EP1379472A1

EP1379472A1 - Device for stirring and aerating a liquid in a treatment vessel

Info

Publication number: EP1379472A1
Application number: EP02727663A
Authority: EP
Inventors: Alain Boulant
Original assignee: Innova Environnement
Current assignee: Innova Environnement
Priority date: 2001-04-19
Filing date: 2002-04-17
Publication date: 2004-01-14
Also published as: US20040155368A1; US7261279B2; CA2443943A1; FR2823742A1; NO20034670L; NO327287B1; IL158482A0; FR2823742B1; NO20034670D0; CA2443943C; WO2002085799A1

Abstract

The invention concerns a device (10) for stirring and aerating a liquid (3) in a treatment vessel, comprising: at least a funnel (11) designed to be arranged in the upper part of said vessel (1) providing a passage (11a) with said vessel (1); at least a casing (12) connected to said funnel (11) and designed to extend towards the bottom of said vessel (1), said casing (12) including at least an opening (12a, 12b) in each of its upper and lower parts; at least a main stirrer (13) located in said sheath (12); means (14, 15) for driving said stirrer (13) in rotation; and means (17, 18) for incorporating air in said liquid. Said device is characterised in that said air incorporating means (17, 18) comprise, besides the upper edge of the funnel (11), peripheral means arranged proximate to said edge, adapted to incorporate in said liquid (3) air at atmospheric pressure under the sole effect of the movement of said liquid (3).

Description

The present invention relates to a device for brewing and aerating a liquid in a treatment tank.

International device WO 98 30319 discloses a device for brewing and aerating a liquid in a treatment tank, comprising:

- at least one funnel intended to be placed in the upper part of said tank by providing a passage with this tank,

at least one sheath connected to said funnel and intended to extend towards the bottom of said tank, said sheath comprising at least one opening in each of its upper and lower parts,

- at least one main propeller located in said sheath,

means for driving said propeller in rotation, and

- Means for incorporating air into said liquid.

In this device of the prior art, the air incorporation means comprise a pipe opening into the sheath under the funnel, and means for sending pressurized air into this pipe.

Although they promote the aeration process of the liquid, in particular with a view to its bacteriological degradation, these air injection means consume a significant amount of energy, which comes to strain the overall energy balance of the device.

This is particularly troublesome especially when it comes to treating large volumes of liquids heavily loaded with organic matter, where the amount of energy to be spent to inject enough air to allow the degradation of the liquid can be prohibitive. The object of the present invention is to provide economic means which can either replace the air injection means, in particular for standard volumes of normally charged liquids, or supplement these injection means, in particular for large volumes of highly charged liquids.

This object of the invention is achieved with a device for brewing and aerating a liquid in a treatment tank, comprising:

at least one sheath connected to said funnel and intended to extend towards the bottom of said tank, said sheath comprising at least one opening in each of its upper and lower parts, - at least one main propeller located in said sheath,

means for driving said propeller in rotation, and

- Means for incorporating air into said liquid, remarkable in that said air incorporation means comprise, in addition to the upper edge of said funnel, peripheral means arranged in the vicinity of this edge, adapted to incorporate into said liquid of the air at atmospheric pressure under the sole effect of the movement of this liquid.

Thanks to these characteristics, use is made of the movement of the liquid in the vicinity of the upper edge of the funnel to incorporate air into it, which makes it possible to carry out this incorporation passively, that is to say without 'it is necessary to use an additional source of energy.

By substituting these fixed means of incorporating air for the air injection means or by supplementing them with these, depending on the volume of liquid to be treated and / or the charge of this liquid in organic matter, we can significantly improve the overall energy balance of the stirring and aeration device compared to the prior art.

