JP5004490B2 - A melting furnace structure that prevents the combustion flame from wrapping around the outer periphery of the canister - Google Patents

Description

  The present invention relates to a melting furnace structure that prevents a combustion flame from wrapping around the outer periphery of a canister.

  Of the low-level radioactive waste generated at nuclear power plants, miscellaneous solid waste is packed in drums, filled with mortar and other fillers, and disposed of in a predetermined burial site. Therefore, it is preferable to reduce the volume of miscellaneous solid waste and reduce the number of embedded drums. Therefore, as a method for reducing the volume of miscellaneous solid waste, for example, a melting volume reduction facility using a high frequency induction heating method has been introduced.

  In the melting facility, the inside of the canister set in a melting furnace in which a high frequency induction coil is spirally wound is heated to about 1500 ° C. to melt and reduce the volume of miscellaneous solid waste. Then, when there is room in the canister, the molten object in the charging container is melted while being sequentially added into the canister, and the additional charging is continued until a predetermined molten metal level is reached.

  The molten state is managed by measuring the outer surface temperature of the canister by arranging radiation thermometers in four orthogonal directions inside the melting furnace main body in the circumferential direction of the canister. The detection signal of each thermometer is input to a temperature control unit provided in the control room, and the temperature control unit controls the voltage to the high frequency induction coil to keep the temperature in the canister constant based on the detected value.

  However, the structure of the conventional melting furnace has a large gap between the top of the canister and the steps of the loading unit and the lifting unit, so that when a melting object containing a large amount of low melting point metal is put into the canister, it melts. The object burned instantaneously and burned up, and this burning flame passed through the gap and continuously circulated around the outer periphery of the canister for several seconds. A radiation thermometer that monitors the outer peripheral surface temperature of the canister judges that this combustion flame is an abnormal heat generation of the canister and automatically activates the interlock function, but there is no need to stop the melting furnace. First, there was a problem of stopping the melting furnace.

  Therefore, making the ratio of the low melting point metal and the high melting point metal constant in order to prevent the flame is problematic in that the sorting operation takes time and the melting operation is delayed.

  Then, a timer function is added to the sequencer program as a detection prevention measure, and a measure is taken to prevent the melting furnace from being stopped by determining that the continuous high-temperature state within a certain period of time is a combustion flame. It was.

  However, even if a timer is added, it is effective when the combustion flame is generated for several seconds, but if it is continuously generated for several tens of seconds, it is determined whether the combustion flame is hot or abnormal canister heat. There was a problem that the time to be used as a threshold for determination could not be determined, and this measure was not perfect.

  Therefore, the present invention has been made in view of the above problems, and provides a melting furnace structure that prevents the combustion flame from wrapping around the outer periphery of the canister.

The melting furnace structure of the present invention that prevents the combustion flame from wrapping around the outer periphery of the canister, which solves the above problems, has a lower inner diameter that is larger than the upper inner diameter, and the boundary portion between the lower and upper portions has a stepped cylindrical shape with different inner diameters. And a loading section for installing a canister on the lower inner side of the cylindrical shape, an elevating section for installing a charging container for supplying an object to be melted to the canister on the upper inner side of the cylindrical shape, and a radiation thermometer for measuring the outer peripheral surface temperature of the canister A melting furnace that controls the temperature in the melting furnace based on the detection signal of the radiation thermometer, and that the minimum dimension of the gap between the top of the canister and the upper end of the loading section is 3 cm Features (first invention).

According to a second aspect of the present invention, the inner diameter of the lower part is larger than the inner diameter of the upper part, the boundary part between the lower part and the upper part has a cylindrical shape with different inner diameters having a step, a loading part in which a canister is installed in the cylindrical inner lower part, An elevating part for installing a charging container for supplying an object to be melted to the canister on the inner upper side, and a radiation thermometer for measuring the outer peripheral surface temperature of the canister, and based on the detection signal of the radiation thermometer, A melting furnace for controlling temperature, a spacer ring for adjusting the amount of combustion oxygen supplied between the top of the canister and the upper end of the loading unit, the outer diameter of which is an inner diameter of the loading unit A spacer ring having an inner diameter equal to that of the elevating part is fixed to the lower part of the step position between the loading part and the elevating part .

According to a third invention, in the first invention, a spacer ring having an outer diameter equal to an inner diameter of the loading part and an inner diameter equal to the raising / lowering part is fixed at a lower part of the step position between the loading part and the lifting part. The minimum dimension of the gap between the lower surface of the ring and the top of the canister is set to 3 cm .

