JPH04250859A - Method and device for pulverizing solid particles suspended and aggregated in liquid - Google Patents

Abstract

PURPOSE: To grinding aggregated solid particles suspended in a liquid by circulating a liquid containing aggregated solid particles in the presence of a pressure action through a Venturi tube. CONSTITUTION: A tank 18 is provided with an inlet passage 40 and an outlet passage 58. In the tank 18, an ejector 30 having a injector 36 and a Venturi tube 44 is mounted. Then, the influent liquid is passed through the ejector 30 to grind the aggregates by the action of a shear force generated from a velocity gradient in a radial direction of the inside and the action of the impingement, and parts of the liquid treated is passed through the ejector 30 again for re- treatment, while the other parts of the liquid is discharged from the outlet passage 58. As a result, it is possible to grind the aggregated solid particles suspended in a liquid, especially to mount and dismantle major parts in a remote handling, particularly, the use in the treatment of the used nuclear fuel.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for crushing or pulverizing agglomerated solid particles suspended in a liquid, and to an apparatus for carrying out the process.

0002

BACKGROUND OF THE INVENTION The method and device according to the invention can be advantageously applied to the grinding of powders. That is, it can be advantageously applied to crushing solid materials of limited grain size obtained during the reprocessing of nuclear fuel by dissolving the cut spent nuclear fuel in a hot nitric acid solvent and purifying this nitric acid solvent. . These powders, whose chemical composition is based on zirconium, molybdenum, ruthenium and other metals used in fuel structures, can be purified in a variety of ways, for example in centrifugal rocking sedimentation tanks. The result is a sludge or solution of moderate thickness, which may be significantly or slightly agglomerated. The highly radioactive powder is transported through appropriate pipes to a vitrification processing plant, where it spends a period of time in a storage tank, where it is encapsulated in a glass matrix. In storage tanks, for nuclear safety reasons, they are periodically agitated, for example using pulsating means.

[0003] During the transfer of sludge into the storage tank,
And during the storage of sludge in storage tanks, agglomerates of varying dimensions that cannot be adjusted create major problems.

[0004] The agglomerates thus constitute abrasive particles which cause abrasion in the bends of the transfer pipe. Furthermore, these agglomerates tend to adhere to non-turbulent areas or rough areas of the transfer pipe, forming blockages or sticking to bends in the pipe. The formation of such a blockage, ie the threat of blockage, poses even more difficult problems. This is due to the fact that the transferred sludge is highly radioactive and therefore any intervention becomes extremely difficult. Moreover, it is difficult to solve this problem by changing equipment or sludge flow parameters. This is due to the difficulty in modeling the behavior of sludge.

A disadvantage due to the presence of agglomerates of non-adjustable size in the sludge transferred to the storage tank is that these agglomerates adhere to the bottom of the tank, which can cause damage to the tanks assembled in the tank. This may disturb the operation of the moving means.
That's what it means. Since intervention in storage tanks is particularly difficult, it is highly desirable to be able to break up the agglomerates dissolved in the sludge transferred to the tank before it is transferred.

Although it is pointed out that the invention is particularly suitable for comminution of agglomerates containing particularly highly radioactive powders obtained during the 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 also for example in the chemical and soil nutrition industries. It has particular application in the treatment of certain industrial wastes.

[0007]

SUMMARY OF THE INVENTION The present invention is particularly directed to the grinding of agglomerated solid particles suspended in a liquid to eliminate the risk of blockage formation or agglomeration during the transport of such particles, for example. It is an object of the present invention to provide a method and a device which makes it possible to eliminate any possibility of clogging of any mechanism due to agglomerated particles and also to reduce the abrasive properties of the particles if necessary.

[0008]

In the broad sense of the invention, for this purpose a method is provided in which a liquid containing agglomerated solid particles is circulated through a Venturi tube under pressure. Ru.

By flowing agglomerated solid particles through a Venturi tube, the particles are exposed to large radial velocity gradients. In other words, in a cross section perpendicular to the axis of the tube, the velocity of fluid movement varies considerably from the center to the periphery. The agglomerated solid particles are therefore subjected to very large shear stresses parallel to the axis of the tube, which have the effect of crushing the agglomerates carried in the liquid.

In two particular embodiments of the invention, liquid is circulated through a substantially vertical Venturi tube from bottom to top and from top to bottom, respectively. Tests have shown that the efficiency of this method increases when the liquid is circulated towards the bottom within the tube. When the dimensions of the agglomerate are very large, preferably and especially a venturi tube is used which forms the ejector and ensures circulation of the liquid.

