WO2024126212A1

WO2024126212A1 - Combined device for filtering and dehydrating natural rubber

Info

Publication number: WO2024126212A1
Application number: PCT/EP2023/084558
Authority: WO
Inventors: Yves Hilbert; Marc NACHTEGAELE; Sébastien GEFFROY; Suriyon KINGPHETRUNGRUANG
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2022-12-14
Filing date: 2023-12-06
Publication date: 2024-06-20
Also published as: FR3143606A1

Abstract

The present invention relates to a method for treating a natural rubber coagulum during which, by means of a single worm screw (3) which is fitted in a combined filtration and dehydration device (1), the natural rubber coagulum is forced to pass successively through at least one screen (11, 12, 13) belonging to a filtration stage (10), in order to filter said natural rubber coagulum in accordance with the filtration mesh (M11) defined by said at least one screen (11, 1, 13), then through expansion openings (25) provided in an expansion stage (20) which is located downstream of the filtration stage (10), in order to subject the natural rubber coagulum to adiabatic expansion which causes dehydration of said natural rubber coagulum by vaporization of at least part of the water contained in said natural rubber coagulum.

Description

COMBINED DEVICE FOR FILTRATION AND DEHYDRATION OF NATURAL RUBBER

[0001] The present invention relates to the field of processing natural rubber, in particular in the context of the manufacture of tire components, in particular pneumatic tires.

[0002] Natural rubber, which contains a polyisoprene matrix, is usually collected by tapping the rubber tree, in order to collect the latex in a container which is called a “cup”.

The latex is then coagulated, either by so-called “natural” or “spontaneous” coagulation, whereby the latex coagulates directly in the cup to form a coagulum called “cup lump”, either by so-called “artificial” or “induced” coagulation, according to which the latex is coagulated using a chemical agent, such as an acid or a salt.

[0004] The natural rubber coagulum thus obtained frequently contains contaminants such as leaves, twigs, pieces of bark, grains of sand and other debris resulting from the collection process, and must therefore be decontaminated.

[0005] For this purpose, it is known in particular, from document WO-2016/162645, to use an extruder which forces the passage of the natural rubber coagulum through a filter which has a mesh of chosen value, adapted to the contaminants that we wish to eliminate.

The filtered natural rubber coagulum must then be dried.

[0007] The natural rubber thus filtered and dried is then generally packaged by compression in the form of balls.

[0008] The processing of natural rubber therefore requires installations which have all the different machines necessary for carrying out the decontamination, drying and packaging operations respectively, which installations therefore have the disadvantage of being particularly cumbersome and energy-intensive. [0009] The objects assigned to the invention therefore aim to remedy the aforementioned drawbacks and propose a new device for processing natural rubber which makes it possible to reduce the size and cost of industrial installations, and to save energy. , while maintaining an acceptable yield.

[0010] The objects assigned to the invention are achieved by means of a device intended to filter and then dehydrate a natural rubber coagulum, said device being characterized in that it comprises:

- an enclosure which extends along and around an axis called the “main axis”,

- an endless screw which is rotatably mounted within a first stage of the enclosure forming a sheath so as to be able to convey the natural rubber coagulum from upstream to downstream of said sheath, along the axis main,

- a filtration stage which forms a second stage of the enclosure located axially downstream of the downstream end of the endless screw, in the extension of the sheath, and which comprises on the one hand at least one sieve which defines a filtration mesh, so that said at least one sieve makes it possible to filter the natural rubber coagulum when the endless screw forces the passage of said natural rubber coagulum through said at least one sieve, and on the other hand a first plate called “filtration plate” which has an upstream face forming a seat which supports the at least one sieve against the pressure that the natural rubber coagulum exerts on said sieve, said filtration plate being provided with a first set orifices, called “filtration orifices”, which allow the natural rubber coagulum having passed through the at least one sieve to pass through said filtration plate, said filtration orifices being arranged in such a way that they each have a section of passage which is greater than or equal to a predetermined reference section, which is itself strictly greater than the passage section of the filtration mesh defined by the at least one sieve, and said filtration orifices defining as a whole a section total passage whose minimum surface area, considered in a plane normal to the main axis, is called “cumulative filtration section”,

