JP3138293B2 - Processing method and apparatus for crushing agglomerated solid particles suspended in a liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pulverizing, i.e., refining, agglomerated solid particles suspended in a liquid, and an apparatus for implementing the method.

[0002]

BACKGROUND OF THE INVENTION The method and the device according to the invention can be advantageously applied to the grinding of powders. That is, after dissolving the spent nuclear fuel cut in a high-temperature nitric acid solvent, it can be advantageously applied to pulverize a solid material having a limited grain size obtained in reprocessing of the nuclear fuel for purifying the nitric acid solvent. . These powders, whose chemical composition is based on zirconium, molybdenum, ruthenium and other metals used in fuel structures, can be mixed, for example, in a centrifugal oscillating sedimentation tank after purification. The sludge or solution has a large thickness and is largely or slightly agglomerated. The highly radioactive powder is transported through a suitable pipe to the vitrification plant, where it spends time in a storage tank where it is encapsulated in a glass preform. The storage tank is agitated periodically, for example using pulsating means, for reasons of nuclear safety.

[0003] During the transfer of sludge into the storage tank,
And the non-adjustable agglomeration of various dimensions during storage of the sludge in the storage tank poses a major problem.

[0004] In this way, the agglomerates constitute attrition particles, which cause attrition at the curved part of the transfer pipe. In addition, these agglomerates tend to adhere to areas of the transfer pipe where turbulence does not occur or to rough areas of the surface, causing clogging or sticking to curved sections of the pipe. The formation of such clogs, or the risk of blockage, creates a more difficult problem to solve. This is due to the fact that the transfer sludge is highly radioactive, so that any intervention is very difficult. Also, it is difficult to solve this problem by changing the equipment and sludge flow parameters. This is due to the difficulty in modeling sludge behavior.

[0005] A disadvantage due to the presence of non-adjustable agglomerates in the sludge transferred to the storage tank is that the agglomerates adhere to the bottom of the tank and this is the rate at which the sludge is assembled in the tank. Will disturb the operation of the moving means,
That is. Because of the particularly difficult intervention in storage tanks, it is highly desirable to be able to crush the agglomerates dissolved in the sludge transferred to the tank before transfer.

It is pointed out that the present invention is particularly suitable for grinding agglomerates containing particularly radioactive powder obtained during reprocessing of spent nuclear fuel. Without limitation, it can be used whenever it is desired to grind agglomerated solid particles suspended in a liquid and can be used, for example, in the chemical and soil nutrition industries. In particular, it is particularly applicable to the treatment of certain industrial wastes.

[0007]

SUMMARY OF THE INVENTION The present invention is particularly directed to the pulverization of agglomerated solid particles suspended in a liquid, for example, to reduce the risk of clogging during the transfer of such particles, It is an object of the present invention to provide a method and a device which make it possible to eliminate all the risk of blockage of any mechanism by agglomerated particles and, if necessary, to reduce the attrition properties of the particles.

[0008]

SUMMARY OF THE INVENTION In a broad sense of the invention, for this purpose, there is provided a method of circulating a liquid containing agglomerated solid particles through a venturi tube under the action of pressure. You.

By flowing the agglomerated solid particles through a Venturi tube, the particles are exposed to a large radial velocity gradient. In other words, in a section perpendicular to the axis of the tube, the speed of movement of the fluid varies considerably from the center to the periphery. Thus, the agglomerated solid particles are subjected to a very large shear stress parallel to the axis of the tube, which has the effect of crushing the agglomerates carried in the liquid.

In two particular embodiments of the present invention, liquid is circulated from bottom to top and from top to bottom in substantially vertical Venturi tubes. Tests have shown that the efficiency of this method increases when liquid is circulated in the tube towards the bottom. When the size of the agglomerate is very large, preferably and in particular a venturi tube forming an ejector is used to ensure circulation of the liquid.

[0011] The efficiency of the method is also enhanced by flowing liquid through the baffle device. In this case, the effect of the agglomerate colliding with the baffle device arranged at the outlet of the venturi tube is combined with the effect of the velocity gradient.

