WO1999012652A1

WO1999012652A1 - Apparatus for separating and purifying polluting agents from at least one fluid mixture

Info

Publication number: WO1999012652A1
Application number: PCT/FR1998/001863
Authority: WO
Inventors: Pierre Saget
Original assignee: Pierre Saget
Priority date: 1997-09-08
Filing date: 1998-08-28
Publication date: 1999-03-18
Also published as: FR2768067A1; EP1011872A1

Abstract

The invention concerns an apparatus (10) for separating and purifying polluting agents from at least one fluid mixture comprising a rotor (16) with at least two open-work stacked plates (18), an intake element (14) for the mixture to be treated located above the rotor (16), means (22A, 22B) for collecting the heavy phase located beneath the rotor (16) and an element (26) for extracting the treated mixture, located above the intake element (14). The fluid entering the apparatus is driven by a descending helical movement in the annular space (20) arranged between the periphery of the rotor plates and the apparatus body, then reverses its trajectory to rise again through the plate recesses describing an ascending helical movement. The apparatus comprises a plurality of blades (42) extending substantially longitudinally at least in the proximity of the periphery of the plates (18) and which are integral with rotor (16) in rotation. Said blades slope rearwards relative to the rotor rotating direction (R)

Description

Apparatus for separating and purifying pollution from at least one fluid mixture.

The present invention relates to an apparatus for separating and purifying pollution from at least one fluid mixture, comprising: - a rotor, mounted in a body and having a stack of at least two perforated plates extending radially towards the wall of said body and arranged substantially transversely to the axis of rotation of the rotor, an annular space remaining between the periphery of the plates and the wall of the body, said rotor cooperating with means for generating a pressure drop at the top of the apparatus and for generating an upward helical movement of the mixture to be treated, the direction of rotation of which is the same as that of the rotor,

a member for entering the mixture to be treated situated above the rotor, this member comprising an annular chamber and a central column, said chamber having a closed upper end and an open lower end connected to said annular space, while the column has open upper and lower ends, the apparatus comprising means for generating, in the annular space, a downward helical movement of the same direction of rotation as said upward helical movement,

means for collecting the heavy phase located under the rotor, and

- a member for extracting the treated mixture, connected to the body above the inlet member.

The mixture to be treated is for example a gaseous or liquid mixture polluted by solid, liquid or mixed impurities.

An apparatus of this type is known from French patent FR 94 07 057. Due to the position of the inlet member of the mixture to be treated between the rotor and the extraction member, the flow of the fluid in the the device is cyclonic, a downward peripheral helical movement being maintained in the annular space formed between the periphery of the plates and the wall of the body, while an upward helical movement is formed in the central column of the device, the fluid passing by the openings in the rotor plates. The fluid is therefore first subjected to the downward helical movement, in which a centrifugal pre-separation is carried out, which makes it possible to separate the larger particles, then to the upward helical movement in which the final centrifugal separation is carried out.

In the known apparatus, the means for generating the downward helical movement comprise a helical distributor which has a plurality of fixed oblique blades whose inclination is determined so as to give the flow a tangential speed adapted to the speed of rotation of the rotor and to limit the appearance of turbulence in the annular space. This known device is effective for separating from the fluid mixture particles whose dimensions are less than 3 microns.

The problem, however, is that, during the helical movement descending in the annular space formed between the wall of the body and the periphery of the plates of the rotor, the fluid tends to be braked by the wall of the body which is fixed. It follows that the tangential speed of the fluid in the annular space is not homogeneous over the width of this space and that the centrifugal field which is created is not quite as high as would be desired. Consequently, the centrifugal pre-separation in the annular space rather affects relatively large particles which are the most sensitive to the action of this centrifugal field, taking into account their masses.

In addition, hard, dry and fine particles entrained in the annular space by centrifugation are only deposited fleetingly on the wall of the body of the device. The fluid circulates at high tangential speeds in the vicinity of this wall and, even if the means for generating the downward helical movement are effective, a turbulent flow is created localized against the wall.

