JP2001228294A - Waste melting method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste melting method and device capable of suppressing foaming in draining out melt after separating waste in two layers of metal and slag and melting and stably and surely separating into metal layer and slag layer when solidifying the drained waste melt. SOLUTION: Foaming in draining the melt is suppressed by controlling the contents of carbon, nitrogen and oxygen in the melt separated in two layers of metal 10a and slag 10b and then drained, or reforming the slag layer in the melt, promoting degassing from the metal layer 10a in the melt and reducing carbon, nitrogen and oxygen quantities remaining in the metal layer 10a during draining.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment for general waste containing various inorganic substances, metals and organic substances, sewage sludge, municipal waste and incinerated ash thereof, and low-level nuclear radioactive waste. The present invention also relates to a waste melting method and a waste melting method in which waste is separated and melted into two layers, a metal layer and a slag layer.

[0002]

2. Description of the Related Art Conventionally, in a waste melting apparatus, after separating and melting waste into two layers, a metal layer and a slag layer, these melts are appropriately discharged from a tap hole, accommodated in a receiver and solidified. This reduces the volume of waste and discards it.

[0003]

However, since the melt was separated and melted into two layers, that is, a metal layer and a slag layer, these melts were directly poured out of the melt, so that the carbon mainly remaining in the melt, especially in the slag layer, was reduced. , Oxygen mainly remaining in the metal layer,
It reacts by the flow stirring of the melt at the time of tapping, causing bubbling in the melt, and the nitrogen dissolved mainly in the metal layer.The nitrogen decreases with the decrease in the nitrogen solubility of the metal when the metal layer solidifies. So-called forming, which occurs as a gas, may occur, causing slag and metal to pop out of the receiver and spill out of the receiver. Further, when solidified in the receiver, the generated bubbles may remain as voids in the solidified material as it is, and the volume reduction rate of the solidified material is reduced. further,
In the melting furnace, the metal layer and the slag layer, which were separated and melted into two layers, when this forming occurs at the time of tapping,
It is also difficult to solidify the two layers in a separated state.

[0004] By the way, miscellaneous solid waste generated in nuclear facilities is going to be melted, reduced in volume and discarded. Therefore, low-level radioactive waste is treated, but in this case, as described above, when the waste is melted and hot water is formed, forming occurs, and the molten material overflows out of the receiver. Then, peripheral equipment will be contaminated by low-level radioactive waste. Also, when forming occurs and the melt solidifies,
If voids and the like remain inside, there is no significance in performing melting treatment for the purpose of volume reduction.

[0005] In the case where such a low-level radioactive substance is melted, it is necessary to control the radioactive nuclides Co and Cs in the waste. These, Co, C
When s is separated and melted into two layers, Co mainly forms a metal layer,
It has been confirmed that Cs mainly transfers to the slag layer.
In addition, the management of these radioactive nuclides of Co and Cs can be managed by X-rays or the like. However, unless the solidified waste is separated into two layers, a metal layer and a slag layer, by forming. At the time of management using X-rays or the like, due to the background of Co having high diffraction intensity, it becomes difficult to read the diffraction line of Cs having low diffraction intensity, and the management becomes difficult. Therefore, there is a strong demand for a waste melting method and a waste melting method capable of reliably solidifying a waste melt in two layers without forming.

[0006] That is, the present invention has been made to solve the above-mentioned problems, and the present invention suppresses forming when a waste is separated and melted into two layers, a metal layer and a slag layer, and when the melt is discharged from a molten metal. It is an object of the present invention to provide a waste melting method and a waste melting method. Another object of the present invention is to provide a waste melting method and apparatus capable of stably and reliably separating a metal melt and a slag layer when a discharged melt is solidified. .

[0007]

According to a first aspect of the present invention, there is provided a waste melting method comprising a waste inlet, an exhaust gas outlet, a hot water outlet, and a plasma torch. Waste melting method in a plasma melting furnace, wherein the waste is separated into two layers, a metal layer and a slag layer, using a mixed gas of an inert gas and a reducing gas as a plasma gas of the plasma torch. Then, the molten material separated and melted into the two layers from the tap hole is poured out and filled in a receiver. According to this configuration, since the reducing gas in the plasma gas reacts with oxygen in the furnace and becomes carbon monoxide or carbon dioxide gas and is discharged out of the furnace, the mixing of oxygen into the metal layer immediately below the plasma can be suppressed. Therefore, it is possible to suppress the reaction between oxygen and carbon due to the flow agitation of the melt at the time of tapping, thereby suppressing forming. It is also possible to reduce the concentration of NO _x.