The present invention also relates to an apparatus for crushing agglomerated solid particles suspended in a liquid, wherein an inflow passage and an outflow passage for a liquid containing the agglomerated solid particles are provided. A venturi tube is mounted in the tank between the inflow passage and the outflow passage.

[0013] In a first embodiment of the present invention, the Venturi tube is disposed along a substantially vertical axis. The venturi tube has a lower inlet end connected to the inflow passage through the inflow chamber, and an upper outlet end connected to the outflow passage through an annular passage formed around the venturi tube.

The venturi tube is advantageously separated from the inlet chamber by an injector and a recirculation chamber connected to the annular passage through a hole formed in the septum.

According to a second embodiment of the present invention, the venturi tube is arranged along a substantially vertical axis,
The upper inlet end is connected to the inflow passage through an outer annular passage formed around the venturi tube, and the lower outlet end is connected to the outflow passage through an outflow chamber formed in the lower part of the tank.

Preferably, the venturi tube is thereby surrounded by an inner annular recirculation passage, the lower end of which is provided above a deflector located opposite the lower outlet end of the venturi tube. The upper end is provided between the ejector and the venturi tube.

In all cases, the baffle device can be located downstream of the Venturi tube.

Embodiments of the present invention will be described in greater detail with reference to the following non-limiting embodiments, and with reference to the accompanying drawings, in which:

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 10 designates a horizontal concrete slab. This slab separates a human accessible upper region 12 and a lower cell 14 in which a hazardous liquid containing agglomerated solid particles desired to be ground is treated.

The apparatus 16 according to the present invention is suspended on the slab 10 and is adapted to be placed in the cell 14. This device 16 includes a cylindrical tank 18 having a vertical axis,
The tank is provided with a flange 20 at the upper end, which is locked on the sludge 10 and is tightly connected, for example by means of a screw 22.

The tank 18 is sealed at its upper end by a cover 24 tightly fixed to the flange 20 by, for example, a screw 25. The sleeve 26 projects downward from the lower surface of the cover 24 coaxially with the tank and into the tank. The sleeve 26 supports an ejector indicated generally by reference numeral 30 at the lower end by a screw 28. The ejector has three main parts 31, 32, 3
3 which are centered on the vertical axis of the tank 18. These three parts comprise a lower part 31, a central inner part 32 and an upper outer part 33.

The lower disk portion 31 includes a screw 34
, And is fixed to the lower end of the central inner portion 32. The disk portion is formed with a convergent injector 36 in the center and along the vertical axis of the tank 18. The lower end of the large diameter end of the injector 36 is located at an inflow chamber 38 formed in the lower portion of the tank 18.
Guided inside. An inflow passage 40 formed in the thickened portion 18a of the tank 18 is also directed into the inflow chamber 38, thereby directing a liquid containing agglomerated solid particles desired to be ground into the inflow chamber. It is possible to enter. The liquid flows into the device 16 under pressure by a pump (not shown). This inflow pressure is for example at least 30
0 kPa.

The inner central portion 3 of the main body of the ejector 30
2 has a lower bell-shaped portion 43. Below this part is attached the lower part 31, as well as the upper part forming the venturi tube 44. A recirculation chamber 42 is formed between the lower bell-shaped portion 43 and the lower portion 32a. The lower end of the venturi tube 44 coaxially arranged with respect to the injector 36 and the tank 18 is provided to the recirculation chamber 42 above the injector 36. Inside the venturi tube 44, a lower relatively short converging inlet region 46 and an upper relatively long diverging outlet region 48 are formed.

The lower bell-shaped portion 43 carries on its outer surface a sealing O-ring 60 which is located above the inner surface of the thickened portion 18a of the tank 18 and above the inflow passage 40. Work closely together. Therefore, the inflow chamber 3
8 is isolated from the rest of the tank.