Thus, when the particles do not "stick" durably against the wall and when these particles have very small dimensions (for example, diameter less than one micron) and equally small masses, this turbulent flow risks putting them back into circulation in the fluid, until they leave the annular space to find themselves in the upward helical movement which prevails in the central region of the rotor.

Some of these particles may therefore escape separation. The present invention proposes to improve the known apparatus to further increase the efficiency of the centrifugal pre-separation which is carried out in the annular space and to prevent as much as possible that the particles located in this space are put back into circulation. towards the center of the device.

This object is achieved thanks to the fact that the apparatus comprises a plurality of blades which extend substantially longitudinally at least in the vicinity of the periphery of the plates and which are integral with the rotating rotor and to the fact that said blades have at least one part. which is inclined with respect to a radius passing through the axis of rotation of the rotor so that the end of said inclined part which is distant from this axis is, in the direction of rotation of the rotor, backwards with respect to the end of this inclined part which is closest to said axis.

Due to the inclination of the blades, the particles which are located in the annular space and which, due to the turbulence phenomena, would tend to be set in motion towards the axis of the rotor come, at least for the most part. 'between them, bounce against the blades; they are therefore again projected towards the wall of the body and tend to be confined in the annular space until they descend towards the means for collecting the heavy phase.

Only particles which could "sneak" between the blades could be brought back towards the central part of the rotor; these particles would have complex trajectories, the probability of which is extremely low. However, the direction of inclination of the blades is such that they do not prevent particles subjected to centrifugal forces from entering the annular space.

In addition, the blades extend at least in the vicinity of the periphery of the plates, that is to say in the immediate vicinity of or in the annular space. They rotate at the same speed as the rotor and constrain the fluid which, when it enters the device, is biased so as to circulate in the annular space, to very quickly adopt a speed of rotation substantially equal to that of the rotor. Thus, at least in the part of the annular space immediately adjacent to the blades and at least over the height of these blades, the tangential speed of the fluid mixture is homogeneous and substantially equal to the tangential speed of the rotor. As a result, as soon as it enters space annular, that is to say immediately after entering the apparatus, the fluid is subjected to a high centrifugal field whose action is felt even on particles of relatively small dimensions.

Advantageously, at least some of the blades have an end portion which extends into the annular space, which in particular promotes centrifugal pre-separation in this space.

The blades are advantageously arranged so that, for each pair of a first blade and a second blade, adjacent to the first blade and located behind it in the direction of rotation of the rotor, the first blade extends towards the 'rear with respect to said direction of rotation, at least until cutting a radius passing through the end of the inclined part of the second blade which is closest to the axis of rotation.

In this case, the blades are close enough to each other, or even in slight circumferential overlap, so that the rebound effect of the particles on the upstream face of the blades is further enhanced. However, the blades remain sufficiently spaced that the intervals between the payrolls form passages allowing the particles subjected to centrifugation to enter the annular space.

Advantageously, certain blades have an extension which extends substantially radially with respect to the axis of rotation away from said axis from the end of the inclined part of the blade which is distant from this axis of rotation.

These extended pay periods further intensify the rotational drive of the fluid in the annular space. Advantageously, they extend over substantially the entire radial width of the annular space formed between the wall of the body and the periphery of the plates of the rotor. Thus, the rotational drive due to the presence of the blades is exerted on practically the entire radial width of the annular space. In fact, it suffices that a small functional clearance of the order of a few millimeters is provided between the radial ends of the extended blades and the wall of the body in the annular space.

Advantageously, the blades are fixed to the periphery of at least one of the plates of said stack of at least two plates.

This arrangement constitutes a very simple way of securing the blades in rotation with the rotor. It is advantageous for the fluid mixture to be subjected to the effect of payroll entrainment upon entering the annular space. In this context, the blades can extend at least in the region of the annular space immediately adjacent to the inlet member of the mixture to be treated in the device, that is to say immediately adjacent to the open lower end of the annular chamber of this inlet member. Conventionally, blades will be at least fixed to the upper plates of the rotor.

According to an advantageous arrangement, the blades extend over substantially the entire height of said stack of at least two plates.