  According to the present invention, the combustion flame does not circulate to the outer periphery of the canister, the detection of the combustion flame temperature of the radiation thermometer can be prevented, and the automatic stop of the melting furnace can be prevented beforehand.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a radioactive waste treatment facility in the first embodiment of the present invention. The miscellaneous solid waste melting facility includes a pretreatment facility 1 for sorting miscellaneous solid waste, a melting facility 2 for melting fusible waste among the sorted miscellaneous solid waste, and a post-melting end It consists of a mortar solidification facility 3 in which a drum can containing molten waste is filled with mortar to obtain a solidified solid body, and a storage facility 4 for temporarily storing the solidified solidified body.

  In the pretreatment facility 1, miscellaneous solid wastes of low-level radioactive wastes with different types of properties (materials, dimensions, shapes, etc.) generated in nuclear power generation facilities are unprocessed wastes 6, direct packing 7 The molten object 8 is divided into three sections.

  The object to be melted 8 separated in the pretreatment facility 1 is a non-combustible material such as metals such as carbon steel and stainless steel, concrete, heat insulating material, and glass inorganic materials that can be reduced in volume by melting. It is stored in the charging container 11 or the canister 12 by the storage means 13 such as work or a conveyor, and is carried out to the melting facility 2 by the carrying-out means 14 such as a crane or a conveyor.

  FIG. 2 is a view showing a melting facility having a melting furnace structure for preventing the combustion flame from wrapping around the outer periphery of the canister in the first embodiment of the present invention. As shown in FIG. 2, the melting facility 2 has a cylindrical shape, and a loading portion 21 a for loading the canister 12 having a lower opening is formed inside the cylindrical shape, and the diameter is reduced by one step from the loading portion 21 a at the upper portion thereof. In addition, a cylindrical elevating part 21b through which the charging container 11 having an open top is inserted is opened, and the passage 21b communicates with a flue 26 on one side and a monitoring camera hole 120 on the other side. A melting furnace 21 in which a high-frequency induction coil 20 is spirally wound around a lower portion of a cylindrical inner surface, and a canister 12 in which an object 8 to be melted is packed in advance as an initial load from the lower side of the melting furnace 21. Is moved to the inside of the high frequency induction coil 20, and after the end of melting, the canister 12 is lowered and moved to the cooling device 22 and the initially loaded melting object 8 is melted. When the volume is reduced, there is room in the canister 12, so that the melting object 8 is lowered from the upper side of the melting furnace 21, and the lower gate is opened to introduce the melting object 8 into the canister 12. A charging device 24, a filter 27 for filtering dust in the exhaust, an exhaust gas blower for sucking the exhaust, and an exhaust treatment device 29 for detoxifying the exhaust sucked by the exhaust gas blower are provided.

  In addition, a total of eight radiation thermometers 140 are arranged in two upper and lower rows in four orthogonal directions inside the melting furnace main body in the circumferential direction of the loading portion 21a, and detection signals of each thermometer 140 are provided in the control chamber. The temperature control unit 141 inputs the voltage, and the temperature control unit 141 controls the voltage with respect to the high frequency induction coil 20 based on the detected value.

  FIG. 3 is a view showing a melting furnace having a melting furnace structure for preventing the combustion flame from wrapping around the outer periphery of the canister in the first embodiment of the present invention. As shown in FIG. 3, a spacer ring 142 made of a heat-resistant material having an outer diameter equal to that of the loading portion 21a and an inner diameter equal to that of the lifting portion 21b is fixed at the lower portion of the step position between the loading portion 21a and the lifting portion 21b. The gap dimension d in the height direction between the lower surface of the spacer ring 142 and the top of the canister 12 is set to the minimum.

  For example, when the outer diameter of the canister 12 is 54 cm, the gap dimension d is preferably 3 cm as an actual dimension, and the thickness of the spacer ring 142 is set accordingly.

  The reason for this is that the amount of oxygen necessary for burning the melted object per unit time is equal to the amount of oxygen that can pass through the gap between the top of the canister 12 and the steps of the loading unit 21a and the lifting unit 21b per unit time. The gap dimension d is 3 cm.

  In addition, when the gap dimension d is smaller than 3 cm, there is a possibility that the spacer ring 142 may be damaged by colliding with the lower end of the spacer ring 142 when the canister 12 is loaded.

  When the gap dimension d is larger than 3 cm, when a combustion flame is generated, a part of the combustion flame passes through the gap and wraps around the outer surface of the canister 12, and the above-described radiation thermometer 140 has an error. Causes detection.

