EP0015210B1 - Apparatus for centrifugal separation of at least two liquid components and one solid component from a mixture - Google Patents

Abstract

The apparatus comprises around a nozzle supplying the mixture to be treated, a rotating sealed enclosure wherein an annular partition separates two chambers communicating together via a peripheral passage, containing chiefly the separated heavy phase and light phase and provided with thresholds for the draining thereof. According to the invention, the two chambers are equipped with separate centrifuge devices, connected to apparatus for driving them in rotation, which apparatus moves them at different angular speeds. The invention finds an application for example in the extraction of animal and vegetable fatty substances, in the extraction of essential oils, in the production of fat-free animal proteins, in the recovery of polymers from solvent-water mixed mediums, in the extraction of antibiotics, in metallurgical refinings with selective solvents, in the desalination of sea water by the solvent method, in the treatment of waste waters, etc.

Description

The present invention relates to an improved apparatus for the centrifugal separation of at least two liquid phases and a rigid sedimentary phase making up a mixture, this mixture possibly being constituted, for example, by crude olive oil.

The type of apparatus to which the improvements of the invention are applied may be that which is the subject of document DE-B-1,103,854. This type of device comprises, around a mouth for distributing the mixture to be treated, a rotating enclosure whose peripheral wall is closed by a coronal bottom and which is coupled to a first device for driving in rotation. This enclosure is integral with an annular partition which plunges into the mixture beyond the phase interface thereof, separates a first chamber containing only the heavy phase, from a second chamber containing the light phase which "floats" the heavy phase, and however spares a peripheral annular passage for the transfer of this heavy phase from the second chamber to the first. The enclosure also has separate thresholds for discharging the phases and cooperates with a helical sediment conveyor. The conveyor is coupled to a second rotary drive device via a plate which plunges into the mixture beyond the aforementioned interface and separates the second chamber from a cavity with which it nevertheless communicates with the periphery by this conveyor for the transfer of sediments through the heavy phase. Finally, the conveyor is also secured to a centrifuge device plunging at least into the light phase of the second chamber.

This type of known device does not give any satisfaction to the user because the light phase extracted - the oil - is not pure and still contains, in significant proportion, the heavy phase - water in particular - thus only a little sediment which affects its clarity, while another proportion of the light phase is lost by escaping with the heavy phase extracted.

The object of the invention is therefore to remedy this major drawback, by perfecting this type of device in such a way that the light phase is extracted from the mixture, perfectly pure and in full, that is to say without loss, and that it is the same for the heavy phase.

First of all, the Applicant has found that the centrifuge device of the second chamber containing the light phase which "floats" on the heavy phase does not entail this light phase at a strictly constant angular speed and that this centrifuge device only fills 'a limited part of this second bedroom. The Applicant has also found that the first chamber is free from a centrifuge device capable of driving the heavy phase at constant angular speed. The Applicant has finally found that there is nothing to prevent sediments from being entrained by the heavy phase towards the first chamber and blocking the passage connecting the two chambers.

Furthermore, the Applicant has observed, during specific tests, that if the mixture to be treated is rotated at constant speed throughout its mass and at all points permanently, the tangential speed of each particle in flow is strictly proportional to this constant angular velocity and to the radius of the point where said particle is located; such a flow obviously generates the separation of the constituent phases of the mixture which are distributed in concentric "superposed" layers, perfectly defined and separated by a very clearly localized interface.

The Applicant has also observed that if the mixture to be treated is not, on the contrary, driven at constant angular speed at all points of its mass by the rotating enclosure, it quite naturally adopts an irrotational vortex flow, that is to say -to say a flow in which each particle moves at a tangential speed inversely proportional to the radius and at the same time turns around the neighboring particles but not on itself. This type of flow generates a mixture, unlike the previous flow which generates a separation.

The Applicant has further observed that the transition zone between the two types of flow is extremely narrow; thus, a few millimeters from the centrifuge device - when it exists and truly drives the entire mass of mixture in which it is immersed at constant angular speed - said mixture flows in an irrotational vortex; in other words, while, in the intervention zone of the centrifuge device, the phases of the mixture tend to separate, outside of this centrifuge device, the phases tend to remain mixed; in addition, it is important to note that the stable phenomenon is that of the vortex and that it tends to propagate within the centrifuge device while causing a remixing of the phases as and when they are separated by these measures.