This arrangement makes it possible for the drive and sequestration effect of the blades to be exerted over substantially the entire height of the annular space. It is even advantageous for the blades to extend slightly lower than the bottom plate of the stacking of the rotor plates, which, by maintaining a high centrifugal field even beyond the bottom plate, accentuates the projection and the compaction, on the wall of the body, separate products or impurities constituting the heavy phase, even beyond the lower plate, that is to say in a region which is not far from the means for collecting the heavy phase . The blades can be made of sheet metal, the extension of the extended blades possibly being punctured, which makes it possible, while using extended pays which extend substantially over the entire width of the annular space, to prevent these pays from have the effect of compartmentalizing the annular space into several annular sectors practically isolated from each other. The perforations, without harming the acceleration of the fluid mixture due to the blades, allow the circulation of this mixture between the different "compartments" formed between the extended blades. In the same vein, it may be advantageous to provide the blades with serrated or wavy axial edges, without this being compulsory, the edges of the blades also being able to be straight.

The invention will be clearly understood and its advantages will appear better on reading the detailed description which follows, of an embodiment shown by way of nonlimiting example. The description refers to the appended drawings in which: FIG. 1 is a view in longitudinal section of an apparatus according to the invention, - Figure 2 is a partial view in radial section, showing a plate seen from above.

FIG. 3 is a partial longitudinal section along the line III-III of FIG. 2, - FIG. 4 is a view similar to FIG. 3, schematically showing a variant,

FIG. 5 is a view according to arrow V in FIG. 3,

FIG. 6 is a top view of the helical distributor,

FIG. 7 is a developed sectional view of the dispenser of FIG. 6, and

- Figure 8 is a partial sectional view along line VIII-VIII of Figure 2.

The general reference 10 in FIG. 1 designates an apparatus for separating and purifying the pollution of at least one fluid mixture, in particular a gas mixture, according to the invention. This device comprises a fixed cylindrical body 12, a member 14 for entering the fluid mixture into the body 12, a rotor 16, which is mounted in the body 12 and which has a stack of at least two perforated plates 18 which are 'extend radially towards the wall of the body 12 while leaving an annular space 20 between the periphery of the plates and said wall.

In the following, we will consider that the axis of the device is vertical and that the means for collecting the heavy phase are located downwards, which is a generally advantageous arrangement, which makes it possible to benefit both from the field centrifugal and gravitational field. In known manner, the rotor 16 cooperates with means generating a pressure drop at the top of the device 10 comprising for example a suction fan 1 1. This rotor, whose direction of rotation is indicated by the arrow R, generates a helical movement of the mixture to be treated in the same direction of rotation. The apparatus further comprises means for collecting the heavy phase situated under the rotor, which for example comprise two extraction chutes 22A and 22B each provided with a forced evacuation means 24 isolated from the outside. A collection hopper can be used in place of the troughs 22A and 22B. The apparatus also comprises a member 26 for extracting the treated mixture which is connected to the cylindrical body above the member inlet 14, itself disposed above the rotor 16. The fan 11 is located in the region of the extraction member 26.

In the example shown, it has been chosen to have the motor 17 for driving the rotor in rotation below this rotor, which, due to the high mass of the motor, promotes the stability of the device when it is arranged vertically. The motor, which is supplied by an electric or other power supply 19, directly attacks the shaft 16A of the rotor and is placed in a chamber 9 isolated from the fluid flowing in the device by a casing 8, for example a conical casing going to s flaring down. The fact that this casing is conical makes it possible to guide the heavy phase, that is to say the impurities which would deposit on its wall, towards the collection spouts 22A and 22B. It should be noted here that the bottom wall 7 of the device can also be shaped so as to guide the impurities towards the collecting spouts. The bearings 6 of the shaft 16A may, depending on the mass of the plates, be located only in the lower part of this shaft.

The inlet member 14 has an annular chamber 28 whose upper end 28A is closed, while the lower end 28B is open and is connected to the annular space 20. The member 14 further has an inlet 30 of the mixture to be treated which opens into the annular chamber 28. Advantageously, as shown in FIG. 1, this inlet 30 can be produced by a tangential inlet volute.

The member 14 also has a central column 32 which is separated from the annular chamber 28 by a cylindrical or frustoconical wall 34. The column 32 has an upper end 32A open and a lower end 32B also open.