The outer upper part 33 of the body of the ejector 30 has a lower ring-shaped part 49 which is fixed to the lower end of the sleeve 26 by means of a screw 28 and which surrounds a venturi tube 44. Are located in This lower ring-shaped part 49 is connected to the thick part 1 of the tank 18 via two sealing O-rings 62.
8a.

The upper outer part 33 also comprises a ring-shaped part 4.
9 has a tubular portion 50 above. This cylindrical portion is formed by a cup-shaped portion 51 at the upper end above the venturi tube 44. The tubular portion 50 is coaxially disposed about the venturi tube 44 and supports the venturi tube by a welded tie rod 53. An annular passage 54 formed between the venturi tube 44 and the portion 33 connects the upper end of the venturi tube to an outflow passage 58 formed in the thick portion 18 a of the tank 18. This outflow passage is O-ring 6
0 and 62 are provided.

A hole 64 formed in the upper horizontal portion of the lower bell-shaped portion 43 connects the lower end of the annular passage 54 to the recirculation chamber 42. These holes allow a portion of the recirculated fluid to be routed to the venturi tube 44, as described in more detail below.

A liquid containing agglomerated solid particles desired to be ground is introduced into the apparatus by an inlet passage 40, preferably at a pressure of at least 300 kPa. This pressurized liquid directed to the inlet chamber 38 flows from bottom to top through the ejector 30 and subsequently through the injector 36 and the converging and diverging regions 46 and 48 in the venturi tube 44. . The flow of liquid through the injector 36 and then through the venturi tube 44 is high.
Thus, if the flow rate of the liquid guided to the device 16 is about 5 m ³ / hour and the outlet diameter of the injector 36 is about 10 mm, the liquid reaches a flow rate of about 18 m / sec.

For the main flow rate of liquid flowing through injector 36 and then from bottom to top through venturi tube 44, recirculation chamber 42 through hole 64
The induced liquid is drawn into the main flow and the induced flow is added. Tests have shown that this induced flow is very close to the main flow. Accordingly, the flow rate of the liquid flowing through the venturi tube 44 corresponds to about 10 m ³ / hour in the above example.

The liquid flowing at a high velocity from the upper end of the venturi tube 44 having a diameter of, for example, about 40 mm collides with the cup-shaped portion 51 and flows down again through the annular passage 54. A portion of this liquid then exits the device 16 through the outflow passage 58 and a portion of the remaining liquid is recirculated through the hole 64 into the chamber 42.

The liquid flowing through the injector 36 and then through the venturi tube 44 has a very large radial velocity gradient. That is, the flow rate of the liquid along the vertical axis of the device is much higher near the axis than the flow rate along the wall of the injector or venturi tube. The liquid and the agglomerated solid particles flowing therethrough are subjected to very high shear forces in the injector 36 and the venturi tube 44 as a result, and the agglomerate is decomposed.

The particles exposed to such a shear force are:
The particles are broken up into smaller particles until their dimensions are small enough that shear forces due to radial velocity gradients induced in injector 36 and venturi tube 44 can no longer be crushed. .

For example, 30 in the device 16 according to the invention
It has been found that, upon inflow of a suspension containing particles of an average diameter close to μm, the average diameter shrinks to 10-15 μm after a single flow and to an average diameter close to 5 μm after recirculation. Was.

In another test, recordings were made on suspended particles with a diameter of more than 100 μm. First liquid 4
% Into the apparatus 16. However, after exiting the Venturi tube 44 after the first flow, the content is only 3%, this percentage being reduced to 1.5% after one recirculation, and after two recirculations. It was reduced to 0.7%.

Thus, it is clear that the active parts of the device 16, namely primarily the injector 36 and the venturi tube 44, are subject to relatively rapid wear. This is due both to the presence of abrasive particles in the liquid being treated and to the fact that the liquid is corrosive. Therefore, in the device shown in FIG. 1, the ejector 30 can be removed. This is done from an area 12 accessible to persons above and also allows for replacement if needed.

