JP2008107233A - Incineration processing method of molding used in nuclear power generation facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of performing inexpensive, efficient and stable incineration processing of a rubber or plastic molding used in a nuclear power generation facility. <P>SOLUTION: In the method for performing the incineration processing of the rubber or plastic molding used in the nuclear power generation facility, the molding is frozen and embrittled in an atmosphere of an ultra-low temperature, and the frozen and embrittled molding is crushed into particles, and then mixed with a combustible binder to form a solidified body, and then incinerated. The atmosphere of the ultra-low temperature is below -70°C, and the molding crushed into particles has a particle size of 5 mm, preferably 1.5 mm or less. The binder has a melting point of 80°C or below, and solid oil paraffin or vegetable wax can be used therefor at a room temperature, and the mixing ratio between the binder and crushed objects of the molding may be 3/1-1/3 in the weight ratio, and slaked lime may be mixed additionally at a mixing time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to processing technology for molded products used in nuclear power generation facilities, and in particular freeze-grinds molded products containing radioactive materials such as rubber gloves, rubber boots, and flame retardant sheets that are generated in large quantities during equipment operation and inspection work. However, the present invention relates to a technique for incineration, and provides an effective means for easily incinerating a radioactive molded product with an existing incinerator.

  Radioactive rubber gloves, rubber boots, flame retardant sheets, and other molded articles that are difficult to incinerate (hereinafter referred to as flame retardants) are generated within the power generation facility. Incinerators are incinerated with a large amount of combustible materials. Recently, the introduction of combustible materials into power generation facilities has been restricted due to disaster prevention reasons, and combustible materials have been reduced. As a result, the treatment of incombustible materials has become unsmooth and is stored as solid waste in the facility. The amount is increasing. Moreover, since the above-mentioned radioactive flame retardant has a large body, when it is incinerated as it is, it is not combusted sufficiently, the incineration residue increases, and there is a problem that efficient incineration cannot be performed. Furthermore, these radioactive flame retardants also have problems in handling such that they cannot be pulverized by ordinary means.

As a method for treating radioactive flame retardant materials, many methods have been proposed and applied.
Specifically, as a chemical treatment method, a wet decomposition method that utilizes the oxidizing power of hydrogen peroxide ("development of waste resin volume reduction device"; FAPIG 121, 1989-3; p.42-46). ), Or supercritical water treatment system that decomposes organic molecules using activated water molecules in a gas-liquid integrated state obtained by putting water in a pressure vessel and raising the temperature and pressure (""Waste treatment system using supercritical water"; Toshiba review Vol. 56 No. 9 (2001); As a thermal decomposition method, a rotary kiln method, an IC plasma (high frequency inductively coupled plasma) method (“demonstration performance test of a real scale 1C plasma waste resin volume reduction device”, thermal nuclear power generation Vol. However, since they dislike the presence of moisture, it is necessary to remove the water in the resin grains in advance. As a steam method, a steam reformer method (THOR method: Thermal reduction process: thermal organic reduction method) in which water vapor is contacted and decomposed has been proposed ("Recent movements in radioactive waste treatment"; FAPIG No. 157). (2001-3), p18), there is a problem that the apparatus becomes large and the equipment investment and running cost are high. As a melting method, a high-frequency melting method in which a synthetic resin is added and melted in a metal melted by high-frequency (“Development of a high-frequency melting processing system for radioactive solid waste”; FAPIG No. 162 (2002-11); p. 18-23) are in the development stage. As a direct treatment method, an incineration method (“incineration of used ion exchange resin”; thermal nuclear power generation Vol. 41 No. 5, May 1990; p. 70-77) has been studied for practical use. However, there is a problem of SOx generation during synthetic resin incineration. In addition, a dehydrating cement solidification method (“Radioactive Waste Management Japanese Technology Development and Planning”, Japan Nuclear Industry Council, July 31, 1997; p. 80-82) has been proposed in which synthetic resin is added to the cement. There is a problem that the volume cannot be reduced and the disposal cost becomes too high.