The apparatus comprises means for generating, in the annular space 20, a downward helical movement in the same direction of rotation R as the rotor. The trajectory of the fluid mixture in the apparatus, without taking account of the centrifugal fields, is indicated by the arrows F. More precisely, the fluid mixture entering the apparatus in the direction E by the input member 14 rotates in the annular chamber 28 and descends in the annular space 20 by swirling, that is to say that it is animated in this space with a descending helical movement. Then, once under the rotor, the fluid mixture reverses its trajectory to describe an upward helical movement in the rotor, pass through the central column 32 of the input member 14, then exit through the extraction member 26 as indicated by the arrow S.

The means for generating the downward helical movement include a helical distributor 36 disposed in the upper part of the annular space 20. As can be seen better in FIGS. 6 and 7, this distributor 36 is in the form of an annular element fixed to the wall of the cylindrical body 12 and comprises a plurality of fixed, oblique and curved blades, designated by the general reference 38. At the upper part of FIG. 6, the oblique blade 38A extends over the sum of the angular sectors a and B. On the angular sector b, it is located under the oblique blade 38B, so that the oblique blades are arranged in slight axial overlap. Passing the fluid mixture rotating in the direction R between the oblique blades 38 accelerates the latter and gives its tangential speed a downward component. The inclination of the blades 38 is calculated so that this tangential speed of rotation is adapted to that of the rotor.

The means for generating the downward helical movement also comprise means for guiding the fluid mixture in the annular space 20 which comprise a fixed ring 40 disposed between the lower end of the internal wall 34 of the annular chamber 28 and the periphery of the upper plate 18A of the rotor 16. The distributor 36 is placed at the level of this ring 40. The plates 18 of the rotor 16 may be conical, flared towards the bottom of the device or, as in the example shown, constituted by discs Radials which, as best seen in Figure 2, have openings 58. One can choose to provide the peripheral edges of these plates of frustoconical skirts flared downwards which act as deflectors. This provision is not, however, mandatory as will be seen below.

The apparatus comprises a plurality of blades 42 and 144 which extend substantially longitudinally in the region of the edges of the plates 18. These blades have at least one part inclined relative to the rays passing through the axis A. They are inclined towards the rear relative to the direction of rotation, that is to say that, as seen in FIG. 2, the angle α measured from a radius Ra towards the upstream face 42 ′ of a blade is positive in the tπgonometric direction when the rotor turns in the R direction clockwise. Advantageously, this angle α is between 25 ° and 65 ° and, more precisely, between 40 ° and 50 °. In Figure 2 are shown blades of two types. The blades 42 are formed by the inclined parts. They are substantially flat, but can also be concave or convex, or even slightly helical, as will be seen below (FIG. 5). The blades 144 have, in addition to the inclined part 142, an extension 143 which extends substantially radially in the annular space 20. This extension 143 serves to intensify the entrainment of the fluid in rotation in the annular space as soon as it enters this space, so as to favor centrifugal pre-separation. It is sufficient that only a few regularly distributed blades are equipped with this extension.

The inclined parts of the blades (42, 142) serve to sequester or confine the particles in the annular space. To do this, it is advantageous that the blades are close to each other. Thus, if we consider the pair of blades 42A and 42B of Figure 2, we see that the free edge 42'A of the blade 42A away from the axis A extends rearward relative to the direction of rotation R at least until cutting the radius Rb which passes through the edge 42'B of the blade 42B which is closest to the axis A. We even see a slight circumferential overlap, that is to say that , if we trace the radius Rc passing through the edge 42'A of the blade 42A, we note that the angle γ between the rays Rb and Rc is advantageously of the order of 3 ° to 7 °, for example 5 °.

Figure 2 shows only a few blades 42 and a blade 144. In fact, the blades are continuously distributed along the circumference of the rotor plates. For example, for a rotor 610 mm in diameter, between 65 and 75 blades can be provided, for example 72 blades, of which 6 to 10 pays can be equipped with extensions 143 to form blades 144.

