FR2613956A1 - METHOD AND DEVICE FOR CENTRIFUGAL SEPARATION OF A MIXTURE OF SEVERAL PHASES - Google Patents

Abstract

METHOD AND DEVICE FOR CENTRIFUGAL SEPARATION OF A MIXTURE OF SEVERAL PHASES. THE MIXTURE IS DRAWN THROUGH A ROTOR UNDER THE COMBINED EFFECT OF A PRESSURE DROP BETWEEN THE UPSTREAM AND DOWNSTREAM OF THIS ROTOR AND THE ROTATION OF THE LATTER. ACCORDING TO THE INVENTION, THE ROTOR CONSISTS OF A STACK OF JOINING DISCS 36, EACH OF WHICH IS PERCEIVED FROM A SET OF HELICOIDAL PASSAGES 62. EACH OF THESE PASSAGES 62 IS LIMITED BY SOLID WALLS 64, 66, 68, 70 AND OPENING ON THE UPSTREAM 37 AND DOWNSTREAM 39 SIDES OF THE DISC 36 BY ENTRY 63 AND EXIT 65 NOTCHES RESPECTIVELY. AN OUTPUT CUTOUT 63 ON A GIVEN DISC IS SITUATED EXACTLY IN FRONT OF AN INPUT CUTOUT 65 OF THE NEXT DISC. APPLICATION TO THE SEPARATION OF THE CONSTITUENTS OF A MIXTURE.

Description

METHOD AND DEVICE FOR CENTRIFUGAL SEPARATION OF A MIXTURE OF

SEVERAL PHASES

DESCRIPTION

  The present invention relates to a method and a separation device using the centrifugal force to separate the immiscible components of a mixture of various phases, for example: gas in liquid, liquid in gas, liquid in liquid, solid dispersed in a gas or liquid, or any other combination of products that are not

  totally miscible with each other.

  Centrifugal separation processes and devices are known at present in which the mixture to be treated is rotated through a rotor to create

  an intense centrifugal field inside the mixture.

  The sectional view of Figure 1 attached illustrates such a

centrifugal separation assembly.

  The latter, bearing the general reference 10, comprises firstly a substantially cylindrical and vertically disposed enclosure 12, the mixture to be treated arriving at the lower part of this enclosure via a pipe 14. The centrifugation device proper, bearing the reference 16, is located above the enclosure 12. It is rotated by a motor assembly 18 connected to the device 16 by a bearing system 20. A pipe 22 creates a pressure drop across the device 16 through to a fan (not shown) and to extract the mixture which has passed through the centrifuge device 16. Eventually, a portion of the mixture extracted by the pipe 22 can be recycled through a pipe 24 opening into the pipe 14. The dusts or heavy phases which have been separated by the device 16 fall into a space 26 at least partially surrounding the enclosure 12 and, from there, fall into a cyclone or An equivalent device 26 via a pipe 28. A pipe 30 to the lower part of the cyclone 26 makes it possible to evacuate the dust or heavy phases, while part of the gas passing through the cyclone 26 can be returned to the conduit 14 (in the example illustrated here, the latter is arranged to connect the upper part of the cyclone 26 to the lower part of the pregnant 12). FIG. 1 also shows that the pipe 14 opens tangentially to the base of the enclosure 12, which already gives the mixture a helicoidal movement which allows a first separation of certain constituents, these being evacuated by a

  pipe 32 provided at the lower part of the enclosure 12.

  Optionally, a filter 34 may be provided immediately

  below the device 16, that is to say upstream of it if we consider the flow direction of the mixture through this device. It may comprise, as described for example in the document FR-A-2 468 410, a stack of discs 17 arranged so that a pressure drop between the upstream and downstream of the stack causes the passage of the mixture through this stack following helical veins. Optionally, it is possible to provide an inlet rotary distributor 19 upstream of the disk stack 17 and a rectifier 21 immediately after

downstream of this stack.

  The stack described in FR-A-2 468 410 is illustrated in Figures 2 and 3 attached. FIG. 2 is an expanded section of the stack of disks and FIG. 3 a section along the line III - III of FIG. 2. The stack consists of a series of disks 36, each constituted by a thin plate located at a certain distance from the adjacent upstream and downstream disks. Each disc 36 has a number of perforations 38 angularly offset from each other and staggered from one disc to the next. Thus, a solid portion 40a of the disk 36a (FIG. 2) is immediately below an opening 38b of the disk 36b. It can be seen that, even if this stack does not rotate, the existence of a pressure drop between the upstream and the downstream of this stack of disks leads to the passage of the following mixture of helical veins. This pressure drop can be obtained by any known means, for example a fan placed at the outlet of the rotor so as to create a depression downstream thereof or by a fan placed upstream so as to create an upstream pressure. In the

  description, the terms "upstream" and "downstream" must be

  be heard in relation to the flow direction of the mixture to

treat through the rotor.

  In the particular case of FIG. 2, it is found experimentally that the gaseous streams flow along helicoidal trajectories. However, a mixing vein emerging from an openwork of a disk of rank n does not cross the perforation placed immediately in front of the disc n + 1, but the following opening. If the distance between two consecutive disks is equal to the width of the cuts, the slope of the veins compared to

disks is equal to 1/3.