- an expansion stage which forms a third stage of the enclosure located axially downstream of the filtration stage, in the extension of said filtration stage, and which comprises a second plate, called "expansion plate", which is provided a second set of orifices, called “relaxation orifices”, which are arranged to receive the natural rubber coagulum from the filtration stage and allow said natural rubber coagulum to pass through said expansion plate and leave the enclosure by undergoing an expansion which causes vaporization of at least part of the water contained in the coagulum of natural rubber, said expansion orifices being for this purpose arranged in such a way that on the one hand said expansion orifices each have a passage section which is strictly less than the reference section of the filtration orifices and strictly greater than the section of passage of the filtration mesh, and that on the other hand said expansion orifices define as a whole a total passage section whose minimum surface area, considered in a plane normal to the main axis, and called “cumulative expansion section” , is strictly less than the cumulative filtration section, such that the endless screw is able to force the natural rubber coagulum to pass successively through the filtration stage then through the expansion stage.

[0011] Advantageously, the invention therefore proposes a device which combines the filtration and dehydration functions in a single, particularly compact device.

[0012] Advantageously, the device according to the invention is capable, thanks to the endless screw, of providing energy to the natural rubber coagulum upstream of the filtration stage, by raising the pressure and the temperature of said coagulum of natural rubber, then using this energy to accomplish not only the filtration operation, but also the dehydration operation. In other words, the device according to the invention makes it possible to provide the natural rubber coagulum with the energy which is necessary for the entire filtration and dehydration process in one go, so that it is the same energy which is advantageously used in a shared way, without unnecessary losses, to successively carry out the two operations, namely the filtration operation, then the drying operation by dehydration, which, until now, required two machines distinct and therefore two separate energy inputs. The device according to the invention therefore has better energy efficiency than known installations.

[0013] It will be noted in this respect that, at the level of the filtration stage, the relatively large passage section of the filtration orifices allows the filtration plate not to cause too significant a pressure loss in the flow of the natural rubber coagulum, after said natural rubber coagulum has passed the sieve and therefore been cleared of most of its impurities, while, further downstream, at the level of the expansion stage, the relative narrowness of the expansion orifices as well as the relative smallness of the cumulative expansion section, which allows the coagulum to natural rubber to cross the expansion plate, create a strong pressure loss which tends on the one hand to retain the natural rubber coagulum, under strong pressure, at the entrance to the expansion plate, which allows said natural rubber coagulum to conserve significant potential energy for the dehydration stage, and on the other hand to promote a rapid and large amplitude pressure drop at the outlet of the expansion plate, and therefore to promote strong adiabatic expansion, particularly effective in vaporizing the water contained in the natural rubber coagulum. In other words, the sizing of the filtration orifices and the expansion orifices advantageously provides optimized management, and therefore optimal use, of the energy which is supplied to the natural rubber coagulum by the endless screw, each of the stages filtration then dehydration having, and taking, the quantity of energy which is necessary for the operation which the stage considered must carry out.

[0014] Other objects, characteristics and advantages of the invention will appear in more detail on reading the description which follows, as well as with the aid of the appended drawings, provided for purely illustrative and non-limiting purposes, among which :

[0015] Figures IA and IB illustrate, in overall perspective views, respectively in an exploded view and in an assembled view, a device according to the invention.

[0016] Figure 2 is a longitudinal sectional view of the device of Figures IA and IB, in a sectional plane containing the main axis of the enclosure.

[0017] Figure 3 is an enlarged detail view of Figure 2, showing better the presence of an interface chamber between the filtration plate and the expansion plate.

[0018] Figures 4A, 4B and 4C illustrate, respectively in a perspective view, in a front view from the upstream in projection in a plane normal to the main axis of the sheath, and in a sectional view, a example of filtration plate used within the device of Figures 1 and 2. [0019] Figures 5A, 5B and 5C illustrate, respectively in a perspective view, in a front view from upstream, and in a sectional view, an example of a relaxation plate used within the device of Figures 1 and 2.