As can be seen in FIG. 2, a particle P expelled radially towards the annular space 20 by centnfugation penetrates there without difficulty even if it bounces on the blades 42 (trajectory T). The number blades and their inclination are determined (advantageously with an overlap of angle γ) without the blades being too close together, both to avoid additional cost and to avoid interfering with the expelled particles radially in a centrifugal movement. The inclination of the blades gives their upstream faces 42 ′ a tangential component so that, when they come into contact with the fluid circulating in the annular space 20, they impart to it an additive centrifugal impulse which further reinforces the tendency of this mixture not to penetrate between the rotor plates before reaching the bottom of the annular space 20. In addition, during the rotation of the rotor, the upstream faces of the blades in contact with the fluid mixture present in the space annular 20 constitute collecting walls that certain particles can come into contact with. Due to the inclination of the blades, these particles are then deflected towards the wall of the body 12 of the device. This is rather valid for particles whose dimensions are at least of the order of 5 μ. The inclination of the blades, however, also affects the trajectories of finer particles, for which the forces involved are rather Van Der Waals forces, electrostatic forces and hydrogen bonds. Thus, by combining the centrifugal pre-separation carried out in the annular space 20 and the centrifugal separation carried out in the central region of the rotor, the apparatus is able to isolate very small particles, of dimensions less than 1 μ or even 0, 1 μ.

In the example shown, the blades 42 and 144 extend partly inside the plates 18 of the rotor and partly in the annular space 20. They are integral with the rotating rotor and are for example directly fixed to the outer periphery of the plates 18 of the rotor. If frustoconical skirts equip the plates 18, the blades 42 and 144 can be fixed to the skirts, or these skirts can be formed by sections between which the blades extend. In FIG. 2, the edges of the plates 18 have notches

44 in V, having an edge 44A inclined relative to the radius, on which the blades are welded. Of course, other methods of attachment can be provided.

Note that the blades 42 shown in Figure 1 extend substantially over the entire height of the stack of plates 18. They even extend substantially beyond since the ends upper 41 A of the blades 42 are in the upper region of the annular space 20, immediately below the distributor 36, and that their lower ends 41 B extend downwards, slightly beyond the lower plate 18G, that they protrude over a height H.

The blades 42 are shown schematically in FIG. 1. They can be formed by sheets extending continuously over their entire height. However, as shown in Figure 3, the blades 42 or 144 may include at least two sections of blades arranged in the extension of one another. More specifically, the section of Figure 3 shows only the first rotor plates and a blade 144 which includes a first blade section 144A attached to the upper plate 18A of the rotor and to the plate 18B located immediately below. The blade 144 comprises a second blade section 144B which is fixed to the plate 18C and to the plate 18D situated immediately below.

By choosing to make the blades 42 or 144 in the form of blade sections fixed only to some of the rotor plates, the assembly and disassembly of the apparatus is facilitated, since the elements of the rotor are assembled in groups of two or more plates now blade sections.

It can be seen in FIG. 3 that the extensions 143 of the blades 144 can be provided with orifices 45.

Figure 2 shows the plate 18A of the rotor and illustrates in phantom the openings of the plate 18B located below. We see that the openings of the plates are angularly offset to define a helicoid.

The fully inclined blades 42 extend over only part of the annular space 20, leaving a relatively substantial annular margin against the wall of the body 12.

On the other hand, it can be seen in FIG. 3 that the blades 144, with their extensions 143, can extend over practically the entire radial width Lr of the annular space 20, only a functional clearance j being then preserved. In the variant of FIG. 4, the apparatus comprises a plurality of fixed frustoconical crowns 90 arranged one above the others in the annular space 20 or, more precisely, in a part 21 of the latter close to the wall of the body 12, the blades 42 or, above all, the extensions 143 of the blades 144, extending in the other part of this space. The crowns 90 open downwards and it can be seen (clearance i) that their lower ends are not in contact with the wall of the body 12. For example, the crowns 90 are fixed to the fixed parts of the apparatus using vertical rods 91, shown schematically in broken dashed lines.

