JP2684322B2 - Hazardous waste volume reduction equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reducing the volume of hazardous waste contaminated with heavy metals and radioactive substances generated in nuclear power plants.

[0002]

BACKGROUND ART Wastes generated from a nuclear power plant are roughly classified into combustible wastes such as filters, ion exchange resins, plastics, woods, wastes, clothes and paper.
It is divided into heavy metals such as pipes, steel plates, concrete, and copper wires, and non-combustible wastes containing radioactive substances. Regarding the former, after incineration and volume reduction, it is stored and managed as ash containing heavy metals and radioactive substances directly in a drum, and in the same way as non-combustible waste is stored and managed as is in a drum. There are cases where it will be done. On the other hand, for the latter, as it is, cement, asphalt,
Stored in a drum together with void filling such as resin,
Be managed.

[0003]

As described above, the hazardous waste generated in a nuclear power plant has been stored in a drum of 200 liters conventionally, but the incinerated ash of the combustible hazardous waste is ash. The non-combustible waste has a low bulk density and cannot be sufficiently filled in the drums, so that the number of drums increases, the transportation load increases, and more storage space is required.

A method for reducing the storage space for filling a drum can is disclosed in JP-A-62-153800. This is because the outer circumference of a drum can filled with hazardous waste is transformed into a petal shape in advance and then put in a container, and then the drum can is compressed / volume-reduced by a punch from above through a push plate to reduce the volume of the drum can. It is stored in a new drum.

This method can reduce the required storage space as compared with the conventional method, but the hazardous waste filled in the drum can is
Usually, since the amount of pollution due to heavy metals and radioactive substances is not uniform, parts with a relatively high degree of contamination may come to the outer periphery of the new drum, and leakage of harmful substances due to corrosion of the new drum by rainwater, etc., or There is a risk of radiation exposure. There is also a problem that it is necessary to prevent damage to the drum can.

[0006] Generally, there is a combustion type melting furnace as a device for reducing the volume of industrial waste. However, in this case, the combustion temperature does not rise in principle, so that the metals in the hazardous waste are difficult to melt, Further, since a large amount of oxygen is required for combustion, the exhaust gas treatment equipment becomes huge, and the equipment cost becomes large.
Further, there is a problem that the stirring power is weak and it is difficult to make the melt uniform. Similarly, in the arc type melting furnace,
There is also a problem that the radioactive material after melting is largely scattered with the exhaust gas due to the arc pressure, so that the processing is complicated and the nonmetal cannot be melted.

Further, in Japanese Patent Laid-Open No. 60-186800, a container is installed in a metallic cylindrical heating body provided in a furnace equipped with an induction coil, and a harmful substance generated in a nuclear power plant is generated in the container. A method of melting and solidifying waste and its incinerated ash together with a flux is disclosed. In this method, hazardous waste and its incinerated ash can be melted and solidified at the same time in the same container, and as a result, it is possible to significantly reduce the volume, and the volume-reduced product is a stable inorganic solidified body. So it is safe.

However, in this method, since it is melted by the induction coil arranged outside the furnace, it takes a long time for melting due to the heat capacity, and efficient processing cannot be performed. Further, in this method, an expensive metal or ceramic container is used as a crucible container during melting in order to cope with high temperatures, but this container is discarded every time it is melted and solidified, so that the processing cost is greatly increased.

The present invention solves these various problems in the treatment of hazardous waste and provides a device for safe storage in a more reduced volume.

[0010]

The gist of the present invention is to guide an outer peripheral portion of a container having a space in which a plurality of drums filled with hazardous waste or incinerated ash of hazardous waste are built up in a stacked state. A coil is provided, a plasma torch, a lid, and an exhaust gas port are provided above the container, and a discharge port of a melt melted by the induction coil and the plasma torch is provided below the container. This is a volume reduction device for hazardous waste.

[0011]

[Function] A plurality of drums filled with hazardous wastes or incinerated ash generated in a nuclear power plant are placed in a container in which the drums can completely fit. The induction coil causes the drum to act as a heating / heating element, melting the filling material inside. Further, by supporting the melting of the non-metal having a high melting temperature by the plasma torch provided in the upper part of the container, the hazardous waste and its incinerated ash can be easily melted and solidified in a short time. In particular, if the space inside the container is made small so that a plurality of drums can be accommodated in a stacked state, the heating efficiency by the induction coil can be extremely improved due to preheating effect, induction optimization and the like. Further, in the exhaust gas generated at the time of melting, the radioactive substances are less scattered due to the high temperature oxidation, and the radioactive substances accompanying the exhaust gas are reduced.

When the gas supplied to the plasma torch is heated by the thermal energy of the high-temperature plasma arc generated by the plasma torch, the temperature of the gas ejected from the plasma torch becomes tens to tens of thousands of degrees. Due to convective heat transfer and radiant heat transfer of this overheated gas, asbestos in the radioactive waste that has a particularly high melting temperature that is difficult to melt with an induction coil alone,
It enables melting of ceramics and heavy metals. Further, the high temperature gas ejected from the plasma torch heats the surface of the radioactive material in the drum can, but the melt heated by induction heating by the induction coil causes convection due to the temperature difference in the heating area by the induction coil, causing agitation. The object to be treated can be uniformly heated by heating, and the heating efficiency is improved. That is, by providing different heating means such as an induction coil and a plasma torch, it is possible to efficiently heat each object to be heated, shorten the heating time, and complete melting treatment. In addition, the plasma torch alone has a high plasma flow velocity and causes the harmful substance that is the heating target to be scattered. However, in combination with induction melting, the plasma flow velocity can be reduced and the scattering of the heating target can be prevented. .