[0020] Figures 6A and 6B illustrate, respectively in a front view from upstream and in a sectional view, a sub-assembly grouping together the filtration plate of Figures 4A, 4B, 4C and the relaxation plate of Figures 5A, 5B, 5C, and within which an interface chamber is provided between the filtration plate and the expansion plate.

[0021] Figures 7A and 7B illustrate, in a front view from the upstream and a longitudinal sectional view, another subassembly which groups together a filtration plate and a relaxation plate and which is intended for a variant of the device, said subassembly comprising a filtration plate and a relaxation plate which are this time directly attached to each other, without forming an interface chamber, and which are arranged so that the orifices of trigger are aligned with the filtration ports.

[0022] Figure 8 represents, in a perspective view, a stack of three sieves which can be used in the filtration stage of the device according to the invention, said stack comprising a central sieve which has the finest mesh and which thus defines the filtration mesh, an upstream sieve having a coarser mesh and therefore a more robust structure to resist the torque exerted by the natural rubber coagulum under the effect of the rotation of the endless screw, and a downstream sieve having a mesh of intermediate size between that of the central sieve and that of the upstream sieve, which reinforces the strength of the assembly, and more particularly which reinforces the fine central sieve, with respect to the axial pressure exerted by the natural rubber coagulum. It will be noted that, for better readability of the figure, the size of the meshes of the sieves has been represented in an artificially enlarged manner in relation to the overall diameters of said sieves and to the surfaces occupied by said sieves, while remaining in proportion to a sieve to the other.

The present invention relates to a device 1 intended to filter and then dehydrate a natural rubber coagulum.

Typically, said natural rubber coagulum initially presents, when introduced into said device 1, a water content which is greater than or equal to 12% by weight, for example between 12%, even 15%, low value, and 40%, high value.

As is clearly visible in Figures IA, IB and 2, the device 1 according to the invention comprises:

- an enclosure 2 which extends along and around an axis Z2 called “main axis” Z2,

- an endless screw 3 which is rotatably mounted within a first stage of the enclosure 2 forming a sheath 4 so as to be able to convey the natural rubber coagulum from upstream to downstream of said sheath 4, and more generally from upstream to downstream of enclosure 2, along the main tax Z2.

[0026] In a manner known per se, the enclosure 2, and more particularly the sheath 4, comprises an admission orifice 2_in, such as a hopper, which makes it possible to introduce the natural rubber coagulum into said sheath 4 for subject said natural rubber coagulum to the action of the endless screw 3.

Said endless screw 3 is driven by a suitable motor, preferably an electric motor.

[0028] The rotation of the endless screw 3 advantageously makes it possible to work the natural rubber coagulum and thus to increase the pressure and the temperature of said natural rubber coagulum. In this, device 1 can be compared to an extruder.

Preferably, the sheath 4 contains a single endless screw 3, so that the device 1 forms a single-screw extruder.

The sheath 4 has a circular passage section whose diameter is preferably between 90 mm and 400 mm, for example equal to 300 mm.

The sheath 4, or more generally the enclosure 3, and/or the endless screw 3 may be provided with heating elements, for example heating resistors and/or a heating circuit transporting a heat transfer fluid. These heating elements can contribute, in cooperation with the endless screw 3, to raise the temperature of the natural rubber coagulum and to regulate the temperature of said natural rubber coagulum within the device 1, inside the enclosure 2, and more particularly the sheath 4. [0032] To promote the axial progression of the natural rubber coagulum, the internal wall of the sheath 4 is preferably grooved, over at least a part and preferably over the entire length of the section of the sheath 4 which corresponds to the axial range occupied by the thread of the endless screw 3. Said sheath 4 may thus for example include grooves which form grooves substantially parallel to the main axis Z2. This principle of grooved arrangement of the sheath 4 is known in particular from application WO-2016/162645 already mentioned above. We can therefore usefully refer to the illustrations and sizing formulas presented in said application WO-2016/162645 to define the grooves of the sheath 4 of the present application. This is why said illustrations and formulas are advantageously incorporated by reference into the present application.