As described above, in the various methods proposed so far, the apparatus is complicated and difficult to control, the processing cost is excessive, the stable operation cannot be performed, there are many failures, and there are problems in materials. At present, there are many problems even if it has not been put into practical use for various reasons such as, or has been put into practical use.
In addition, although there exists RDF (waste solid) fuel as a prior art relevant to this invention, this technique is the method of pressure-molding after shredding waste, and the objective is to make waste into fuel. Therefore, this technique is fundamentally different from the technique of safely and easily disposing of radioactive waste by forming a mixture with a binder as in this technique.

“Development of waste resin volume reduction device”; FAPIG No. 121, 1989-3; p. 42-46 “Waste treatment system using supercritical water”; Toshiba Review Vol. 56No. 9 (2001); p. 58-61 “Demonstration performance test of real scale 1C plasma waste resin volume reduction device”; Thermal nuclear power generation Vol. 54No. 1 Jan. 2003 “Development of high-frequency melting treatment system for radioactive solid waste”; 162 (2002-11); p. 18-23 “Incineration of used ion exchange resin”; Thermal Power Generation Vol. 41No. 5, May 1990; 70-77 “Recent developments in radioactive waste treatment”; 157 (2001-3), P18 "Radioactive Waste Management Japanese Technology Development and Planning" Japan Nuclear Industry Council July 31, 1997; p. 80-82

  The present invention belongs to the above-mentioned incineration treatment, flame retardant which is a problem of the prior art cannot be pulverized (cannot be granulated necessary for the incineration treatment), it is difficult to ensure combustible materials, To provide an incineration method that eliminates all the difficulties of incineration in the incinerator (there is rust and does not accumulate enough at the bottom of the incinerator) and enables efficient and stable incineration at low cost. This is the issue.

In order to solve the above problems, in the present invention, in a method of incinerating a rubber or plastic molded product used in a nuclear power generation facility, the molded product is freeze embrittled in an atmosphere at an ultra-low temperature, An incineration processing method characterized in that after freeze-brittled molded product is pulverized into particles, mixed with a combustible binder, formed into a solidified body that can be incinerated in a normal incinerator, and then incinerated. It is a thing.
In the incineration method, the atmosphere under ultra-low temperature may be a temperature at which the molded product can be freeze embrittled, and is −75 ° C. or lower when the molded product is made of rubber, and −70 ° C. when the molded product is made of plastic. The molded product pulverized into particles is preferably 5 mm or less, particularly 1.5 mm or less, and the combustible binder has a melting point of 80 ° C. or less. Therefore, it is preferable to use petroleum paraffin or vegetable wax that is solid at normal temperature, and the mixing ratio of the combustible binder and the pulverized product is 3/1 to 1/3 in weight ratio. Is good.
Further, in the mixing of the combustible binder and the pulverized product, a calcium compound, preferably slaked lime, may be added in order to prevent generation of harmful gases such as SOx during incineration. The rubber or plastic molded product to be incinerated can be mixed with a radioactive ion exchange resin generated in a nuclear power generation facility.

The present invention is difficult to handle normally, these radioactive flame retardants are brought into contact with liquid nitrogen gas, frozen and pulverized, solidified with a low melting point combustible material such as petroleum paraffin, easily transported, existing incineration It is an epoch-making means to solve the problem of radioactive waste disposal by making the incineration process possible with equipment.
In the nuclear power generation facility, the storage amount is increasing because there is no appropriate treatment method, and rubber gloves, rubber boots, flame retardant plastics, which are expected to increase due to aging of the plant in the future. Sheets and other radioactive flame retardants are cut into a string with a Schretter etc., frozen in an ultra-low temperature atmosphere with liquid nitrogen, etc., pulverized into particles, and then mixed uniformly with a combustible binder such as granular petroleum paraffin, Providing technology that enables easy incineration using existing incineration facilities installed at each facility for incineration of radioactive miscellaneous solids by molding into solidified bodies of appropriate dimensions using a kneading type extrusion molding machine Is.
In this way, radioactive flame retardants stored in large quantities at nuclear power generation facilities can be incinerated easily and efficiently at a low cost in the same way as incineration of conventional miscellaneous solids without modifying existing incineration facilities. Therefore, it is a technology that leads to a reduction in radioactive waste disposal costs, and its ripple effect is enormous.