  The mixture is divided into a number of bright veins 42 passing through the perforations 38 of the disks 36. Between the living veins 42 are dead veins 44 in which the gas does not flow continuously, but o

  we note the presence of eddies 46.

  FIG. 2 shows again that flanges 48 perpendicular to the plane of the discs along the front edge of each perforation 38 are provided. The words "before" and "rear" must be understood in relation to the direction of flow of the disc. mix through the discs. These flanges play the role of blades which accelerate the entrainment of the mixture when the rotor is rotated. The height of the flanges 48 is equal to one third of the distance between two consecutive discs. This condition is necessary so that the veins 42 can flow normally through the rotor. Indeed, if the height of the rim was greater, it would enter the circulation zone, that is to say in a vein 42 and greatly disrupt it, reducing the flow and greatly altering the purification characteristics. For this to remain good, the flows through the rotor must be substantially laminar. If on the contrary the rim was too short, the rotation of the rotor to the fluid would be poorly transmitted and it would then slide backwards relative to the rotor. One would also have a very important disturbance of the quality of purification, the circulating veins being badly defined and

largely turbulent.

  It can be seen that when a pressure drop is created

  between upstream and downstream of the rotor and that in addition

  In rotation, the mixture passes through the rotor with an angular velocity greater than that of the latter. It is also noted that an intense centrifugal field is created inside the veins 42, causing the evacuation of the heavy phase (s) towards the periphery of the rotor. A centrifugal field is also created within swirling veins 44, but it is less intense. As these veins are also the seat of many vortices, evacuation and separation are worse than in the veins 42. In addition, there are transient deposits on the discs, on the upstream and downstream faces of the solid parts 40 separating the openwork 38, in the vicinity of

  flange 48 and on the back side thereof.

  However, these deposits are temporary and end up being evacuated under the effect of centrifugal force. But they can be more or less important and require the shutdown of the device

  for disassembling the rotor for cleaning the discs.

  In order to improve the separation efficiency, an illustrated solution has been proposed in the cross-sectional view of FIG. 4. This solution consists in using discs that are no longer perpendicular to the axis of rotation of the rotor, but of diverging conical shape. upstream: in other words, each disk makes an angle i with a plane perpendicular to the axis of rotation of the rotor. The orientation of the veins is disturbed and they are mixed. The heavy phases present in the vortex veins are ejected more efficiently than in the case of Figure 3 and quickly meet a solid surface on which they agglomerate and are progressively guided towards

the suburbs.

  The present invention aims to further improve the separation by providing a method and a device for centrifugal separation of a mixture of several phases leading to a

  more efficient and selective separation.

  - It aims to generate in the mixture a centrifugal field very intense and much higher than that to which is subjected the rotor which is at the origin of the treatment. With this feature, the design and manufacture of the rotor are simplified and less expensive than for a device of the prior art leading to a centrifugal field of the same intensity. Standard production techniques, such as foundry or the use of plastics, then become possible. Another object of the invention is to improve the phase separation efficiency having very similar specific masses, as well as the evacuation of separated products out of

  the treatment area without the risk of remixing.

  It also aims to reduce to a minimum value the energy required for the acceleration of the mixtures to be treated thanks to an effective energy recovery device

kinetics at the exit of the rotor.

  It possibly allows, when the carrier fluid is gaseous, to lower its temperature by expansion at the rotor inlet, which can be used to lead to the condensation and evacuation in liquid form of an initially gaseous phase . More specifically, the subject of the invention is a process for the centrifugal separation of a mixture of several phases comprising at least one heavy phase in which the mixture is passed through a rotating rotor at a given speed, the mixture being divided into a plurality of parallel veins flowing through the rotor along helical paths and being driven at an angular velocity greater than that of the rotor. This has the effect of creating a centrifugal field inside the veins, which

  which allows the ejection of the heavy phase.

  According to the invention, the veins are timed by solid walls connected to the rotor, a centrifugal field thus being created on the surface of these solid walls, and the heavy phase ejected under the action of the centrifugal field prevailing in the veins is colLected on trap elements associated with the solid walls; in addition, it is guided towards the periphery of the rotor by guiding devices associated with these walls, the heavy phase traveling towards the periphery of the rotor under the effect of the field

  centrifugal created on the surface of these walls.

  According to another characteristic of the process which is the subject of the invention, in order to cause the mixture to react, it is subjected on the one hand to the driving action in rotation of the rotor and, on the other hand, to a pressure drop between upstream and downstream of the rotor, the latter being arranged so that this pressure drop causes the mixture to pass through the rotor according to

helical paths;

  According to another aspect of the invention, the helicoldal flow of the mixture is converted into downstream axial flow.

of the rotor.

  According to another advantageous aspect of the invention, the kinetic energy of rotation of the mixture is recovered at the

  output of the rotor to drive it in rtation.

  The invention also relates to a device for implementing this method. This device comprises, in a known manner: a rotor through which the mixture to be treated can pass, means for creating a pressure drop across this rotor, the latter being arranged so that the mixture passes therethrough following helical veins under the effect of this pressure drop, and

  - Means for driving the rotor in rotation about an axis.