To perform this exchange, the operator located in area 12 removes screw 25 and removes cover 24. The cover carries the ejector 30 via the sleeve 26. As regards the particular case, the ejector can be wholly or partly replaced. Therefore, the ejector 30 is fixed to the sleeve 26 and can be disassembled by the screw 28. The part 31 of the case in which the injector 36 is formed is detachably fixed to the part 32, and the venturi tube 44 is assembled by the screw 34.

In the device described here with reference to FIG.
The liquid to be processed flows from bottom to top through the ejector formed by injector 36 and venturi tube 44. In practice, tests have shown that a high level of efficiency can be achieved by flowing the interior of the ejector from top to bottom. A second embodiment of the device according to the invention, in which the liquid flows down the ejector, will be briefly described below with reference to FIG.

In FIG. 2, the various components that perform the same functions as described with reference to FIG. Furthermore, only those features which are characteristic of the apparatus described with respect to FIG. 1 will be described in detail.

As in the first embodiment described, the apparatus 116 shown in FIG. 2 comprises a cylindrical tank 118 having a vertical axis suspended on a horizontal slab 110 and a tank 11 having a vertical axis.
Ejector 13 exchangeably received in 8
0, and the ejector can be exchanged from an area 112 located above the slab 110.

The main body 130 of the ejector has three parts 1
31, 132, 133, these parts being tank 1
Coaxially arranged around eighteen vertical axes. The outer portion 133 has a lower ring-shaped portion 149, as in the embodiment of FIG. This ring-shaped part is connected to the tank 11 via two sealing O-rings 162.
8 on the thick portion 118a. This part 149
Is extended upward by a tubular portion 150, the upper end of which is sealed by a horizontal portion 151. This horizontal portion 151 is fixed to the cover 124, which is accessible from the area 112. A ring 120 arranged above the cover 112 holds the assembly constituted by the cover 124 and the outer part 133 in place, this being assisted, for example, by the screw 121 engaging the upper flange of the tank 118. Assisted.

The part 133 is a welded tie rod 153
Supports the intermediate portion 131 inside. This intermediate portion has a hollow cylindrical shape, and the upper end carries an injector 136 at the center. The lower part of the part 131 carries a sealing O-ring 160,
This O-ring is located below the O-ring 162 in the tank 1
18 cooperates with the part 118a.

The part 131 supports the central part 132 on the inside by means of a tie rod 155. This portion is constituted by a venturi tube 144, and the venturi tube is similar to the injector 136 in the tank 118.
Are arranged coaxially with the vertical axis. The upper inlet end of the venturi tube 144 is rounded upward and faces the outlet end of the injector 136.

A passage for the liquid to be treated, formed in the thickened portion 118a of the tank 118, has an inlet passage 140 between the O-rings 160 and 162, preferably along a tangential direction. Is provided to cause a swirling motion of the liquid in an outer annular passage 170 formed between outer portion 133 and intermediate portion 131. The outer annular passage 170 is connected at its upper end to the upper inlet end of the injector 136,
The injector is connected to a venturi tube 144.

The lower end of the venturi tube 144 is led forward of the deflector 172, and the deflector is formed in the lower part of the intermediate part 131. Due to the shape of the deflector 172, the liquid is directed radially outward,
Then, by changing it upward, it is possible to prevent particles from being deposited at this location. The passage 174 formed in the lower portion of the portion 131 has an upper end provided in the bottom of the deflectator 172 and a lower end provided with an O.
-Provided in an outflow chamber 156 formed at the bottom of the tank 118 below the ring 160; These passages 174 have a common lower portion, which is located along the axis of tank 118 and is located directly above outlet passage 158. The outflow passage is formed at the bottom of the tank 118 along the axis.

An inner annular recirculation passage 176 is formed between the intermediate portion 131 and the central portion 132 forming the venturi tube 144. This passage 17
The lower end 6 is guided above the deflector 172, and the upper end is connected to the injector 136 and the venturi tube 14.
4 and is led.