  Therefore, the present inventors have found that the gap dimension d does not act as the flow space of the combustion flame by setting the gap dimension of about 3 cm in the height direction among the relative dimensions of the respective parts as described above. Obtained.

  FIG. 4 is a diagram showing a state of occurrence of a combustion flame when an object to be melted is put into a canister of a melting furnace provided with a melting furnace structure that prevents wraparound to the outer periphery of the canister in the first embodiment of the present invention.

  As shown in FIG. 4, in a state where the charging container 11 is lowered, the gate is opened, and the contents are charged into the canister 12 containing the melt, a large amount of low melting point metal is present in the contents and abruptly. Even when combustion occurs, all of the combustion flames rise only to the lifting / lowering portion 21b side and prevent the canister 12 from wrapping around the outer peripheral surface.

  In addition to the above embodiment, the canister 12 can be changed in height and the thickness of the canister 12 spacer 12a installed on the support 12 can be changed. However, the canister 12 itself is a standard product. Since the standard change leads to an increase in cost and the current positional relationship between the loading position of the canister 12 and the high frequency induction coil 20 is the position where the optimum efficiency is achieved, the spacer ring 142 is interposed as in the first embodiment. It is desirable.

It is a figure which shows the whole structure of the radioactive waste processing equipment in 1st embodiment of this invention. It is a figure which shows the melting equipment provided with the melting furnace structure which prevents the surrounding of the canister of the combustion flame in 1st embodiment of this invention to the outer periphery. It is a figure which shows the melting furnace provided with the melting furnace structure which prevents the wraparound of the combustion flame to the canister outer periphery in 1st embodiment of this invention. It is a figure which shows the generation | occurrence | production state of a combustion flame when a fusion | melting target object is thrown in in the canister of the melting furnace provided with the melting furnace structure which prevents the wraparound to the canister outer periphery in 1st embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pretreatment equipment 2 Melting equipment 3 Mortar solidification equipment 4 Storage equipment 5 Miscellaneous solid waste 6 Unprocessed waste 7 Direct filling 8 Melting object 9 Sorting table 10 Cutting machine 11 Input container 12 Canister 13 Storage means 14 Unloading means DESCRIPTION OF SYMBOLS 15 Drum can 16 Unloading means 20 High frequency induction coil 21 Melting furnace 21a Loading part 21b Elevating part 22 Cooling device 23 Moving device 24 Input device 25 Monitoring camera 26 Flue 27 Filter 29 Exhaust treatment device 30 Flue piping 31 Molten waste 32 Drum can 140 Radiation thermometer 141 Temperature controller 142 Spacer ring d Gap size

Claims (3)

The lower inner diameter is larger than the upper inner diameter, the boundary between the lower part and the upper part has a stepped cylindrical shape with different inner diameters, and a loading part for installing a canister on the cylindrical inner lower part,
An elevating part for installing a charging container for supplying a melting object to the canister on the cylindrical inner upper part,
A radiation thermometer for measuring the outer peripheral surface temperature of the canister,
A melting furnace for controlling the temperature in the melting furnace based on the detection signal of the radiation thermometer,
A melting furnace structure characterized in that a minimum dimension of a gap between a top portion of the canister and an upper end of the loading portion is 3 cm . The lower inner diameter is larger than the upper inner diameter, the boundary between the lower part and the upper part has a stepped cylindrical shape with different inner diameters, and a loading part for installing a canister on the cylindrical inner lower part,
An elevating part for installing a charging container for supplying a melting object to the canister on the cylindrical inner upper part,
A radiation thermometer for measuring the outer peripheral surface temperature of the canister,
A melting furnace for controlling the temperature in the melting furnace based on the detection signal of the radiation thermometer,
A spacer ring for adjusting the amount of combustion oxygen supplied between the top of the canister and the upper end of the loading unit, wherein the outer diameter is equal to the inner diameter of the loading unit and the inner diameter is equal to the lifting unit A melting furnace structure for preventing a combustion flame from wrapping around an outer periphery of a canister, characterized in that a ring is fixed at a lower part of a step position between the loading part and the elevating part . A spacer ring having an outer diameter equal to the inner diameter of the loading portion and an inner diameter equal to the lifting portion is fixed at the lower part of the step position between the loading portion and the lifting portion, and a gap between the lower surface of the spacer ring and the top portion of the canister The melting furnace structure according to claim 1, wherein the minimum dimension is set to 3 cm .