Abstract:
A device for separating immiscible fluids of different densities from a liquid-containing emulsion, includes a longitudinal rotary drum having a longitudinal axis of rotation. The drum includes, longitudinally from upstream to downstream and between at least one upstream inlet and downstream outlets: a solid body rotation stage having an inlet and including at least one longitudinal inner partition for causing circumferential solid body rotation; a migration and coalescence stage including at least one longitudinal partition for causing circumferential solid body rotation, the partition delimiting at least one longitudinal channel communicating with the solid body rotation stage; and an extraction stage including at least one liquid outlet that has an overflow edge and extends along a longitudinal flow space communicating with the migration and coalescence stage via at least one longitudinal passage, and including a downstream liquid discharge space communicating with the outlet and connected to a downstream discharge port.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to the area of the separation of immiscible fluids of different densities. 
     It may be applied in particular to problems concerning the separation of oil and water in crude oil emulsions, whether in the area of petroleum production, refining or decontamination. It may likewise find an application in the separation of greases in the environment, in the extraction of free gases in one or more liquids, in the treatment of rainwater or in the production of olive oil. In particular, it may find an application in the separation of the phases of an emulsion comprising a majority fluid, referred to as a carrier fluid, in which droplets of a secondary fluid are present. 
     Description of the Related Art 
     In order to carry out this operation, the use of gravity separators is well known, into which the emulsion is introduced at one extremity of a reservoir such that, after a sufficient residence time, the drops of the secondary fluid of the emulsion increase or decrease depending on whether their density is lower or higher than that of the carrier fluid. Two superimposed layers of the two fluids are thus created at the extremity of the reservoir, the lighter fluid being above and the heavier fluid being below, which fluids are pumped by appropriate means. 
     Gravity separators suffer from the major shortcoming that they require very long separation periods. It has been estimated that a period of 5 minutes is required, for example, in order for a drop of oil having a diameter equivalent to 200 micrometers, having a density of 0.85, to rise to a height of 1 m in still, fresh water at a temperature of 20° . Furthermore, gravity separators are bulky, heavy and expensive. As a result, they are incapable of being moved or transported on lightweight and rapid platforms, such as hovercrafts, whose use is particularly well suited to the treatment of oil spillages in zones which are not readily accessible, such as wetlands. 
     The use of rotary separators with a centrifugal effect, which allow much shorter separation periods than those of gravity separators to be achieved, such as fixed cyclones, rotary cyclones and centrifuges, is also well known. In the current embodiments, these rotary separators are generally complex in nature and are also very heavy, bulky and very expensive. Furthermore, they do not lend themselves readily to being moved or transported. 
     A separator with a centrifugal effect is described in particular in the patent published under the reference number WO95/26223. This separator comprises a rotating drum defining a compartment exhibiting an axial inlet for an emulsion at one extremity, and inside which there are arranged, for a first length, radially extending longitudinal paddles, followed, for a second length, by a porous cylindrical coalescence body formed by rolled coils of mesh or layers of mesh. This drum comprises, downstream of this compartment, annular overflows intended for the extraction of the liquids, separately, and axial passageways intended for the discharge of the separated liquids. This separator exhibits, in particular, the disadvantages of being very limited in respect of the ratios between the densities of the liquids in the emulsion to be treated and the volumetric ratios of the liquids in the emulsion to be treated, and of becoming clogged rapidly. 
     Another separator with a centrifugal effect is likewise described in the patent published under the reference number WO 93/25294. This separator comprises a rotating drum of truncated conical form defining a compartment exhibiting an axial inlet for an emulsion at its smallest extremity, and comprises, downstream of this compartment, annular overflows intended for the extraction of the liquids, separately, and axial passageways intended for the discharge of the separated liquids. Arranged in a first section of said compartment, far away from its downstream extremity, are radially extending longitudinal paddles, the stated purpose of which is to permit an axial alignment of the emulsion. However, these vanes exhibit the disadvantage of generating a considerable shear effect during rotation of the drum and circumferential percussion of the emulsion, contrary to the desired object of the separation of the liquid. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to improve separators with a centrifugal effect. 
     A device for separating immiscible fluids of different densities from an emulsion containing at least one liquid, comprising a longitudinal rotary drum having a longitudinal axis of rotation is proposed. 
     The drum comprises, internally, longitudinally from upstream to downstream and between at least one upstream inlet and a number of downstream outlets, a solid body rotation stage, a migration and coalescence stage and an extraction stage. 
     The solid body rotation stage comprises at least one chamber, inside which is arranged at least one longitudinal inner partition for causing circumferential solid body rotation delimiting at least one flow space communicating with said inlet. 
     The migration and coalescence stage comprises at least one chamber, inside which is arranged at least one longitudinal interior partition for causing circumferential solid body rotation, delimiting a plurality of longitudinal flow channels exhibiting respectively one upstream extremity communicating with said flow space of said solid body rotation stage and one downstream extremity connected to said outlets, said partition comprising at least one longitudinal partition delimiting at least one of said longitudinal channels and extending as far as said downstream extremity. 
     The extraction stage comprises at least one liquid overflow comprising an overflow edge turned facing towards said axis of rotation and extending along a longitudinal flow space communicating, upstream, with said longitudinal channels of the migration and coalescence stage via at least one longitudinal passageway, and comprising, downstream, a downstream liquid discharge space communicating with the longitudinal flow space and connected to one of said downstream outlets. 
     The upstream inlet may discharge into a section of said flow space of the solid body rotation stage situated close to the axis of rotation. 
     The device may comprise an axial pipe or an axial tube that is integral with the drum for the purpose of conveying the emulsion into the central section of the chamber of the solid body rotation stage. 
     The partitioning of the migration and coalition stage may define, from upstream to downstream, a plurality of circumferentially distributed longitudinal channels. 