[0011] The efficiency of this method is also increased by flowing the liquid through a baffle arrangement. In this, the effect of the agglomerate impinging on a baffle device located at the outlet of the venturi tube is combined with the effect of the velocity gradient.

The present invention also provides an apparatus for grinding agglomerated solid particles suspended in a liquid, the inlet and outlet passages for the liquid containing the agglomerated solid particles being guided. A venturi tube is provided within the tank between an inflow passage and an outflow passage.

In a first embodiment of the invention, the venturi tube is arranged along a substantially vertical axis. The venturi tube has a lower inlet end communicating with the inlet passage through an inlet chamber, and an upper outlet end communicating with the outlet passage through an annular passage formed around the venturi tube.

The venturi tube is advantageously separated from the inflow 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 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 at the bottom 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 disposed opposite the lower outlet end of the venturi tube. and the upper end is provided between the ejector and the venturi tube.

[0017] In all cases, a baffle device can be placed downstream of the venturi tube.

Embodiments of the invention will now be described in greater detail with reference to non-limiting examples and with reference to the accompanying drawings, in which: FIG.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 10 designates a horizontal concrete slab. This slab separates an upper region 12, which is accessible by personnel, and a lower cell 14, where hazardous liquids containing agglomerated solid particles that are desired to be crushed are treated.

A device 16 according to the invention is suspended above the slab 10 and adapted to be placed within the cell 14. The device 16 includes a cylindrical tank 18 with a vertical axis;
The tank is provided with a flange 20 at its upper end, which flange is adapted to rest on the sludge 10 and to be tightly connected, for example by screws 22.

The tank 18 is sealed at its upper end by a cover 24 which is tightly fixed to the flange 20, for example by screws 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, generally designated 30, at its lower end by means of a screw 28. The ejector has a body in three parts 31, 32, 3
3, which are centered on the vertical axis of the tank 18. The three parts are comprised of a lower part 31, a central inner part 32 and an upper outer part 33.

[0022] The lower disk portion 31 has a screw 34
is fixed to the lower end of the central inner portion 32 by. The disk portion is centrally formed with a converging injector 36 along the vertical axis of the tank 18. The lower, larger diameter end of the injector 36 is led into an inlet chamber 38 formed in the lower part of the tank 18 . An inlet passageway 40 formed in the thickened portion 18a of the tank 18 is also led into the inlet chamber 38, thereby directing into the inlet chamber the liquid containing the agglomerated solid particles that are desired to be crushed. It is possible to enter. This liquid is introduced into the interior of the device 16 under pressure by a pump, not shown. This inlet pressure is, for example, at least 300
It is assumed to be kPa.

[0023] Inner central portion 3 of the main body of the ejector 30
2 has a lower bell-shaped portion 43. Attached to the underside of this part is the lower part 31, and likewise the upper part forming the venturi tube 44. A recirculation chamber 42 is formed between this lower bell-shaped portion 43 and the lower portion 32a. The lower end of a venturi tube 44, which is disposed coaxially with respect to the injector 36 and the tank 18, is provided in a recirculation chamber 42 above the injector 36. The interior of the venturi tube 44 is formed with a lower, relatively short, converging inlet region 46 and an upper, relatively long, diverging outlet region 48 .

The lower bell-shaped portion 43 carries on its outer surface a sealing O-ring 60 which is connected to the inner surface of the thickened portion 18a of the tank 18 at a position above the inlet passageway 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 the screw 28 and which extends around the venturi tube 44. It is located in This lower ring-shaped part 49 is connected to the thick walled part 1 of the tank 18 via two sealing O-rings 62.
8a.

The upper outer part 33 also has a ring-shaped part 4
It has a cylindrical portion 50 above 9. This cylindrical portion has an upper end formed by a cup-shaped portion 51 above the venturi tube 44 . The tubular portion 50 is disposed coaxially around the venturi tube 44 and supports the venturi tube by welded tie rods 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 walled portion 18a of the tank 18. This outflow passage is O-ring 6
0 and 62.