The device 116 described herein with reference to FIG.
The fluid to be treated, pumped under pressure through the inlet passage 140, first rises in the outer annular passage 170 in the ejector 130. At the lower end of the Venturi tube, some of the liquid flows directly through passages 174 and 158. Meanwhile, the remaining portion is recirculated into the venturi tube by the annular reprocessing passage 176.

The apparatus described herein with reference to FIGS. 1 and 2 includes an ejector which in each case recirculates in a non-cavitation state. This ejector constitutes, according to tests, the ejector with the highest performance characteristics to achieve the desired decomposition of the particles.

It is possible to convert the ejector into an cavitation circulating ejector by changing the parameters in the treatment method. This can increase the efficiency of the device but increases the risk of attrition. This solution can only be used when the liquid to be treated requires a reduced operating time.

As a variant, it is also possible to use a device incorporating a venturi tube without recirculation if the particles carried in the liquid are only slightly agglomerated. If maximum decomposition of the particles has to be obtained, it is preferred to use a recirculating ejector, especially for nuclear applications.

FIG. 3 shows very schematically a variant of the device 216 according to the invention. As in the embodiment described with reference to FIG.
8, the structure being such that the liquid to be treated is flowed from the top to the bottom inside, and then the injector 236 and then the venturi tube 2
44. However, the outlet of venturi tube 244 is directed into baffle device 280, reducing the height and increasing the diameter of that portion of the ejector. The baffle device 280 includes a passage 282 between two coaxial opposing shaped portions 284,286.
Formed by

In the apparatus 216 shown in FIG. 3, the inflow passage 24 formed in the tank 218 with the liquid to be treated
The liquid directed through 0 to the ejector 230 is continuously circulated through the injector 236, the venturi tube 244, and then through the passage 282 of the baffle device 280. Therefore, as described above, the decomposition effect of the agglomerate particles obtained by the shearing force in the injector and the Venturi tube is added to the decomposition effect of the auxiliary particles obtained by the collision effect on the wall surface of the baffle device 280. It is.

As described above, the venturi tube 2
A portion of the liquid flowing through 44 flows out of the apparatus through an outflow passage 258. Meanwhile, the remaining liquid is recirculated into the venturi tube 244 through a passage 264 formed in the base.

As already pointed out, the device according to the invention is particularly suitable for the treatment of powders obtained after dissolving nuclear fuel in a nitric acid solvent, but the suspension of agglomerated solid particles which it is desired to grind. It can be used to treat any turbid fluids, especially in industrial effluents.

Obviously, the invention is not restricted to the embodiments described here by way of example, but in fact covers all variants thereof. Therefore, the baffle device disposed at the outlet of the venturi tube in which the liquid is caused to flow upward according to the embodiment of FIG. 3 can be disposed at the outlet of the venturi tube where the liquid flows downward. Further, the orientation and arrangement of the liquid inlet and outlet passages formed in the tank of the device can be varied without departing from the scope of the present invention.

[0055]

As described above, according to the present invention,
The liquid to be treated is circulated through the ejector, and the agglomerate is crushed by this circulation, and a part of the treated liquid is again circulated through the ejector to repeat the crushing process, and the remaining liquid flows out The pipes are clogged by agglomeration of powder, especially as in the reprocessing of nuclear fuel, because they can be discharged to the outside through a passage and the ejector can be easily removed and installed by remote control. By using this in situations where it is extremely necessary to avoid such problems, problems such as blockage and wear of pipes can be solved, and adverse effects on the human body such as radioactivity can be prevented. Further, the structure is simple, and when applied to various other fields, there is an effect that it can greatly contribute to purification of factory wastewater and the like.

[Brief description of the drawings]

FIG. 1 illustrates a device according to the invention capable of grinding agglomerated solid particles suspended in a liquid, wherein the liquid is adapted to flow from bottom to top in a Venturi tube. Vertical sectional view shown.

2 is a vertical sectional view similar to FIG. 1 showing a second embodiment according to the present invention, wherein the device is adapted to allow liquid to flow from the top to the bottom of the Venturi tube.