     The partitioning of the migration and coalition stage may define, from upstream to downstream, an intermediate plurality of circumferentially and radially distributed longitudinal channels, followed by a downstream plurality of circumferentially distributed longitudinal channels, of which each channel communicates with a number of the channels in the first plurality of channels. 
     The partitioning of the migration and coalition stage may define, from upstream to downstream, an upstream plurality of circumferentially distributed longitudinal channels, followed by an intermediate plurality of circumferentially and radially distributed longitudinal channels, of which a number of channels communicate with each channel in the upstream plurality of channels, followed by a downstream plurality of circumferentially distributed longitudinal channels, of which each channel communicates with a number of the channels in the first plurality of channels. 
     The extraction stage may comprise an overflow, of which the overflow edge is annular, and an annular downstream liquid discharge space communicating with a downstream peripheral outlet. 
     The extraction stage may comprise an overflow, of which the overflow edge is close to the axis of rotation, the downstream liquid discharge space of this overflow being connected to a downstream liquid outlet and to a downstream gas outlet. 
     The device may comprise partitions for causing circumferential rotation positioned inside the downstream liquid flow space. 
     Circumferentially driving vanes may be positioned inside the longitudinal flow space. 
     The extraction stage comprises an interior overflow for lighter liquid, of which the longitudinal flow space communicates with the migration and coalescence stage via a longitudinal interior passageway, and an exterior overflow for a heavier liquid, of which the longitudinal flow space communicates with the migration and coalescence stage via a longitudinal exterior passageway located further from said axis of rotation than the longitudinal interior passageway. 
     The overflow edge of the exterior overflow may be located further away from said axis of rotation than the overflow edge of the interior overflow. 
     The overflow edge of the exterior overflow may be situated, in the radial sense, between the exterior longitudinal passageway and the overflow edge of the interior overflow. 
     The interior overflow and the exterior overflow may be connected to different downstream outlets by means of different downstream discharge spaces. 
     Circumferentially driving vanes may be positioned inside the intermediate flow space connecting the exterior passageway and the exterior overflow. 
     Said circumferentially driving vanes may exhibit an interior edge situated outside and at a distance from the overflow edge of the exterior overflow. 
     Circumferentially driving vanes may be positioned inside the longitudinal flow space of the interior overflow. 
     Circumferentially driving vanes may be positioned inside the downstream discharge space of the interior overflow. 
     Circumferentially driving vanes may be positioned inside the downstream discharge space of the exterior overflow. 
     The device may comprise a support for said drum, exhibiting a section provided with outlet pipes, at least one of said outlet pipes communicating with a downstream outlet for liquid from said drum. 
     The device may comprise a rotating fluid seal formed between the drum and the support, adjoining the extraction stage, said rotating seal comprising two fixed radial walls that are integral with the support and delimit a space that is open in the radial sense towards the interior and a rotating radial wall that is integral with the drum engaged at a distance between said fixed radial rings, said open space being connected to the chamber of the migration and coalition stage, the rotating radial wall being provided on both sides with circumferentially driving vanes. 
     The drum may be equipped with a radial interior wall separating the chamber of the solid body rotation stage and the chamber of the migration and coalescence stage, said radial interior wall being provided with through passageways. 
     The drum may be equipped with a radial interior wall separating the chamber of the migration and coalescence stage and the extraction stage, said radial interior wall exhibiting at least one longitudinal communication passageway between these stages. 
     The device may comprise a pipe connecting the internal space of the interior overflow and the internal space of the exterior overflow. 
     The device may comprise a pipe for connecting the internal space of the interior overflow to the exterior and a pipe for connecting the internal space of the exterior overflow to the exterior. 
     The device may comprise gas pressurization/depressurization sources that are connected to the flow spaces of the overflows of the extraction stage, in such a way that these pressures act respectively on the free surfaces of the liquids. 
     The extraction stage may be situated above the migration and coalescence stage. 
     The device may likewise comprise an inlet chamber connected axially to the central section of the chamber of the solid body rotation stage, said inlet chamber being supplied tangentially in the direction of rotation of said drum in order to bring about a rotation of the emulsion as far as the solid body rotation stage. 
     Likewise proposed is a device for separating immiscible fluids of different densities from an emulsion containing at least two liquids, comprising a longitudinal rotary drum having a longitudinal axis of rotation, and in which the drum comprises, longitudinally from upstream to downstream and between at least one upstream inlet and a number of downstream outlets: 
     a migration and coalescence stage for the liquids; 
     and an extraction stage comprising one interior overflow for lighter liquid, of which the longitudinal flow space communicates with the migration and coalescence stage via an interior longitudinal passageway, and one external overflow for a heavier liquid, of which the longitudinal flow space communicates with the migration and coalescence stage via an exterior longitudinal passageway situated further away from said axis of rotation than the interior longitudinal passageway. 
     The above device may comprise at least one gas pressurization/depressurization source that is capable of adjustment or regulation and is connected to at least one of the flow spaces of the overflows of the extraction stage, in such a way that the supplied pressure acts on the free surface of the corresponding liquid. 
