JPH0697278B2 - Radioactive waste granulator - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a radioactive waste granulating apparatus, and particularly to a pretreatment suitable for smoothly molding pellets having a predetermined strength required for pressure molding. A granulator having a device.

[Background of the Invention]

Conventionally, as a method for treating radioactive waste generated in a nuclear power plant, so-called radioactive sludge waste (ion exchange resin for condensate and waste liquid purification, super-auxiliary agent for reactor water and waste liquid purification (e.g. powder ion exchange) Resin, cellulose, etc.), filter sludge, radioactive waste liquid, etc.) are formed into dry powder or, if necessary, further ashed and then granulated into pellets. Known as No. 55-95900, etc., it is generally practiced because it has excellent volume reduction and handling properties.

By the way, other radioactive wastes generated at nuclear power plants have not been pelletized as described above, but among them, so-called combustible miscellaneous solid wastes (wood-based materials, plastic-based materials such as vinyl chloride, etc.). If it is possible to perform the same pelletizing process as in the above sludge waste by incineration / ashing, it is possible not only to reduce the volume of waste and to improve the handling but also Furthermore, it can be said that it will be extremely useful for realizing a desirable waste treatment system that is a unified treatment of waste.

However, when the ashing-pelletizing process of such combustible miscellaneous solid waste is carried out by using the existing pelletizing device for pelletizing as it is, the pressure-molded pellets are However, there is a problem in that the case where the prescribed strength required as a seed pellet is not satisfied may be considered. This is because, for example, incineration ash obtained by incinerating and ashing the above combustible miscellaneous solid waste, it is considered that a substance with a large particle size is mixed as a defective combustion product or an incombustible product, resulting in granulation. When the pellets are composed of powder with non-uniform particle size and are stored as pellets as they are, or when they are further solidified with cement glass, etc., they have a sound and stable crush strength and fall. It is explained as a problem that it becomes difficult to retain the strength, and in addition, it is also explained that the mixing of the above-mentioned large-sized grain system causes a clogging of the granulator. Specifically, as the above-mentioned unsuitable granulation product,
Examples include unburned materials such as stones and metals, and poorly burned materials such as plastic and paper.

[Object of the Invention]

The present invention has been made in view of the above problems,
The purpose of the present invention is to provide a granulating apparatus suitable for ashing-pelletizing radioactive / combustible miscellaneous solid waste.

Another object of the present invention is to provide a granulating apparatus suitable for unifying the radioactive and combustible miscellaneous solid waste and the radioactive sludge waste for granulation and pelletizing.

[Outline of Invention]

The features of the radioactive waste granulating apparatus according to the present invention made to achieve the above-mentioned object are an incinerator for ashing radioactive / combustible miscellaneous solid waste generated in a nuclear power plant, and this incinerator. The incinerated ash obtained by
A separation device for separating the inadequate granules having a particle size of more than 5 mm from this incinerated ash, and a granulator for granulating the remaining incinerated ash of the inadequate granulated product are provided, and also The present invention is characterized by a granulating device configured to granulate sludge waste that has been dried and powdered (or further ashed if necessary) in a mixed state with the incinerated ash after the separation.

In the case of granulating the latter sludge waste in a mixed state, it is considered that there is basically no mixing of unsuitable granulation in the sludge waste. It is sufficient that the body (or ash) is mixed with the incinerated ash after the granulation-unsuitable matter is separated and subjected to unification treatment,
If necessary, the unsuitable granulation may be separated for the mixed state.

The powder (or ash) from the sludge waste and the incineration ash can be mixed at any ratio.

Example of Invention

 The present invention will be described below based on embodiments shown in the drawings.

Example 1 FIG. 1 shows a granulating apparatus for radioactive waste (pellet solidification) in which a substance suitable for granulation and a substance not suitable for granulation are sifted with a sieving machine as a pretreatment for granulation to make the particle size uniform. Equipment) System diagram is shown.

The concentrated sludge, the used resin, the used filter sludge, or the radioactive sludge waste which is a mixture of these in any ratio, is supplied to the circulation pump 2 in the supply tank 1.
The circulation is repeated by means of which uniform agitation is achieved. Further, the supply tank 1 is kept at a constant temperature so that the waste is not deposited. The waste sent to the dryer 4 at a constant flow rate by the metering pump 3 is dried and powderized by a known method, and then sent to the granulator 8.