According to a second aspect of the present invention, there is provided a waste melting apparatus comprising a waste inlet, an exhaust gas outlet, a tap, a plasma torch, and a melting furnace. Has an inert gas introduction line and a reducing gas introduction line to the plasma torch. According to this configuration, a mixed gas of an inert gas and a reducing gas can be used as the plasma gas.

According to a third aspect of the present invention, there is provided a method for melting waste in a plasma melting furnace having a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch. Using an inert gas for the plasma gas, after separating and melting the waste into two layers, a metal layer and a slag layer, before tapping the molten material separated and melted into the two layers, the plasma gas of the plasma torch is After switching to the oxygen-containing gas and spraying the melt, the melt is discharged from the tap hole and filled in a receiver. According to this configuration, the carbon in the metal layer becomes carbon monoxide or carbon dioxide gas and is discharged out of the furnace, so that it is possible to suppress the reaction between oxygen and carbon due to the flow agitation of the melt during tapping.

A waste melting apparatus according to a fourth aspect of the present invention is a waste melting apparatus comprising a waste inlet, an exhaust gas outlet, a tap, a plasma torch, and a melting furnace. However, there is provided a means for switching between an inert gas and an oxygen-containing gas on a gas introduction line to the plasma torch. According to this configuration, the plasma gas used for the plasma torch can be easily switched between an inert gas and a gas containing oxygen.

A waste melting method according to a fifth aspect of the present invention is a method for melting a waste in a plasma melting furnace having a waste input port, an exhaust gas outlet, a tap hole, and a plasma torch. Using an inert gas as the plasma gas, the waste gas is separated and melted into two layers, a metal layer and a slag layer, and before the molten material separated and melted into at least the two layers is discharged, the plasma gas of the plasma torch is discharged. Is blown onto the melt with argon gas, and then the melt is discharged from the tap hole and filled into a receiver. According to this configuration, since the melt is stirred by the argon gas before tapping, the nitrogen dissolved in the metal layer is released as a gas, removed, and the nitrogen generated when the metal layer solidifies after tapping. The amount of gas can be reduced.

According to a sixth aspect of the present invention, there is provided a method for melting waste in a plasma melting furnace having a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch. When the waste is separated and melted into two layers, a metal layer and a slag layer, using a nitrogen-containing gas as the plasma gas, the height of the plasma torch from the waste is set to 400 mm or more, and the waste is melted. Then, the molten material is discharged from the tap hole and filled in a receiver. According to this configuration, even when a nitrogen-containing gas such as nitrogen or air is used as the plasma gas when the waste is melted, the amount of dissolved nitrogen in the molten metal layer can be reduced.

According to a seventh aspect of the present invention, there is provided a method for melting waste in a melting furnace provided with a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch. After separating and melting into two layers, a layer and a slag layer, before tapping the molten material separated and melted into the two layers, iron or an iron compound is introduced into the slag layer to reduce the iron content of the slag layer to 2%.
After adjusting to 0 to 25 wt%, the melt is discharged from the tap and filled in a receiver. According to this configuration, the viscosity of the slag layer is reduced, and carbon monoxide, carbon dioxide gas, and nitrogen gas, which are one of the causes of forming, are easily released from the metal layer, which is the lower layer of the slag layer, during melting. Oxygen concentration of 200ppm or less,
Forming at the time of hot water can be suppressed. Here, iron or iron oxide can be used as the iron or iron compound to be charged.

[0014] A waste melting method according to claim 8 is a method for melting waste in a melting furnace provided with a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch. After separating and melting into two layers, a layer and a slag layer, before the molten material separated and melted into the two layers melts, a deoxidizer is introduced into the metal layer to reduce the oxygen concentration in the metal layer to 200 pp.
After adjusting to less than m, the melt is discharged from the tap and filled into a receiver. According to this configuration,
The oxygen concentration in the molten metal layer can be reduced, and the reaction between oxygen and carbon due to the flow agitation of the melt during tapping can be suppressed, and the occurrence of forming can be suppressed.

According to a ninth aspect of the present invention, in the waste melting method according to the eighth aspect, the deoxidizing material comprises:
Aluminum, the amount of which is 0.1% to 2% of the iron contained in the metal layer. According to this configuration, the oxygen and nitrogen contents in the molten metal layer are reduced,
The occurrence of forming at the time of tapping can be further suppressed.

A waste melting apparatus according to a tenth aspect is a waste melting apparatus comprising a waste input port, an exhaust gas outlet, a tap hole, and a melting furnace, wherein the melting furnace comprises a metal layer. And a deoxidizing material charging means capable of directly charging a deoxidizing material to the metal layer of the melt separated and melted into two layers of a slag layer and a slag layer. According to this configuration, the deoxidizer can be directly introduced into the metal layer, and the oxygen concentration in the molten metal layer can be reduced.