The Applicant has finally observed that if the aforementioned vortex flow is established in the first chamber, while a flow at constant angular velocity is already established in the second chamber, the interface is unstable and its "level" fluctuates from all the more broadly as the specific masses of the two liquid phases are very similar. This phenomenon seems to be due to the fact that the pressure field in the first chamber where there is a flow the vortex is ill-defined and irregular over time; therefore, the hydrostatic balance of the phases in the two chambers cannot be ensured, if stabilized. Consequently, the fluctuations of the interface irreparably lead to periodic partial defusing of the thresholds, that is to say massive outputs of the heavy phase with the light phase or of the light phase with the heavy phase. This phenomenon becomes practically negligible only if the specific masses of the phases are markedly different.

These observations make it possible to determine one of the causes of the ineffectiveness of the aforementioned known apparatus for properly separating the phases of a mixture and therefore to determine the improvements to be made. Thus, it is necessary that the centrifuge device of the second chamber is truly shaped to generate a flow at constant angular speed and that this centrifuge device concerns all the mass of mixture contained in this second chamber up to the vicinity of the annular passage which puts it in communication with the first chamber; this first chamber must also contain a centrifuge device operating on almost all of the heavy phase that said chamber contains.

Another cause of the ineffectiveness of the known apparatus is that the transfer of the heavy phase between the two chambers is not ensured under the best conditions and generates disturbances relative to the flows of the phases in the two chambers, flow which should be at constant angular speed.

Yet another cause of the ineffectiveness of the aforementioned known apparatus is due to the considerable instability of the phase interface in the second chamber. In fact, the tests carried out by the Applicant have shown that a small variation in the ratio of the speeds of rotation of the liquid phases in the chambers results in a significant variation in the radius of the interface, especially if these speeds of rotation are close. On the other hand, the same tests have shown that if the specific masses of the two liquid phases are close, the instability of the interface is amplified. Moreover, the Applicant has experimentally established the equilibrium law and it has found that the ratio of the rotational speeds k intervenes by the factor k ^{2 -} 1 and that the ratio m of the specific masses of the phases intervenes by the factor m - 1.

Consequently, in order to stabilize the interface in the case where the ratio of the specific masses is rigorously constant, it is necessary that the two devices for driving the rotation of the centrifuge devices are controlled by means of a device regulating the ratio of their speeds. In addition and since the specific mass ratio of the phases is generally not constant, it is necessary, always to stabilize the interface, to make the regulating device cooperate with a control member sensitive to the specific mass of one liquid phases, to the clarity of one of these or others, quantities which can be measured at the corresponding discharge threshold.

It is important to note that these improvements are essential in order to be able to benefit from the advantage which results from the rotational drive at different speeds of the enclosure, on the one hand, and of the conveyor integral with the centrifuge device, on the other hand go. This advantage is that the phases are actually subjected to centrifugal fields of different intensities, while the specific masses of these phases can be very close.

In accordance with the invention, a first centrifuge device is housed in the first chamber, is integral with the walls of the latter and has, whether it is of the type with radial or inclined blades, with conical plates, with slotted and lined plates or others, surfaces extending throughout the treated volume, across their circular scrolling, to transmit the rotation of the first drive device to the heavy phase at a rigorously constant angular speed throughout its mass and at all points; the second centrifuge device housed in the second chamber, is integral with the plate, extends along this chamber to reach as close as possible to the separating partition, the discharge threshold of the light phase and the annular passage of the heavy phase and present, whether of the type with radial or inclined blades, with conical plates, with split and edged plates or others, surfaces extend in all the treated volume, across their circular scrolling, to transmit the rotation of the second drive device in the light phase at least, at a rigorously constant angular speed throughout its mass and at all points, and the two drive devices of the centrifuge devices are controlled by means of a stabilizing and regulating device of the ratio of their respective rotational speeds.

According to other particular embodiments of the invention according to the first claim, the regulating device for the combined control of the two rotary drive devices cooperates with a control member sensitive to the specific masses or to the clarities of the two liquid phases. measured at the spill threshold.