  According to the invention, the rotor comprises: solid walls limiting said hemodynamic veins, trapped elements associated with these walls, for collecting said heavy phase, and guiding elements associated with these walls, for guiding said Heavy phase towards the periphery of the rotor. According to a particular embodiment, the rotor comprises a set of contiguous disks whose axis coincides with the axis of rotation of the rotor, each disk having an upstream face and a downstream face and comprising at least one circulation channel of the mixture. disposed along a helical portion and bounded by solid walls, this channel opening on the upstream face by an inlet opening and on the downstream face by an outlet opening. In this case, the output opening of a channel formed in a given disk is immediately opposite the entry ajoint of a channel formed in the next disc, said

perforations having the same shape.

  Thus, through the rotor, continuous circulation channels of helicoidal shape and limited by

solid walls.

  As for the expression "joined discs", it means that two consecutive discs of the stack are in contact with each other on at least part of their surface. As will be seen below, in a preferred embodiment, the discs are in peripheral contact thanks to studs formed on the upstream face of one and which rest on the downstream face of the other, these studs being separated by slots allowing the extraction of

some particles.

  According to one embodiment, said channel being of helicoidal shape with respect to the axis of the rotor and being limited by a bottom wall, an upper wall and two side walls, the latter being concentric with the axis of the rotor, the lower wall and / or the upper wall has crunches

  whose edges are arranged radially with respect to the disk.

  According to another embodiment, still in the case where the channels are helioTdale-shaped and limited by a bottom wall, an upper wall and two side walls, the latter being concentric with the axis of the rotor, the bottom wall and / or the upper wall has (s) at least one prominent element disposed in a portion of the helix with respect to the axis of the rotor. The upstream and downstream faces of each disk may be flat and perpendicular to the axis of the rotor. However, in another embodiment, the upstream and downstream faces of each disk may be designed to have a truncated cone portion of the same angle at the top and diverging upstream

  relative to the flow direction of the mixture through the rotor.

  In another embodiment, each disk is in the form of a hollow circular housing comprising: an inlet opening on its upstream face, an outlet opening on its downstream face, guide means constraining the mixture to be made; at least one complete turn inside the disc between these two cut-outs, - a set of elements in the form of truncated cones, located inside the casing and diverging upstream, and

  a peripheral slot for ejection of the heavy phase.

  This device may further comprise, upstream of the rotor, a rotary distributor comprising a set of blades oriented from the center to the periphery and whose concavity opens downstream, each blade having a trailing edge whose inclination corresponds to the slope of said helicoidal veins relative to the rotor. According to a preferred embodiment, the trailing edges of the vanes are integral with the first upstream disc of the rotor and coincide with the rear edges of the perforations.

  provided on the upstream side of this disc.

  The device may also include, downstream of the rotor, a rectifier comprising a set of blades oriented from the center to the periphery and whose concavity opens upstream, each blade having a leading edge whose inclination by relative to the rotor corresponds to the slope of said helical veins. Advantageously in this case, the leading edges of the vanes coincide with the edges before the exit openings of the

last disk downstream of the rotor.

  According to another aspect of the invention, the rotor is placed inside an enclosure having an internal surface which diverges

upstream.

  In a first embodiment, the inner surface of the enclosure is smooth and of conical general shape diverging

upstream.

  According to another embodiment, usable when the rotor consists of a stack of disks, the inner surface of the enclosure has a set of circular parts each of which is opposite the lateral edge of a rotor disk, the diameter said circular portions increasing from downstream to upstream. In this case, the distance between the edge of a disk and the inner face of the enclosure may be constant or

  grow steadily from downstream to upstream.

  The invention will appear better on reading the

  description which will follow, given as an example purely

  illustrative and non-limiting, with reference to the accompanying drawings, in which: - Figure 1 is a schematic vertical sectional view of the whole of a centrifugal separation system in which can be used the device of the invention, - the FIG. 2 is a schematic cross-sectional view of the rotor described in document FR-A-2 468 410; FIG. 3 is a section along line III-III of FIG. 2; FIG. 4 is a view similar to FIG. FIG. 3, in the case where the discs have a conical part, FIG. 5 is a diagrammatic view in section and in perspective of a centrifugal separation device according to the invention, FIG. 6 is a schematic perspective view. a stack of disks used in the device of the invention, the upstream and downstream faces of the disks being perpendicular to the axis of rotation of the rotor, - Figure 7 is a view similar to Figure 6 in the case where the upstream and downstream faces of disks 8 are a schematic perspective view of a disk such as those illustrated in FIG. 6 showing how grooves can be provided on the upper and lower walls of the helicoidal channels formed in the disks, FIGS. 9a to 9d are expanded sectional views showing various possible shapes for these grooves; FIG. 10 is a diagrammatic perspective view similar to FIG. 8 showing another possible shape for the prominent elements provided on the upper and lower walls; helicoidal channels, - Figure 11 is a diagrammatic sectional and perspective view showing another possible embodiment of a disk used in the device object of the invention, and - Figure 12 is a schematic sectional view of a stack of disks similar to that illustrated in FIG. 11, some disks being shown cut in accordance with a

sector only.