According to an eleventh aspect of the present invention, in the waste melting apparatus according to the tenth aspect, the deoxidizing material is an aluminum rod, and the deoxidizing material charging means causes the deoxidizing material to enter the metal layer. At a speed of 3 m / s or more. According to this configuration, it is possible to reliably introduce aluminum into the metal layer.

According to a twelfth aspect of the present invention, there is provided a waste melting apparatus, comprising: a plasma melting furnace having a waste inlet, an exhaust gas outlet, a tap, a plasma torch, a receiver, and an upper part of the receiver. A tapping chamber provided with a heating device for heating and maintaining the temperature, a waste melting device comprising:
A container made of a thin steel plate for holding a melt separated and melted into two layers, a metal layer and a slag layer, by the plasma torch, and a holding container that holds the container in close contact with the bottom and periphery of the container. And the slag layer formed on the upper part of the container is heated and maintained by the heating device. According to this configuration, the slag layer formed on the upper portion of the receiver is heated and kept warm when the melt separated and melted into two layers, the metal layer and the slag layer, is generated from the metal layer formed on the lower portion. Gas can easily escape, which ensures that waste is
The layers can be separated and solidified stably.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a waste melting apparatus according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments described below. FIG. 1 is an overall cross-sectional schematic view of a waste melting apparatus according to the present invention. In FIG. 1, a waste melting apparatus according to the present invention has a melting furnace 1 lined with a refractory 13, a waste inlet 4 provided in the melting furnace 1 to which waste is supplied, and a waste melting port 1. Plasma torch 7 for melting waste
And an exhaust gas outlet 2 for exhausting exhaust gas generated when the waste is melted, a tap hole 3 for discharging a waste melt 10, and an iron for reforming a slag layer 10b formed on the upper portion of the melt 10. Or an iron or iron compound input port 14 for inputting an iron compound, and a metal layer 10a formed below the melt 10
And a deoxidizing material input port 18 for directly inputting a deoxidizing material. Below the tap 3, a receiver 5 for receiving the molten metal 10 from the tap 3 is installed in a tap chamber 6 surrounding the receiver 5. The tapping chamber 6 and the melting furnace 1 do not hinder the tilting of the melting furnace 1 and
The tapping chamber 6 and the melting furnace 1 are connected by a bellows 8 so that airtightness can be ensured. In addition, a heating device 32 attached to the upper part of the tapping chamber so as to move forward and backward.
(See FIG. 2), so that the upper part of the receiver 5 can be heated and kept warm.

The melting furnace 1 can be tilted by raising and lowering a lifting cylinder 15. In this case, by adopting a structure that supports the exhaust gas outlet 2 and the like, the structure of the melting furnace 1 itself becomes simple, which is preferable.

The tap 3 is preferably provided above the surface of the melt 10 so as to be in contact with the melt by tilting the melting furnace 1. Further, it is preferable that the outlet portion 9 of the tap hole 3 is inclined toward the receiver 5 side. By tilting, when the melting furnace 1 is tilted, the outlet portion 9 faces more toward the receiver 5, and the molten metal 10 easily flows down, so that the melt 10 can be reliably introduced into the receiver 5. In addition, if the tap hole 3 is formed toward the receiver 5,
For example, it may be provided at the bottom of the furnace body 1 and closed by a lid or the like at times other than when tapping, and may have a structure in which the lid is opened and tapping is performed when tapping.

The plasma torch 7 is preferably provided so as to be able to move up and down and tilt up and down the melting furnace 1. This makes it possible to adjust the position of the plasma torch 7 in accordance with the amount of waste input, and to evenly apply plasma to the waste in the melting furnace 1,
The waste can be stirred and melted. Further, when a nitrogen-containing gas is used as the plasma gas,
It is possible to suppress the amount of nitrogen dissolved in the melt at the time of melting the waste. When the waste is melted, due to the difference in specific gravity,
The slag layer 10b is formed on the upper part, and the metal layer 10a is formed on the lower part.

The plasma torch 7 is provided with a plasma gas switching means 20 on a plasma gas introduction line. The plasma gas switching means 20 is provided with an inert gas introduction line 21, a reducing gas introduction line 22, and an oxygen-containing gas introduction line 23. The reactive gas introduction line 22 and the oxygen-containing gas introduction line 23 can be appropriately selected alone or in combination.

The iron or iron compound inlet 14 is provided with the slag layer 1
In order to carry out the reforming of the slag layer 10b, the iron or iron compound is provided above the melting furnace 1 so as to reach the entire slag layer 10b. It is preferable that it is provided.