Furthermore, the extreme turn of the conveyor located near the partition which separates the chambers is perforated to establish additional direct communication between these two chambers, this perforation making it possible to avoid pumping back from the light phase to the heavy phase.

The end of the conveyor located near the partition which separates the chambers is integral with at least one scraper element extending near the peripheral wall and directed into the annular passage to avoid any accumulation of sediment in the first heavy phase chamber, this scraping element forming with an enclosure generator an angle of between 0 and 45 °.

A labyrinth seal is interposed between the partition (which separates the two chambers) and a continuous central ring of the conveyor.

The discharge thresholds are adjustable tubes carried by the peripheral wall and extending from the center towards the periphery to open out of the enclosure and flush with the free surfaces of the heavy and light phases respectively in the chambers which contain them; the partition is stepped and has a skirt connecting a central flank to a peripheral flank; the tubes taking the light phase pass through the skirt by pressing against the peripheral flank in the first heavy phase chamber and against the central flank in the second light phase chamber at this location.

Various other advantages of the invention will also emerge from the detailed description which follows.

Embodiments of the object of the invention are shown, by way of nonlimiting examples, in the accompanying drawing.

• - la Fig. 1 est une demi coupe élévation, illustrant une première forme de réalisation d'un appareil de centrifugation, conforme à l'invention, qui permt concomitamment de séparer les phases liquides et de décanter ou clarifier,
• - la Fig. 2 est une coupe transversale partielle prise, à plus grande échelle, suivant la ligne 11-11 de la Fig. 1,
• - la Fig. 3 et la Fig. 4 sont des coupes transversales prises, à plus petite échelle, respectivement suivant les lignes III-III et IV-IV de la Fig. 1,
• - la Fig. 5 et la Fig. 6 sont des coupes partielles prises, à grande échelle, suivant les lignes V-V et VI-VI de la Fig. 3,
• - la Fig. 7 et la Fig. 8 sont des perspectives partielles montrant en détail, à grande échelle, deux modes d'exécution de la première spire du convoyeur, d'un élément de raclage et des moyens pour contrôler l'écoulement de la phase lourde,
• - la Fig. 9 est une élévation-coupe partielle représentant une deuxième forme de réalisation du dispositif centrifugeur mis en oeuvre dans la chamber de traitement,
• - la Fig. 10 est une coupe axiale synoptique des assiettes du dispositif centrifugeur selon la Fig. 9, les assiettes de l'empilage étant écartées les unes des autres,
• - la Fig. 11 est une vue en plan prise suivant la ligne XI-XI de la Fig. 10, les deux moitiés de cette vue faisant ressortir deux modes d'exécution particuliers des barrettes d'écartement,
• - la Fig. 12 est une élévation-coupe analogue à la Fig. 9, illustrant une troisième forme de réalisation du dispositif centrifugeur,
• - la Fig. 13 est une vue en plan d'un disque ajouré, prise suivant la ligne XIII-XIII de la Fig. 12.

On this drawing:

• - Fig. 1 is a half elevation section, illustrating a first embodiment of a centrifugation apparatus, in accordance with the invention, which allows concomitantly to separate the liquid phases and to decant or clarify,
• - Fig. 2 is a partial cross-section taken, on a larger scale, along line 11-11 of FIG. 1,
• - Fig. 3 and FIG. 4 are cross-sections taken on a smaller scale, respectively along lines III-III and IV-IV of FIG. 1,
• - Fig. 5 and FIG. 6 are partial sections taken, on a large scale, along the lines VV and VI-VI of FIG. 3,
• - Fig. 7 and FIG. 8 are partial views showing in detail, on a large scale, two embodiments of the first turn of the conveyor, of a scraping element and of means for controlling the flow of the heavy phase,
• - Fig. 9 is a partial elevation-section showing a second embodiment of the centrifuge device used in the treatment chamber,
• - Fig. 10 is a synoptic axial section of the plates of the centrifuge device according to FIG. 9, the plates of the stack being separated from one another,
• - Fig. 11 is a plan view taken along the line XI-XI of FIG. 10, the two halves of this view showing two particular embodiments of the spacer bars,
• - Fig. 12 is a sectional elevation similar to FIG. 9, illustrating a third embodiment of the centrifuge device,
• - Fig. 13 is a plan view of an openwork disc, taken along the line XIII-XIII of FIG. 12.