FIG. 3 is a schematic sectional view similar to FIGS. 1 and 2 and showing a device having a baffle device according to a third embodiment of the present invention.

[Explanation of symbols]

 10, 110 Slab 12, 112 Upper region 14 Lower cell 16 Equipment 18, 118, 218 Tank 20 Flange 24 Cover 26 Sleeve 30, 130, 230 Ejector 31, 32, 33 Ejector part 36 Injector 38 Inflow chamber 40, 140, 240 Inflow passage 42 Circulation chamber 44, 144, 244 Venturi tube 54 Annular passage 58, 158, 258 Outflow passage 64 hole 172 Deflector 280 Baffle device

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B02C 19/00-25/00 G21F 9/04 G21F 9/30

Claims (11)

(57) [Claims] 1. An ejector for assuring the circulation of a liquid containing agglomerated solid particles under pressure.
Venturi tube to form a restrictor (44,14
4,244), wherein the agglomerated solid particles suspended in the liquid are pulverized. 2. The processing method according to claim 1, wherein the substantially vertical venturi tube is provided.
4. A method for pulverizing agglomerated solid particles suspended in a liquid, which comprises the step of flowing the liquid from the bottom to the top in 4). 3. The method of claim 1, further comprising the step of flowing the liquid from top to bottom in a substantially vertical Venturi tube (144). A processing method of crushing suspended agglomerated solid particles. 4. A have been processing method according to any one of claims 1 to 3, that the flow of the liquid into the baffle assembly (280) at the outlet of the venturi tube (244) A processing method for pulverizing agglomerated solid particles suspended in a liquid. 5. A passage (40, 140, 240) including a tank (18, 118, 218) through which a liquid containing agglomerated solid particles flows, and a passage (58, 158) through which a liquid is discharged. , 258), a venturi tube (44, 144, 244) is mounted in the tank between the inflow passage and the discharge passage, and a recirculation device (42, 64; 176, 264) is provided.
Exit from Venturi tube (44,144,244)
A part of the fluid was venturized into tubes (44, 144,
244), wherein the agglomerated solid particles suspended in the liquid are ground. 6. Apparatus according to claim 5 , wherein the venturi tubes (44, 244) are arranged along a substantially vertical axis, the lower end of which is formed in the lower part of the tank. The suspension in the liquid characterized by being connected to the inflow passage via the inflow chamber (38) and the outlet at the upper end being connected to the discharge passage via an annular passage (54) formed around the venturi tube. A device for grinding turbid agglomerated solid particles. 7. The apparatus according to claim 6 , wherein the venturi tube (44) is connected to the injector (36).
And suspended in a liquid characterized by being separated from the inlet chamber by a recycling chamber (42) connected to the annular passage (54) through a hole (64) formed in the septum. A device for crushing agglomerated solid particles. 8. Apparatus according to claim 5 , wherein the venturi tube (144) is arranged along a substantially vertical axis, the upper end of which is formed around the venturi tube. In the liquid, the outlet is connected to the inflow passage (140) through the annular passage (170), and the outlet at the lower end is connected to the discharge passage through the discharge chamber (156) formed in the lower part of the tank. A device for crushing agglomerated solid particles suspended in a liquid. 9. The apparatus according to claim 8 , wherein the venturi tube (144) is surrounded by an inner annular recycling passage (176), the lower end of which is located in front of the lower end outlet of the venturi tube. An apparatus for grinding agglomerated solid particles suspended in a liquid, the apparatus being provided above a deflector (172) provided at an upper end between the injector and the venturi tube. 10. any of claims 5 to claim 9 1
Item 280. A baffle device (280).
The apparatus for pulverizing agglomerated solid particles suspended in a liquid, wherein the apparatus is disposed downstream of the venturi tube (244). 11. A the apparatus described in any one of claims 5 to claim 10, venturi (44,
144, 244) can be exchanged with the ejector (30, 1).
30, 230), wherein the agglomerated solid particles suspended in a liquid are crushed.