The deoxidizing material inlet 18 is preferably provided at the lower part of the melting furnace 1 so that it can be directly injected into the metal layer 10a. Preferably, aluminum is used as the deoxidizing material. However, aluminum has a low melting point.
Since the temperature is high before and after, it is difficult to directly charge the metal layer 10a if it is charged as it is. Therefore,
For example, an aluminum rod is
It is preferable to adopt a structure having a means for introducing the deoxidizing material 18 (not shown) so that it can be fed at a feed speed of 3 m / s or more, preferably 5 m / s or more. This makes it possible to directly input aluminum to the metal layer 10a.

The tapping chamber 6 is connected to the melting furnace 1 and the bellows 8 so as to maintain airtightness, and a receiver 5 capable of receiving tapping water from the tapping port 3 is provided therein. Above it, a heating device 32 capable of heating the upper layer of the receiver 5 is provided to be able to advance and retreat.

As shown in FIG. 2, the receiver 5 comprises a thin steel container 31 and a holding container 30. 2A is a plan view, and FIG. 2B is a sectional front view. In the drawing, the accommodation machine 31 has a cylindrical shape with an upper part opened, and a holding container 30 is provided around the accommodation part 31 in close contact with the bottom part and the cylindrical part, respectively. The holding container 30 is formed of a high heat conductive material, and has left and right cylindrical holding containers 30a and 30b and a disc-shaped bottom 30c.
It is preferable to be configured as a split type. Further, the cylindrical portion may be divided into three or four instead of two.
These can be fastened by an arbitrary method such as a metal band. Further, as shown in FIG. 2 (b), when the melt contained in the receiver 5 is solidified, the melt 10 contained in the receiver 5 is placed in the upper layer due to a difference in specific gravity. The slag layer 10b is separated into two layers, a metal layer 10a in a lower layer. At this time, the receiver 5 can heat and maintain the slag layer 10b formed in the upper layer by the heating device 32 provided in the tapping chamber 6. By heating and maintaining the temperature of the slag layer 10b, the viscosity of the slag layer 10b can be kept low, and a state in which gas from the lower metal layer 10a can easily escape can be maintained. Thereby, the melt can be completely separated and solidified into the two layers of the slag layer and the metal layer.

Further, it is preferable that the holding container 30 is made of a high heat conductive material. In particular, the thermal conductivity is 5.8
W / m · K, more preferably 11.6 W /
It is preferable to use a material having m · K or more, for example, a stainless steel material, a carbon steel material, a copper material, and an aluminum material alone or a laminate of two or more. by this,
The molten material discharged from tap hole 3 is placed in a thin steel container 31.
Even if the molten material is injected and stored in the container, the heat of the molten material is quickly transferred from the container 31 to the holding container 30, and the thin steel container 3
1 is exposed to a high temperature for a short time, so that the molten material can be rapidly cooled and solidified, in addition to preventing deformation and erosion of the container 31. Further, thereby, the space of the tapping chamber 6 can be reduced, and large-scale cooling equipment is not required, so that cost reduction can be expected. Further, the melt can be surely separated into two layers.

Further, the holding container 30 may be provided with a cooling medium passage. By providing the flow path of the cooling medium in this way, the heat radiation of the melt 10 in the container 31 is further promoted, and the melt in the container 31 is surely prevented, in addition to preventing deformation and melting of the container 32. It can be separated into two layers.

Further, as shown in FIG. 3, the holding container 30 may have at least a vertical groove at a portion closely contacting the periphery of the container 31. By providing the concave groove, the expansion of the container 31 caused when the melt 10 is injected and stored in the container 31 can be absorbed.
Although FIG. 3 shows the case where the concave grooves are provided at four positions, the present invention is not particularly limited.

The holding container 3 is provided on the outer peripheral side of the holding container 30.
A cooling medium spraying device that sprays a cooling medium toward the outer wall of the “0” may be provided. By providing such a cooling medium spraying device, it is possible to enhance the heat radiation effect from the outer peripheral side of the holding container, and to prevent deformation and melting of the container 31 as well as to surely melt the melt in the container 31. It can be separated into two layers.

The waste melting apparatus of the present invention is constructed as described above.
Has been established. Below, about the suitable melting method,
explain. First, waste is put into the melting furnace 1 shown in FIG.
Through port 4, an arbitrary amount of waste is introduced. And discard
When the waste is charged, the waste is melted by the plasma torch 7.
Melt. At this time, the switching means 20 supplies the plasma gas.
Select an inert gas and a reducing gas
It is preferable to use a gas containing a small amount of reducing gas.
No. As a result, oxygen present in the furnace is
To react with the reducing gas in the
Oxygen in the melt is prevented from being drawn into the melt,
The oxygen content in the melt can be reduced. Also,
NO generated _XBecause the concentration can be reduced,
The load on the denitration equipment of the exhaust gas treatment system can also be reduced.
Here, as the inert gas used, nitrogen gas,
Lugon gas or the like can be used. In addition, reducing gas
Methane gas, ethane gas, propane gas, etc.
Gas or a mixture of these with steam
be able to. Melting should be performed only with an inert gas.
Can also be.

