JPS61133133A - Method for controlling briquetting type - Google Patents

Abstract

PURPOSE:To enable to change the rigidity of burr without impairing the strength of the pellets themselves by maintaining a product of the roll linear load and driving power of the roll in a briquetting type granulator at a fixed value and adjusting the both variably. CONSTITUTION:Concentrated waste liquid produced in an atomic power station and received in a feed tank 9 is dried and pulverized by a dryer 13 and granulated with a briquetting type granulator 12. Immediately after granulation, the screened pellets 7 via a screening machine 14 is packed in a vessel 8. As for the operation condition, the linear load of the roll P of the granulator is controlled by setting a set value at a high value, and the driving power W of the roll of the granulator is controlled so as to satisfy the formula (I), thus, the strength of the pellet is held at a desired fixed value. The linear load P of the roll is controlled by the adjustment of pressure of a roll 4 of the granulator, and the driving power W of the roll is controlled by the adjustment of the forcing amt. of a forcing screw 3 of the granulator.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a method for granulating powder, for example, when radioactive waste powder generated from facilities handling radioactive materials such as nuclear power plants is granulated into pellets. This invention relates to a method for controlling the granulation properties of granules.

[Background of the invention]

Although the present invention is not limited to the granulation of radioactive waste generated from facilities handling radioactive materials such as nuclear power plants, this will be described above as an example.

Such radioactive waste is to be managed and stored and then disposed of. Radioactive waste is generally processed in various ways for the purpose of reducing management, storage and disposal costs, and reducing management and storage space.

The appropriate treatment technology for these radioactive wastes is selected depending on the properties of the radioactive waste, but granulation is currently in practical use and is one of the treatment technologies with the highest volume reduction ratio for radioactive waste. There is processing technology.

The granulation treatment technology targets concentrated waste liquid, used ion exchange resin, and flammable miscellaneous solids, which account for the majority of the five types of radioactive waste. Concentrated waste liquid and used ion exchange resin are processed into dry powder. The combustible miscellaneous solids are incinerated and then granulated into 4 left particles.

Radioactive waste pellets are different from pellets used in general industry due to their radioactive nature, and have the following severe restrictions on their properties and granulation methods.

(1) The pellets must have sufficient strength to prevent them from being broken and scattered during handling and controlled storage after granulation.

(2) The granulation method must be capable of automatic operation.

(3) The 4lets have a size and shape suitable for the solidification method to be performed thereafter.

(4) The granulation method has a throughput that corresponds to the amount of radioactive waste generated from each source.Due to several constraints, compression granulation is actually applied to the granulation of radioactive waste. Only the grain method is used. Among these compression granulation methods, the briquetting granulation method is employed when relatively large-scale processing is required.

Figure 2 shows the structure of the Tsurikerating type granulator, in which radioactive waste powder or incinerated ash (hereinafter collectively referred to as powder) 2 stored in the hora 1 is fed into a screw feeder. 3, the pellets are pushed between two rotating rolls 40 that have depressions corresponding to the pellets on their surfaces. The rolls 4 are pressed together by a spring 5, and the powder 2
is compressed into pellets 6.

FIG. 3 shows the general shape of the granulated product coming out of the granulator. In the briquetting granulation method, the powder is granulated continuously, and since there is a gap between two rolls, the third
As shown in the figure, the result is a granulated product in which the pellets are connected in a plate shape.

This plate-shaped granule is ultimately separated into individual pellets (called granulation), but depending on the conditions between the granulator and the pellet storage location, the granulation may be sized immediately after granulation. In some cases, it is preferable to carry out particle grading just before the pellet storage area, and in some cases, it is desirable to have particle grading characteristics suitable for each of these cases. That is, in the former case, it is desirable that the rigidity of the flat plate-shaped portions 6' (hereinafter referred to as burrs) between each pellet 6 of the granule is sufficiently low. Conversely, in the latter case, it is desirable that the burrs 6' of the granules have high rigidity.

Generally, the following two methods can be considered for controlling the rigidity of the burr. That is, during granulation in the granulator, (1) the strength of the burr, that is, the strength of the granulated product itself, is controlled by controlling the pushing force of the powder, and (2) the thickness of the burr is controlled.

The above (1) is specifically achieved by a method of controlling the roll driving power, but this method has the disadvantage that it changes the strength of the burr itself and also changes the strength of the pellet itself. In addition, (2) is specifically achieved by a method of controlling the roll linear pressure, but this method weakens the strength of the pellet when lowering the roll linear pressure and increasing the burr thickness. It has the following drawback. FIG. 4 shows the relationship between roll drive power and burr strength (therefore, 4-let strength), and FIG. 5 shows the relationship between roll linear pressure and burr strength (therefore, pellet strength). (In addition, Fig. 5 also shows the relationship between the roll linear pressure and burr thickness that the inventors found.) As described above, among the granulator operation/4' parameters, roll driving power or Although the rigidity of the burr can be controlled by the method of controlling a parameter called roll linear pressure, it also has the disadvantage that it also affects the strength of the pellet. However, it has been difficult to adopt a method of controlling multiple parameters at the same time because it was unclear what would happen to the burr rigidity and 4-ret strength in such a case.