The sheath 4 may also include kneading fingers (“breaker pins” in English) placed inside the sheath 4, projecting radially relative to the internal wall of said sheath, and which contribute, with the screw without end 3, mixing the natural rubber coagulum.

[0034] For convenience of description, we will designate by “axial” a direction parallel to the axis considered, here more particularly a direction parallel to the main axis Z2, and by “radial” a direction perpendicular to the axis considered, here more particularly a direction perpendicular to the main axis Z2.

The “upstream-downstream” direction, and therefore the notions of “upstream” and “downstream”, are understood taking into consideration the overall direction of the flow of the natural rubber coagulum through the device 1, along the main axis Z2.

[0036] By usual convention, we will also designate by “passage section” of a conduit or an orifice the surface which is open to the flow of a fluid, here open to the passage of the natural rubber coagulum, through said conduit or orifice. Said passage section is defined geometrically as the surface portion which on the one hand belongs to a fictitious cutting plane which is normal to the general direction of flow of the fluid within the conduit or orifice considered, this is that is to say in practice a cutting plane which is normal to the main axis of said conduit or said orifice, and which on the other hand is delimited by the curve, typically a circle, formed by the intersection of said fictitious cutting plane with the internal wall which radially delimits said conduit or said orifice.

[0037] Furthermore, reference could be made to the “hydraulic diameter” Dh of a passage section considered, here more particularly of a passage section considered in a plane normal to the main axis Z2. By “hydraulic diameter”, we mean the equivalent diameter as calculated by the following formula:

Dh = 4 x Area of the section considered / perimeter of the section considered

It will be noted that, in the case of a passage section with a circular base, the hydraulic diameter is equal to the geometric diameter of the circular base; in fact, if the base has a radius R, and therefore a geometric diameter worth 2*R, then the hydraulic diameter Dh circ is worth:

Dh circ = 4 x (Pi*R ² ) / (2*Pi*R) = (4*Pi*R ² ) / (2*Pi*R) = 2*R

[0039] In the case of a square base passage section whose side has a length “a”, the hydraulic diameter Dh square is equal to the length of the side: Dh_square = 4 x (a ² ) / (4a) = a

[0040] According to the invention, the device 1 comprises a filtration stage 10 which forms a second stage of the enclosure 2 located axially downstream of the downstream end of the endless screw 3, in the extension of the sheath 4 .

Said filtration stage 10 thus receives the natural rubber coagulum which comes out of the endless screw 3, and which has been brought to the desired temperature and pressure.

The filtration stage 10 comprises at least one sieve 11, 12, 13 which defines a filtration mesh Ml 1, so that said at least one sieve 11, 12, 13 makes it possible to filter the natural rubber coagulum when the endless screw 3 forces the passage of said natural rubber coagulum through said at least one sieve 11, 12, 13.

Said at least one screen 11, 12, 13 covers the passage section of the enclosure 2, that is to say that the at least one screen 11, 12, 13 extends over the entire section passage of the enclosure 2, considered at the level of the filtration stage 10, and therefore bars said passage section so that, to be able to cross the axial position of said at least one sieve 11, 12, 13 in the direction of upstream-downstream flow, and more generally to be able to exit the sheath 4 and pass through the filtration stage 10, the natural rubber coagulum must necessarily pass through said at least one sieve 11, 12, 13, without being able to bypass it.

The filtration stage 10 also comprises a first plate 14, called a “filtration plate” 14, which has an upstream face 14U forming a seat which supports the at least one sieve 11, 12, 13 against of the pressure that the natural rubber coagulum exerts on said at least one sieve 11, 12, 13.

The filtration plate 14 is advantageously provided with a first crown 16, preferably a first circular crown 16, which forms part of the wall of the enclosure 2 and which allows the fixing plate 14 to be clamped on the sheath 4 which precedes the filtration stage 10.

Said first crown 16 also advantageously allows the centering of the sieves 11, 12, 13 with respect to the filtration plate 14, and more particularly with respect to the main axis Z2.