When an argon gas is used as an inert gas for the plasma gas, nitrogen is rarely mixed in the melt, but when a nitrogen-containing gas such as a nitrogen gas or air is used, the hot water is discharged. It is conceivable that nitrogen, which contributes to the occurrence of forming at the time, is mixed into the melt. For this reason, when the plasma torch 7 is adjusted by position adjustment so that the height from the waste to be melted is 400 mm or more, the mixing of nitrogen into the melt can be suppressed.
In this case, the height of the plasma torch naturally varies depending on the gas flow rate of the plasma gas, the concentration of the nitrogen-containing gas, and the like. In the case of the present embodiment, the output of the plasma torch is 1 unit.
This is the case where the MW and the nitrogen gas flow rate are 180 Nm ³ / h, and the lower the nitrogen gas flow rate is, the lower the torch height is.

In this way, the waste is melted by the plasma torch 7, and the slag layer 10b is formed in the upper layer and the metal layer 10b is formed in the lower layer due to the difference in specific gravity. During melting, it is preferable to tilt or rotate the plasma torch 7 so that the plasma from the plasma torch 7 uniformly hits the waste in the melting furnace 1. Thereby, unburned carbon, nitrogen, and the like in the melt can be evenly dispersed in the melt without segregating near the inner wall 13 of the melting furnace 1. As a result, the efficiency of removing unburned carbon and the like in the melt described below is improved, and nitrogen is released without remaining as nitrogen gas in the melt, thereby suppressing the forming of the melt at the time of tapping. Can be.

After melting the waste and before tapping the hot water, the plasma gas introduction line of the switching means 20 is switched to the oxygen-containing gas line 23. By using an oxygen-containing gas for the plasma gas, the unburned carbon remaining in the melt reacts with the oxygen in the plasma gas to generate carbon monoxide gas or carbon dioxide gas, and the unburned gas is emitted from the melt. Of carbon can be removed. Thereby, the formation of forming due to the reaction between oxygen and carbon due to the stirring of the molten metal at the time of tapping can be suppressed. Here, oxygen, air, and the like can be used as the oxygen-containing gas.

Before and after this, it is preferable to change the plasma gas to argon gas and spray it on the melt. As a result, it is possible to release the melt, particularly the nitrogen gas dissolved in the metal layer 10a. In addition, this treatment in which the plasma gas is an oxygen-containing gas or an argon gas before tapping can provide the same effect regardless of which is performed first. Further, by using a mixed gas of an argon gas and an oxygen-containing gas, this process can be performed simultaneously.

Further, before the tapping after the waste is melted, the plasma gas introduction line of the plasma gas switching means 20 is switched to the oxygen-containing gas line 23 as described above.
It is preferable that the plasma gas be argon gas, and that the iron or iron compound be charged toward the slag layer 10b from the iron or iron compound charging port 14. By introducing iron or an iron compound toward the slag layer 10b, the content of metallic iron in the slag layer 10b is adjusted to about 20 to 25% by weight. Thereby, the viscosity of the slag layer 10b can be adjusted, and the nitrogen gas in the melt, the carbon dioxide gas generated by the plasma using the oxygen-containing gas, and the like are released without being hindered by the slag layer 10b. Is done. For this reason, it is possible to suppress the reaction between oxygen and carbon due to stirring of the molten metal at the time of tapping and the formation of forming due to the generation of nitrogen gas.

In addition, iron or an iron compound is charged into the slag layer 10b, and the deoxidizing material is supplied through the deoxidizing material charging port 18.
It is preferable to directly charge into a. As described above, for example, the deoxidizing material is charged into the deoxidizing material 18 so that an aluminum rod can be fed from the deoxidizing material charging port at a feed speed of 3 m / s or more, preferably 5 m / s or more. It is preferable to have a structure having a charging means (not shown). This makes it possible to directly input aluminum, which is a deoxidizing material, to the metal layer 10a without being affected by the atmosphere in the melting furnace 1. As described above, by introducing aluminum into the metal layer 10a, oxygen in the metal layer 10b reacts with aluminum, and an intense deoxidation reaction occurs. Further, together with this deoxidation reaction, it reacts with nitrogen and a denitrification reaction occurs simultaneously, so that the oxygen concentration and the nitrogen concentration in the metal layer 10b can be reduced. The input amount of aluminum may not be too large or too small, and the input amount is preferably 0.1% to 2% of the iron contained in the metal layer.