According to other characteristics of the device according to the invention:

said peripheral means comprise a plurality of projections distributed over the upper edge of said funnel, said peripheral means comprise an annular member extending inside said funnel,

- said annular member is shaped as an annular gutter,

said annular member is shaped as an annular grid,

said sheath extends to above the upper edge of said funnel, and said air incorporation means comprise at least one window formed in the upper part of said sheath,

said air incorporation means comprise anti-vortex means arranged inside said sheath above said main propeller,

said air incorporation means comprise a liquid accelerator inside said sheath,

said means for incorporating air comprise means for aerating the surface of said liquid,

said air incorporation means comprise a vortex pump inside said sheath, said air incorporation means comprise a single-channel propeller inside said sheath,

said air incorporation means comprise a two-channel propeller inside said sheath, said main propeller is of the mainly axial flow type,

said device comprises anti-vortex means arranged inside said sheath below said main propeller,

said device comprises dynamic stirring means,

said device comprises static means for stirring by turbulence arranged inside said sheath,

said device comprises means for sucking the foam formed on the surface of said liquid inside said sheath,

- Said device comprises means for injecting pressurized air into said sheath. The present invention also relates to a liquid processing tank, remarkable in that it is equipped with a device according to any one of the preceding claims.

Other characteristics and advantages of the present invention will become apparent in the light of the description which follows and on examination of the appended drawing, in which:

FIG. 1 is a schematic sectional view of a liquid treatment tank equipped with a first embodiment of the device according to the invention,

FIG. 2 is a sectional view along line 2-2 of FIG. 1,

- Figure 3 is a perspective view of the treatment tank of Figure 1, - Figure 3bis is a schematic sectional view of a liquid treatment tank equipped with a second embodiment of the device according to the invention,

FIG. 4 is a sectional view along line 4-4 of FIG. 3,

- Figure 5 is a partial schematic sectional view of a third embodiment of the device according to the invention, - Figure 6 is a schematic sectional view of a liquid accelerator, associated with the third embodiment of the device according to the invention,

FIG. 7 is a schematic sectional view of means for aerating the surface of the liquid associated with the accelerator of FIG. 6,

FIG. 8 is a partial schematic view in section of a fourth embodiment of the device according to the invention, FIG. 9 is a schematic view on a larger scale of the vortex pump of the fourth embodiment of the device according to the invention,

FIG. 10 is a sectional view along line 10-10 of FIG. 9,

FIG. 11 is a partial schematic view in section of a fifth embodiment of the device according to the invention,

FIG. 12 is a sectional view along line 12-12 of FIG. 11,

FIG. 13 is a partial schematic view in section of a sixth embodiment of the device according to the invention, and

- Figure 14 is a sectional view along line 14-14 of Figure 13. In these figures, identical references designate identical or similar members or sets of members.

In Figure 1, there is shown a tank 1 provided at its upper part with an orifice 2 for entering a liquid 3 to be treated, such as for example greasy effluents extracted from urban effluents of wastewater. The treatment tank 1 can be covered on its external face with an insulator 4 and comprises a device for stirring and aerating the liquid according to the invention, generally designated by the reference 10.

This device 10 disposed inside the tank 1 comprises a funnel 11 flared upwards, placed in the upper part of the tank 1, the upper edge of which provides with the wall of the tank 1 a free space 11a for passage liquid 3.

This device also comprises a sheath 12 connected to this funnel and extending in the direction of the bottom of the tank 1, this sheath comprising an opening 12a in its upper part opening into the bottom of the funnel 11, and an opening

12b in its lower part opening out in the vicinity of the bottom of the tank 1. The device 10 is also provided with means for sucking the liquid inside the sheath 12, comprising a main propeller 13 disposed under the bottom of the funnel 11, fixed to a vertical shaft 14 itself capable of being driven in rotation by a geared motor 15.

The propeller 13 is preferably of the type known per se with predominantly axial flow, that is to say of the type capable of generating a field of speeds slightly inclined relative to the axis of the propeller.

This type of propeller is used in particular in applications where it is essential, for safety reasons, to fair the propeller: the fact that this propeller generates a mainly axial flow, it makes it possible to limit the energy losses on the fairing walls, and thus optimize the performance. This type of propeller is found, for example, in towing ships, the propellers of which it is essential to protect to prevent them from getting caught in the ropes of the ships to be towed.

An anti-vortex member 16 is preferably placed inside the sheath 12 below the propeller 13 to prevent the rotation of the liquid 3 in the sheath 12.