     The device may also comprise two gas pressurization/depressurization sources that are capable of adjustment or regulation and are connected respectively to the flow spaces of the overflows of the extraction stage, in such a way that the supplied pressures act respectively on the free surfaces of the corresponding liquids. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Devices for separating fluids from an emulsion containing at least one fluid and their operating modes are now described in a non-restrictive manner with reference to the drawings, in which: 
         FIG. 1  represents a vertical cross section through a device for separating two liquids from an emulsion, in two offset planes identified angularly in  FIG. 2  by the reference I-I, the axis of the separation device being positioned vertically; 
         FIG. 2  represents a radial cross section according to II-II, facing upwards, through a solid body rotation stage of the separation device in  FIGS. 1 ; 
         FIG. 3  represents a radial cross section according to III-III, facing downwards, through a migration and coalescence stage of the separation device in  FIG. 1 ; 
         FIG. 4  represents a radial cross section according to IV-IV, facing upwards, through the migration and coalescence stage of the separation device in  FIG. 1 ; 
         FIG. 5  represents a radial cross section according to IV-IV, facing upwards, through an extraction stage of the separation device in  FIG. 1 ; 
         FIG. 6  represents an enlarged vertical cross section through the upper section of the separation device in  FIG. 1 , including the extraction stage; 
         FIG. 7  illustrates pressure curves in the device depicted in  FIG. 1 ; 
         FIG. 8  illustrates other pressure curves in the device depicted in  FIG. 1 ; 
         FIG. 9  represents half a vertical cross section through the upper section of a variant embodiment of the separating device depicted in  FIG. 1 ; 
         FIG. 10  represents a vertical cross section through another separating device, according to X-X in  FIG. 11 ; 
         FIG. 11  represents a radial cross section according to XI-XI through a migration and coalescence stage of the separation device depicted in  FIG. 10 , according to a first variant embodiment; 
         FIG. 12  represents a corresponding radial cross section through the migration and coalescence stage of the separating device depicted in  FIG. 10 , according to a second variant embodiment; 
         FIG. 13  represents a corresponding enlarged vertical cross section through a section of the migration and coalescence stage of the separating device depicted in  FIG. 10 ; 
         FIG. 14  represents a vertical cross section through another separating device, according to XIV-XIV in  FIG. 15 ; and 
         FIG. 15  represents a radial cross section according to XV-XV through a migration and coalescence stage of the separating device depicted in  FIG. 10 , according to a first variant embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First, it is necessary to define what the expression “liquid driven circumferentially in solid body rotation” is intended to denote in the following description. A liquid is said to be “driven circumferentially in solid body rotation” when it is contained inside a compartment, which is decentered in relation to an axis of rotation and which extends over a limited angular sector, between partitions that are spaced circumferentially, such that the compartment rotates about the axis of rotation and the liquid is accordingly subjected to the effects of the centrifugal force. 
     A separation device  10  illustrated in  FIGS. 1 to 6  comprises a fixed support  11  having a vertical axis  12 , which comprises a cylindrical peripheral wall or a ferrule  13 , a lower radial wall  14  and an upper radial cover  15 . 
     Arranged inside the support  11  is a rotating drum  16  rotating about the vertical axis  12 . This drum  16  comprises a lower radial wall  17 , in the form of a disc, situated at a distance above the lower radial wall  14  and provided towards its bottom with a section of an axial cylindrical shaft  18  engaged in the lower radial wall  14  and supported on the latter by means of a rotating supporting bearing  19  of the drum  16 . 
     The drum  16  is caused to rotate by a drive motor  20  by a means of connection which comprises, for example, a pulley  21  carried by the cylindrical shaft  18 , a pulley  22  carried by the shaft of the motor  20  and a belt  23  connecting these pulleys. 
     The drum  16  comprises an interior axial cylindrical tube  24 , having a small diameter, of which the lower extremity is integral with the lower radial wall  17 , and of which the upper extremity is engaged in the radial cover  15  and is mounted on this cover by means of a rotating supporting bearing  25  of the drum  16 . 
     The drum  16  comprises an axial cylindrical peripheral wall  26  situated internally at a short distance from the ferrule  13 , the lower extremity of which is integral with the periphery of the lower radial wall  17 , and the upper extremity of which is situated at a distance below the radial cover  15 . 
     The drum  16  comprises an intermediate interior radial wall  27 , of annular form, which is situated to the side of and at a distance from the lower radial wall  17 , and which connects together the interior cylindrical tube  24  and the cylindrical peripheral wall  26 . The lower radial wall  17  and the intermediate radial wall  27  between them form an inlet chamber  28 . 
     The portion of the interior cylindrical tube  24  situated between the lower radial wall  17  and the intermediate radial wall  27  exhibits radial inlet orifices  29  distributed in an angular manner and situated close to the axis of rotation  12 . The intermediate radial wall  27  exhibits a plurality of communicating longitudinal through passageways  30 , which are distributed, for example, over the whole of the surface of the intermediate radial wall  27  ( FIGS. 2 and 3 ). 
     Arranged inside the inlet chamber  28  is a system of partitioning comprising a plurality of longitudinal interior partitions  31 , intended to provide circumferential solid body rotation, extending in planes containing the axis  12  and distributed in an angular manner ( FIG. 3 ). These longitudinal partitions  31  extend radially from the cylindrical peripheral wall  26  until a small distance from the interior cylindrical tube  24  and between them define a plurality of longitudinal flow spaces or channels  32  that are distributed circumferentially. 
     In a variant embodiment, the section of the axial tube situated between the radial wall  17  and the intermediate radial wall  27  could be eliminated. 
     In particular in the above-mentioned case, the interior partitioning  31  could possibly be extended as far as the axis  12  and could also be extended to the interior of the axial tube  24  and upwards beyond the intermediate radial partition  27 . 
     A lower solid body rotation stage  33  is thus defined between the lower radial wall  17  and the interior radial wall  27  and inside the chamber  28 . 
     The drum  16  comprises an intermediate interior radial wall  34 , having an annular form, which is situated above and at a rather large distance from the intermediate radial wall  27  and below and at a distance from the radial cover  15 . The intermediate radial wall and the intermediate radial wall  34  form between them a chamber  35  and form an upstream extremity and a downstream extremity of this chamber  35 . The intermediate radial wall  34  extends from the cylindrical peripheral wall  26 , without reaching the interior cylindrical tube  24 , in such a way as to form a communicating interior longitudinal annular passageway  36  surrounding the interior cylindrical tube  24 . 
     The intermediate radial wall  34  exhibits a plurality of exterior longitudinal through passageways  37 , which are arranged at a short distance from the cylindrical peripheral wall  26  and, for example, are distributed on a circle ( FIG. 4 ). The exterior longitudinal through passageways  37  are thus more remote from the axis of rotation  12  of the drum  16  than the interior longitudinal annular passageway  36 . 
