Furnaces – Refuse incinerator – For explosive or radioactive material
Reexamination Certificate
2000-07-13
2003-01-07
Bennett, Henry (Department: 3749)
Furnaces
Refuse incinerator
For explosive or radioactive material
C110S211000, C110S250000, C110S345000
Reexamination Certificate
active
06502520
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a solid material melting apparatus, and more particular, it relates to a solid material melting apparatus suitable to incineration and melting of radioactive solid wastes (including combustible materials, less combustible materials and incombustible materials) discharged from radioactive material handling facilitates such as nuclear power plants.
BACKGROUND ART
Combustible radioactive solid-wastes such as rags, clothing and plastics, such as vinyl chloride and incombustible radioactive solid wastes such as metal wastes and thermal insulation materials are discharged from radioactive material handling facilities such as nuclear power plants. The combustible materials and incombustible materials are separated, and incineration processing for the combustible materials and compression processing of wastes or melting processing of melting wastes at high temperature to reduce the volume for incombustible materials have been investigated. Further, for the residues and incineration ashes after incineration of the combustible materials, melting processing has been considered.
As an incineration furnace for processing combustible radioactive solid wastes, an apparatus described in “Research and Development on Processing and Disposal of Radioactive Wastes” (Sangyo Gijutsu Shuppan, p175) have been used generally. In this incineration furnace, combustible radioactive solid wastes are burnt by a gas burner inside of a furnace main body lined with refractories and exhaust gases are discharged from the upper portion of the furnace main body. The exhaust gases are removed with coarse particulates by ceramic filters and high performance filters provided in two stages, and then released out of the system. Further, residues and incineration ashes accumulated at the bottom of the furnace main body are discharged by opening a shutter at the bottom into drams and stored therein.
On the other hand, melting furnaces for processing incombustible solid wastes include two types, depending on the difference of the heating system, that is, a plasma heating type melting furnace and an induction heating type melting furnace. In the induction heating type melting furnace, alternating current is supplied to induction coils wound around a melting vessel, thereby generating radio frequency induced electromagnetic fields at several tens to several hundreds Hz in the melting vessel. Under the effect of the radio frequency induced electromagnetic fields, eddy current is generated to conductive materials disposed in the melting vessel. The solid wastes in a melting vessel are heated and melted by Joule heat caused by the eddy current.
An example of melting processing using such an induction heating type melting furnace is described in Japanese Publication of Patent Application No. Hei 6-64192. In the melting processing, an electroconductive ceramic container is heated by electromagnetic induction to melt solid wastes supplied into the ceramic container and then both the ceramic container and the solid wastes are taken out of the system together for making ingots by cooling.
Another melting processing by using the induction heating type melting furnaces is described in Japanese Patent Publication No. 2503004. In this melting processing, a conductive heat generation body made of carbon filled in the inside of the furnace main body heated by radio frequency magnetic fields and solid materials charged from above the filled layer of the conductive heat generation body are heated and melted by the heated conductive heat generation body. The molten solid materials flow down through gaps formed between each of the conductive heat generation bodies and are then discharged from the bottom of the furnace main body.
Among the prior arts described above, the incineration furnace for treating combustible solid wastes uses burners as a heat source, and so it is difficult to perform melting processing for incombustible solid wastes. Further, as for the handling of incineration ashes, it is necessary to take a countermeasure such as inhibition of scattering ashes.
Then, the melting processing described in Japanese Publication of Patent Application NO. Hei 6-64192 uses a conductive container based on carbon materials, so that it is not suitable to incineration processing of combustible materials in which combustion air is supplied. Further, since the melting processing is batchwise, it imposes a limit on the processing speed for the solid wastes.
The melting processing disclosed in Japanese Patent Publication No. 2503004 can additionally supply the carbon material for the heat generation body, and accordingly, it can also incinerate the combustible solid wastes in principle. Further, since the molten solid materials can be taken out continuously from the bottom of the furnace main body, the processing speed for the solid materials is increased. However, since the exhaust gases are discharged from the upper end of the furnace main body, soots, coarse particulates and combustion gases are exhausted as they are as gaseous wastes. This remarkably increases the burden on the exhaust gas processing. Further, since the solid materials are charged on the filled layer of the conductive heat generation body, dioxins and other noxious gases are generated by incomplete combustion of the solid materials, which may possibly be discharged from the upper end of the furnace main body together with exhaust gases without being decomposed. In addition, there is a possibility that air at low temperature is sucked from a discharging port at the bottom of the furnace to the inside of the furnace along with discharge of the exhaust gases to possibly lower the temperature at the discharging port. Since this may possibly coagulate molten products at the discharging port and clog the same, it is necessary to provide an auxiliary burner or the like.
An object of the present invention is to provide a solid material melting apparatus for suppressing formation of noxious gases such as dioxins and the likes without causing clogging at a discharging port.
DISCLOSURE OF INVENTION
A feature of the first invention for attaining the foregoing object resides in an apparatus for melting solid materials comprising a furnace main body having an opening/closing charging port for solid materials and a molten product discharging port at a lower end thereof, and being filled the inside thereof with a conductive heat generation body, and induction coils disposed at the periphery of the furnace main body for induction heating the conductive heat generation body, in which the solid materials supplied to the inside of the furnace main body are melted, characterized in that it comprises a combustion air supply means connected to an upper portion of the furnace main body and an exhaust gas discharging port disposed to a lower end of the furnace main body.
Since the combustion air supply means is connected to the upper portion of the furnace main body and the exhaust gas discharging port is disposed to the lower end of the furnace main body, combustion air is supplied to the upper portion of the furnace main body and exhaust gases generated by the combustion of combustible solid materials are discharged through gaps between each of the conductive heat generation bodies at a high temperature and then discharged from the exhaust gas discharging port at the lower end of the furnace main body to the outside of the furnace main body. Particularly, a portion below the upper end of the filled layer of the conductive heat generation body is at a high temperature. Accordingly, unburned gases and noxious gases contained in the exhaust gases are thermally decomposed while the exhaust gases pass through a high temperature region in the filled layer of the conductive heat generation body so as to promote non-toxification. Accordingly, the amount of dioxins contained in exhaust gases discharged from the exhaust gas discharging port is remarkably lowered and the amount of dioxins discharged to the external environment is also reduced remarkably.
As t
Hashida Hideo
Kondo Takeyuki
Matsuda Masami
Matsuo Toshiaki
Nishi Takashi
Bennett Henry
Mattingly Stanger & Malur, P.C.
Rinehart K. B.
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