  Referring to FIG. 5, it can be seen that the device that is the subject of the invention is located inside an enclosure 50. The rotor essentially consists of a stack 17 of disks 36 mounted on an axis. 52. This can be rotated by a motor (not shown in Figure 5). In the particular case described here, the axis 52 is vertical, but it would not depart from the scope of the invention by arranging this axis in another direction, horizontal or oblique. A fan 54 placed above the stack 17 makes it possible to create a pressure drop across the rotor. This fan may consist of a set of blades 56 mounted on the axis 52 and made integral therewith, the gas or the mixture being discharged through a tangential tubing 58. The fan 54 is housed inside a volute 60 connected to the enclosure 50 by a convergent connection 62. The tangential tubing 58 makes it possible to evacuate the treated mixture

free of heavy phases.

  Of course, the fan may be of another type, for example an axial fan, and may be replaced by a compressor arranged upstream. The key is to have an apparatus to create a pressure drop across the rotor from upstream to downstream considering the direction of flow of the mixture. In the case where the latter is a liquid, one can use a suction or pressure pump to create this pressure drop. In certain particular cases, the device intended to ensure the circulation of the mixture through the rotor can be

  outside the enclosure and driven by an independent motor.

  In the lower part of FIG. 5, the chamber 12 inside which the mixture to be treated circulates before reaching the rotor; the space 26 between the enclosure 12 and the enclosure 50 is used for the evacuation of heavy ohases ejected under the effect of the centrifugal fields created inside the mixture

and falling by gravity.

  We also see the rotary distributor 19 provided at the bottom of the stack of disks, that is to say upstream of the rotor. This dispenser consists of a set of blades 23 arranged to deflect the mixture flowing under the effect of this pressure drop along helicoidal trajectories. For this, each blade has a concavity oriented downstream if we consider the flow direction of the mixture and each blade has a trailing edge (not visible in Figure 5) whose inclination relative to the rotor axis is equal to the slope of the helical veins of the mixture in the rotor. Preferably, this trailing edge coincides with the front edge of an inlet opening of the first upstream disk to the lower part of the stack 17: thus, the space between two successive blades of the distributor 19 constitutes a continuous path with the helicoidal channel whose entry ajoint is at this point of the disc. Thus, the ditributor 19 transforms the axial speed of the

2 6 1 3 9 5 6

  melt upstream of the rotor at high speed through the rotor, reducing turbulence and corresponding energy losses. In addition, because of the deviation it creates, the distributor 19 also has a primary function of primary separation of heavy phase that it channels to the periphery. The curvature of the concavity of the blades 23 and the conformation of their leading edge are established according to the aero characteristics

  or hydrodynamic mixing and operating regime.

  Similarly, at the outlet of the rotor, a rectifier 21 may be provided consisting of a turbine with a given action or degree of reaction. This rectifier consists of a set of blades 27 whose concavity faces upstream, if we consider the direction of flow of the mixture through the rotor. Each blade 27 has a leading edge which coincides with the front edge of an outlet opening on the downstream face of the last disk of the stack 17 and the inclination of this leading edge is equal to the slope of the veins helicodales according to which the mixture circulates inside the rotor. Since the mixture circulates along a helical path, its velocity has a tangential component and an axial component. The design of the concavity of the blades 27 is designed to cancel the tangential component. There remains only the axial component and the mixture leaves the rectifier 21 in a direction parallel to

the axis 52.

  Another interesting aspect of the rectifier 21 is that the mixture leaving the last disc at the upper part of the rotor has a certain speed, therefore a certain kinetic energy. This kinetic energy pushes the rectifier 21 in the direction of rotation of the rotor and thus contributes to driving it in rotation. This makes it possible to reduce the power required of the drive motor of the shaft 52. The blades 27 of the rectifier 21 also have a finishing function and guide the separated fractions towards the periphery. In the example described here, the rotor 17, the distributor 19, the rectifier 21 and the fan 54 are mounted on the same shaft 52 and thus rotate in synchronism. However, it would not depart from the scope of the invention using a mounting o some of these elements would be driven independently of others. This device is also useful for ensuring suction by the fan 54 under satisfactory conditions of efficiency. In the case, in fact, o the flow is not rectified, and according to a phenomenon well known to the professionals, the rotation component of the mixture greatly impairs the performance of the fan 54. The curvature of the concavity of the blades 27 and the conformation of their trailing edge are determined according to the characteristics

  aero or hydrodynamic mixing and operating regime.

  In addition, the conformation of the blades 27 is such that they channel the residual traces of heavy phase towards the periphery. We still see in Figure 5 that the enclosure 50

  has an inner surface 51 which diverges downwards, i.e.

  say upstream considering the flow direction of the mixture through the rotor. In the example described here, the surface 51 has a number of circular portions 53 whose height is equal to the thickness of each disk. There is thus a

  surface 53 facing the lateral edge of each disc.

  In the particular case illustrated in FIG. 5, the diameter of the disks is constant and that of the parts 53 increases from the downstream to the upstream, so that the thickness of the space 26 also increases from the downstream towards upstream considering the direction of flow of the mixture through the rotor. However, it would not be outside the scope of the invention using discs of variable diameter so that the distance between the lateral edge of a

  disc and the parts 53 of the surface 51 is constant.