Figure 5 is an end view along arrow V of Figure 3 and shows that the blades 42 or 144 are also advantageously inclined relative to the direction of the axis of rotation of the rotor, direction indicated by the line D in this figure. The angle of inclination β is small and is for example between 1 ° and 5 °, advantageously of the order of 1.5 ° to 2 °. The blades are inclined towards the rear in the direction going from their upper ends to their lower ends, with respect to the direction of rotation R. In other words, the upstream faces 42 ′ of the blades are very slightly inclined downwards. This slight general slope gives the fluid (gaseous) part of the mixture a slight downward pulse, which further encourages it to travel through the annular space 20 to the bottom of this space and also gives a shock impulse towards the bottom to the particles encountered by the blade.

In the region of the apparatus situated between the rotor and the collecting means 22A and 22B, preferably near the lower ends 42B of the blades 42, the apparatus comprises oblique fins 50 which are fixed to the internal face of the wall of the body of the device by fixing lugs 52. These fins 50 extend radially towards the inside of the device, their internal radial ends being substantially located in line with the external periphery of the plates 18. Thus, the fins 50 only concern the vein of fluid which leaves the annular space 20. They are slightly inclined relative to the horizontal downwards when they are considered in the direction of rotation R. The angle δ of inclination of these fins relative to the horizontal is of the order of a few degrees, for example between 10 and 20 degrees. The inclination of the fins is therefore sufficiently low for them to ensure a partial straightening of the tangential speed of the stream of fluid which comes into contact with them. However, the fluid tends to penetrate under the fins and this results in a low vacuum on the upper face of the latter which tends to prevent a return of the gas towards the axis of the device before its exit from the rotor. The fins 50 are distributed regularly and, depending on the dimensions of the device, their number can vary, for example between 6 and 18.

The apparatus also comprises an intermediate member 60 which is located under the rotor (under the fins 50 when they are present) and which comprises a plurality of elements of concentric cylinders 62. This intermediate member is fixed, the concentric cylinders 62 being able to be held together by openwork connecting bars 64, the openings of which are large enough to prevent them from constituting an obstacle to the rotation of the fluid in this region. This intermediate member 60 makes it possible to create, between the space located immediately under the rotor 16 and the collection means 22A and 22B, a tranquilization buffer zone.

In this zone, due to the cylindrical conformation of the elements 62, a swirling movement of the fluid is maintained which has little tendency to escape from the member 60. In other words, the flow of the fluid in this region has practically no vertical component and is not downward discharging. Thanks to these arrangements, the fluid mixture leaving the annular space 20, which thanks to the aforementioned means is effectively forced to travel through this space to its lower end, reverses its trajectory before reaching the zone of the collection means 22A and 22B. Indeed, the impurities to be evacuated accumulate in this zone and the fact of preventing the fluid leaving the annular space from entering this zone makes it possible to prevent this fluid from being charged again with separated particles before go back into the rotor. On the other hand, the movement of the fluid in the vortex zone 60 does not prevent the descent of the particles separated from the fluid under the effect of the centrifugal field, as far as the collection means 22A and 22B. It should also be noted in this regard that the fluid vortex tends to sweep the walls of the elements of concentric cylinders 62 in order to ensure only a temporary accumulation of the separated products in this zone, and favor their movement towards the collection means 22A and 22B. The cylinder elements 62 may have solid walls. However, it may be desirable to ensure a radial transfer of the fluid present in this region between the annular compartments formed between the cylinder elements to promote adaptation to the trajectory of the fluid, which is mainly desirable in the upper region of the 'member 60 near which is the inversion zone of the path F of the fluid between the downward helical and upward helical movements. To do this, these cylinder elements may have openings such as vertical slots whose width may vary over their height, or have serrated upper edges.

In Figure 1, there is shown in broken lines an outer jacket 70, arranged around the body of the device in the region of the rotor, and delimiting an enclosure in which a coolant can be circulated using an injection nozzle 74 and a lower outlet

76.

It is also possible to use the annular space 20 to carry out a final washing of the fluid mixture therein by injecting a washing fluid therein through nozzles 80 regularly distributed at its upper end. The section of Figure 8 passes through an aperture 58 of the plate

18A. As best seen in FIG. 3, the openings in the plates have radial edges, the upstream radial edge 58A and the downstream radiated edge 58B.