As is clear from Figs. 1 to 6, the apparatus comprises a rotating enclosure 1 constituted by a cylindrical peripheral wall 2 extended by a frustoconical wall 3 and closed by a coronal bottom 4 secured to a hub 5 also frustoconical which penetrates inside.

In this example, the axis of rotation 6 of the device is vertical and said device contains a helical conveyor 7 extending as close as possible to the internal surface of the walls 2 and 3, for the evacuation of the rigid sediments projected against said surface by the corresponding centrifugal field.

On a fixed frame 8 of the device, there is attached a sheath 9 extending coaxially in the hub and provided with internal bearings supporting a tubular shaft 10 the ends of which are integral with a driving pulley 11 and, respectively, of a flange 12 to which said hub 5 is coupled; the tubular shaft 10 is also provided with internal bearings coaxially supporting a central shaft 13, the ends of which are provided with a drive pulley 14 contiguous to the previous one and, respectively, two plates 15, 16 coupled to each other and made integral, by any appropriate means, with a centrifuge device which is designated according to its embodiment by the marks 17 (Fig. 1 to 8), 18 (Fig. 9 to 11) or 19 (Fig. 12 and 13) .

The description which follows relates to the first embodiment 17, but it is obvious that the means thus defined also apply to the two other embodiments.

The conveyor 7 is fixed around the device 17 and is therefore driven at the same speed of rotation as the latter by the pulley 14, a speed which is different from that of the enclosure 1 driven by the pulley 11.

Furthermore, a separating partition 20 is fixed against a shoulder of the hub 5 and extends towards the wall 2 of the enclosure; the beveled peripheral edge 21 of this partition defines with said wall an annular passage 22 which establishes permanent communication between two chambers 23 and 24 separated by said partition.

The chamber 23, of annular shape, is delimited by the wall 2, the bottom 4 and the partition 20; it is intended to contain only the heavy liquid phase which, in the established centrifugation regime, reaches the cylindrical level 25 concentrated at the axis of rotation 6. The chamber 24, also of annular shape, is delimited by the wall 2, the partition 20 and the plate 15; it is intended to receive the mixture to be treated and to contain, in particular in the central zone, the light phase which, at the same speed as above, reaches the cylindrical level 26 also concentric with the axis of rotation 6 but closer to it than the level 25 of the heavy phase. The interface between the heavy phase and the light phase is located at the cylindrical level 27 only in the chamber 24, the plate 15 opposing any crossing and flow of the light phase towards the cavity 28 for evacuating rigid sediments.

The mixture to be treated is distributed by a central nozzle 29 in a tube 30 coaxially integral with the plate 15 and extending in the cavity 28; this mixture reaches the plate 16 which projects it radially into the centrifuge device 17, 18 or 19.

The heavy phase is evacuated from the chamber 23 by an overflow threshold; preferably, this threshold is constituted by at least one radial tube 31 (six in the example shown in Fig. 3) carried by the peripheral wall 2, a threaded connection 32 making it possible to adjust its protrusion and thus the level of its mouth which then determines that of the free surface 25 of the heavy phase in said chamber 23.

Similarly, the light phase is evacuated from the chamber 24 by an overflow threshold of the same type; this threshold is then constituted by at least one radial tube 33 carried by the peripheral wall 2, a threaded connection 34 also making it possible to adjust its protrusion and thus the level of its mouth which then determines that of the free surface 26 of the light phase in said chamber 24.

But, so that the centrifuge device 17, 18 or 19 can intervene positively until passage 22, the partition 20 is stepped and has a skirt 35 connecting a central flank 36 which is fixed to the hub 5, to a peripheral flank 37 which delimits the passage 22 actually. The tubes 33 intended to take the light phase in the chamber 24 extend in the chamber 23 against the peripheral flank 37, pass through the skirt 35 and open very close to the latter in said chamber 24 against the flank central 36; these tubes therefore open flush with the surface in the chamber 24. Consequently, the centrifuge device 17 (or 18 or 19) can occupy the entire treatment volume of said chamber 24; it is integral, by one of its ends, with the plate 15 and, by its periphery, with the conveyor; it extends along the chamber 24 and ends, at its other end, as close as possible to the stepped partition 20; as a result, this last end of the centrifuge device is conformally complementary to the stepped profile of the partition 20 provided with the tubes 33, leaving only a minimum clearance which is of the order of 1 or 2 mm, this clearance being necessary since the centrifuge device 17 does not rotate at the same angular speed as the enclosure 1 and the partition 20 consequently.