As shown in FIG. 2, this anti-vortex member 16 comprises three vertical plates 16a distributed at 120 ° inside said sheath 12.

The device according to the invention comprises means arranged in the vicinity of the upper edge of the funnel 11, adapted to incorporate liquid 3 at air at atmospheric pressure under the sole effect of the movement of this liquid.

As shown in Figures 1, 3 and 3a, these peripheral incorporation means may include a plurality of projections 17 disposed on the upper edge of the funnel 1 and which may have the shape of regularly spaced teeth. As shown in Figures 1 and 3, these peripheral incorporation means may include an annular member 18 extending inside the funnel 11, in the vicinity of its upper part.

This member can for example be formed by an annular gutter, as shown, or by an annular metal grid. Optional, as taught for example in the application

WO 98 30319, a pipe for injecting pressurized air into the sheath 12 (not shown) can be provided.

The device 10 can be connected to the interior of the tank 1 by lugs 19a which provide between them passages for the liquid 3. Reference is now made to FIG. 3bis, on which a second embodiment of the invention.

We will content ourselves with describing in the following the characteristics which differentiate this embodiment from the previous one.

The sheath 12 extends to above the upper edge of the funnel 11, and the upper end of this sheath is closed by a plate 20 supporting the geared motor 15.

The sheath 12 has a first series of windows 21 uniformly distributed around the periphery of this sheath 12 and located at the level of the liquid 3 inside the funnel 11. This sheath 12 is also provided with a second series of windows 22 uniformly distributed around the circumference of the sheath 12 and located above the bottom of the funnel 11.

The device 10 is provided with means for adjusting the flow rate of liquid 3 and of foam 23 drawn in by the main propeller 13 inside the sheath 12 through the windows 21 and 22.

These adjustment means are formed, on the one hand, by a first sleeve 25 disposed around the sheath 12 at the first series of windows 21 and, on the other hand, by a second sleeve 26 disposed around said sheath 12 at the second series of windows 22. The position of each sleeve 25 and 26 relative to the windows 21 and 22 respectively is adjustable vertically by suitable clamping means, not shown.

In this second embodiment, the device 10 also comprises means for regulating the level of liquid 3 in the funnel 11. These means may include an overflow pipe 27 disposed inside the funnel 11 and of which the position is adjustable vertically.

In this second embodiment, the device 10 also comprises static means 30 for turbulently stirring the liquid 3 inside the sheath 12 arranged below the anti-vortex member 16 in the sheath 12. As shown in FIGS. 3bis and 4, the static means 30 are formed, on the one hand, by a vertical tube 31 disposed inside the sheath 12 and extending from the bottom of the tank 1 to the underside of the anti-vortex member 16 and, on the other hand, by superimposed obstacles 32, disposed inside the sheath 12 and fixed to the tube 31. The tube 31 is fixed to the bottom of the tank 1 by appropriate means .

The obstacles 32 form passages with the internal wall of the sheath 12 for the circulation of the liquid.

As shown in FIG. 3a, the obstacles 32 are preferably distributed over the tube 31, on the one hand, below the anti-vortex member 16 and, on the other hand, at the bottom of the sheath 12.

For example, the tube 31 has at its upper part, below the anti-vortex member 16, two superimposed obstacles 32 and at the lower part of the sheath 12 also two superimposed obstacles 32.

According to a variant not shown, the obstacles 32 can be regularly distributed over the entire portion of the tube 31 disposed in the sheath 12. As shown in FIG. 3a, the obstacles 32 are preferably formed by cups whose concavity is directed towards the bottom of the tank 1.

According to a variant not shown, the obstacles 32 can be formed by discs.

According to another variant, not shown, the static means for stirring by turbulence can be formed by obstacles placed on the internal wall of the sheath 12 and providing an axial passage for the circulation of the liquid 3.

These obstacles can be regularly distributed over the entire portion of the sheath 12 located below the anti-vortex member 16, or be grouped on the one hand below the anti-vortex member 16 and on the other hand in the lower part of the sheath 12.