  Nor would one go beyond the scope of the invention using discs whose diameter would increase from the downstream upstream, but slower than that of the parts 51, the diameter of the space 26 thus increasing, or using a smooth surface 51

  and of conical shape diverging upstream.

  The major advantage of this arrangement lies in the use of each instantaneous variation of the diameter of the rotor, combined with the corresponding variation of the internal diameter of the body, to generate a gas blowing or liquid pumping effect, repressing the heavy phases. collected to the larger diameter area of the rotor and stator. These

  successive stages operate in series with each other.

  Peripheral or axial clearance is calculated based on flow performance and heavy phase concentration

extracted to insure.

  FIG. 6 illustrates a first embodiment

  of a disk that can be used in the device that is the subject of the invention.

  In this embodiment, a stack of disks 36 of constant thickness p is used. Each disc is pierced with a number of passages or helical channels 62. Each of these channels 62 opens on the upstream or lower face 37 of the disc by an inlet ajoint and opens on the upper face 39 of the disc 36 by a output override65. The arrangement is such that the output opening 65 located on the upper face of a given disc is exactly opposite the entry cutout 63 on the underside of the next disc. Thus, through the stack of disks, substantially continuous helicoidal channels 69 bounded by solid walls are defined. In order for the heavy phases routed to the periphery to be efficiently collected on the inner wall of the enclosure 5 and not to tend to resuspend within the rotor as a result of various phenomena such as turbulence and twists, the transfer of rotor to the fixed wall 51 is made through peripheral slots formed between the successive disks, as shown at 71 in FIG. 6. However, these slots are locally interrupted by studs 73 whose purpose is to improve the rigidity of the rotor. They ensure the support of successive discs on each other. Their internal profile is intended to prevent

  accumulated heavy phase accumulations.

  The fact that the disks are contiguous makes it possible to obtain, subject to sufficient axial clamping, a very rigid one-piece rotor. This arrangement results in an effective separation between the inside of the rotor and the area between it and the wall of the fixed body, which limits the dispersion discounts. In addition, it is possible to achieve higher rotational speeds, and therefore more intense separator fields, than with the devices of the prior art, while avoiding the

risk of deformation.

  In the particular case illustrated in Figure 6, the openwork 65 are distributed equiangularly on a given disk and extend from the center to the periphery. They are separated by solid portions 67. Considering the direction of rotation T of the disks, the output opening of a given channel is located downstream of the inlet opening. In FIG. 6, the perforations 65 are limited by radii of the disc 36 and therefore have a substantially trapezoidal shape, as do the parts 67. Each channel 62 is thus limited by a lower wall 64, an upper wall 66 and two side walls 68 and 70. The lower 64 and upper faces 66 are generally helicoldal shape of the same slope as the channels. As will be seen below, they may be provided with steps or steps for locally and temporarily imprisoning constituents of the mixture and to facilitate the agglomeration of phases.

  heavy. The first lateral face 68 limiting a channel 62, is it

  that is, the one closest to the axis of the rotor, is cylindrical and of axis coincident with that of the rotor. The other side face 70 is located near the periphery of the disc and is inclined relative to the axis of the rotor. In other words, it is in the form of a portion of truncated cone diverging upstream if we consider the direction of flow of the

mixing through the rotor.

  The mixture is thus separated into a plurality of helical veins. Since the mixture is subjected on the one hand to the pressure drop across the rotor and, on the other hand, to the effect of driving it in rotation, it flows through the discs with a tangential velocity greater than that of the rotor. It can be seen that, for a rotor rotating at speed w, the absolute tangential velocity of a particle located at a radial distance R is: - uR if this particle is in a zone of sequestration of the mixture, -, * R + V if this particle is in the circulating part t of the vein, at the tangential velocity V. t The tangential velocity V varies approximately as tk / R, k being a constant depending on the geometry of the rotor and proportional to the flow through the rotor . The centrifugal force at the radius R is therefore written: -1 2 (w * R + k * R)

F = - -------------

c R

2 -1 2 -3

  F = w * R + 2kR + k * R c When R varies, this function has a minimum and, on either side of this minimum, the centrifugal field increases. This results in a high centrifugal field in the vicinity of the axis of rotation, unlike what happens in conventional centrifuges. Moreover, in all points of the curve F (R), c the value of F is much higher than for a c

  conventional centrifuge rotating at the same angular speed.

  Similarly, when the flow of the mixture varies, the effectiveness

  of separation goes through a minimum for a value of k = w * R.

  It always remains superior to that of a conventional centrifuge for all the values of the flow rate, for a dimensioning of the rotor and a speed of identical rotation (k

  is directly proportional to the flow).

  This phenomenon, like the results described below that follow, are unpredictable and unexpected in the classic context of centrifugation. These are the experimental facts based on the process and apparatus of the invention

  which make it possible to ensure the veracity of the results obtained.

  It is indeed verified that the heavy particles of the helical veins subjected to a very intense centrifugal force precipitate towards the periphery by slowing and agglomerating before reaching the annular zone of minimum centrifugal force, then, from this zone, accelerate b again in

  bigger masses towards the periphery.