The light and heavy phases flow through the tubes 31 and 33 respectively and spring outside where they are collected by fixed annular gutters.

In the embodiment illustrated in Figs. 1 to 6, the centrifuge device 17 consists of a plurality of blades 38 extending longitudinally, that is to say parallel to the axis of rotation 6. These blades are arranged side by side (Fig. 2 ) and are inclined, with respect to the radial directions, at an angle "a". The angle "a" can be understood, depending on the nature and composition of the mixture, the intensity of the centrifugal field ... between 20 and 90 °; however, in the example shown concerning the purification of olive oil, this angle is substantially equal to 40 °. In any case, the blades 38 delimit two by two of the passages 39 in which the heavy particles 40 precipitate centrifugally, on one face of the blade and accumulate to form a film which flows in the direction of the arrow F .1 along the slope towards the periphery to move towards the chamber 23, while the light particles 41 precipitate, in a centripetal manner, on the opposite face of blade and accumulate to form another film which flows in the direction of arrow F.2 along the slope towards the center to accumulate in chamber 24.

The blades 38 are rigidly held in place to form a rotor capable of supporting the centrifugal field. To this end, the blades are welded at one of their ends to the plates 15, 16 and, near their other end, on a central ring 42 and a peripheral ring 43 connected together by spokes 44 suitably distributed; it is obvious that intermediate holding wheels similar to the previous one, 42 to 44, can be provided if the length of the blades 38 is too large.

Of course, it is desirable for the heavy phase which remains in the cavity 28 to the cylindrical level 45 (FIGS. 1 and 4) to be driven at substantially the same speed of rotation as the heavy phase in the chamber 25. Consequently, the cavity 28 is free of liquid animation means; however, the conveyor 7 must be maintained and for this purpose, its turns are connected together by longitudinal bars 46 directly coupled to the plate 15 and, via arms 47 and 48, to the tube 30 thereof. Under these conditions, if the enclosure 1 rotates faster than the conveyor 7, the total thickness of the phases treated in the chamber 24 can be increased while maintaining the heavy phase at level 45 in the cavity 28.

According to the embodiment illustrated by FIGS. 1 to 6, the chamber 23 contains a centrifuge device 49 driven by the pulley 11 at the same speed of rotation as the enclosure 1 and, consequently, at a speed different from that of the aforementioned centrifugal device 17 which is driven by the pulley 14. The device 49 comprises, in the example shown (Fig. 3, 5 and 6) six blades 50 extending in radial planes between the threshold tubes 31 and made integral, for welding in particular, with the wall 2 and from the bottom 4 by marrying the stepped shape of the partition 20; so as not to disturb the flow of the heavy phase, from the chamber 24 towards the chamber 23, the blades 50 have a notch 51 opposite the annular passage 22.

The pulleys 11 and 14 or other coupling means must be rotated at different angular speeds which are those used for the centrifuge devices 17 and 49. These centrifuge devices rigorously transmit said speeds to the liquid masses contained in the chambers 24 and 23 so that said masses rotate in block. As already indicated, the ratio of these rotational speeds must be controlled and regulated with extreme precision. To this end and in accordance with the embodiment shown schematically by way of example only in FIG. 1, the driving pulleys 11 and 14 or other coupling means are connected by two independent transmissions T.1 and T.2 to the two outputs of a variable speed drive V driven by a motor M. On these two outputs of the variator are connected to the speed sensors C.1 and C.2 which transmit the signals corresponding to the detected speeds to a regulating device R which is intended to stabilize the ratio of said speeds; for this purpose, the regulating device R sends control signals to the terminals C.3 and C.4 of the circuits of the variator V controlling the two output speeds.