In this case also, the obstacles can be formed by cups whose concavity is directed towards the bottom of the tank 1 or by discs. In the second embodiment, the device 10 does not include an annular member 18 (see Figure 3).

However, it should be understood that the invention also relates to a device which, in addition to the characteristics of the second embodiment, would include such an annular member. More generally, it should be understood that the invention relates to any device combining some or all of the characteristics of the first and second embodiments described above, provided that such a device comprises peripheral means allowing the incorporation of air in the vicinity of the upper edge of the funnel 11.

Thus, for example, the invention also relates to a device comprising windows 21, 22, but no static means 31 for swirling by turbulence.

The invention also relates to a device having dynamic means for stirring the liquid located in the sheath, in accordance for example with the teaching of patent application EP 0 687 497.

It will be recalled here that these dynamic stirring means may comprise a "long shaft", that is to say a shaft extending under the main propeller 13 inside the sheath 12 and provided with means for brewing the liquid inside the sheath 12.

The device which has just been described operates in the following manner. The liquid 3 to be treated is poured through the orifice 2 into the tank 1 up to a level situated above the upper edge of the funnel 1 (see Figures 1 and 3a). This liquid 3 also pours inside this funnel 11. The gear motor 15 rotates the shaft 14 which itself rotates the main propeller 13.

The rotation of the main propeller 13 causes a suction of the liquid 3 in the sheath 12 so that this liquid 3 circulates continuously from top to bottom, in this sheath

12, then passes into the space 33 separating the lower end of the sheath 12 from the bottom of the tank 1 and flows from bottom to top between the sheath 12 and the internal wall of the tank 1 and so on.

The anti-vortex member 16 prevents rotation of the liquid in the sheath 12 below the propeller 13.

Due to the depression caused by the propeller 13, the liquid level 3 inside the funnel 1 is below the liquid level inside the tank 1.

This results in the formation of a cascade of liquid 3 over the entire periphery of the funnel 1.

The presence of the peripheral air incorporation means such as the projections 17 and / or the annular member 18 makes it possible to complete the incorporation of air due to the mere presence of the upper edge of the funnel 11, which edge causes the fall of the liquid 3 inside the funnel 11. In fact, the projections 17 form obstacles making it possible to separate the flow of liquid 3 into a plurality of veins which, by joining, naturally trap air.

As for the annular member 18, it forms an obstacle making it possible to create additional cascades contributing to the incorporation of air. In the second embodiment (see Figure 3bis), the depression caused by the propeller 13 also has the effect of creating an additional cascade inside the sheath 12, which contributes to the incorporation of air into the liquid 3.

It will be noted that the overflow pipe 27 makes it possible to adjust the level of the liquid 3 inside the funnel 11 so that this level is substantially at mid-height of the windows 2.

It will also be noted that the windows 21 allow the foam 23 located on the surface of the liquid 3 to be absorbed in the sheath 12, thus preventing this foam from flying away and polluting the environment.

It will also be noted that the liquid flow rate 3 can be adjusted by moving the sleeves 25 and 26 relative to the windows 21 and 22. During the circulation of the liquid 3 inside the sheath 12, the obstacles 32 create, below each of these, a turbulence effect, making it possible to divide the air bubbles 34 into micro-bubbles, which promotes the process of biological degradation, and thus the yield of the device according to the invention. In each of the embodiments described above, the gas bubbles between the internal wall of the tank 1 and the sheath 12 accelerate the ascent of the liquid, promoting the circulation of this liquid inside the tank 1, which allows improve performance.

Thus, the liquid to be treated passes several times through the sheath 12 and therefore undergoes several oxygenation treatments.

At each passage, the projections 17 and / or the annular member 18 make it possible to incorporate air into the liquid 3 at atmospheric pressure under the sole effect of the movement of this liquid, this air making it possible to carry out the process of biological degradation of the liquid 3. The optional use of a main propeller 20 of the type described above, that is to say with mainly axial flow, makes it possible to increase the height of fall of the liquid 3 on the edge upper of the funnel 11, and thus to promote the action of the projections 17 and / or of the annular member 18 and, ultimately, to improve the performance of the device.