In addition, there is a method of controlling the operating conditions of the sizing machine in order to properly perform sizing. However, the principle of a granulating machine is to apply a predetermined impact to the granules to destroy the burrs, so if the burrs are sufficiently rigid, the impact that should be applied to the granules may be excessive. However, the impact given to the pellet is also excessive (there is also the possibility of damaging the pellet itself).

[Purpose of the invention]

An object of the present invention is to provide a control method for changing the granulation properties of granules, that is, the rigidity of burrs, without impairing the strength of the pellets themselves in briquetting type granulation.

[Summary of the invention]

As mentioned above, for the purpose of providing a method for controlling the sizing characteristics of the granulated material without impairing the strength and properties of the pellets themselves, there is a method for controlling the operating conditions of the sizing machine. cannot be adopted.

The present inventors have focused on a method of controlling burr rigidity by simultaneously controlling burr thickness and burr strength in Turike soting type granulation.

By the way, the conventional briquetting type granulation method used in general industry is different from the granulation method for radioactive waste, and it is extremely easy to monitor by close proximity of humans, and the occurrence of irregular granules has an impact on the entire system. This was significantly lower than in the radioactive waste granulation method, which requires fully automatic operation. Therefore, no particular attention has been paid to the relationship between the operating parameters of the granulator and the sizing characteristics of pellets. That is, conventionally, the operating parameters of the granulator and the pellet sizing characteristics were determined based on the relationship between roll drive power and burr strength (i.e. pellet strength) shown in Figure 4, and the relationship between roll drive power and burr strength (i.e. pellet strength) shown in Figure 5.
Only the relationship between the roll linear pressure and the burr strength (ie, 4 left strength) shown in the figure was confirmed, and what was attracting attention was not the burr strength but the let strength.

The present inventors experimentally clarified the relationship between roll linear pressure and burr thickness in order to realize a method for simultaneously controlling burr thickness and burr strength. (The relationship between the two is shown in FIG. 5). The pellet strength was determined to be an appropriate value based on the conventionally known relationship between roll drive power and burr strength (Figure 3) and the relationship between roll linear pressure and burr thickness that the inventors found above. However, the present invention will be described in detail below. In the briquetting type granulator, as shown in Fig. 4 and WXS diagram, there are the following three relationships among burr strength σ, burr thickness t10 - roll driving power W, and roll linear pressure P. Be independent.

σ=AIW (1) σ=A
2P (2)t =A3-
A4 P (3) Therefore, roll power W and roll +I! When both pressures are changed at the same time, the burr strength, that is, the pellet strength σ becomes σ=B, FW (4).

In addition, the rigidity of the burr, that is, the granulation property H of the burr, is expressed as the product of the burr strength σ and the burr thickness t, so H= σ t = B 2 PW B 3 P2W (
5).

Therefore, the necessary condition to keep the let strength constant under any operating conditions is σ = B IPW : const,
(6) Therefore, by controlling the roll linear pressure P and the roll drive power so that the condition ``(71) is satisfied between them, the let strength σ can be kept constant.Here, the constant C1 is the hardness of the granulator. It is decided according to.

In this case, the stiffness of the burr is H= Cz −Cs P t81
Therefore, under the control condition (7), the rigidity H of the burr can be uniquely controlled to a desired value by changing only the value of the roll linear pressure P.

Figure 6 shows the method for controlling the grain size characteristics by controlling only the roll drive power W, Figure 7 shows the method for controlling the grain size characteristics by controlling only the roll linear pressure P, and Figure 8 shows the method for controlling the grain size characteristics by controlling only the roll linear pressure P. Pellet strength σ and particle size property H in the case of the particle size property control method of the present invention by controlling both electric power W and roll linear pressure P
As is clear from Figures 6 to 8, which show the situation, in the method of controlling particle size characteristics by controlling only the roll drive power or only the roll linear pressure, changing the particle size characteristics of the pellets also changes the strength of the pellets. Although this is unavoidable, the method of controlling the particle size characteristics by controlling both the roll drive power and the roll linear pressure using the developed FiAK makes it possible to control the particle size characteristics of the pellet while maintaining a constant pellet strength. .

