JP6670037B2 - Processing method of fly ash containing radioactive material - Google Patents

Description

The present invention relates to contamination by radioactive material incineration, calcination, to how to process the fly ash containing radioactive substances generated in such when melted.

  When contaminants contaminated by radioactive materials such as cesium scattered in the nuclear accident accompanying the earthquake, such as plants such as trees and dead leaves, household waste, soil, rubble, etc., heat treatment by means such as incineration, firing, melting, etc. Radioactive substances such as cesium-134 and cesium-137 are volatilized, and then cooled and solidified to generate incinerated fly ash and molten fly ash in which the radioactive substance is concentrated. This fly ash has a radioactivity concentration several tens times that of the contaminants before the heat treatment.

  Therefore, such fly ash has been appropriately treated in accordance with the radioactive substance content. Fly ash with a radioactive material content of 8,000 Bq / kg or less is disposed of in the same manner as general waste, and fly ash with a content of 8,000 Bq / kg to 100,000 Bq / kg is cemented so that the radioactive material does not elute. Fly ash exceeding 100,000 Bq / kg is stored and managed in an interim storage facility or cut-off type disposal site after being disposed of after taking measures such as solidification.

However, it is not easy to secure a landfill that disposes of the fly ash in the same way as general waste, and it requires a great deal of cost to prevent radioactive substances from being eluted from the fly ash. There was a limit to the amount of fly ash that could be stored and managed at the landfill site. In addition, fly ash is generally small in particle size of several microns and has a bulk density of 0.2 to 0.4 g / cm ³ and is easy to be scattered. There was room for improvement in handling such as storage and transportation.

  Therefore, it is easy to secure landfills, reduce the cost of preventing the elution of radioactive materials from fly ash, reduce the storage and management costs of fly ash, and facilitate the handling of fly ash storage and transportation. Therefore, it is effective to reduce and solidify the fly ash by pressure molding for treatment.

  As a technique related to the pressure molding, Patent Literature 1 describes a method in which a binder and water are added to incinerated ash, mixed, and then subjected to pressure molding to reduce the volume and solidify. Patent Document 2 describes a method in which a binding agent such as slaked lime, gypsum, clay or cement and water are added to coal ash and mixed, and the kneaded material is pressure-formed by a roll-type pressure forming machine. ing. Further, Patent Literature 3 discloses a method in which cement fly ash is pressure-formed by a continuous roll pressure forming method.

JP-A-10-202219 JP-A-9-75890 JP 2000-140793 A

  However, in the methods described in Patent Literature 1 and Patent Literature 2, since it is necessary to add a binder, a binder, and water to incineration ash or coal ash, which are objects of pressure molding, these adding devices are used. And a mixing device, which increases the cost of the device and the cost of operation. Further, according to the method described in Patent Document 3, fly ash having a low bulk specific gravity is not easy to be caught between rolls even when vibrated and degassed. And it is difficult to obtain a molded product.

  Therefore, the present invention has been made in view of the above-described problems in the related art, and has an object to efficiently and efficiently process fly ash containing a radioactive substance at low cost.

To achieve the above object, the present invention provides a method of treating fly ash containing radioactive materials, including radioactive materials, fly ash bulk density of 0.2-0.4 g / cm ³ by a hydraulic press It is characterized by performing pressure molding and pulverizing a molded product obtained by the pressure molding.

  According to the present invention, fly ash containing a radioactive substance is formed by pressure molding with a hydraulic press, so that fly ash having a low bulk specific gravity can be formed at a high volume reduction rate without using a binder, a binder and water. It can be molded under pressure. Further, when a molded product of the hydraulic press machine is stored and stored in its original shape, a gap is generated. However, by shredding the molded product, the volume reduction rate can be further increased.

Further, by setting the molding pressure to 0.5 t / cm ² or more and 2.5 t / cm ² or less, a high volume reduction rate can be obtained while appropriately maintaining the molding pressure and suppressing an increase in operating cost. .

  Furthermore, the 50 mm passage of the crushed product is 100 mass%, the 10 mm passage is 80 mass% to 100 mass%, the 5 mm passage is 70 mass% to 90 mass%, and the 1 mm passage is 10 mass% to 60 mass%. The molded product can be crushed so that the amount of passage through 0.5 mm is 10% by mass or more and 40% by mass or less, and the bulk density of the crushed product can be increased.

  The fly ash containing the radioactive material can be obtained by heat treatment such as incineration, burning, and melting of the radioactive waste, and the fly ash generated by the incineration of the radioactive waste and the like. Ash can be efficiently treated at low cost.

  As described above, according to the present invention, fly ash containing a radioactive substance can be efficiently processed at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows an example of the apparatus for implementing the processing method of the fly ash containing a radioactive substance which concerns on this invention. It is a graph which shows the operation example of the hydraulic press of the fly ash processing apparatus shown in FIG. It is a graph which shows the operation example of a compacting machine. It is a graph which shows the operation example of the hammer mill of the fly ash processing apparatus shown in FIG.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of an apparatus for carrying out a method for treating fly ash containing a radioactive substance according to the present invention. A dust collector 2, a hydraulic press machine 3 for press-molding fly ash A collected by the dust collector 2, a hammer mill 4 for crushing a molded product P by the hydraulic press machine 3, and a crushed product Q by the hammer mill 4. And a storage container 5.