It also goes without saying that by combining the projections 17 with the annular member 18, the efficiency of the device is increased.

Of course, the optional option of injecting pressurized air inside the sheath 12 also makes it possible to increase the efficiency of the device.

The choice of the speed of rotation of the main propeller 20 makes it possible to adapt the speed of the device according to the invention to the nature of the liquid to be treated. As can now be understood, use is made of the movement of the liquid 3 in the vicinity of the upper edge of the funnel 11 in order to incorporate additional air into it, which makes it possible to carry out this incorporation passively. that is, without the need for an additional source of energy. By substituting the air incorporation means 17, 18 for the air injection means or by supplementing them with these, according to the volume of liquid to be treated and / or the charge of this liquid in organic matter , the overall energy balance of the stirring and aeration device can be significantly improved compared to the prior art. We will now review other embodiments comprising mobile means making it possible to complete the effect of incorporating air obtained with the peripheral means 17, 18.

In the third embodiment shown in FIG. 5, the device comprises a second anti-vortex member 40 disposed inside the sheath 12 and above the main propeller 13.

This second anti-vortex member 40 is formed by at least two vertical plates 40a and each extended upwards by a reinforcing rib 41 extending to the upper end of said sheath 12.

Preferably, the second anti-vortex member 40 is formed by four vertical plates 40a uniformly distributed inside the sheath 12 and each extended upwards by a reinforcing rib 41.

The second anti-vortex member 40 makes it possible to create a friction force on the liquid 3, which force generates eddies facilitating the incorporation of air into the liquid 3. According to a variant represented in FIG. 6, the device comprises an accelerator liquid inside the sheath 12.

This liquid accelerator is formed by a secondary propeller 45 disposed above the second anti-vortex member 40 and integral in rotation with the shaft 14.

The secondary propeller 45 has a pitch oriented in the same direction as the pitch of the main propeller 13.

In addition, the liquid accelerator also comprises an anti-vortex member 46 disposed above the secondary propeller 45 and inside a cylindrical chimney 47.

The chimney 47 is fixed to the internal edge of the reinforcing ribs 41 so as to provide with the sheath 12 and between the reinforcing ribs 41 passages 48 for the liquid.

The secondary propeller 45, the anti-vortex member 46 and the chimney 47 are located between the two series of windows 21 and 22 which are, in this variant, provided with adjustment sleeves 25, 26. The rotation of the propeller main 13 causes suction of the liquid 3 in the sheath 12 through the windows 21 and 22 so that this liquid 3 circulates continuously from top to bottom in this sheath 12.

In addition, due to the rotation of the secondary propeller 45, the aspiration of the liquid 3 into the sheath 12 through the windows 21 and 22 is accelerated and part of the liquid rises through the passages 48 formed between the sheath 12 and the fireplace 47 which further accentuates this phenomenon of acceleration of the liquid inside said sheath 12.

The anti-vortex member 46 prevents rotation of the liquid in the chimney 47.

The acceleration and aspiration of the liquid have the effect of subjecting it to significant eddies favoring the incorporation of air into this liquid.

This variant is particularly suitable for products which are particularly foaming.

Indeed, due to the acceleration of the suction of the liquid 3 inside the chimney 47 and a recirculation of part of this liquid in the passages 48, the foam floating on the surface of the liquid 3 is sucked inside said chimney 47.

According to a variant shown in FIG. 7, the device comprises means for aerating the surface of the liquid 3 inside the tank 1.

As shown in this figure, the means for aeration of the surface of the liquid 3 are formed by a secondary propeller 50 disposed above the second anti-vortex member 40 and integral in rotation with the shaft 14.

This secondary propeller 50 has an inverted pitch with respect to the pitch of the main propeller 13.

The means for aerating the surface of the liquid 3 also comprise an anti-vortex member 51 disposed above the secondary propeller 50 and inside a cylindrical chimney 52.

The chimney 52 is fixed to the internal edges of the reinforcing ribs 48 so as to form with the sheath 12 and said reinforcing ribs 48 passages 55 for the liquid 3.