Next, as shown in FIG. 4, the melting furnace 1 is tilted by the elevating cylinder 15, and the melt is discharged from the tap 3 toward the receiver 5. At this time, since the melting furnace 1 and the tapping chamber 6 are connected while maintaining the airtightness by the bellows 8 as shown in the figure, even when the molten material jumps out of the receiver 5 at the time of tapping, Since it does not fly out of the tapping chamber 6, it does not adversely affect peripheral devices.

After the molten material in the melting furnace 1 has been poured into the receiver 5, the melting furnace 1 is returned to the original position by the lifting cylinder 15, and the waste is again input from the waste inlet 4 to remove the waste. Melting takes place.

On the other hand, in the receiver 5 containing the melt, the slag layer 10b is formed in the upper layer as shown in FIG. 2, for example, due to the difference in specific gravity between the slag layer and the metal layer in the melt. Metal layer 10a is formed in the portion. And the heating device 32 provided above the tapping chamber 6 is:
The slag layer 10b is moved above the slag layer 10b, and is heated and kept warm. As a result, the slag layer 1
0b, the solidification rate of the metal layer 1 formed in the lower layer is adjusted.
The gas or the like generated when the solidification of the slag layer 10a is carried out by the slag layer 10b
Can be prevented from becoming hard to be removed by solidification of the waste, and the number of pores in the solidified waste can be reduced,
Waste volume can be reduced. Further, the solidification can be performed in a state where the metal layer 10a and the slag layer 10b are surely separated into two layers.

According to the present invention, as described above, deoxidation, decarburization, denitrification, and the like are performed during melting of the waste, so that the forming at the time of tapping can be suppressed. The degassing inside can be efficiently performed, and the waste can be surely separated and solidified into two layers of a metal layer and a slag layer. Incidentally, the present invention, as described above, deoxidation,
Decarburization, denitrification, and other treatments can be performed continuously, but even when each treatment is performed independently, it is possible to suppress forming during tapping or to separate and solidify into two layers. The effect can be obtained.

Although the invention is beyond the scope of the present invention, the technical idea of the present invention according to the seventh to twelfth aspects of the present invention is to use, for example, a high-frequency induction heating as a waste melting method in addition to the plasma. Even in this case, it is applicable, and even in this case, it is possible to reduce the amount of carbon, oxygen, and nitrogen in the molten material, to suppress forming at the time of tapping, and to separate into two layers. The effect that can be solidified can be obtained.

[0044]

Next, an embodiment of a waste melting apparatus according to the present invention will be described to specifically describe the present invention.

(Example 1) In-furnace leak air amount 5 Nm ³ /
h, nitrogen gas 25 Nm ³ /
h, methane gas was melted under the condition of 0.5 Nm ³ / h, and the NO _x concentration in the exhaust gas in this case was examined.

[0046] As a result, NO _X concentration in the exhaust gas discharged was reduced from 3000ppm without the addition of methane to the 20 ppm. This is probably because oxygen present in the melting furnace reacts with methane gas added to the plasma gas to generate carbon monoxide gas. This carbon monoxide gas can be completely burned by blowing combustion air in a secondary combustion furnace. Thus, the addition of reducing gas methane or the like during plasma gas, the addition amount of the reducing gas, namely by adjusting the mixing ratio and the mixed flow rate and the like with an inert gas, reducing the concentration of NO _X in the exhaust gas At the same time, mixing of oxygen into the melt can be suppressed. Thereby, it is possible to suppress the occurrence of forming at the time of tapping the molten material. Note that the reducing gas is effective not only in the addition to the plasma gas as in the present embodiment but also in the direct supply into the melting furnace.

(Example 2) Leakage air amount in the melting furnace 5 Nm
³ / h, nitrogen gas was used as the plasma gas, the nitrogen gas flow rate was 180 Nm ³ / h, and the plasma output was 1M.
As W, the waste was melted, the height of the plasma torch from the waste at that time was adjusted, and the relationship between the amount of dissolved nitrogen in the melt and the height of the plasma torch from the waste was examined.

FIG. 5 summarizes the results. In FIG. 5, ○ indicates that no forming was recognized at the time of tapping, and X indicates that the forming was recognized. As can be seen from FIG. 5, when the plasma torch height is 400 mm or less, the dissolved amount of nitrogen in the melt becomes high, and when the plasma torch is 400 mm or more, the dissolved amount of nitrogen in the melt becomes 200 ppm or less, and forming does not occur. You can see that
This is considered to be because if the height of the plasma torch is 400 mm or less, the waste is strongly affected by the temperature of the plasma arc, and nitrogen is easily mixed into the melt.
Therefore, the height of the plasma torch from the waste is 40
By adjusting the position so that it becomes 0 mm or more and melting,
It is possible to reduce the amount of dissolved nitrogen in the melt to 200 ppm or less, thereby suppressing forming at the time of tapping.