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

[0028] The liquid containing the agglomerated solid particles that it is desired to crush is introduced into the apparatus by an inlet passage 40, preferably at a pressure of at least 300 kPa. This pressurized liquid directed into the inlet chamber 38 flows from the bottom to the top through the ejector 30 and then through the injector 36 and the converging region 46 and diverging region 48 in the venturi tube 44. . The flow of liquid through the injector 36 and then through the venturi tube 44 is high velocity. Therefore, the flow rate of liquid introduced into the device 16 is approximately 5 m3/
In time, if the outlet diameter of the injector 36 is about 10 mm, the liquid reaches a flow velocity of about 18 m/sec.

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

Liquid flowing out at high velocity from the upper end of the venturi tube 44, which has a diameter of, for example, about 40 mm, impinges on 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 outlet passageway 58 and the remaining portion of the liquid is recycled into the chamber 42 through the hole 64.

The liquid flowing through injector 36 and then through venturi tube 44 has a very large radial velocity gradient. That is, the flow rate of liquid along the vertical axis of the device is much greater in the immediate vicinity of the axis than along the walls of the injector or venturi tube. As a result, the flowing liquid and the agglomerated solid particles are subjected to very large shear forces in the injector 36 and venturi tube 44, causing the agglomerates to break up.

Particles exposed to such shear force are
It is broken up into smaller and smaller particles until its size is small enough that the shear forces due to the radial velocity gradient induced in the injector 36 and venturi tube 44 can no longer crush it. .

For example, in the device 16 according to the invention 30
It has been found that when flowing a suspension containing particles with an average diameter close to μm, the average diameter decreases to 10-15 μm after one flow, and after recirculation to an average diameter close to 5 μm. Ta.

In other tests, records were made of suspended particles with diameters greater than 100 μm. Liquid is first 4
% to the device 16. However, the content is only 3% as it exits the venturi tube 44 after the first flow, and this percentage is reduced to 1.5% after one recirculation, and after two recirculations. It was reduced to 0.7%.

It is therefore clear that the active parts of the device 16, ie primarily the injector 36 and the venturi tube 44, are subject to relatively rapid wear. This is due to both the presence of abrasive particles in the liquid being treated and the corrosive nature of the liquid. Therefore, in the device shown in FIG. 1, the ejector 30 can be removed. This is done from an upper, human-accessible area 12, allowing for its replacement if required.

To accomplish this exchange, an operator located in area 12 unscrews screws 25 and removes cover 24. The cover carries an ejector 30 via a sleeve 26. As for the particular case, the ejector can be replaced in whole or in part. Therefore, the ejector 30 is fixed to the sleeve 26 and can be disassembled by the screw 28. A portion 31 of the case in which the injector 36 is formed is removably fixed to a portion 32, and a venturi tube 44 is assembled with a screw 34.

In the apparatus described herein with reference to FIG.
The liquid to be treated flows from the bottom to the top through the ejector formed by the injector 36 and venturi tube 44. In practice, tests have shown that high levels of efficiency can be achieved by flowing from top to bottom inside the ejector. A second embodiment of the device according to the invention, in which liquid is flowed downwards through an ejector, will be briefly described below with reference to FIG.

In FIG. 2, various parts of the device that perform the same functions as described with respect to FIG. 1 are designated with the same reference numerals plus 100. Furthermore, only those features of the device that differ from those described with respect to FIG. 1 will be described in detail.

As in the first embodiment described, the apparatus 116 shown in FIG.
Ejector 13 exchangeably received within 8
0, and the ejector can be replaced from a region 112 located above the slab 110.

The ejector body 130 has three parts 1
31, 132, 133, these parts are tank 1
18 vertical axes. The outer portion 133 has a lower ring-shaped portion 149, as in the embodiment of FIG. This ring-shaped part connects the tank 11 through two sealing O-rings 162.
It is locked on the thick part 118a of No.8. This part 149
is extended upwardly by a cylindrical 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 disposed above the cover 112 holds in place the assembly constituted by the cover 124 and the outer part 133, aided by, for example, a screw 1 engaging the upper flange of the tank 118.
21.

Portion 133 is welded tie rod 153
supports the intermediate portion 131 on the inside. This middle section has a hollow cylindrical shape, and the upper end carries an injector 136 in the center. The lower portion of section 131 carries a sealing O-ring 160;
This O-ring is connected to the tank 1 below the O-ring 162.
18 portion 118a.

Portion 131 supports central portion 132 inwardly by tie rods 155 . This part is made up of a venturi tube 144, and the venturi tube is connected to the tank 118 as well as the injector 136.
is arranged coaxially with the vertical axis of. The upper inlet end of the venturi tube 144 is rounded upward and is opposite the outlet end of the injector 136.