These radial edges may have fins formed by folds. Thus, fins 59A inclined downward and backward relative to the direction of rotation R can be fitted to the upstream radial edges

58A and / or fins 59B inclined upwards and forwards (parallel to the fins 59A) can be fitted to the downstream radial edges 58B.

These fins are used to guide the fluid during its ascent in the openings of the rotor.

Claims

1. Apparatus (10) separating and purifying the pollution of at least one fluid mixture, comprising: - a rotor (16), mounted in a body (12) and having a stack of at least two plates (18) to openings (58) extending radially towards the wall of said body and arranged substantially transversely with respect to the axis of rotation of the rotor, an annular space (20) remaining between the periphery of the plates (18) and the wall of the body (12 ), said rotor (16) cooperating with means for generating a pressure drop at the top of the apparatus and for generating an upward helical movement of the mixture to be treated, the direction of rotation (R) of which is the same as that of rotor,

a member (14) for entering the mixture to be treated located above the rotor (16), this member comprising an annular chamber (28) and a central column (32), said chamber having a closed upper end (28A) and an open lower end (28B) connected to said annular space (20), while the column (32) has open upper and lower ends, the apparatus comprising means (36, 40) for generating, in the annular space ( 20), a downward helical movement in the same direction of rotation (R) as said upward helical movement,

- means (22A, 22B) for collecting the heavy phase located under the rotor (16), and - a member (26) for extracting the treated mixture, connected to the body

(12) above the inlet member (14), characterized in that it comprises a plurality of blades (42; 144) which extend substantially longitudinally at least in the vicinity of the periphery of the plates (18) and which are integral with the rotating rotor (16) and in that said blades (42; 142) have at least one part (42; 142) which is inclined relative to a radius (Ra) passing through the axis (A ) of rotation of the rotor (16) so that the end (42A) of said inclined part which is distant from this axis (A) is, in the direction of rotation of the rotor, rearward relative to the end of this inclined part which is closest to said axis.

2. Apparatus according to claim 1, characterized in that at least some of the blades (42; 144) have an end portion (42'A; 143) which extends into the annular space (20) remaining between the periphery of the plates (18) and the wall of the body (12).

3. Apparatus according to claim 1 or 2, characterized in that the blades (42; 144) are arranged such that, for each pair of a first blade (42A) and a second pay (42B), adjacent to the first blade and located behind it in the direction of rotation (R) of the rotor, the first blade (42A) extends rearward (42'A) relative to said direction of rotation at least until cutting a radius (Rb) passing through the end (42'B) of the inclined part of the second blade (42B) which is closest to the axis of rotation (A).

4. Apparatus according to any one of claims 1 to 3, characterized in that the inclination (α) of the blades (42; 144) relative to the rays passing through these blades is between 25 ° and 65 °.

5. Apparatus according to any one of claims 1 to 4, characterized in that certain blades (144) have an extension (143) which extends substantially radially relative to the axis of rotation (A) moving away of said axis from the end of the inclined part of the blade considered which is distant from this axis of rotation.

6. Apparatus according to any one of claims 1 to 5, characterized in that the blades (42; 144) are fixed to the periphery of at least one of the plates of said stack of at least two plates (18) .

7. Apparatus according to any one of claims 1 to 6, characterized in that the blades (42; 144) extend over substantially the entire height of said stack of at least two plates (18).

8. Apparatus according to any one of claims 1 to 7, characterized in that each blade (42) comprises at least two sections of blades (42A, 42B) arranged in the extension of one another.

9. Apparatus according to any one of claims 1 to 8, characterized in that it comprises an intermediate member (60), located under the rotor (16) and comprising a plurality of concentric cylinder elements (62).

10. Apparatus according to any one of claims 1 to 9, characterized in that it comprises a plurality of fixed oblique fins (52), located near the lower end of the annular space (20) and extending from the wall of the body towards the axis of rotation (A) of the rotor

(16).

11. Apparatus according to any one of claims 1 to 10, characterized in that it comprises a plurality of fixed frustoconical crowns (90), arranged one above the other in the annular space (20).