The secondary propeller 50 and the anti-vortex member 51 are located between the two series of windows 21 and 22 and the chimney 52 extends substantially from the middle part of the first series of windows 21 to the upper edge of the second series of windows 22.

A cover 53 is mounted on the shaft 14 above the upper edge of the chimney 52. The vertical position of the cover 53 is adjustable so as to provide with the upper edge of the chimney 52 an adjustable passage 54.

The rotation of the main propeller 13 causes a suction of the liquid 3 through the windows 21 and 22 so that this liquid 3 circulates from bottom to top in the sheath 12.

Thus, part of the liquid 3 is drawn into the sheath 12 through the windows 22 and another part of the liquid 3 is drawn through the windows 21 and flows from top to bottom in the passages 55 formed between the chimney 52 and the sheath 12.

In addition, taking into account the pitch of the secondary propeller 50 which is reversed with respect to the pitch of the main propeller 13, part of the liquid is drawn into the chimney 52 from bottom to top and is projected into the air on the surface of the liquid 3 inside the funnel 11 passing through the passage 54.

Thus, the projection of part of the liquid makes it possible to incorporate air into this liquid and, moreover, to reduce the formation of foam on the surface of this liquid.

The anti-vortex member 51 prevents the rotation of the liquid in the chimney 52 above the secondary propeller 50. In this variant also, the flow of liquid 3 in the sheath 12 can be adjusted by moving the sleeves 25 and 26 compared to windows 21 and 22.

According to a fourth embodiment shown in FIGS. 8 to 10, the device according to the invention comprises a vortex pump 60 for suctioning the surface of the liquid inside the sheath 12. This vortex pump 60 is arranged at above the second anti-vortex organ

40 and at the level of the first series of windows 21.

This vortex pump 60 is driven in rotation by the shaft 14 and comprises, on the one hand, a circular plate 61 fixed on this shaft 14 and provided on its upper face with radial and vertical blades 62 and, on the other hand, a chimney 63 fixed to the upper edge of said blades 62.

The assembly constituted by the plate 61, the blades 62 and the chimney 63 is held on the shaft 14 by means of a sleeve 61 a whose vertical position on this shaft 14 is adjustable.

The sleeve 61a is fixed to said shaft 14 by means of a member constituted for example by a fixing screw, not shown.

As shown in FIGS. 8 and 9, the upper edge of the blades 62 is fitted with a crown 64 extending towards the outside of the chimney 63.

This chimney 63 extends upwards from the tank 1 substantially from the middle part of the first series of windows 21 to the upper edge of the blades 62. This chimney 63 provides an internal passage 65 which communicates, at its lower part, with the inside of the sheath 12 by annular passages 66 formed between the blades 62 and between the crown 64 and the plate 61.

Preferably, the chimney 63 is conical and the conicity is directed towards the upper part of the tank 1, as shown in FIG. 9. According to a variant, the chimney 63 can be cylindrical. The blades 62 are flat or curved and are preferably three in number, regularly distributed over the plate 61, as shown in FIG. 10.

The rotation of the main propeller 13 causes a suction of the liquid 3 in the sheath 12 through the windows 21 and 22 so that this liquid 3 circulates continuously from top to bottom in the sheath 12.

In addition, the rotation of the vortex pump 60 driven by the shaft 14, that is to say the rotation of the assembly constituted by the plate 61, the blades 62 and the chimney 63 causes suction of the surface of the liquid. 3 in the passage 65 so that this liquid then passes through the annular passages 66 and is reinjected into the tank 1.

In this embodiment, the adjustment of the liquid flow rate through the sleeves 25 and 26 inside the sheath 12 is not necessary.

Under the effect of the vortex pump 60, the liquid 3 is subjected to significant eddies promoting the incorporation of air into this liquid. This embodiment is particularly suitable for very foaming products because the foam floating on the surface of the liquid 3 is sucked by the vortex pump 60 which allows this foam to be removed quickly and efficiently.

