2 Furnace body (processing vessel)
3 Downhole (discharge section)
5 Main electrode (electric heating means)
14 Insertion auxiliary electrode (auxiliary heating means)
17 1st storage tank 18 1st storage tank 20 2nd storage tank 30 Circulation piping (return path)
32 Retransmission piping (return route)
C canister (storage container)
D High-level radioactive waste liquid (object to be treated)
G Glass raw material (object to be processed)

Claims (8)

A processing container into which an object to be processed containing a metal element is charged;
Electric heating means for energizing and melting the object to be processed put in the processing container;
In a melting furnace provided with a discharge unit provided at the bottom of the processing container and discharging the processed material melted by the heating means to a storage container in which the processed material is solidified and stored,
Before the object to be processed discharged from the discharge unit is guided to the storage container, the molten object to be processed is stored, and a first storage tank having a larger volume than the storage container is provided. A melting furnace.   The first storage tank can store an amount of the object to be processed corresponding to the volume of the plurality of storage containers, and the first storage tank distributes the stored object to be processed. The melting furnace according to claim 1, comprising:   The melting furnace according to claim 1, further comprising auxiliary heating means that is inserted into the processing vessel and can be positioned below the electric heating means and above the discharge portion.   The return path for returning the molten object to be processed in the first storage tank to the processing container is provided between the first storage tank and the processing container. The melting furnace according to 1.   The melting furnace according to claim 4, wherein the first storage tank is capable of storing an amount of the processing object corresponding to the processing object that can be held in the processing container.   The melting furnace according to claim 4 or 5, wherein a second storage tank in which the melted object to be processed is stored is provided at an intermediate position of the return path.   The melting furnace according to claim 6, further comprising melting point depressant feeding means for feeding a melting point depressant that lowers the melting point of the melted workpiece. A processing container into which an object to be processed containing a metal element is charged;
Electric heating means for energizing and melting the object to be processed put in the processing container;
An operation of a melting furnace provided with a discharge unit provided at the bottom of the processing container and discharging the processed material melted by the heating means to a storage container in which the processed material is solidified and stored In the method
With respect to the first storage tank for storing the object to be processed before the object to be processed discharged from the discharge unit is guided to the storage container, an amount of the object to be processed is larger than the volume of the storage container. A method of operating a melting furnace characterized by discharging.

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