  But during this centrifugal displacement, the heavy particles (solid or liquid) migrate, for various reasons explained below, to the dead zones or the zones

  in which they are captured and trapped.

  These dead zones or depression are obtained by means of steps or other prominent elements provided on the lower and upper faces of the channels 62, as will be described

further.

  These heavy particles are then supported by a centrifugal force, certainly lower, but high enough to inevitably lead them to the periphery. During this routing, trapping elements and conductive elements, defined below, oppose the return of the particles to the debiting veins and participate in their routing to the periphery where they rush on the inner wall 51 of

the enclosure 50.

  The angular offset of the discs and the thickness p thereof, as well as the shape and dimensions of the perforations are chosen to accurately determine the relative slope P of the helicoidal veins (that is, their slope with respect to discs when they turn). The parameters in question thus make it possible to regulate the separating power and the flow of the apparatus. In general, these parameters are constant for a given device, but it may be advantageous to vary them from upstream to downstream depending on the speed of operation.

  of the device, and that of the treatment to be obtained.

  In any case, the choice of these parameters makes it possible, in relation to the regime of the apparatus and the composition of the mixture, to define the preferred helicoidal progression of the mixing veins through the perforations of a disc. The mixture can continue its path through the homologous opening of the next disc, that is to say that which is offset downstream of the disc offset angle. This offset angle is such that the output opening of the first disk is in front of

  the entry ajourage of the second disc.

  The preceding discussion shows that the aero or hydrodynamic flow of the mixture through the apparatus undergoes, between the upstream and the inside of the rotor, an increasing variation of the speed. Therefore, there is naturally a relaxation within the rotor, and therefore a drop in temperature can be used to condense a vapor phase during the

separation.

  FIG. 7 is a view similar to FIG. 6 and illustrates a variant in which the upstream and downstream faces of the discs 36 are no longer perpendicular to the axis of rotation of the rotor, but are inclined upstream by an angle c relative to a plane perpendicular to this axis. In other words, the upper face 39 and the lower face 37 are in the form of cone frustums diverging upstream with respect to the direction of flow of the mixture through the rotor. It has been found that the best results are obtained when the value of the angle ç is close to 30. The arrangement of the perforations and helical channels in the disks of FIG. 7 is exactly the same as in

case of Figure 6.

  We would not go beyond the scope of the invention by giving

  still other forms to the upstream and downstream faces of the disks.

  These can include curved generators and, if they are straight or curved, concurrent with or left to the axis of rotation with any angle of any indication. In other words, the disks can be delimited by regulated surfaces, such as conical or any balanced surfaces of revolution, which can not constitute a major difficulty of execution since the disks can be, because of reduced stresses they undergo, manufactured by molding and even plastic. The perspective view of FIG. 8 shows how steps, protrusions or other prominent elements can be provided on the lower and / or upper faces of the channels 62. In FIG. 8, only the steps 72 on the underside of the channels 62, but there are identical bleachers on the face

  upper, the latter being invisible in Figure 8.

  The sectional views developed from FIGS. 9a to 9d

  show other possible forms for these prominent elements.

  In the case of Figure 9a, the upper and lower surfaces of the channel 62 comprise steps whose edges are radial edges, that is to say that these edges are perpendicular to the axis of rotation of the rotor. In the case of Figure 9a, the steps 72 are like the steps of a spiral staircase whose axis is that of the rotor. Angles

  internal bleachers are therefore right angles.

  The edges of the steps have two different functions depending on whether it is the upper wall or the lower wall limiting the channel 62. In the first case (steps 72a on the upper wall of the channel 62), the vertical radial surfaces of the Steps create low-pressure areas that tend to pick up impurities in the attached swirl they create. In the second case (steps 72b on the bottom wall of the channel 62), the vertical radial surfaces function as multiple-impact dividers. They temporarily stop the particles or the heavy droplets. The agglomeration effect they bring accelerates the transport towards the periphery of the heavy phases and improves

  correlatively the overall efficiency of the device.

  In the case of FIG. 9b, the internal angles of the steps are more acute than in the case of FIG.

  to increase the retention effect of heavy phases.

  In the case of Figure 9c, two different arrangements are combined. The steps 72b of the bottom wall are identical to those of Figure 9a. As for the steps of the upper wall of the channel 62, they have inclined portions 74 whose slope is slightly greater than the slope chosen for the helical liquid veins of the mixture, the parts 74 being connected by parts 76 whose height is less than width of the parts 74. A chamfer 75 is provided at the lower part of the lower face 64, but this is not mandatory. This arrangement causes alternating divergent and convergent oblique zones, which creates a more pronounced corrugation of the mixing vein and a higher probability of lateral exit of the heavy fractions which are then collected in the steps. Finally, in the case of Figure 9d, the steps 72 are replaced by grooves 78 of semicircular section and arranged radially, that is to say that their axis is perpendicular to the axis of rotation of the rotor. The semicircular radial channels thus created are at the origin of swirling zones which slow down and collect the heavy phases. It is also possible to use other arrangements, for example forms of radial machining that do not penetrate the circulating vein, but play a role of extraction of heavy phases and a role of agglomeration, which increases the efficiency

overall device.