[0049]

The present invention is configured as described above.
According to the first aspect of the present invention, since the reducing gas in the plasma gas reacts with oxygen in the furnace and becomes carbon monoxide or carbon dioxide gas and is discharged out of the furnace, oxygen is mixed into the metal layer immediately below the plasma. can be suppressed, and can suppress the reaction of oxygen and carbon by the flow agitation of the melt during pouring, it is possible to suppress the forming, an effect that may reduce the concentration of NO _x.

According to the second aspect of the present invention, a mixed gas of an inert gas and a reducing gas can be used as the plasma gas, so that the oxygen content in the melt can be reduced and the forming at the time of tapping can be suppressed. To play.

According to the third aspect of the present invention, carbon in the metal layer becomes carbon monoxide or carbon dioxide gas and is discharged out of the furnace, and it is possible to suppress the reaction between oxygen and carbon due to the flow agitation of the melt during tapping. It has the following effects.

According to the fourth aspect of the present invention, the plasma gas used for the plasma torch can be easily switched between an inert gas and a gas containing oxygen, and unburned carbon in the melt at the time of tapping. Therefore, nitrogen in the melt can be agitated, and the effect of suppressing forming due to carbon and nitrogen remaining in the melt generated at the time of tapping can be achieved.

According to the fifth aspect of the present invention, since the molten material is stirred by the argon gas before tapping, nitrogen dissolved in the metal layer is released as a gas and removed, and after the tapping, the metal layer solidifies. The amount of nitrogen gas generated at the time of forming can be reduced, forming can be suppressed, the generation of voids in the solidified material after solidification can be reduced, and the volume of the solidified material can be efficiently reduced.

According to the sixth aspect of the present invention, even when a nitrogen-containing gas such as nitrogen or air is used as the plasma gas at the time of melting the waste, the amount of dissolved nitrogen in the molten metal layer is reduced. Can reduce the amount of nitrogen gas generated at the time of solidification after tapping, can suppress forming, can reduce the generation of voids in the solidified material after solidification, and can efficiently reduce the volume of the solidified material. To play.

According to the seventh aspect of the present invention, the viscosity of the slag layer is reduced, and carbon monoxide gas, carbon dioxide gas and nitrogen gas, which are one of the causes of forming, are formed from the metal layer which is the lower layer of the slag layer during melting. It is easy to come off, the oxygen concentration in the metal layer can be 200 ppm or less, and the effect of suppressing forming at the time of tapping can be achieved.

According to the eighth aspect of the present invention, the oxygen concentration in the molten metal layer can be reduced, the reaction between oxygen and carbon due to the flow stirring of the molten material at the time of tapping can be suppressed, and the effect of suppressing the occurrence of forming can be suppressed. Play.

According to the ninth aspect of the present invention, the oxygen and nitrogen contents in the molten metal layer are reduced, and an effect that the occurrence of forming at the time of tapping can be further suppressed can be achieved.

According to the tenth aspect of the present invention, the deoxidizing agent can be directly introduced into the metal layer, the oxygen concentration in the molten metal layer can be reduced, and the effect of suppressing forming at the time of tapping can be obtained. .

According to the eleventh aspect, it is possible to reliably introduce aluminum into the metal layer, and the effect of the tenth aspect can be more reliably achieved.

According to the twelfth aspect of the present invention, the slag layer formed on the upper portion of the receiver when the melt separated and melted in the two layers of the metal layer and the slag layer is accommodated is heated and kept warm.
The gas generated from the metal layer formed at the lower portion can be easily released, whereby the waste can be surely separated into two layers and the solidified material can be stably solidified.

[Brief description of the drawings]

FIG. 1 is a schematic overall sectional view of a waste melting apparatus according to the present invention.

FIG. 2 is a schematic view showing a receptor according to the present invention;
(A) is a top view, (b) is a figure which shows a front view.

FIG. 3 is a schematic view showing another embodiment of the receiver according to the present invention, wherein (a) is a plan view and (b) is a front view.

FIG. 4 is a schematic cross-sectional view of the waste melting apparatus according to the present invention at the time of tapping.