On the other hand, the combustible miscellaneous solid waste is incinerated in the incinerator 5 by a known method. The incineration ash generated as a result of the incineration is sent to the sieving machine 7 by the feeder 6 and screened by a sieving machine (not shown) having a fixed mesh interval. The incinerated ash separated by the sieve is sent to the granulator 8. Each powder sent into the hopper 9 at the upper part of the granulator 8 is pushed into the pellet forming punch section by the stirring blade 10 and the stirring supply blade 11 which rotate at a constant speed. The pressed powder is granulated under a constant molding pressure, molding time, etc. by a rod 13 that is moved left and right by driving a hydraulic cylinder 12, and pellets having a constant shape are formed.
14 is molded.

The granulated pellets 14 are not stored according to a known method, and further solidified with cement glass, plastic or the like. Further, the unsuitable granules 15 separated by the sieving machine 7 are processed according to a known method without being pelletized, but the amount thereof is extremely small.

Next, the detailed structure of the sieving machine 7 will be further described with reference to FIG. 2. In the sieving machine of this example, a mesh that moves to the left or right by the power of the motor M is, for example, a 5 mm-interval mesh (mesh spacing is a pellet for pressure molding). The shape, granulation operation, crushing strength, drop strength, etc. are determined so as to satisfy the optimum values). Is removed, and only the powder having a particle size equal to or smaller than a certain value suitable for granulation is sent to the granulator through the feeder 17 to perform pressure molding of the pellet.

Further, after the screening operation, remaining on the sieve, unsuitable for granulation 15 having a certain particle size or more is uniformly put in a solidification container 18 different from the pressure-molded pellets 14 by tilting the screen, It is stored as it is, or is solidified with an appropriate solidifying agent such as cement glass or plastic.

Example 2 The present Example 2 shown in FIG. 3 is a granulation apparatus for radioactive waste (pellet solidification facility) when classifying substances suitable for granulation and incompatible substances by air as a pretreatment for granulation. A system diagram is shown.

As in the case of Example 1, the concentrated waste liquid, the used resin, the used filter sludge, or the radioactive sludge waste obtained by mixing these at an arbitrary ratio is dried into powder by the dryer 4 and then granulated. Sent to 8.

On the other hand, the combustible miscellaneous solid waste is incinerated by the incinerator 5, pulverized, and then cyclized by the feeder 6.
Sent to.

The incinerated ash sent to the cyclone 19 is classified by the air blown at a constant pressure, and then collected by the collector 20.
The incineration ash collected by the collecting machine 20 is sent to the granulating machine 8.

Thereafter, each powder sent into the hopper 9 at the upper part of the granulator 8 is granulated by the same method as in the first embodiment.

The air pressure of the cyclone 19 described above is appropriately determined based on predetermined conditions required for pelletizing operation, crushing strength, drop strength, etc. In contrast to the classification based on the standard, in this example, the classification based on the specific gravity is performed.

As described above, according to each of the examples, by dividing the powder into a substance suitable for granulation and a substance not suitable for granulation as a pretreatment for granulation, it is possible to eliminate clogging of the granulator. Grain motion can be performed.

Moreover, the fluctuation range of the pellet density when granulating various powders is 0 to 3%, and the fluctuation rate of the crushing strength is 0 to 20%, and the conventional pellets granulated without separating work by sieving or air. It has been confirmed that it is possible to secure a pellet having a more healthy and stable strength as compared with the above.

Next, the relationship between the particle size of incinerated ash, the strength of pellets, and the like in the case where the granulation suitable and unsuitable materials are separated and the case where the separation is not carried out will be described below with reference to Example 1.

Generally, the particle size distribution of substances contained in incineration ash obtained from combustible miscellaneous solid waste is shown in Table 1.

From this result, by performing pellet molding with the maximum particle size of incinerated ash set to 5 mm, it is possible to secure pellets with more sound and stable strength compared to conventional pellets that were granulated without performing sieving work. Was confirmed as follows (when the maximum particle size is 5 mm, it is desirable that 70 wt% or more of the particles with a particle size of 0.5 mm or less are present as shown in Table 1.) (1) Doublet granulation When using a crusher, the change in crushing strength of pellets made from powder containing 70 wt% of particles with a particle size of 0.5 mm or less and changing the maximum particle size of the remaining 30 wt% using a sieving machine is a standard pellet. 20φ × 10t
(Diameter 20 mm, height 10 mm) is subjected to strength test at 1500 kg / cm ² (rod surface pressure) and 1000 kg / cm ² , respectively, and pellet size is changed to 28φ × 28t 1500 kg / cm ² , 1000 kg / cm About ² results of each strength test in shown in Figure 4.