The nuclear power generation facility has an incinerator for processing combustible waste. In general, flame retardants such as rubber gloves, rubber boots, and flame retardant plastic sheets are flame retardant but can be decomposed and burned at high temperatures, so they can be mixed with other wastes into incinerators. It is thrown in and incinerated. However, rubber gloves, rubber boots, flame retardant plastic sheets, etc. are large and therefore remain unburned.
For this reason, in each current nuclear power generation facility, these radioactive flame retardants are incinerated with small amounts of flammable waste, but the amount of processing cannot keep up with the amount generated, It is stored in a solid waste storage area, and its storage volume is also increasing.
In the future, it is expected that the amount of radioactive flame retardants generated annually will increase further with the aging of power generation facilities. Therefore, the treatment of these radioactive flame retardants has become one of the top priorities for nuclear power plants.
The present invention freezes and pulverizes radioactive flame retardants such as rubber gloves, rubber boots and flame retardant plastic sheets during storage, and then has a relatively low melting point such as petroleum paraffin and vegetable wax, and is solid at room temperature. Existing plant owned by nuclear power generation facilities by mixing with a certain granular material and forming it into a solidified solid body such as a spherical or rod-like size that can be easily loaded into an incinerator and incinerated by a kneading extrusion molding method. It provides a means that can be handled by an incineration facility.

The present invention will be described in detail below.
The rubber or plastic molded products to be incinerated in the present invention are rubber gloves, rubber boots, flame retardant plastic sheets, etc., and these are usually incinerated due to the large amount of gas accumulated at the bottom of the furnace. In the present invention, these are referred to as flame retardants.
In the present invention, the molded product can be appropriately cut and frozen, and the ultra-low temperature atmosphere is a temperature at which the molded product is frozen and embrittled. Is a temperature of −70 ° C. or lower, for example, a method of contacting with a cryogenic refrigerant such as liquid nitrogen (−195.8 ° C.), liquid air (−195.8 ° C.), liquid oxygen (−183 ° C.), or dry A cryogen of ice or dry ice and a solvent such as methanol, ethanol, acetone, or ether can be used.

In addition, the freeze-fried molded product can be easily pulverized using a commonly used pulverizer such as a hammer mill, a ball mill, etc. The particle size of the pulverized molded product is mixed with a combustible binder. Considering the strength and shape of the solidified body, it should be 5 mm or less, particularly 1.5 mm or less.
The combustible binder that can be used in the present invention is preferably made of a substance having a melting point of 80 ° C. or lower and a solid at room temperature. Preferably, the melting point is about 50 ° C. to 70 ° C., and particularly preferably 50 ° C. or more and 60 ° C. or less. Although it is not impossible to use a combustible binder having a melting point exceeding 80 ° C., it is not preferable because the energy required for liquefying the combustible binder increases.
In the present invention, when the combustible binder is kneaded, it is preferable to use the combustible binder in a softened state below the melting point.

Preferred examples of the combustible binder that can be used in the present invention include petroleum paraffin, vegetable wax, wood wax, and white wax. As the petroleum paraffin, a paraffin wax having a melting point of 50 ° C. or more, for example, 125P, 130P, 135P, 140P, 145P, 150P, 155P, etc. defined in JISK2235 can be preferably used. When the combustible binder is used in liquid form, 130P is preferable. When the combustible binder is used in powder or granular form, 155P (granular, granular, powdery) or 140P (granular) is preferred. Note that the “melting point” of paraffin wax is the temperature at which the temperature drop rate of the sample falls below a prescribed rate when the molten sample is allowed to cool under predetermined conditions (JISK2235).
In the present invention, the mixing ratio of the combustible binder and the pulverized product is preferably 3/1 to 1/3, more preferably 2/1 to 1/2. Moreover, in these mixing, a calcium compound, especially slaked lime can be appropriately added according to the content of sulfur in the molded product to be treated. Usually, 5% by weight or less of the molded product to be treated is sufficient.