According to a fifth embodiment shown in FIGS. 11 and 12, the device according to the invention comprises a single-channel propeller 70 for sucking the liquid 3 inside the sheath 12.

This single-channel propeller 70 is disposed above the second anti-vortex member 40 and at the level of the first series of windows 21.

The single-channel propeller 70 is rotated by the shaft 14 and comprises, on the one hand, a circular plate 71 fixed on this shaft 14 and disposed above the level of the liquid 3 in the tank 1 and, on the other part, inside the liquid 3, a vertical plate

72 forming a spiral and fixed on the underside of said plate 71 around the shaft

14.

As shown more particularly in FIG. 12, the plate 72 delimits a lateral inlet 73 for the liquid extending over the entire height of said plate 72, a vertical channel 74 for circulation of this liquid from top to bottom and a lower outlet 75 of said liquid.

The assembly constituted by the plate 71 and the vertical plate 72 is held on the shaft 14 by means of a sleeve 71a whose vertical position on this shaft 14 is adjustable. For this purpose, the sleeve 71 a is fixed on said shaft 14 by means of a member constituted for example by a fixing screw, not shown.

The internal edge of the vertical plate 72 comprises a vertical deflector 76 inclined in the direction of the center of the spiral formed by said plate 72.

On the other hand, the distance separating the plate 72 and the axis of the shaft 14 gradually decreases, as shown in FIG. 12.

The rotation of the single-channel propeller 70 driven by the shaft 19, that is to say the rotation of the assembly formed by the plate 71 and the plate 72 in the direction indicated by the arrow in Figure 12, causes suction liquid inside said plate 72 through the side inlet 73. This liquid is stirred inside the vertical channel 74 and flows in this channel 74 from top to bottom to be evacuated inside the sheath 12 through the lower outlet 75.

The deflector 76 improves the stirring of the liquid inside the vertical channel 74 and prevents a return of the liquid through the lateral inlet 73.

The mixing performed by the single-channel propeller 70 promotes the incorporation of air into the liquid 3.

According to a sixth embodiment shown in FIGS. 13 and 14, the device according to the invention comprises a two-channel propeller 80 for sucking the liquid 3 inside the sheath 12.

This two-channel propeller 80 is disposed above the second anti-vortex member 40 and at the level of the first series of windows 21.

The two-channel propeller 80 is driven in rotation by the shaft 14 and comprises, on the one hand, a circular plate 81 fixed on this shaft 14 and disposed above the level of the liquid 3 in the tank 1 and, on the other hand part, inside the liquid 3, two vertical plates 82 and 83. The vertical plates 82 and 83 are fixed on the underside of the plate 80 and each have the form of two half-shells which are opposite and offset one relative to each other as shown in Figure 14.

The two plates 82 and 83 delimit two lateral inlets 84 and 85 of the liquid, two channels 86 and 87 for circulation of these liquids from top to bottom and a lower outlet 88 of said liquid.

The assembly constituted by the plate 81 and the vertical plates 82 and 83 is held on the shaft 14 by means of a sleeve 81a whose vertical position on this shaft 14 is adjustable.

The sleeve 81a is fixed to the shaft 14 by means of a member constituted for example by a fixing screw, not shown. As shown more particularly in FIG. 14, the edge of each plate 82 and 83 situated opposite the channel 86 or 87 delimited by the other plate comprises a vertical deflector, respectively 89 and 90.

The rotation of the two-channel propeller 80 driven by the shaft 14, that is to say the rotation of the assembly formed by the plate 81 and the two vertical plates 82 and 83 in the direction indicated by the arrow in Figure 14 causes suction of the liquid 3 through the windows 21.

This liquid enters through the lateral inlets 84 and 85 and is stirred inside the channels 86 and 87 and circulates from top to bottom inside these channels 86 and 87, then is then discharged into the sheath 12 through the outlet lower 88.

The deflectors 89 and 90 increase the stirring of the liquid inside the channels 86 and 87 and prevent this liquid from flowing back through the lateral inlets 84 and 85.