[0013]

EXAMPLE An example of the apparatus of the present invention shown in FIG. 1 will be described.

The inside of the drum 1 is filled with hazardous waste generated in a nuclear power plant or its incinerated ash. Container 2 having a space inside which a plurality of drums can fit in
The induction coil 8 is arranged outside the furnace. The container 2 has a lid 3 for filling the drum 2 into the container 2, an exhaust gas port 4 for exhausting exhaust gas generated during melting, a plasma torch 5 above the container 2, and a non-metal melt generated during melting. A discharge port 6 for discharging the metal to the outside of the furnace, and a discharge port 7 for discharging the metal melt generated during melting to the outside of the furnace.

First, open the lid 3 provided on the upper portion of the container 2,
A plurality of drums 1 are stacked and filled in the container 2. Then, the induction coil 8 arranged outside the furnace is energized and the plasma torch 5 arranged above the container 2 is activated. With the lapse of time, the drum 1 is heated to generate heat, and the hazardous waste inside or the incinerated ash thereof is rapidly melted with the assistance of the heating action of the plasma torch 5.

When all the melting is completed, a non-metal melt is produced in the upper part and a metal melt is produced in the lower part due to the difference in specific gravity of the melt. The upper non-metallic melt is discharged from the discharge port 6 to the outside of the furnace, filled in a new drum and stored. The metal melt in the lower part is discharged to the outside of the furnace through the discharge port 7, filled in a new waste container, and stored or agglomerated, so that it can be effectively used for manufacturing a waste container and steel bar. .

Exhaust gas generated at the time of melting is discharged to the outside of the furnace through an exhaust gas port 4 by an exhaust fan (not shown).

As the induction coil 8, it is preferable to use a low frequency or a high frequency generally used for molten steel at present in order to reduce the equipment cost.

As the plasma torch 5, for example, a direct current non-transfer type plasma torch having a cathode and an anode in a plasma torch and generating a plasma arc by an arc discharge between them can be used, and the plasma torch is opposed to the inside of the furnace. It is also possible to use a direct current transfer type plasma torch which has an electrode and supplies a current to an object to be heated, or an alternating current type plasma torch which generates plasma by alternating current.

The plasma torch has a cathode and an anode that are water-cooled by a cooling water supply device. The cathode and the anode are connected to a DC power supply, and generate a plasma arc between both electrodes. Air, nitrogen, argon, or the like can be used as a supply gas for the plasma torch. In this example, cheap argon gas was used because a relatively stable plasma arc can be obtained. However, in order to realize a higher arc voltage and increase the electric power supplied by the plasma torch, it is preferable to use air or nitrogen gas. The gas supplied to the plasma torch is heated by the thermal energy of the high-temperature plasma arc generated by the plasma torch, and due to convective heat transfer and radiant heat transfer of the gas, the melting temperature of radioactive waste that is difficult to melt with an induction coil alone It enables high melting processing of asbestos, ceramics and heavy metals.

Further, the plasma torch 5 may be arranged at one place, but in order to realize more uniform heating of the upper surface of the material to be melted, it is more preferable that it is arranged at a plurality of places in the outer peripheral direction at a few positions. At this time, for example, when arranging two,
If two AC transfer type plasma torches are placed at the target position, an AC plasma arc can be generated between the plasma torch and the material to be melted, and since the plasma arc is in direct contact with the material to be melted, the heating efficiency is increased and effective. Is. When three are arranged, it is effective to arrange three three-phase AC transfer type plasma torches at the target position and generate a plasma arc by three-phase AC.

[0022]

INDUSTRIAL APPLICABILITY The apparatus of the present invention is capable of melting a drum in which hazardous waste generated in a nuclear power plant or its incinerated ash is filled in a short time, and the volume can be greatly reduced. The volume of the incinerated ash to be treated is about 1/3 of the conventional volume, and the volume of non-combustible waste is about 1/7 of the conventional volume. In addition, the volume is reduced by about 1/600 as compared with the conventional case where flammable waste is directly treated. And
The amount of radioactive substances entrained in the exhaust gas is small, which facilitates subsequent exhaust gas treatment.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a hazardous waste volume reduction processing apparatus of the present invention.

[Explanation of symbols]

 1 Drum can 2 Container 3 Lid 4 Exhaust gas port 5 Plasma torch 6 Discharge port 7 Discharge port 8 Induction coil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 58-800 (JP, A) JP 60-186800 (JP, A) JP 6-273587 (JP, A)

Claims (1)

(57) [Claims] 1. An induction coil is arranged on the outer peripheral portion of a container having a space for accommodating a plurality of drums, which are filled with hazardous waste or incinerated ash of hazardous waste, and the induction coil is disposed above the container. A plasma torch, a lid and an exhaust gas port are provided in the container, and a discharge port for the melted material melted by the induction coil and the plasma torch is provided in the lower part of the container.