The shape and size of the solidified product of the pulverized product and the binder of the present invention are not particularly limited, but may be a shape and size that can be incinerated with ordinary incineration facilities possessed by steam power generation facilities and the like. preferable. For example, it is preferably a size that does not pass through the grate of the incinerator, preferably a size of about 2 to 3 cm in diameter and about 3 to 5 cm in length, and has a spherical shape, a cylindrical shape, a prismatic shape, or the like.
Further, the solidified body has such a strength that it can be incinerated with an incineration facility owned by a general nuclear power plant. Specifically, the solidified body with a strength not to be crushed when it is put into an incineration facility, typically 3 cm in diameter and 5 cm in length, is freely dropped from a height of 3 meters onto a flat concrete floor. In such a case, it is preferable to have a strength that does not cause significant deformation or cracking by visual observation.

Next, an example of incineration using rubber gloves that can be regarded as equivalent to a flame-retardant material held in a nuclear power generation facility is shown.
Prepare a large amount of used rubber gloves that can be regarded as equivalent to the rubber gloves used in nuclear power generation facilities, and cut them with a shredder if necessary.
The cut rubber gloves are transferred to the freezer compartment by a conveyor or the like, and when the mist of liquid nitrogen at −196 ° C. is dropped on the cut rubber gloves, the mist immediately evaporates and the cut rubber gloves are cut. Is deprived of heat and becomes brittle. By circulating nitrogen gas into the freezer compartment, the cooling effect can be promoted.
The frozen rubber gloves are transferred to a pulverization process by a conveyor or the like and pulverized by a hammer mill or the like.
The particle size at the time of pulverization is adjusted to about 0.5 to 1.0 mm.

In order to fix the pulverized product, particulate petroleum paraffin was used as an example. The mixing ratio was as follows by weight ratio.
Grinded rubber gloves: 70 parts Petroleum paraffin: 30 parts Weighed and mixed granular petroleum paraffin as a binder and crushed rubber gloves, put them into a kneading type extrusion molding machine, and mixed in an incinerator. A solidified body is produced.
The manufactured solid is sampled and inspected for appearance, shape, hardness and strength to confirm that it is within the standards.
Appearance: Visually confirm that the resin and binder are uniformly mixed and that there are no harmful cracks, shrinkage cavities, etc.
Dimensions: φ20 × 30mm Strength: Drop from a height of about 3m and confirm that it does not break.
Shape: Visually confirm that there is no deformation or crushing.
Using an incinerator or the like possessed by each nuclear power generation facility, the solidified body produced by the above-described means is incinerated at an incineration temperature of 700 to 800 ° C.

Next, description will be made with reference to the flow configuration diagrams of FIGS. 1 and 2 showing an example of the processing flow of the present invention.
In FIG. 1, a molded product such as a rubber glove used in a nuclear power generation facility is stored in a storage tank 1, and the stored molded product is taken out from the storage tank 1 and introduced into a freeze brittle apparatus 10 in an ultra-low temperature atmosphere. Then, the freeze-fried molded product is pulverized into particles by the pulverizer 20, and the pulverized product is supplied to the mixing tank 40 using the conveying means 30. The mixing tank 40 includes a stirrer. In the mixing tank 40, petroleum paraffin is dissolved in the dissolution tank 50 as a combustible binder, and the dissolved petroleum paraffin is kept at about 80 ° C. while maintaining the temperature of the molded product. Mix with pulverized product until uniform to form slurry.
The obtained slurry is molded by the molding machine 60 to obtain a solidified body, which is sent to the solidified body receiving tank 70 and stored until it is subjected to incineration.

FIG. 2 is a flowchart showing another example of the present invention. In FIG. 2, processing is performed according to the following flow.
Prepare used rubber gloves → Cut with a shredder → Transfer to a freezer and freeze with liquid nitrogen to embrittle → Send to the crushing process and pulverize with a hammer mill → Weigh and then mix with petroleum paraffin → Then it is put into a kneading type extrusion molding machine. → The molded solidified body is received in a transport container and transported to an incinerator for incineration.