     Arranged inside the chamber  35  is a system of partitioning which comprises a plurality of longitudinal interior partitions  38 , intended to provide circumferential solid body rotation, extending in planes containing the axis  12  and distributed in an angular manner ( FIGS. 3 and 4 ). 
     These longitudinal partitions  38  extend radially between and are attached to the interior cylindrical tube  24  and the cylindrical peripheral wall  26  and extend longitudinally between and are attached to the intermediate radial wall  27  and the intermediate radial wall  34 . These longitudinal partitions  38  define between them a plurality of longitudinal flow channels  39 . 
     These longitudinal channels  39  exhibit one upstream extremity adjoining the intermediate radial wall  27  and one downstream extremity adjoining the intermediate radial wall  34  and are distributed circumferentially. The number of longitudinal partitions  38  may be equal to the number of longitudinal partitions  31 . The longitudinal partitions  38  may be arranged in the extension of the longitudinal partitions  31 . 
     An intermediate migration and coalescence stage  40  is thus defined between the intermediate radial wall  27  and the intermediate radial wall  34  and inside the chamber  35 . 
     An upper extraction stage  41  situated above the migration and coalescence stage  40  is defined between the intermediate radial wall  34  and the upper radial cover  15 . 
     As illustrated more particularly in  FIG. 6 , this extraction stage  41  comprises an interior overflow  42 , which comprises a longitudinal cylindrical wall  43 , of which the lower extremity is connected to the interior annular edge of the intermediate radial wall  34 , and which extends upwards as far as a distance from the radial cover  15 . 
     A longitudinal annular flow space  44  is thus defined between the longitudinal cylindrical tube  24  and the longitudinal cylindrical wall  43 , which communicates with the chamber  35  through the longitudinal annular passageway  36 . 
     The interior face of the cylindrical wall  43  thus forms an annular overflow edge  45  turned facing towards the axis of rotation  12  and extending along the longitudinal flow space  44 . 
     Arranged in an optimal manner inside the longitudinal annular flow space  44  is a plurality of longitudinal partitions  46 , intended to provide circumferential solid body rotation, which extend in planes containing the axis  12 , between the longitudinal tube  24  and the longitudinal wall  43 , and which are distributed in an angular manner. These longitudinal partitions  46  provide an upward extension for the longitudinal partitions  38  of the migration and coalescence stage  40  by passing through the longitudinal passageway  36 . 
     The interior overflow  42  additionally comprises a radial wall  47 , of annular form, of which the interior edge is connected to the upper edge of the cylindrical wall  43 , and of which the exterior edge is situated at a short distance from the cylindrical peripheral wall  26 , in such a way as to define a downstream peripheral discharge space  48  between the radial cover  15  and the radial wall  47 . This downstream discharge space  48  communicates internally with the longitudinal annular flow space  44  and is open radially towards the cylindrical peripheral wall  26  in such a way as to form an annular downstream outlet  49 . 
     Arranged inside the downstream discharge space  48  are a plurality of longitudinal vanes  50 , intended to provide circumferential solid body rotation, which are arranged in planes containing the axis of rotation  12  and are distributed in an angular manner, and which are supported laterally by the radial wall  47  and extend upwards until they are close to the cover  15 . A self-adjusting downstream centrifugal pump  50   a  integrated with the drum is formed in this way. 
     The cylindrical peripheral wall  13  of the fixed support exhibits a through discharge orifice  51  situated opposite the downstream discharge space  47  and extended by an exterior discharge pipe  52 . A number of discharge orifices  51  distributed around the cylindrical peripheral wall  13  could be provided. 
     The extraction stage  41  likewise comprises an exterior overflow  53  which is formed between the radial walls  34  and  47  and around and at a distance from the cylindrical wall  43 . 
     The exterior overflow  53  comprises a longitudinal cylindrical wall  54  situated around and at a distance from the cylindrical wall  43 , of which the lower edge is at a distance above the intermediate radial wall  34 , and of which the upper wall is at a distance below the radial wall  47 . 
     The exterior overflow  53  additionally comprises a radial wall  55 , of annular form, which is situated at a distance above the intermediate radial wall  34 , and which connects the upper edge of the cylindrical peripheral wall  26  and the lower edge of the cylindrical wall  54 , as well as a radial wall  56 , of annular form, which is situated at a distance below the radial wall  47 , of which the interior edge is connected to the upper edge of the cylindrical wall  54 , and of which the exterior edge is situated at a small distance from the cylindrical peripheral wall  13  of the support  11 . 
     An intermediate flow space  57 , of annular form, is thus defined between the radial walls  34  and  55  and in the interior of the section of the upper extremity of the cylindrical peripheral wall  26 , said intermediate flow space  57  communicating with the chamber  35  by means of exterior longitudinal through passageways  37  of the radial wall  34 . 
     Arranged inside the intermediate flow space  57  are a plurality of longitudinal vanes  58  arranged in planes containing the axis of rotation  12  and distributed in an angular manner or circumferentially, said longitudinal vanes  58  being connected to the cylindrical peripheral wall  26  and to the radial walls  34  and  35  ( FIG. 5 ). The number of longitudinal vanes may be equal to the number of longitudinal partitions  38 . The longitudinal vanes  58  may be arranged in the extension of the longitudinal partitions  38 . 
     According to the variant embodiment illustrated in  FIGS. 1 and 8 , the longitudinal interior edges  58   a  of the longitudinal vanes  58  are situated at a distance from the exterior of the interior face of the cylindrical wall  54 . According to another variant embodiment illustrated in  FIG. 7 , the longitudinal vanes  58  are extended as far as the longitudinal wall  43 . 
     A longitudinal flow space  59 , of angular form, is likewise defined between the cylindrical wall  43  and the cylindrical wall  54 , which communicates with the intermediate flow space  57 . The interior face of the cylindrical wall  54  forms an annular overflow edge  60  turned facing towards the axis of rotation  12  and extending along the longitudinal flow space  59 . 