The internal wall 161 of said first ring 16 delimits the passage section of the enclosure 2, here preferably a circular passage section, at the level of the filtration stage 10.

[0048] It will be noted that, preferably, the passage section of the enclosure 2 at the level of the filtration stage 10, passage section which corresponds here to the section S 14 occupied by the upstream face 14_U of the plate of filtration, is wider than the passage section of the sheath 4, considered at the end of the endless screw 3.

[0049] This makes it possible in particular to distribute the flow of natural rubber coagulum to be filtered over an extended surface of sieves 11, 12, 13, and thus to delay the progressive obstruction of the sieve 11, 12, 13 by clogging, and therefore to reduce the frequency of replacement and cleaning of the sieve 11, 12, 13.

To do this, the passage section of the enclosure 2 at the level of the filtration stage 10, and more particularly the passage section delimited by the internal wall 161 of the first crown 16, and therefore the section S 14 occupied by the upstream face 14U of the filtration plate 14, may have a hydraulic diameter Dh_14U, and more particularly a geometric diameter in the preferred case of a circular basic shape, which is strictly greater than the hydraulic diameter, here the geometric diameter, of the sheath 4, for example which is between 1.2 times and 1.4 times the diameter of the sheath 4 considered at the downstream end of the endless screw 3, for example equal to 1.33 times the diameter of the sheath 4 considered at the downstream end of the endless screw.

[0051] By way of example, for a sheath 4 whose internal diameter is 300 mm to 305 mm in the plane which is normal to the main axis Z2 and considered axially at the end of the endless screw 3, we can provide a diameter Dh_14U of the upstream face 14U of the fixing plate 14, and therefore a diameter of the sieves 11, 12, 13, which will be equal to 360 mm or even 400 mm, and more generally which will be between these two values.

[0052] In a manner known per se, and as visible in Figure 8, the sieve(s) 11, 12, 13 may be formed by metal grids, for example grids formed by a network of intersecting metal wires which delimit square meshes.

[0053] As an indication, we could in particular use one or more sieves 11, 12, 13 having one or the other of the following meshes (expressed in “mesh”):

- mesh 6: wires with a diameter of 0.81 mm define square openings with a side of 3.42 mm;

- mesh 10: wires with a diameter of 0.91 mm define square openings with a side of 1.63 mm;

- mesh 20: wires with a diameter of 0.42 mm define square openings with a side of 0.85 mm;

- mesh 30: wires with a diameter of 0.253 mm define square openings with a side of 0.594 mm;

- mesh 40: wires with a diameter of 0.253 mm define square openings with a side of 0.382 mm.

[0054] It will be noted, however, that, to promote the mass flow rate of the device 1, and therefore the efficiency of said device 1, we could favor, in practice, a filtration mesh Ml 1 whose opening is equal to or greater than that of a mesh 20. [0055] For convenience of description, we will note SI 1 the individual passage section of each opening of the sieve 11 which corresponds to the filtration mesh Ml 1 defined by said sieve 11.

[0056] Preferably, we will implement an axial stack of several sieves 11, 12, 13, typically three sieves 11, 12, 13, so that the natural rubber coagulum successively passes through each of said sieves placed in series. The sieve with the finest mesh within this stack will in practice define the filtration mesh mentioned above.

[0057] Said stack may include, as visible in Figure 8:

- a central sieve 11 which has a first mesh Mi l which is the finest of the stack, for example mesh 20, and which thus defines the filtration mesh,

- an upstream sieve 12 which has a second coarser mesh M12, for example mesh 6, and therefore a more robust structure capable of resisting the torque exerted on the stack of sieves 11, 12, 13 by the rubber coagulum natural to which the rotation of the endless screw 3 tends to communicate a rotary movement,

- and a downstream sieve 13 which has a third mesh Ml 3 of intermediate size between the first mesh Ml 1 of the central sieve 11 and the second mesh M12 of the upstream sieve 12, said downstream sieve 13 reinforcing the strength of the stack, and more particularly reinforcing the central screen 11, with respect to the axial pressure which is exerted by the natural rubber coagulum, under the thrust of the endless screw 3.