Hereinafter, the present invention will be specifically described by way of examples.
Example 1
Prepare a rubber glove that can be regarded as equivalent to the rubber glove used at nuclear power generation facilities, cut it into a string with a shreter, put the cut rubber glove into a metal container, inject liquid nitrogen, cut the rubber glove When it becomes brittle and discolored, it is taken out and placed in a mortar and crushed.
Adjust the particle size of the powder to about 0.5 mm.
Weigh 0-15 g of petroleum paraffin and 5 g of crushed rubber gloves.
The petroleum paraffin used is a granular solid paraffin represented by C _n H _{2n + 2} having 100% hydrocarbon, and has a melting point of 69 ° C. and a flash point of 270 ° C.
Petroleum paraffin is put into a beaker, heated to 80 ° C. to dissolve, and a rubber glove crushed into the dissolved petroleum paraffin is added and stirred with a stirrer until visually uniform.

A mixture of petroleum paraffin and crushed rubber gloves is poured into a cylindrical form prepared in advance and cooled and solidified at room temperature.
After sufficiently cooling, the mold was removed and the solidified body was taken out. The appearance and shape were confirmed, and the hardness was measured with a hardness meter to confirm that the solidified body could be incinerated. (As shown in FIG. 3 and hardness data) Further, as a result of the drop test of the solidified body, it was confirmed that there was no breakage and that there was no problem in strength when it was put into the incinerator.
The solidified body was incinerated using an electric furnace with the same temperature conditions as the actual incinerator, and it was confirmed that it could be completely incinerated. (As shown in FIGS. 5-7)
For comparison, FIG. 4 shows an incineration state when the rubber gloves are incinerated as they are.
A plurality of solidified bodies can be prepared by changing the ratio of crushed rubber gloves and binder, and the ratio of binder / crushed rubber gloves can be molded and incinerated from 3/1 to 1/3 by weight. It was confirmed.
The results are shown in Table 1.

  As for the type of the binder, the same test was performed on vegetable wax in addition to petroleum paraffin, and as a result, satisfactory results equivalent to those of petroleum paraffin were obtained.

It is a flow block diagram which shows an example of the processing flow of the incineration processing method of this invention. It is a flow block diagram which shows another example of the processing flow of this invention. 2 is a photograph showing the solidified body of the present invention molded in Example 1. FIG. It is a photograph which shows the residue state after incineration processing at the time of incinerating rubber gloves as it is for comparison. It is a photograph which shows the residue state after the incineration processing of the solidified body of this invention shape | molded in Example 1. FIG. It is a photograph which shows the residue state after the incineration processing of the solidified body of this invention shape | molded in Example 1. FIG. It is a photograph which shows the residue state after the incineration processing of the solidified body of this invention shape | molded in Example 1. FIG.

Explanation of symbols

  1: Raw material storage tank, 10: Freezing embrittlement apparatus, 20: Crushing apparatus, 30: Conveying means, 40: Mixing tank, 60: Molding machine, 70: Solidified body receiving tank

Claims (7)

  In a method of incinerating a rubber or plastic molded product used in a nuclear power generation facility, the molded product is freeze embrittled in an atmosphere at an ultra-low temperature, and the freeze embrittled molded product is pulverized into particles. An incineration treatment method comprising: mixing with a combustible binder, forming into a solidified body that can be incinerated in a normal incinerator, and then incinerating.   2. The incineration treatment method according to claim 1, wherein the atmosphere under ultra-low temperature is −75 ° C. or lower when the molded product is made of rubber, and −70 ° C. or lower when the molded product is made of plastic.   The incineration processing method according to claim 1 or 2, wherein the molded product pulverized into particles has a particle diameter of 5 mm or less.   4. The incineration processing method according to claim 1, wherein the combustible binder is petroleum paraffin or vegetable wax having a melting point of 80 ° C. or less and solid at room temperature.   The incineration processing method according to any one of claims 1 to 4, wherein a mixing ratio of the combustible binder and the pulverized product is 3/1 to 1/3 in weight ratio. .   The incineration processing method according to any one of claims 1 to 5, wherein the combustible binder and the pulverized product are mixed by adding a calcium compound.   The incineration processing method according to any one of claims 1 to 6, wherein a radioactive ion exchange resin generated in a nuclear power generation facility is mixed with the molded product made of rubber or plastic.

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