The inlet passage 140, which is a passage for the liquid to be treated and is formed in the thick walled part 118a of the tank 118, is formed between the O-rings 160 and 162, preferably along the tangential direction. It is arranged to cause a swirling movement of the liquid in the outer annular passage 170 formed between the outer part 133 and the middle part 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 guided in front of a deflector 172, which is formed in the lower portion of the intermediate portion 131. The shape of the deflector 172 directs the liquid radially outward;
Next, by changing the direction upward, it is possible to prevent particles from accumulating at this location. A passage 174 formed in the lower portion of portion 131 has an upper end disposed within the bottom of deflation tank 172 and a lower end disposed within the bottom of deflation tank 172.
- in an outflow chamber 156 formed in the bottom of the tank 118 below the ring 160; These passageways 174 have a common lower portion that is located along the axis of the tank 118 and immediately above the outlet passageway 158. Outflow passage is tank 1
18 along the axis.

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

Apparatus 116 as described herein with reference to FIG.
In this, the fluid to be treated, pumped under pressure through the inlet passage 140, first ascends the outer annular passage 170 in the ejector 130. At the lower end of the venturi tube, some of the liquid exits directly through passages 174 and 158. Meanwhile, the remaining portion is recycled into the venturi tube by an annular reprocessing passageway 176.

The apparatus described herein with reference to FIGS. 1 and 2 includes an ejector which in each case provides recirculation in non-cavitating conditions. This ejector constitutes, according to tests, the ejector with the best performance characteristics to achieve the desired decomposition of particles.

It is possible to convert the ejector into a cavitation circulating ejector by changing the parameters in the treatment method. Although this may increase the efficiency of the device, it increases the risk of wear and tear. This solution can only be used if the liquid to be treated requires shortened operating times.

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 is to be obtained, as is especially the case in nuclear power applications, it is preferable to use recirculating ejectors.

FIG. 3 shows very diagrammatically a variant of the device 216 according to the invention. As in the embodiment described with respect to FIG.
8, the structure of which allows the liquid to be treated to flow inside from top to bottom, successively through the injector 236 and then through the venturi tube 2.
44 is now being swept away. However, the outlet of the venturi tube 244 is directed into a baffle arrangement 280, reducing the height and increasing the diameter of that portion of the ejector. This baffle arrangement 280 includes a passage 282 between two coaxially opposed shaped sections 284, 286.
formed by.

In the apparatus 216 shown in FIG. 3, an inlet passage 24 formed in a tank 218 with the liquid to be treated.
0 to the ejector 230 is continuously circulated through the injector 236, the venturi tube 244, and then the passageway 282 of the baffle device 280. Therefore, as explained earlier, the agglomerated particle decomposition effect obtained by the shear force within the injector and venturi tube is supplemented with the auxiliary particle decomposition effect obtained by the impact action against the wall surface of the baffle device 280. It is.

As mentioned above, the venturi tube 2
A portion of the liquid that has flowed through 44 exits the device through outlet passageway 258. Meanwhile, the remaining liquid is recycled into the venturi tube 244 through a passageway 264 formed in the base.

As already pointed out, the device according to the invention is particularly suitable for the treatment of the powder obtained after dissolving nuclear fuel in a nitric acid solvent, but also for the suspension of agglomerated solid particles which it is desired to crush. It can be used to treat any cloudy fluid, especially industrial wastewater.

It is clear that the invention is not limited to the embodiments described here by way of example, but in fact encompasses all variants thereof. Accordingly, the baffle device placed at the outlet of a venturi tube in which liquid is allowed to flow upward according to the embodiment of FIG. 3 can be placed at the outlet of a venturi tube in which liquid is allowed to flow downward. Furthermore, the orientation and arrangement of the liquid inlet and outlet passageways formed in the tank of this device may be varied without departing from the scope of the invention.

[0055]

[Effects of the Invention] As explained above, according to the present invention,
The liquid to be treated is circulated through the ejector, and this circulation crushes the agglomerates, and a portion of the treated liquid is recirculated through the ejector again to repeat the crushing process, and the remaining liquid is drained. The ejector is designed to flow to the outside through a passageway, and the ejector can be easily removed and installed by remote control, which prevents pipes from becoming clogged due to agglomeration of powder, especially in cases such as nuclear fuel reprocessing. By using it in situations where it is necessary to avoid such problems to the utmost, it is possible to solve problems such as blockages and pipe wear and tear, and to prevent harmful effects such as radiation on the human body. In addition, the structure is simple, and if applied to various other fields, it can greatly contribute to the purification of industrial wastewater, etc.