The filtration plate 14 will preferably be oriented along a plane normal to the main axis Z2.

[0059] Said filtration plate 14 advantageously covers the entire passage section of the enclosure 3, at the level of the filtration stage 10, in order to provide the downstream face of at least one sieve 11, 12 , 13, and more particularly on the downstream face of the stack of sieves 11, 12, 13, a robust and well distributed support over said passage section.

The fixing plate 14 can preferably be made of steel.

[0061] It will also be noted that the endless screw 3 opens directly into the filtration stage 10, which forms a first extension of the sheath 4, so that the coagulum of natural rubber which comes out of the endless screw 3 engages directly into the filtration stage 10, and more particularly directly through the at least one sieve 11, 12, 13 then through the filtration plate 14, without it is necessary to provide an intermediate pump, such as a gear pump, between the endless screw 3 and the filtration stage 10, and more particularly between the endless screw 3, upstream, and the at least a sieve 11, 12, 13 and the filtration plate 14, downstream. The endless screw 3 is in fact sufficient on its own to create the conditions necessary for the flow of the natural rubber coagulum through the filtration stage 10.

[0062] As is clearly visible in Figures 3, 4A, 4B, 4C, 6A, 6B, 7A and 7B, the filtration plate 14 is provided with a first set of orifices 15, called “filtration orifices » 15, which allow the natural rubber coagulum having passed through at least one sieve 11, 12, 13 to pass through said filtration plate 14, here in the direction of the thickness E14 of said filtration plate 14.

The thickness E14 corresponds to the distance which axially separates the downstream face 14D of the filtration plate 14 from the upstream face 14U of said filtration plate 14. Said thickness E14 will thus correspond to the axial length of the filtration orifices 15 .

[0064] Said filtration orifices 15 are arranged in such a way that they each have a passage section S15 which is greater than or equal to a predetermined reference section S ref, reference section S ref which is itself strictly greater than the passage section SI 1 of the filtration mesh Ml 1 as defined by Tat least one sieve 11, 12, 13.

[0065] Thus, the filtration orifices 15 will each have a passage section SI 5 which is larger than the individual passage section of the meshes of the finest sieve 11, 12, 13 used, which will allow the natural rubber coagulum to having passed the sieve to continue its flow through the thickness E14 of the filtration plate 14 using large filtration orifices 15, and therefore without suffering too great a pressure loss.

[0066] In this respect, it will also be noted that the filtration plate 14 preferably has a thickness E14 of between 40 mm and 60 mm. [0067] Such a thickness is both sufficiently large on the one hand to limit the bending of the filtration plate 14, and even more so to prevent the filtration plate 14 from giving in under the axial pressure exerted by the coagulum of natural rubber, and sufficiently fine on the other hand to limit the length of the filtration orifices 15 and thus avoid causing excessive pressure losses in the flow of the natural rubber coagulum, so as not to excessively degrade the flow and therefore the performance of device 1.

Preferably, the hydraulic diameter Dh_15 of the smallest passage section of each of the filtration orifices 15 is greater than or equal to 8 mm, preferably between 10 mm and 14 mm, for example equal to 12 mm.

Preferably, for convenience of production, and as can be seen in Figures 4A, 4B, 6A and 7A, the filtration orifices 15 are formed by cylindrical holes with a circular base. The axes of these cylindrical holes with a circular base are preferably parallel to each other. The axes of said cylindrical holes of circular base are preferably perpendicular to the upstream 14U and downstream 14D faces of the filtration plate 14, and therefore substantially or even exactly parallel to the main axis Z2. The thickness E14 then corresponds to the total length of each filtration orifice 15.

[0070] Particularly preferably, the majority, and more preferably all, of the filtration orifices 15 will be identical to each other, that is to say they will have the same shape and identical dimensions from a filtration orifice 15 to the other, more particularly the same diameter Dh_15 and therefore the same passage section S15 from one filtration orifice 15 to the other.