A bag filter or the like can be used as the dust collector 2, and a filter capable of collecting fly ash A having a particle size of several microns and a bulk density of 0.2 to 0.4 g / cm ³ can be used.

  The hydraulic press 3 is a device that pressurizes the supplied fly ash A with a hydraulic cylinder in a mold to form a column having a diameter of about 100 mm, and a general-purpose hydraulic press can be used. The molding pressure can be changed by adjusting the hydraulic pressure of the hydraulic cylinder.

  The hammer mill 4 is provided for pulverizing the molded product P. Although not shown, the hammer mill 4 rotates a cylinder or the like having a plurality of hammers mounted on the outer periphery, and crushes the molded product P by impact and friction. Instead of the hammer mill 4, a feather mill for rotating a knife-shaped hammer at a high speed, a cutter mill having a cutter blade mounted on a rotor and a fixed blade mounted on a casing, and the like can be used. Can also be used.

  Next, the operation of the processing apparatus 1 having the above configuration will be described with reference to FIG.

  A dust collector that removes fly ash A containing radioactive substances from exhaust gas from incinerators and melting furnaces that incinerates and melts contaminants due to radioactive substances such as cesium, for example, exhaust gas G1 from a rotary kiln that removes radioactive substances from soil containing radioactive substances The exhaust gas G2 after collection and dust collection is exhausted, and the collected fly ash A is supplied to the hydraulic press machine 3 and molded to obtain a cylindrical molded product P.

FIG. 2 shows that the bulk density is 0 . The relationship between the molding pressure when the fly ash A of about 2 g / cm ³ is molded by the hydraulic press 3 and the density of the molded product P is shown. As the molding pressure increases, the density of the molded article P also increases, and the density of the molded article P can be increased to about 2.0 g / cm ³ which is about 10 times that before molding. Therefore, the molding pressure is desirably 0.5 t / cm ² or more, and more desirably 1.0 t / cm ² or more, in order to increase the density of the molded article P. When the molding pressure exceeds 2.5 t / cm ² , the density of the molded article P is approximately constant at about 2.0 g / cm ^3. cm ² or less, more preferably 2.0 t / cm ² or more.

On the other hand, FIG. 3 shows a compacting machine in which fly ash is forcibly supplied between two rolls by a vertical screw, and fly ash A having the same physical properties as above is compression-molded between the two rotating rolls. The example of operation of FIG. The density of the molded product was calculated from the dimensions and mass of the obtained molded product. It can be seen from the figure that there is no significant difference in the density of the molded product even when the roll pressure or the roll interval is changed, and the density of the molded product does not exceed 1 g / cm ³ .

  From FIGS. 2 and 3, it can be seen that a molded product having a higher density can be obtained by using a hydraulic press than by using a roll press such as a compacting machine.

  Returning to FIG. 1, the molded product P generated by the hydraulic press 3 is crushed by the hammer mill 4 and the crushed product Q is stored in the storage container 5.

  Table 1 shows the particle size distribution and bulk density of a crushed product Q obtained by crushing a molded product P obtained by the hydraulic press 3 with a hammer mill 4. FIG. 4 is a graph of the particle size distribution of the crushed product Q. From these, when the ratio of each particle size of the crushed product Q is nearly equal (Examples 1 to 3), the bulk density of the crushed product Q is large, but the ratio of each particle size of the crushed product Q is on the coarse side or the fine side. It can be seen that in the case of a bias (Examples 4 to 9), the bulk density of the crushed product Q is small.

  As described above, according to the present embodiment, the fly ash A containing a radioactive substance is pressure-molded by the hydraulic press 3, so that the bulk specific gravity is small without using a binder, a binder and water. Fly ash A can be pressure molded at a high volume reduction rate. Further, when the molded product P of the hydraulic press 3 is stored and stored in the shape as it is, a gap is generated. However, by disintegrating the molded product P, the volume reduction rate can be further increased.

  In addition, the particle size distribution of the crushed product Q is adjusted by adjusting the type, number or rotation speed of the hammer used for the hammer mill 4, using a feather mill or a cutter mill instead of the hammer mill, or using a combination of sieves. Can be adjusted.

Reference Signs List 1 Processing device for fly ash containing radioactive substances 2 Dust collector 3 Hydraulic press machine 4 Hammer mill 5 Storage container A Fly ash G1, G2 Exhaust gas P Molded product Q Disintegrated product

Claims (4)

The fly ash containing a radioactive substance and having a bulk density of 0.2 to 0.4 g / cm ³ is pressure-formed by a hydraulic press machine,
A method for treating fly ash containing a radioactive substance, wherein the molded article obtained by the pressure molding is crushed. The method for treating fly ash containing a radioactive substance according to claim 1, wherein the molding pressure is set to 0.5 t / cm ² or more and 2.5 t / cm ² or less.   100% by mass for 50mm passage of the crushed product, 80% by mass or more and 100% by mass or less for 10mm passage, 70% by mass or more and 90% by mass or less for 5mm passage, 10% by mass or more and 60% by mass or less for 0mm passage The method for treating fly ash containing a radioactive substance according to claim 1 or 2, wherein the molded product is pulverized so that a passage amount of 0.5 mm is 10% by mass or more and 40% by mass or less.   The method for treating fly ash containing a radioactive substance according to claim 1, wherein the fly ash containing a radioactive substance is obtained by heat-treating waste containing a radioactive substance.

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