  FIG. 10 illustrates a variant in which the prominent elements for collecting the heavy phases are arranged in a tangential and non-radial direction. It can be seen in this figure that the lower wall of each channel 62 comprises two prominent elements 80 each helically arranged around the axis of the rotor. These elements consist of two faces connected by an upper edge. Both faces are parallel to the flow of the mixture relative to the rotor. The radial displacement of the heavy phases under the action of the centrifugal field brings them in contact with the inner face of the elements 80. This contact creates a gathering effect of the heavy phases which then slide on the surface and are resuspended but after having been more or less strongly agglomerated. The consequent increase in their grain size accelerates their radial movement towards the periphery of the rotor and increases correspondingly

  the separation efficiency of the device.

  Figures 11 and 12 illustrate another embodiment in which each disk 36 is in the form of a hollow circular housing. The disc 36 is composed of a bottom wall 82 in the form of a flat disc, connected to an upper wall 84 by a ferrule 86. The upper wall 84 has a central portion 87 in the form of a flat disk of the same axis than the wall 82, but of smaller diameter. The portion 87 is connected to a peripheral edge 88 by a truncated cone-shaped portion 90. The edge 88 is circular and of the same diameter as the bottom wall 82. It is separated therefrom by a peripheral slot 92 whose width is less than the distance between the bottom wall 82 and the central portion 87 of the upper wall. A set of cone-shaped elements or truncated conical ferrules 94 is provided inside the casing thus defined. In the particular case described here, the frustoconical ferrules 94 have an upper edge which is welded to the central portion 87 of the upper wall 84 while their lower edge is located at a distance from the lower wall 82. 11 and 12 an inlet opening 63 formed in the bottom wall 82 and an outlet opening 65 formed in the central portion 87 of the upper portion 84. The angular position of the cutouts 63 and 65 with respect to the disk 36 is exactly the even. A deflector 96 has a lower edge welded to the bottom wall 82 behind the opening 63 and an upper edge welded to the upper wall 84 in front of the perforation 65. With this arrangement, the mixture that enters the disc by the openwork 63 is obliged to make a complete turn by walking in the spaces between the frustoconical ferrules 94 before emerging through the output opening 65. The deflector 96 must ensure a good seal to prevent direct leakage of the mixture of L 'ajoint entry to the output ajoining. With this arrangement, the radial displacement of the heavy phases under the action of the centrifugal field brings them in contact with the surface of these rings. This contact creates a gathering effect of the heavy phases, which then slide on the surface and are resuspended, but after being more or less strongly agglomerated. The consequent increase in particle size accelerates their radial movement towards the periphery of the rotor and correspondingly increases the separation efficiency of the apparatus. The frustoconical ferrules 94 also play a role of guiding surface and limiting turbulence, their surface being parallel to the direction of flow of the mixture.

inside the disc.

  This arrangement leads, for the same rotor dimensions, the same number of disks and the same flow rate, at a tangential speed of the mixture relative to the rotor which, being inversely proportional to the slope of the veins, and maximum for

  the single-vein flow has one turn per disc.

  The average slope per disc is then equal to: p

p = ---

2 R

  at the radius R, where p is the thickness of the disk.

  The centrifugal field is also maximum for this configuration, since it is proportional to the square of the sum of the tangential drive speed and the speed

  tangential of the mixture relative to the rotor.

  The invention is not limited to the embodiments and modes of execution shown and described in detail in the foregoing, since various modifications can be made thereto.

without leaving his frame.

  The method and the apparatus which are the subject of the invention can be used for the separation in a mixture of phases of any state. More specifically, they are applicable to the elimination

  oily mists such as those generated by machinery

  tools, stamping presses, spray lubrication devices, the elimination of water mists on industrial washing machines at the outlet of air washing devices, the elimination of heavy solvent mist on polymerization furnaces, printing dryers, oil scrubbing of various gases,

  clarification of the soluble oils on the bins of machines-

  tools, clarification of laundry baths on industrial washing machines, clarification of gas wash water, clarification of polluted water in general, preclarification of liquids before high efficiency centrifuges or finishing filters, etc. The method and the device of the invention are particularly applicable in the nuclear field, in particular for the separation of solid or liquid dispersions and the separation of gaseous phases at the molecular level. They are also well suited for difficult special applications in certain industries, for example in continuous processes or for some operations previously difficult to perform, such as sterilization of air by centrifugation or the elimination of

very active toxic products.