Under the effect of stirring caused by the two-channel propeller 80, the incorporation of air into the liquid is favored. In these last two embodiments, the adjustment of the liquid flow rate through the sleeves 25 and 26 of the sheath 12 is not necessary and these last two embodiments are more particularly used in the case where the liquid level inside the tank 1 is variable.

To improve the flow rate of the single-channel propeller 70 or the two-channel propeller 80, a pumping propeller, not shown, can be placed on the shaft 14 below the single-channel propeller or below the propeller dual-channel.

The device according to the invention applies for example to the treatment of water, urban effluents, industrial waste water, grease by biodegradation, draining materials, livestock waste and in general to all biodegradable industrial products.

Of course, the present invention is not limited to the embodiments described and shown, provided by way of illustrative and nonlimiting example.

Claims

1. Device (10) for stirring and aerating a liquid (3) in a treatment tank (1), comprising:

- at least one funnel (11) intended to be placed in the upper part of said tank (1) by providing a passage (11 a) with this tank (1),

- At least one sheath (12) connected to said funnel (1 1) and intended to extend towards the bottom of said tank (1), said sheath (12) comprising at least one opening (12a, 12b) in each of its upper and lower parts,

- at least one main propeller (13) located in said sheath (12), - means (14, 15) for driving said propeller (13) in rotation, and

- means (17, 18; 21; 40; 45, 46, 47; 50, 51, 52; 60; 70; 80) for incorporating air into said liquid, characterized in that said means for incorporating air comprise, in addition to the upper edge of said funnel (11), peripheral means arranged in the vicinity of this edge, adapted to incorporate into said liquid (3) air at atmospheric pressure under the sole effect of the movement of said liquid (3) .

2. Device (10) according to claim 1, characterized in that said peripheral means comprise a plurality of projections (17) distributed over the upper edge of said funnel (11).

3. Device (10) according to one of claims 1 or 2, characterized in that said peripheral means comprise an annular member (18) extending inside said funnel (1 1).

4. Device (10) according to claim 3, characterized in that said annular member (18) is shaped as an annular gutter.

5. Device (10) according to claim 3, characterized in that said annular member (18) is shaped as an annular grid.

6. Device (10) according to any one of the preceding claims, characterized in that said sheath (12) extends above the upper edge of said funnel (1 1), and in that said means of incorporation air comprise at least one window (21) formed in the upper part of said sheath (12).

7. Device (10) according to any one of the preceding claims, characterized in that said means for incorporating air comprise anti-vortex means (40) arranged inside said sheath (12) above of said main propeller (13).

8. Device (10) according to any one of the preceding claims, characterized in that the said air incorporation means comprise an accelerator (45, 46, 47) of liquid (3) inside the said sheath ( 12).

9. Device (10) according to any one of the preceding claims, characterized in that said means for incorporating air comprise means for aerating (50, 51, 52) the surface of said liquid (3).

10. Device (10) according to any one of the preceding claims, characterized in that said air incorporation means comprise a vortex pump (60) inside said sheath (12).

1 1. Device (10) according to any one of the preceding claims, characterized in that said air incorporation means comprise a single-channel propeller (70) inside said sheath (12).

12. Device (10) according to any one of the preceding claims, characterized in that said air intake means comprise a two-channel propeller (80) inside said sheath (12).

13. Device (10) according to any one of the preceding claims, characterized in that said main propeller (13) is of the mainly axial flow type.

14. Device (10) according to any one of the preceding claims, characterized in that it comprises anti-vortex means (40) arranged inside said sheath (12) below said main propeller (13 ).

15. Device (10) according to any one of the preceding claims, characterized in that it comprises dynamic stirring means.

16. Device (10) according to any one of claims 1 to 14, characterized in that it comprises static means for stirring by turbulence

(30) arranged inside said sheath (12).

17. Device (10) according to any one of the preceding claims, characterized in that it comprises means for sucking inside said sheath (12) foam (23) formed on the surface of said liquid (3 ).

18. Device (10) according to any one of the preceding claims, characterized in that it comprises means for injecting pressurized air into said sheath (12).

19. Liquid treatment tank (1), characterized in that it is equipped with a device (10) according to any one of the preceding claims.