[Embodiments of the invention]

An embodiment of the invention is shown in FIG. In this embodiment, concentrated waste liquid generated from a nuclear power plant and received in a supply tank 9 is dried and powdered in a dryer 13 and granulated in a pulverizing type granulator 12. Immediately after granulation, a granulator 14 This is a system for filling a container 8 with pellets 7 that have been sized through the process. In this system, in order to improve the filling efficiency of the 4-lets 7 in the container 8, it is desirable that the 4-lets 7 be completely separated by the granulator 14. Bali 6
′ is desirable to have low stiffness. Therefore, [based on the detailed description of the invention, the operating conditions are as follows:
In FIG. 8, the granulator roll linear pressure P is controlled to a high set value, and the granulator roll drive power W is controlled so that the above equation (7) is satisfied, so that the 4-let strength is adjusted to the required value. Keep it at a constant value. This roll linear pressure P is equal to the pressing force of the granulator roll 4! By adjusting i#, the roll driving power W
is adjusted by adjusting the pushing amount by the pushing screw 3 of the granulator, and the control is performed by the feedback control computer 11. 10 is its operation panel. Manual control may be used instead of automatic control.

Radioactive waste pellets in nuclear power plants are usually granulated to have a crushing strength in the range of 50 to 150kliF/kg, and the operating conditions for waste liquid pellets are: , throughput 100 to 9/hr
In the case of a granulator, the roll pressure is 8 ton/cm to 12 t.
on/an is desirable, and the roll power is 8 kW to 1
2 kW is desirable. In the case of this example, the roll linear pressure is set at 12 ton/m and the roll power is set at 8 kWVc in order to improve particle size regulation.

If for some reason you want to worsen the granulation properties of the granules (that is, increase the rigidity of the burrs), lower the roll linear pressure (for example, 8 ton/c) while still satisfying equation (7).
In), increase the roll power (e.g. 12 kW
In particular, it becomes possible to increase the rigidity of the burr without impairing the pellet strength.

As an application of the present invention, if the strength of the sealet itself changes due to a significant change in the composition of the waste liquid, the rigidity of the burr will not be affected by changing the roll drive power while keeping the roll linear pressure constant. can be used to recover pellet strength. For example, roll linear pressure 12 ton/
An, when operating at a roll power of 10 kW, if a component that reduces the strength of the pellet itself flows in, the roll drive power is increased to 12 kW, and in the opposite case, the roll drive power is increased to 12 kW. It is sufficient to reduce the power to 8 kW.

In addition, since the range of variation in roll drive power is proportional to the range of variation in pellet strength, if the roll drive power is varied remotely according to the prediction of fluctuations in pellet strength estimated from the composition of waste liquid, it is possible to It is possible to produce pellets of constant strength regardless of composition. In this case, since the roll linear pressure is constant up to 1, there is no effect on the granulation properties of the granules, that is, the rigidity of the burrs.

〔Effect of the invention〕

According to the present invention, in a briquetting type granulator having the same specifications as the conventional one, control is performed to change the granulation properties of the granulated product, that is, the burr rigidity, to a desired value without deteriorating the pellet strength. becomes possible.

Therefore, a granulator with the same specifications can be applied to different plants that require different granulation characteristics depending on the downstream system of the granulator. Furthermore, in the case of waste powder, changes in properties specific to the powder, such as its composition, can be easily accommodated by changing the set values of the granulator operating conditions.

[Brief explanation of drawings]

Fig. 1 is a flow diagram of a radioactive waste liquid disposal system according to an embodiment of the present invention, Fig. 2 is a schematic front view of the main parts of a briquetting type granulator, and Fig. 3 is a granulated product produced from the granulator. Figures 4 and 5 are graphs showing the relationship between the operating parameters of the granulator and the characteristics of the granulated product, and Figures 6 and 7 are graphs showing the pellet strength of the control method by adjusting individual parameters. FIG. 8 is a graph of pellet strength and particle size regulating characteristics according to the control method of the present invention. 1: Hopper, 2: Powder, 3 Niscrew feeder, 4: Roll, 5: Pressure spring, 6: Nilet, 6I: Burr, 7: Sized pellets, 8 Two containers, 9: Supply tank, ]0: operation panel, 11: feedback control computer, 12: granulator, 13: dryer, 14: granulator. Fig. 1 Fig. 2 Fig. 4 Roll power W Fig. 5 Roll linear pressure P- No. 6: ``N! Power W

Claims (1)

[Claims] 1. By keeping the product of the roll linear pressure and roll drive power of the briquetting type granulator constant and variably adjusting both, the pellet strength of the granulated product can be kept constant. While the burr stiffness of the granules (product of burr strength and burr thickness)
A control method for a briquetting type granulator, characterized by making variable the briquetting type granulator. 2. The briquetting mold structure according to claim 1, wherein the roll linear pressure is adjusted by adjusting the roll pressing force, and the roll driving power is adjusted by adjusting the amount of powder pushed between the rolls. How to control a grain machine.