From these results, it was confirmed that by performing sieving work so that the maximum particle size of incinerated ash is 5 mm or less for 20 φ 10 t pellets and 7 mm or less for 28 φ 28 t pellets, it is possible to granulate sound and stable pellets. To be done.

(2) When using a briquette type granulator As in the case of the above doublet type granulator, a standard pellet of 27 mm in length × 18 mm in width × 8 mm in height is subjected to a roll linear pressure of 8,000 kg and 10,000 kg, respectively. The results of the strength test are shown in FIG.

From these results, it is confirmed that the pellets of 27 mm × 18 mm × 8 mm can be granulated into healthy and stable pellets by performing the sieving operation so that the maximum particle size of incinerated ash is 6 mm or less.

Further, FIG. 6 shows that the crushing strength of pellets obtained by granulation changes with time, and stabilizes to a state of low strength after a certain degree of strength reduction. The tendency and degree of sigma appeared almost the same in both the sieving and non-sieving products, and therefore the sieving product with a high initial crush strength shows higher stability against crushing over a long period of time. confirmed.

〔The invention's effect〕

As described above, according to the present invention, the following effects can be obtained because coarse particles unsuitable for granulation having a particle size of more than 5 mm are removed from the incinerated ash, that is, the incinerated ash having a particle size of 5 mm or less is collected. .

(1) The radioactive and combustible miscellaneous solid waste can be pelletized, and in that case, sound and stable pellets can be granulated.

(2) Smooth granulation operation without blockage can be obtained.

[Brief description of drawings]

Fig. 1 is a system diagram of a granulation device (pellet solidification equipment) for radioactive waste when a wire mesh sieving machine is used, Fig. 2 is a schematic view of the wire mesh sieving machine, and Fig. 3 is a case where an air classifier is used. The system diagrams of the radioactive waste granulation equipment (pellet solidification equipment) are shown respectively. FIG. 4 is a diagram for explaining the relationship between pellet strength and incinerated ash particle size when a tablet granulator is used, and FIG. 5 is
It is a figure explaining the same relation when there is a briquette type granulator. FIG. 6 is a diagram showing changes over time in pellet crush strength. 1 ... Supply tank, 2 ... Circulation pump, 3 ... Supply pump, 4 ... Dryer, 5 ... Incinerator, 6 ... Feeder, 7 ... Sieve, 8 ... Granulator, 9 ... … Hopper, 10 …… Stirring blade, 11 …… Stirring supply blade, 12 …… Hydraulic cylinder, 13 …… Rod, 14 …… Pellet, 15 …… Inadequate granulation, 16 …… Wire mesh, 17 …… Feeder, 18 ... Solidification container, 19 ... Cyclone, 20 ... Recovery machine.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Horiuchi 3-1-1, Saiwaicho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Ren Kikuchi 3-chome, Hitachi City, Ibaraki Prefecture No. 1 Stock company Hitachi Ltd. Hitachi factory (56) Reference JP-A-60-69600 (JP, A) JP-A-51-59772 (JP, A) JP-A-53-14977 (JP, A)

Claims (2)

[Claims] 1. An incinerator for ashing radioactive / combustible miscellaneous solid waste generated in a nuclear power plant and an incinerator ash obtained by the incinerator are sieved to obtain a particle size from the incinerator ash.
An apparatus for granulating radioactive waste, comprising: a separating device for separating unsuitable granules having a size of more than 5 mm, and a granulator for granulating the remaining incinerated ash from which the unsuitable granules have been sorted. 2. An incinerator for ashing radioactive / combustible miscellaneous solid waste generated at a nuclear power plant, and a radioactive sludge waste powdered separately from this incinerator and further ashed as required. A sludge treatment device to separate, a separation device that screens the incineration ash to separate granules having a particle size of more than 5 mm from the incineration ash, and the remaining incineration ash that has been fractionated from the granules that are not suitable for granulation, and And a granulator for granulating the sludge waste after the treatment in a mixed state.