The apparatus described in the foregoing makes it possible to separate, in a mixture, two liquid phases whose specific masses are very similar, since these liquid phases can be subjected to centrifugal fields, truly separating, of different intensities.

Furthermore, if the treated mixture is composed of liquid phases whose specific masses are not absolutely constant, it suffices to modify the ratio of the rotational speeds of the pulleys 11 and 14 to precisely stabilize the interface of the light and heavy phases in the chamber 24, at level 27 depend on the levels 25 and 26 to which the threshold tubes 33 and 31 are adjusted.

For example, the mixture can consist of crude olive oil and it is known that the specific mass of the purified oil can vary, depending on the origin of the olives and many other parameters elsewhere.

To modify the rotation speed ratio, it is sufficient to automatically measure a significant quantity at the output of the threshold tubes, and to compare the instantaneous values with control values to emit signals representative of the variations thus detected, these signals then being directed towards the regulating device R so that it intervenes on the variator V as indicated in the foregoing.

The significant quantity can be the specific mass of the phases flowing through the threshold tubes considered or else the clarities of these phases or others. In any case, whatever the significant quantity chosen, sensor-comparators C.5 and C.6 of these quantities are connected to the threshold tubes 33 and 31, for example and connected by means of slaving A.1 and A.2 to the aforementioned regulating device R.

Furthermore, if the mixture contains mucilaginous sediments, the conveyor 7 cannot evacuate them towards the mouth of the conical wall 3. It is then necessary to avoid any harmful accumulation, to eliminate them as they appear against the cylindrical wall 2. For this purpose, the latter has at least one calibrated orifice 52 which opens into the chamber 24 near the stepped partition 20 and channels these sediments mixed with heavy phase outwards so that they squirt in a fixed annular drain. The orifice (s) 52 are scraped by the helical conveyor 7 to oppose any clogging. Of course, in order to maintain the equilibria, it is desirable to compensate for this leakage rate, with a heavy phase supply rate. For this purpose, a nozzle 53 fixed in the frame 8 and suitably supplied under low pressure, emerges opposite an annular gutter 54 secured to the bottom 4 of the rotating enclosure 1, this gutter communicating with the chamber 23 by at least one opening 55.

In the apparatus, as illustrated in Figs. 1 to 6, it is important to use means to avoid repumping of the light phase contained in the chamber 24, towards the heavy phase contained in the chamber 23, through the annular passage 22; this pumping back is likely to occur due to the ebb and flow which the first turn of the conveyor 7 causes to appear in the vicinity of the stepped partition 20.

One recommended way to avoid the pumping considered is to provide openings in this first turn 56 (Fig. 7) or 57 (Fig. 8) to establish direct additional communication between the chambers 23 and 24 through the conveyor 7 itself .

According to the embodiment shown in FIG. 7, the first turn 56 delimits openings 58 sufficiently close to one another to annihilate the fluctuations in the flow of the heavy phase from one chamber to the other.

According to the other embodiment shown in FIG. 8, the first turn 57 is constituted by two threads 59 and 60 extending respectively, in the peripheral part and in the central part of the conveyor, these threads being kept apart from one another by spacers 61 delimiting between them windows having the same functions as the aforementioned openings 58.

In the apparatus as shown in Figs. 1 to 6, it is also important to use means making it possible to avoid any accumulation of rigid sediment in the chamber 23 containing the heavy phase and in the annular passage 22 which gives access thereto. To this end, the sediments which deposit against the wall 2 in the vicinity of the partition 20 must be scraped and taken up by the conveyor 7. For this, a flat ring 62 is fixed, by welding for example, to the rotor 17 at its end close to the first turn 56 or 57. This ring supports, by means of a foot 63, at least one scraper element 64 extending as close as possible to the cylindrical wall 2 of the enclosure, from said first turn 56 or 57 and into the access passage 22. In the example shown, two scraping elements are provided, but it is obvious that there may be more.

Furthermore, according to the first embodiment (Fig. 7), the scraping elements 64 extend along the generatrices of the wall 2; on the other hand, according to the second embodiment (Fig. 8), said scraping elements form with the above generators an angle b which is between 0 and 45 °.