     The cylindrical peripheral wall  13  of the fixed support supports an interior radial wall  61 , of annular form, situated at a small distance below the radial wall  47  and at a distance from the radial wall  56  and extending until it is close to the cylindrical wall  43 . The radial wall  47  is provided, facing towards the radial wall  61 , with circumferentially driving radial vanes  47   a  in order to form a rotating fluid seal. According to one variant embodiment, a lining forming a mechanical seal could be positioned between the rotating radial wall  47  and the fixed radial wall  61 . A downstream peripheral discharge space  62 , of annular form, is likewise defined between the radial wall  56  and the radial wall  61 . This downstream discharge space  62  communicates with the longitudinal flow space  59  and is open radially towards the cylindrical peripheral wall  26  in such a way as to form a downstream outlet  63 , of annular form. 
     Arranged inside the downstream discharge space  62  are a plurality of longitudinal vanes  64 , intended to provide circumferential solid body rotation, which extend in planes containing the axis of rotation  12 , which are distributed in an angular manner and which are supported laterally by the radial wall  56 . A self-adjusting and integrated downstream centrifugal pump  64   a  is formed in this way. 
     The cylindrical peripheral wall  13  of the fixed support exhibits a through discharge orifice  65  situated opposite the downstream discharge space  62  and extended by an exterior discharge pipe  66 . A number of discharge orifices  51  distributed around the cylindrical peripheral wall  13  could be provided. 
     The cylindrical wall  43  supports, radially, communicating radial tubes or pipes  43   a , projecting into the longitudinal flow space  44 , in such a way as to bring this longitudinal flow space  44  and the longitudinal flow space  59  into communication. 
     It follows from the above, radially, that the exterior longitudinal passageways  37  are more remote from the axis of rotation  12  than the interior longitudinal passageway  36 , that the overflow edge  60  of the exterior overflow  53  is more remote from the axis of rotation  12  than the overflow edge  45  of the interior overflow  42 , and that the overflow edge  60  of the exterior overflow  53  is situated between the through passageways  37  of the radial wall  34  and the overflow edge  45  of the interior overflow  42 . 
     Arranged inside the space between the radial walls  55  and  56 , the longitudinal wall  54  of the drum  16  and the cylindrical peripheral wall  13  of the fixed support  11  is a rotating fluid seal  67 . This seal  67  comprises a central radial wall  68  supported by the longitudinal wall  54  and extending until it is close to the cylindrical peripheral wall  13  and the radial walls  69  and  70  supported by the cylindrical peripheral wall  13 , arranged between and close to the radial walls  55  and and the radial walls  56  and  68  respectively. The central radial wall  68  is provided on its opposing faces with radial vanes  68   a  and  68   b  intended to provide a circumferential drive. The longitudinal wall  54  exhibits at least one through orifice  54   a , of small diameter, bringing the intermediate flow space  57  and the internal space of the fluid seal  67  into communication. According to a variant embodiment, the integral rotating fluid seal  67  could be replaced by linings forming mechanical seals. 
     The fixed support  11  is equipped with an axial cylindrical delivery pipe  71  passing through the cover  15 , which extends inside the interior of the cylindrical tube  24 , and of which the lower extremity is at a distance from the lower radial wall  17  of the drum  16  and is situated inside the zone of the intermediate radial wall  27 . 
     According to one variant embodiment, the axial pipe  71  could be shortened or eliminated, and a fixed inlet chamber communicating with the upper extremity of the axial pipe  71 , shortened as appropriate, or of the axial tube  24 , could be arranged below the fixed radial wall  15 . This fixed inlet chamber could be supplied tangentially in order to bring about a rotation of the emulsion in the interior of the axial tube  24  in the direction of rotation of the drum, and having the ability to persist as far as the solid body rotation stage  33 . 
     According to another variant embodiment, the supply could be provided axially through the radial wall  17  and the axial shaft  18 , the axial tube  24  in this case being obstructed in the zone of the intermediate radial wall  27 . 
     The cover  15  of the support  11  exhibits, in its central section, at least one through orifice  72  which communicates with the connecting space between the longitudinal flow space  44  and the downstream discharge space  48  of the interior overflow  42 . 
     The separation device  10  may function in the following manner. 
     The drum  16  is caused to rotate by the motor  20  and turns at a substantially constant appropriate speed. 
     An emulsion E containing a light liquid L 1  and a heavy liquid L 2 , to be separated from one another, enters the fixed supply pipe  71  and is introduced, through radial inlet orifices  29  in the rotating tube  24 , into the flow spaces  32  of the chamber  28  of the solid body rotation stage  33 , inside which it is caused to rotate as a solid body under the effect of the longitudinal vanes  31 . 
     The emulsion E then passes through the longitudinal through passageways  30  of the intermediate radial wall  27  and enters into the longitudinal flow channels  39  of the chamber  35  of the migration and coalescence stage  40 , in which the rotation as a solid body is maintained under the effect of the longitudinal vanes  38  as far as the intermediate radial wall  34  of the downstream extremity of the chamber  35 . 
     As the longitudinal flow takes place, from upstream to downstream, under the effect of the centrifugal force resulting from the rotation of the drum  16 , and in each of the longitudinal flow channels  39 , the light liquid L 1  has a tendency to be displaced towards the axis of rotation  12 , and the heavy liquid L 2  has a tendency to be displaced towards the peripheral wall  26 , in such a way that the liquids L 1  and L 2  are separated before reaching the intermediate radial wall  34  of the downstream extremity of the migration and coalescence stage  40 . 