[Brief explanation of the drawing]

FIG. 1 illustrates a device according to the invention capable of comminuting agglomerated solid particles suspended in a liquid, the device being arranged for the liquid to flow from the bottom to the top in a Venturi tube; Vertical sectional view shown in FIG.

FIG. 2 is a vertical cross-sectional view similar to FIG. 1 showing a second embodiment of the device according to the invention, in which liquid flows from the top to the bottom of the venturi tube;

FIG. 3 is a schematic cross-sectional view similar to FIGS. 1 and 2 showing a third embodiment of the invention, which is a device equipped with a baffle device.

[Explanation of symbols]

10,110 Slab 12,112 Upper region 14 Lower cell 16 Device 18,118,218 Tank 20 Flange 24 Cover 26 Sleeve 30,130,230 Ejector 31,32,3
3 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

Claims (12)

[Claims] Claim 1: A liquid containing agglomerated solid particles is passed through a Venturi tube (4) under pressure.
4,144,244) A process for comminuting agglomerated solid particles suspended in a liquid. 2. A method according to claim 1, characterized in that substantially vertical venturi tubes (44, 24
4) A method for pulverizing agglomerated solid particles suspended in a liquid, comprising the step of flowing the liquid from the bottom to the top. 3. Process according to claim 1, characterized in that it comprises the step of flowing said liquid from top to bottom in a substantially vertical venturi tube (144). A process for grinding suspended agglomerated solid particles. [Claim 4] Any one of claims 1 to 3
The treatment method described in Section 1, in which a Venturi tube (forming an ejector that ensures circulation of the liquid)
44,144,244) A process for comminuting agglomerated solid particles suspended in a liquid, the process comprising the step of flowing said liquid through a liquid. [Claim 5] Any one of claims 1 to 4
A method for treating agglomerated solid particles suspended in a liquid, characterized in that the liquid is passed through a baffle device (280) at the outlet of a venturi tube (244). Processing method of crushing. 6. A tank (18,118,218) comprising a passageway (40,140,240) for inflowing and a passageway (58,158) for discharging a liquid containing agglomerated solid particles into the tank. , 258), and a Venturi tube (44, 144, 244) is installed in the tank between the inlet passage and the outlet passage. A device that crushes agglomerated solid particles. 7. The device according to claim 6,
A venturi tube (44, 244) is disposed along a substantially vertical axis, the inlet at its lower end being connected to the inflow passage through an inflow chamber (38) formed in the lower part of the tank, and the outlet at its upper end Apparatus for comminuting agglomerated solid particles suspended in a liquid, characterized in that it is connected to a discharge passage via an annular passage (54) formed around a venturi tube. 8. The device according to claim 7,
The venturi tube (44) is connected to the injector (36).
) and separated from the inlet chamber by a recycling chamber (42) which is connected to the annular passage (54) through a hole (64) formed in the septum. A device that crushes agglomerated solid particles. 9. The device according to claim 6,
A venturi (144) is disposed along a substantially vertical axis, the inlet at its upper end being connected to the inlet passageway (140) via an outer annular passageway (170) formed around the venturi tube, and the inlet at its lower end A device for crushing agglomerated solid particles suspended in a liquid, characterized in that the outlet is connected to a discharge passage through a discharge chamber (156) formed at the bottom of the tank. 10. The device according to claim 9, wherein the venturi (144) is surrounded by an inner annular recycling passageway (176), the lower end of which is located in front of the lower end outlet of the venturi tube. A device for crushing agglomerated solid particles suspended in a liquid, characterized in that it is provided above a deflector (172), and its upper end is provided between an injector and a venturi tube. 11. The device according to claim 6, wherein the baffle device (28
2. A device for crushing agglomerated solid particles suspended in a liquid, characterized in that a venturi tube (244) is disposed downstream of a venturi tube (244). 12. The device according to any one of claims 6 to 11, comprising a venturi (44
, 144, 244) is replaceable ejector (30,
130, 230) Apparatus for grinding agglomerated solid particles suspended in a liquid, characterized in that the device is disposed in a liquid.