FIG. 5 is a diagram showing the relationship between the plasma gas torch height and the amount of nitrogen dissolved in a melt.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Melting furnace 2 Exhaust gas outlet 3 Outlet 4 Waste inlet 5 Receptor 6 Outlet chamber 7 Plasma torch 8 Bellows 9 Outlet outlet 10a Metal layer 10b Slag layer 12 Support part 13 Refractory 14 Iron or iron compound inlet 15 Up / down Cylinder for use 18 Deoxidizing material inlet 20 Plasma gas switching means 21 Inert gas introduction line 22 Reducing gas introduction line 23 Oxygen-containing gas introduction line 30 Holding member 31 Container 32 Heating device 35 Escape groove

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuyuki Yoshikawa 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Research Institute, Kobe Steel Ltd. (72) Koichi Sakamoto Takatsuka, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Co., Ltd.Kobe Research Institute, Kobe Steel Co., Ltd. (72) Inventor Tomio Suzuki 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inventor Takeshi Noura 4-3-1, Bingo-cho, Chuo-ku, Osaka-shi, Osaka Kobe Steel, Ltd. Osaka branch office (72) Inventor Akiyoshi Yamane 4-3-1, Bingo-cho, Chuo-ku, Osaka-shi, Japan Shares Company Kobe Steel Osaka Branch Office

Claims (12)

[Claims] 1. A method for melting a waste in a plasma melting furnace comprising a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch, wherein the plasma gas of the plasma torch includes an inert gas and a reducing gas. After the waste is separated and melted into two layers, a metal layer and a slag layer, using a mixed gas composed of a volatile gas, the melt separated and melted into the two layers is discharged from the tap hole and filled into a receiver. Waste melting method. 2. A waste melting apparatus comprising: a waste input port, an exhaust gas outlet, a tap hole, a plasma torch, and a melting furnace, wherein the melting furnace includes an inert gas supplied to the plasma torch. A waste melting device including an introduction line and a reducing gas introduction line. 3. A waste melting method in a plasma melting furnace having a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch, wherein an inert gas is used as a plasma gas of the plasma torch. After the waste is separated and melted into two layers, a metal layer and a slag layer, the plasma gas of the plasma torch is switched to an oxygen-containing gas before tapping of the melt separated and melted in the two layers, And then discharging the melt from the tap hole and filling it in a receiver. 4. A waste melting apparatus comprising a waste inlet, an exhaust gas outlet, a tap hole, a plasma torch, and a melting furnace, wherein the melting furnace includes a gas introduction line to the plasma torch. A waste melting apparatus comprising a switching means for switching between an inert gas and an oxygen-containing gas. 5. A waste melting method in a plasma melting furnace having a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch, wherein an inert gas is used as a plasma gas of the plasma torch. After the waste is separated and melted into two layers, a metal layer and a slag layer, before the molten material separated and melted into at least the two layers is discharged, the plasma gas of the plasma torch is changed to argon gas, and the melt is melted. And then discharging the melt from the tap hole and filling it in a receiver. 6. A waste melting method in a plasma melting furnace having a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch, wherein a nitrogen-containing gas is used as a plasma gas of the plasma torch. When the waste is separated and melted into two layers of a metal layer and a slag layer, the height of the plasma torch from the waste is set to 400 mm or more, and the waste is melted. Waste melting method of tapping and filling the receiver. 7. A method for melting waste in a melting furnace having a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch, wherein the waste is separated into two layers, a metal layer and a slag layer. Then, before tapping of the melt separated and melted into the two layers, iron or an iron compound is charged into the slag layer, and the iron content of the slag layer is adjusted to 20 to 25 wt%. A waste melting method in which the molten material is tapped and filled into a receiver. 8. A method for melting a waste in a melting furnace having a waste inlet, an exhaust gas outlet, a tap hole, and a plasma torch, wherein the waste is separated into two layers, a metal layer and a slag layer. Then, before tapping of the molten material separated and melted into the two layers, a deoxidizer is charged into the metal layer, and the oxygen concentration in the metal layer is adjusted to 200 ppm or less, and then the molten metal is discharged from the tap hole. A waste melting method in which an object is discharged and filled into a receiver. 9. The deoxidizing material is aluminum, and its input amount is 0.1% to 2% of iron contained in the metal layer.
The waste melting method according to claim 8, wherein 10. A waste melting apparatus comprising a waste inlet, an exhaust gas outlet, a tap hole, and a melting furnace, wherein the melting furnace separates and melts into two layers, a metal layer and a slag layer. A waste melting apparatus comprising a deoxidizing material charging means capable of directly charging a deoxidizing material to the metal layer of the molten material. 11. The deoxidizing material is an aluminum rod, and the deoxidizing material charging means allows the metal layer to contain three or more aluminum rods.
The waste melting device according to claim 10, which can be charged at a speed of m / s or more. 12. A tapping chamber comprising a plasma melting furnace having a waste inlet, an exhaust gas outlet, a tapping port, and a plasma torch, a receiver, and a heating device for heating and maintaining the upper part of the receiver. A waste-melting apparatus comprising: a thin-walled steel-sheet-shaped container for housing a molten material separated and melted into two layers, a metal layer and a slag layer, by the plasma torch; A waste melting apparatus comprising a holding container that holds the container in close contact with the bottom of the container and the periphery thereof, and is configured so that the slag layer formed on the upper part of the container can be heated and maintained by the heating device.