     The result is that, at least in the terminal section of the chamber  35 , the light liquid L 1  forms an interior cylinder exhibiting a substantially cylindrical free surface IG 1  turned facing towards the axis of rotation and situated at a distance from the longitudinal tube  24 , and that the heavy liquid L 2  forms an exterior cylinder in contact with the cylindrical peripheral wall  26 , said interior and exterior cylinders of liquids L 1  and L 2  exhibiting a cylindrical interface IC which is situated between the interior longitudinal passageway  36  and the exterior through passageways  37  of the intermediate radial wall  34 . The extremities of the connecting tubes  43   a  are in the interior of the cylindrical free surface IG 1 . 
     The light liquid L 1  then passes through the interior longitudinal passageway  36  of the intermediate radial wall  34  and then flows longitudinally inside the longitudinal flow space  44  on the overflow edge  45  of the interior overflow  42  in the form of a cylindrical sheet N 1 , of which the surface is in the extension of the cylindrical free surface IG 1 . The solid body rotation can be maintained thanks to the longitudinal partitions  46 . 
     The light liquid L 1  then flows, radially towards the exterior, into the downstream discharge space  48 , continues to flow through the downstream outlet  49  of the drum  16 , then continues to flow through the outlet orifice  51  of the fixed support  11 , and finally flows into the discharge pipe  52 . Under certain conditions, the liquid L 1  may form an annular layer in the periphery of the downstream flow space  48  and on the corresponding peripheral zone of the peripheral wall  13  of the support  11 . 
     In parallel, the heavy liquid L 2  passes through the exterior longitudinal passageways  37  of the partition  34  and enters the intermediate flow space  57 . The heavy liquid L 2  then flows radially towards the interior inside the intermediate flow space  57 , inside which the solid body rotation is maintained thanks to the longitudinal vanes  58 , at least in the periphery of this flow space  57 . The heavy liquid L 2  then flows longitudinally inside the longitudinal flow space  59  on the overflow edge  60  of the exterior overflow  53  in the form of a cylindrical sheet N 2  exhibiting a cylindrical free surface IG 2  formed at a distance from the exterior face of the longitudinal wall  43 . The pressure on the free surfaces IG 1  and IG 2  is the same because of the existence of the radial pipes  43   a.    
     The heavy liquid L 2  then overflows, radially towards the exterior, into the downstream discharge space  62 , continues to flow through the downstream outlet  63  of the drum  16 , then continues to flow through the outlet orifice  65  of the fixed support  11 , and finally flows into the discharge pipe  66 . Under certain conditions, the liquid L 2  may form an annular layer in the periphery of the downstream flow space  62  and on the corresponding peripheral zone of the peripheral wall  13  of the support  11 . 
     The radial thicknesses of the sheets N 1  and N 2  of liquids L 1  and L 2  on the overflow edges  45  and  60  depend in particular on the speed of rotation of the drum  16 , on the rate of flow of treated emulsion, on the respective proportions of the liquids L 1  and L 2  in the emulsion E, and on the respective radial positions of the overflow edges  45  and  60 . The thicknesses of the sheets N 1  and N 2  are small in proportion to the various other thicknesses of the liquids L 1  and L 2 . 
     In the event of the separation of the emulsion E leading to the production of a gaseous phase in the interior of the free cylindrical surfaces IG 1  and IG 2 , this gaseous phase is discharged via the orifice  72  of the upper cover  15 . 
     The flows that have been described above may be achieved to the extent that the longitudinal spaces  44  and  59  are not congested, and to the extent that the interface IC is established in an intermediate radial position between the interior longitudinal passageway  36  and the exterior longitudinal passageways  37  of the intermediate radial wall  34 , in such a way that only the light liquid L 1  exits via the interior longitudinal passageway  36 , and that only the heavy liquid L 2  exits via the exterior longitudinal passageways  37 . 
     For a given radial position of the overflow edges  45  and  60 , and on the assumption that the gases below the free surfaces IG 1  and IG 2  are at the same pressure because of the existence of the connecting pipes  43   a , the radial position of the interface IC between the light liquid L 1  and the heavy liquid L 2  depends in principle on the difference between the densities of the liquids L 1  and L 2  and on the speed of rotation of the drum  16 , in particular for the following reasons. 
     In the migration and coalescence chamber  35 , the presence of the longitudinal circumferentially driving vanes  38 , which hold circumferential portions between them, on limited angular sectors, of the emulsion E and then of the light liquid L 1  and the heavy liquid L 2 , at least in the terminal section of the chamber  35 , imposes a radial development of the circumferential speeds of the solid body type, that is to say the circumferential speeds of the emulsion E and then of the liquids L 1  and L 2  develop proportionally to the radius. 
     In the intermediate flow space  57 , the presence of the longitudinal circumferentially driving vanes  58 , which hold circumferential portions of the heavy liquid L 2  between them, imposes a radial development of the tangential speeds of the liquid L 2  of the solid body type, that is to say the circumferential speeds of the liquid L 2  develop proportionally to the radius. 
     In the event that the circumferentially driving vanes  58  extend towards the interior, at least as far as the exterior overflow edge  60 , the solid body rotation is maintained inside the intermediate flow space  57  as far as this overflow edge  60 . 
     In the event that the longitudinal interior edges  58   a  of the longitudinal circumferentially driving vanes  58  are situated at a distance from the exterior of the exterior overflow edge  60 , the solid body rotation is maintained inside the intermediate flow space  57  as far as these longitudinal interior edges  58   a . Once past these edges  58   a , the flow of the liquid L 2  has a tendency to become cyclonic, the circumferential speeds of the liquid L 2  having a tendency to become inversely proportional to the radius. 
     A description will now be given of the pressure conditions in the liquids L 1  and L 2  to either side of the radial wall  34 , on the one hand in the downstream section of the chamber  35  of the migration and coalescence stage  40 , and on the other hand inside the intermediate space  57 . 
     Illustrated in  FIG. 7  is the case in which the circumferentially driving vanes  58  inside the intermediate flow space  57  extend towards the interior at least as far as the exterior overflow edge  60 . 