Figs. 5 to 8 clearly show that a labyrinth seal 65 is interposed between the ring 62 and the stepped partition 20 to prevent any disturbance from propagating from the passage 20 and from the first turn 56 of the conveyor towards the chamber 24 and / or room 23.

In the second embodiment illustrated in Figs. 9 to 11, the centrifuge rotor 18 is constituted by a stack of conical plates 66 connected together by longitudinal members 67 and 68 suitably distributed over their central and peripheral edges respectively. This rotor is fixed on the drive plates 15 and 16 coupled to the drive pulley 14 as well as in the conveyor 7 and, if its rigidity is not sufficient, an extreme holding wheel 42 to 44 and possibly intermediate wheels can be planned.

The taper of these plates 66 is between 70 and 100 ° and preferably equal to 80 °, in order to trap and channel the heavy and light particles with the same phase separation result as in the previous embodiment. Said plates also have protruding, on one of their faces, bars 70 or 71, which are located, when the rotor is formed, in the conical tubular chimneys 72 separated by these plates and through which the phases circulate . These bars make it possible to transmit to said phases the rotation at constant angular speed. In the embodiment illustrated by the upper half of FIG. 11, the bars 70 extend along the generatrices of the plates, in radial planes. In the other embodiment emerging from the lower half, the bars 71 are inclined relative to said radial planes.

According to the third embodiment (Figs. 12 and 13), the centrifuge rotor 19 is constituted by a stack of substantially flat coronal discs 73; these are interconnected by internal side members 74 and by a perforated grid 75 or a peripheral cage on which the conveyor 7 is fixed.

This rotor 19, possibly reinforced by at least one holding wheel 42 to 44, is fixed to the drive plates 15 and 16 coupled to the drive pulley 14.

Each plate 73 delimits a plurality of trapezoidal windows 76 distributed equianglely and separated from each other by screens 77 formed by the solid parts of the plate itself. It is important to note that the plates are angularly offset from each other.

In addition, each window or slot is delimited, on one side, by a clear edge 78 and, on the other side, by a flange 79 protruding into the intermediate spaces 80. The flanges 79 channel the heavy phase towards the periphery and participate very effectively in driving the rotating phases at constant angular speed. These lateral flanges 79 are radial in the example shown, but they can also be inclined relative to the radial directions at an angle at most equal to 40 °; in addition, they can be extended by a marginal edge 80.

Of course, nothing is opposed and it may even be advantageous for the centrifuge device 49 to be shaped like the centrifuge devices 17, 18 or 19.

The invention is not limited to the embodiments shown and described in detail, since various modifications can be made thereto without departing from its scope.

The method and the apparatus for its implementation are applicable in particular to the extraction of animal and vegetable fatty substances, to the extraction of essential oils, to the production of defatted animal proteins, to the recovery of polymers in mixed solvent medium -water, the extraction of antibiotics, metallurgical refining by selective solvents, the desalination of sea water by the solvent process, the treatment of waste water, etc.

Claims (12)

1. Improved apparatus for the centrifugal separation of at least two liquid phases and one solid sedimentary phase, the said apparatus comprising around a nozzle (29, 30) supplying the mixture to be treated, a rotating enclosure (1) closed by a coronal base (4) and coupled to a first means for driving it in rotation (11), the said enclosure which is integral with an annular partition (20) which plunges into the mixture beyond the interface (27) of the phases thereof, separating a first chamber (23) containing only the heavy phase, from a second chamber (24) containing the light phase "floating" on the heavy phase, providing however a peripheral annular passage (22) for the transfer of the said heavy phase from the second chamber towards the first, the enclosure further presenting separate thresholds (31, 33) for the draining of the phases and cooperating with a helical sediment conveyor (7), coupled to a second rotation means (14) via a plate (15) which plunges into the mixture beyond the said interface (27) and separating the second chamber (24) from a cavity (28) with which it nevertheless communicates on the periphery via the conveyor for transferring the sediments through the heavy phase, the said conveyor being moreover integral with a centrifuge device (17, 18 or

19) plunging at least into the light phase of the second chamber, characterized:

- in that another centrifuge device, so- called first centrifuge device (49), is housed in the first chamber (23), is integral with walls (2, 4 and 20) thereof, and depending on whether it is of the type with radial (50) or inclined blades, or with conical plates or perforated and flanged plates, or any other type, is provided with surfaces extending inside the entire treated volume, across their circular movement, in order to transmit the rotation of the first driving means (11) to the heavy phase according to an angular speed which is scrupulously constant throughout its whole mass and in every one of its points;

- in that the second centrifuge device (17, 18 or 19), housed in the second chamber (24), is integral with the plate (15), extends along the said chamber to arrive as close as possible to the partition wall (20), to the light phase draining threshold (33) and to the annular passage of the heavy phase (22), and is provided, whether it is of the type with radial or inclined blades (38), with conical plates (66), or with perforated and flanged plates (73) or any other type, with surfaces extending through the entire treated volume, across their circular movement, in order to transmit the rotation of the second driving means (14) to at least the light phase, according to an angular speed which is scrupulously constant throughout its whole mass and in every one of its points,

- and in that the two means (11 and 14) for driving the centrifuge devices are controlled by means of a device for stabilizing and regulating the ratio of their respective rotation speeds.

2. Apparatus according to claim 1, characterized in that the means for regulating the conjugated operation of the two rotation means (T.1 and T.2) cooperate with a control member (A.1 and A.2) which is sensitive to the densities of the two liquid phases measured at the draining threshold (31, 33).

3. Apparatus according to claim 1, characterized in that the means for regulating the conjugated operation of the two rotation means (T.1, T.2) cooperates with a control member (A.1, A.2) which is sensitive to the limpidities of the liquid phases measured optically at the draining thresholds.

4. Apparatus according to claim 1 comprising longitudinal driving blades, characterized in that the said blades (50), arranged in the first chamber (23) are substantially radial and present an indentation (51) of limited size opposite the annular passage (22).

5. Apparatus according to claim 1, comprising longitudinal driving blades characterized in that said blades (38), arranged in the second chamber (24) are inclined with respect to the radial directions so as to form therewith an angle which can vary between 20 and 70°, and is preferably equal to 40°.

6. Apparatus according to claim 1, comprising a stack of conical plates, characterized in that said plates (66), situated in the first (23) and/or second (24) chambers for positively driving the liquid phase or phases, have a conicity which may vary between 70 and 100°, and present projecting between them, inclined bars (70, 71) - with respect to the tangential directions - and preferably radial.

7. Apparatus according to claim 1, comprising a stack of perforated and flanged plates, (73), perpendicular to the axis of rotation and whose perforations (76) are defined by a projecting flange (79), characterized in that the said flanges form with the radial directions an angle varying between 0 and 40°.

8. Apparatus according to claim 1, characterized in that the outmost spire (56, 57) of the conveyor (7) situated near the partition (20) separating the two chambers (23) and (24), is perforated to establish another direct communication between the said chambers, said perforation (58) permitting to avoid the re-pumping of the light phase up towards the heavy phase.

9. Apparatus according to claim 1 or 9, characterized in that the end (62) of the conveyor (7) situated near the partition (20) separating the chambers (23 and 24) is integral with at least one scraping element (64) extending close to the peripheral wall (2), and is directed into the annular passage (22) in order to avoid any deposit of sediments in the first chamber (23) containing the heavy phase, said scraping element forming with a generatrix of the enclosure an angle varying between 0 and 45°.

10. Apparatus according to claim 8 or 9, characterized in that a labyrinth pack (65) is interposed between the partition (20) (separating the two chambers 23, 24) and a continuous central ring (62) of the conveyor (7).

11. Apparatus according to claim 1, whose draining thresholds are adjustable pipes (31, 33) carried by the peripheral wall (2) and extending from the centre towards the periphery to issue on the outside of the enclosure and flush with, respectively, the free surfaces (25, 26) of the light and heavy phases in the chambers (23, 24) containing them, characterized:

- in that the partition (20) rises in step manner and is provided with a skirt (35) connecting a central flank (36) with a peripheral flank (37),

- and in that the pipes (33) picking up the light phase traverse the skirt (35) by resting against the peripheral flank (37) in the first chamber (23) containing the heavy phase and against the central flank (36) in the second chamber (24) containing the light phase in that spot.

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