Claims (21)

  A method of centrifugal separation of a mixture of several phases comprising at least one heavy phase in which the mixture is passed through a rotor (17) rotating at a given speed, the mixture being divided into a plurality of parallel veins ( 69) flowing through the rotor (17) along helicoidal paths and being driven at an angular velocity higher than that of the rotor (17), whereby a centrifugal field allowing the ejection of said heavy phase is created inside. said veins, characterized in that the latter are bounded by solid walls (64, 66) connected to the rotor (17), whereby a centrifugal field is created on the surface of these solid walls (64, 66), and in that the heavy phase ejected under the action of the centrifugal field in the veins is collected on trapping elements (72) associated with said solid walls and guided towards the periphery of the rotor (17) by means of gears uidage associated with these walls (64, 66), the heavy phase traveling towards the periphery of the rotor (17) under the effect   centrifugal field created on the surface of these walls (64, 66).   2. Method according to claim 1, characterized in that, to drive the mixture in rotation, it is subjected on the one hand to the driving action in rotation of the rotor (17) and, on the other hand, to a pressure drop between the upstream and downstream of this rotor (17), which is arranged so that this pressure drop causes the mixture to pass through the rotor (17)   following helical paths.   3. Method according to claim 1, characterized in that the helicoldal flow of the mixture is transformed into   axial flow downstream of the rotor (17).   4. Method according to claim 3, characterized in that the kinetic energy of rotation of the mixture is recovered for   driving the rotor (17) in rotation.   5. Device for implementing the method according to claim 1, comprising: 26 3956   - a rotor (17) through which the mixture can pass, - means (54) for creating a pressure drop through the rotor (17), which is arranged so that the mixture passes through the veins hollicles under the effect of this pressure drop, and - means for driving the rotor (17) in rotation about an axis, characterized in that the rotor comprises - solid walls (64, 66) limiting said veins Helical elements; trapping elements (72) for collecting said heavy phase; and guiding elements for guiding said heavy phase towards the periphery of the rotor.   6. Device according to claim 5, characterized in that the rotor comprises a set of contiguous discs (36) of generally circular shape whose axis coincides with that of the rotor (17) and each having an upstream face (37) and a downstream face (39), each disc (36) comprising at least one channel (62) for circulating the mixture bounded by solid walls (64, 66) and opening on the upstream face (37) by an inlet opening ( 63) and   on the downstream face (39) by an outlet opening (65).   7. Device according to claim 6, characterized in that the output opening (65) of a channel formed in a given disk is immediately opposite the entry ajourage (63) of a channel in the following disc, said openwork (63, ) having the same shape.   8. Device according to claim 6, characterized in that, said channel (62) being of helical shape, equal to the axis of the rotor (17) and being limited by a bottom wall (64), an upper wall ( 66) and two side walls (68, 70), the latter being concentric with the axis of the rotor, the lower wall (64) and / or the upper wall (66) having (nt) protruding elements (72) having radially arranged edges relative to the disk (36).   9. Device according to claim 6, characterized in 26 13956   said channel (62) being helically shaped and being limited by a bottom wall (64), an upper wall (66) and two side walls (68,70), the bottom wall (64) and / or the wall upper (66) has at least one protruding element (80) disposed along a portion of the helix with respect to the axis of the rotor (17).   10. Device according to claim 6, characterized in that the upstream faces (37) and downstream (39) of each disk (36)   are flat and perpendicular to the axis of the rotor.   11. Device according to claim 6, characterized in that the upstream faces (37) and downstream (36) of each disk have a truncated cone-shaped portion of the same angle at the apex and diverging upstream relative to the direction. flow   mixing through the rotor (17).   12. Device according to claim 6, characterized in that each disc is in the form of a hollow circular housing comprising: - an inlet opening (63) on its upstream face, - an outlet opening (65) on its face downstream, - guiding means (96) forcing the mixture to perform at least one complete turn inside the disc between these two cut-outs (63, 65), - a set of elements (94) in the form of trunks of cone located inside the casing, and   - A peripheral slot (92) for the ejection of the heavy phase.   13. Device according to claim 5, characterized in that it comprises, upstream of the rotor (17), a rotary distributor (19) comprising a set of vanes (23) oriented from the center to the periphery and whose concavity s' opens downstream, each blade (23) having a trailing edge whose inclination corresponds to   the slope of said helicoidal veins relative to the rotor (17).   14. Device according to claim 13, characterized in that the trailing edges of the blades (23) are integral with a disc coupled to the rotor and coincide with the rear edges of the perforations of this disc. 26 3956   15. Device according to claim 5, characterized in that it comprises, downstream of the rotor, a rectifier (21) comprising a set of vanes (27) oriented from the center to the periphery and whose concavity opens towards the upstream, each blade having a leading edge whose inclination relative to the rotor (17) corresponds   at the slope of said helical veins.   16. Device according to claim 15, characterized in that the leading edges of the vanes (27) coincide with the front edges of the outlet openings of the last downstream disc of the rotor (17).   17. Device according to claim 4, characterized in that the rotor (17) is placed inside a chamber (50)   having an inner surface (51) diverging upstream.   18. Device according to claim 17, characterized in that the inner surface (51) of the enclosure (50) is smooth and of   general conical shape diverging upstream.   19. Device according to claim 17, characterized in that, the rotor (17) consisting of a stack of disks, the inner surface (51) of the enclosure (50) has a set of circular parts (53) of which each is facing the lateral edge of a rotor disk and whose diameter increases downstream upstream.   20. Device according to claim 19, characterized in that the distance between the lateral edge of a disc (36) and the   internal face (51) of the enclosure (50) is constant.   21. Device according to claim 19, characterized in that the distance between the lateral edge of a disc (36) and the inner surface (51) of the enclosure (50) increases from downstream to upstream.