     On the peripheral wall  26 , the pressures P ext  of the liquid L 2  are substantially equal to either side of the radial wall  34 , inside the chamber  35  and inside the intermediate space  57 , which are connected by the through passageways for communication  37 . 
     The pressures P int  are substantially equal on the substantially cylindrical interior free surface IG 1  of the liquid L 1 , inside the chamber  35  and inside the longitudinal space  44 , and on the substantially cylindrical interior free surface IG 2  of the liquid L 2 , at the location of the communication space  57  and inside the longitudinal space  59 . 
     The pressure reduces according to two successive curves inside the chamber  35  and radially from the exterior towards the interior. Between the peripheral wall  26  and the interface IC, the pressure in the heavy liquid L 2  decreases from the pressure P ext , according to a pressure curve ΔPL 2 ( 35 ). Then, between the interface IC and and the free surface IG 1 , the pressure in the light liquid L 1  decreases to the pressure P int , according to a pressure curve ΔPL 1 ( 35 ). 
     Inside the intermediate space  57  and radially from the exterior towards the interior, between the peripheral wall  26  and the interior free surface IG 2 , the pressure in the heavy liquid L 2  decreases from the pressure P ext  to the pressure P int , according to a pressure curve ΔPL 2 ( 57 ). 
     The pressure curves ΔPL 2 ( 35 ), ΔPL 1 ( 35 ) and ΔPL 2 ( 57 ) depend on the densities of the liquids L 1  and L 2  and are respectively formed, substantially, by portions of concave parabola facing towards the axis of rotation  12 . The pressure curve ΔPL 2 ( 57 ) and the pressure curve ΔPL 2 ( 35 ) follow substantially the same curve. 
     Illustrated in  FIG. 8  is the case in which the circumferentially driving vanes  58  do not extend towards the interior as far as the exterior overflow edge  60  and exhibit the interior edges  58   a , the thicknesses of the liquids L 1  and L 2  inside the chamber  35  being similar. 
     Inside the chamber  35 , the pressure conditions are similar to those of the previous example. 
     On the other hand, inside the intermediate space  57  and radially from the exterior towards the interior, between the peripheral wall  26  and the interior edges  58   a  of the circumferentially driving vanes  58 , the pressure in the heavy liquid L 2  decreases from the pressure P ext , according to a curve ΔPL 2   a ( 57 ), as in the previous example. On the other hand, between the interior edges  58   a  of the circumferentially driving vanes  58  and the interior free surface IG 2 , the pressure in the heavy liquid L 2  decreases to the pressure P int  according to another curve ΔPL 2   b ( 57 ). 
     Given the fact that the flow tends to be cyclonic between the interior edges  58   a  of the circumferentially driving vanes  58  and the interior free surface IG 2 , as indicated previously, this decrease according to the curve ΔPL 2   b ( 57 ) is more rapid than the decrease identified according to the example in  FIG. 7 , in which the solid body rotation of the liquid L 2  is maintained at least as far as the overflow edge  60 . This curve ΔPL 2   b ( 57 ) is formed, substantially, by a portion of a convex hyperbole facing towards the axis of rotation  12 . 
     It is for this reason, in the example illustrated in  FIG. 8 , having retained the radial position of the interior overflow edge  44  and the radial position of the interface IC of the example illustrated in  FIG. 7 , that the exterior overflow edge  60  in  FIG. 8  exhibits a larger diameter than that of the overflow edge  60  in the example illustrated in  FIG. 7 . 
     The presence of the cyclonic flow according to the example in  FIG. 8  permits a larger radial distance to be obtained between the overflow edges  45  and  60  than in the case illustrated in  FIG. 7 . The separation device  10  is thus able to separate the liquids having selected densities within a wider range, and it is then possible to separate liquids L 1  and L 2  having very similar densities. 
     According to a variant application, the emulsion E is introduced into the supply pipe  71  by means of a volumetric pump (not illustrated here), the orifice  72  of the cover  15  is at atmospheric pressure, and the need exists for the pressure loads in the outlets  51  and  65  to be greater than atmospheric pressure, for example in the event that these outlets  51  and  65  are connected to discharge pipes  52  and  66 , leading to losses in load. In this case, the downstream centrifugal pumps  50   a  and  64   a  formed by the downstream vanes  50  and  64  serve the purpose of providing the rates of flow of liquids L 1  and L 2 , which originate from the overflow edges  44  and  60  and overflow radially towards the exterior, with the pressure loads permitting these losses in load to be compensated. 
     According to another variant application, the orifice  72  of the cover  15  is connected to a vacuum pump in order to generate a reduced aspiration pressure, for example lower than the atmospheric pressure, permitting the aspiration of the emulsion E. The downstream centrifugal pumps  50   a  and  64   a  formed by the downstream vanes  50  and  64  serve the purpose of providing the rates of flow of liquids L 1  and L 2 , which overflow, with the pressure loads permitting the aspiration pressure and any losses in load in the previous example to be compensated. 
     According to another variant application, if the interior pressure imposed through the orifice  72  is lower than the pressure in the outlets  51  and  65 , for a given difference, the result is the self-regulation of the radial level of the liquids L 1  and L 2  in the downstream flow spaces  48  and  62 , regardless of the rates of flow and regardless of the ratio between the densities of the liquids L 1  and L 2 . 
     According to another variant application, the downstream flow spaces  48  and  62  are able to communicate directly with the atmosphere via through passageways  51  and  65  in the peripheral wall of the support  11 , with a view to a discharge by overflowing of the liquids L 1  and L 2 . In this case in particular, the downstream vanes  50  and  58  could be eliminated if the emulsion E is placed under pressure and if the interior pressure is equal to the atmospheric pressure. 
     According to another variant application, illustrated in  FIG. 9 , the connecting pipes  43   a  are eliminated. The flow space  59 , on this occasion, is connected to a gas pressurization/depressurization source  73  by means of a radial pipe  74  passing trough the longitudinal wall  54  and by means of a radial pipe  75  passing through one interior radial wall  76 , of annular form, of the support  11 , arranged in the rotating fluid seal  67 , whereas the orifice  72  is connected to a gas pressurization/depressurization source  77 . 
     Thus, the pressure supplied by the source  77  acts on the free surface IG 1  of the liquid L 1 , in the interior overflow  42 , and the pressure supplied by the source  73  acts on the free surface IG 2  of the liquid L 2 , in the exterior overflow  53 . 
     By causing a variation in the difference between the pressurization/depressurization supplied by the sources  73  and  77 , it is then possible to cause a variation in the radial position of the interface IC and to adapt it in such a way as to position the interface IC radially between the interior overflow edge  60  and the longitudinal orifices  30  in order to obtain a satisfactory separation. 
     The actual desired position of the interface IC may thus be adjusted or regulated as a function of the variations in the densities of the liquids L 1  and L 2  and/or as a function of the variations in the position of the interface IC which could be detected by a measuring apparatus. 
     In one particular case, one of the sources of pressurization/depressurization may be the atmospheric pressure. Only the other source of pressure is then capable of being adjusted or regulated. 
     As far as the rotating fluid seal  67  is concerned, its function may be as follows. Liquid L 2  originating from the intermediate flow space  57  is introduced via the through orifice  54   a . Under the effect of the radial vanes  68   a  and  68   b  supported by the rotating radial wall  68  facing the fixed radial walls  69  and  70 , this liquid is maintained in the peripheral section of the seal, between the walls  69  and  70 , which creates sealing between the downstream flow space  62  and the space, and the atmosphere, between the peripheral wall  13  of the support  11  and the peripheral wall  26  of the drum  16 . 
     In a similar manner, under the effect of the vanes  47   a  supported by the rotating radial wall  47  facing the fixed radial wall  61 , the liquid L 1  is displaced radially towards the exterior, which creates sealing between the exterior overflow  53  and the downstream flow space  48 . 
     With reference to  FIGS. 10 to 12 , it can be appreciated that a separation device  100  is illustrated here which differs from the separation device  10  in respect of the structure of the system of partitioning arranged inside the chamber  35  of the migration and coalescence stage  40 , the other sections being similar. 
     This system of partitioning comprises, in the upstream section of the chamber  35  adjacent to the intermediate radial wall  27 , a plurality of longitudinal partitions  101  and, in its downstream section adjacent to the intermediate radial wall  34 , a plurality of longitudinal partitions  102  and, in its median longitudinal part, a plurality of longitudinal partitions  103 . 
     The longitudinal partitions  101  and the longitudinal partitions  102  are arranged, in a similar manner to the partitions  38  of the separation device  10 , in such a way as to form pluralities of longitudinal flow channels  104  and  105  that are distributed circumferentially. 
     The longitudinal partitions  103  are arranged in such a way as to form a plurality of intermediate longitudinal flow channels  106  that are distributed circumferentially and radially. The longitudinal flow channels  106  thus exhibit cross sections that are smaller than the longitudinal flow channels  104  and  105  and are present in a larger number. 
     By way of example, the length of the longitudinal channels  104  may be equal to 15% of the length of the chamber  35 , the length of the longitudinal channels  106  may be equal to 40% of the length of the chamber  35 , and the length of the longitudinal channels  105  may be equal to 35% of the length of the chamber  35 . 
     According to a variant embodiment illustrated in  FIG. 11 , the longitudinal partitions  103  are arranged in such a way that, in cross section, the longitudinal flow channels  106  form honeycombs. 
     According to another variant embodiment illustrated in  FIG. 11 , the longitudinal partitions  103  comprise longitudinal partitions  103   a  which are distributed in an angular manner, and cylindrical longitudinal partitions  103   b  which are arranged at a distance from one another in the radial sense. 
     Thanks to the existence of the upstream longitudinal partitions  101 , and then the intermediate longitudinal partitions  103 , and then the downstream longitudinal partitions  102 , the result is the circumferential solid body rotational driving, inside the upstream longitudinal channels  104 , and then inside the intermediate longitudinal channels  106 , and then inside the downstream longitudinal channels  105 , of the emulsion and then the liquids L 1  and L 2 , in a similar manner to that which has been described previously in relation to the separation device  10 . 
     On this occasion, however, as illustrated in  FIG. 13 , the existence of the intermediate longitudinal channels  106 , in a very much greater number and distributed circumferentially and radially, makes it possible to produce a migration and coalescence of the liquids L 1  and L 2  in each of these intermediate longitudinal channels  106 . This may lead to an improvement in the performance of the separation of the liquids L 1  and L 2 , which may permit a reduction in the dimensions of the separation device. 
     With reference to  FIGS. 14 to 15 , it can be appreciated that a separation device  200  is illustrated here which differs from the separation device  10  in respect of the fact that the exterior overflow  53  is eliminated and that the intermediate partition  34  no longer exhibits the through passageways  37 , the other sections being similar. 
     This separation device  200  is more particularly suitable for extracting from an emulsion E a free gas that is conveyed by a liquid L 1  in the form of bubbles. 
     In a similar manner to that which has been described previously, the liquid L 1 , after having been introduced into the chamber  35 , is subjected to being driven in a solid body rotation under the effect of the rotation of the drum  16 , exhibits a cylindrical free surface IG 1 , passes over the overflow edge  45  of the interior overflow  42 , and then overflows into the downstream flow space  48  before being discharged. The gas that has been extracted from the liquid L 1  and is present inside the space between the cylindrical tube  24  and the free cylindrical surface IG 1  is discharged via a plurality of orifices  72  arranged in the cover  15 . 
     The separators described above could be arranged upside down, that is to say that their separation stage could be at the bottom. Furthermore, their principal axis could be inclined or horizontal. 
     The present invention is not restricted to the examples described above. Other variant embodiments are possible without departing from the scope of the invention.