[0071] As a whole, the filtration orifices 15 define a total passage section whose minimum surface area, considered in a plane normal to the main axis Z2, which is called “cumulative filtration section” S15_tot.

[0072] This cumulative filtration section S15_tot corresponds to the sum of the individual passage sections S15 of the filtration orifices 15, and where appropriate to the minimum of said sum if the value of said sum varies as a function of the axial position of the normal plane which we consider, in the axial range occupied by the thickness E14 of the filtration plate 14. [0073] In practice, said cumulative filtration section S15_tot may represent between 70% and 120%, more preferentially between 100% and 120%, and for example 105%, of the cumulative passage section of the sieve 11, called “section of cumulative sieving » SI l_tot, such that this cumulative sieving section SI l_tot results from the filtration mesh, that is to say here between 70% and 120%, preferably between 100% and 120%, for example 105%, of the cumulative passage section represented by the sum of the individual surfaces of the openings of the sieve 11 having the finest mesh of the stack of three sieves 11, 12, 13.

[0074] Preferably, we ensure that the cumulative filtration section S15_tot represents more than 100% of the cumulative passage section of the finest sieve 11, so that the filtration plate 14 offers the natural rubber coagulum a greater large overall passage opening than the finest sieve 11. In other words, the total hollow surface of the filtration plate 14 is greater than the total hollow surface of the finest sieve 11. Thus, we prevent the filtration plate 14 from constituting in itself, in relation to the sieve 11, a significant additional brake on the flow of the natural rubber coagulum through the filtration stage 10. Such an arrangement therefore allows to best preserve the flow rate of device 1.

[0075] Furthermore, and always in order to preserve the flow rate of the device 1 by minimizing the pressure losses induced by the filtration plate 14, the filtration orifices 15 will preferably be arranged so that the minimum total passage section that they define together, that is to say the cumulative filtration section S15_tot, preferably represents at least 45%, for example between 50% and 60% of the passage section of the enclosure 2 at the level of the plate. filtration 14, that is to say here of the section S14 of the upstream face 14U of the fixing plate, considered in projection in a plane normal to the main axis Z2, which receives the at least one sieve 11, 12, 13 and which is therefore wetted by the natural rubber coagulum.

[0076] According to the invention, the device 1 also comprises an expansion stage 20 which forms a third stage of the enclosure 2 located axially downstream of the filtration stage 10, in the extension of said filtration stage 10, and which comprises a second plate 24, called "expansion plate" 24, which is provided with a second set of orifices 25, called "orifices relaxation » 25, which are arranged to receive the natural rubber coagulum from the filtration stage 10 and allow said natural rubber coagulum to pass through said expansion plate 25 and to leave the enclosure 2 while undergoing expansion, here more precisely an adiabatic expansion, which causes vaporization of at least part of the water contained in the natural rubber coagulum.

The expansion plate 24 is preferably made of steel.

The expansion plate 24 preferably has a thickness E24 of between 25 mm and 50 mm. This thickness corresponds to the distance which axially separates the downstream face 24D of the expansion plate 24 from the upstream face 24U of said expansion plate 24, and therefore to the axial length of the expansion orifices 25.

[0079] Said thickness E24 is chosen sufficient to allow the expansion plate 24 to resist the internal pressure which prevails in the enclosure 2, downstream of the filtration plate 14, at the entrance to the expansion stage 20, here more particularly to the pressure which is exerted against the upstream face 24U of the expansion plate 24 which is exposed to the natural rubber coagulum. More particularly, this thickness E24 allows the expansion plate 24 to resist the axial thrust force exerted on it by said natural rubber coagulum.

The expansion stage 20 advantageously forms a second extension of the sheath 4, which communicates directly with the first extension formed by the filtration stage 10. The expansion plate 24 thus forms the downstream end of the enclosure 2 , and therefore the downstream axial limit of the pressurized zone of said enclosure 2, and more generally of the device 1.

[0081] Just like the filtration plate 14, the expansion plate 24 is preferably provided with a second annular crown 26 which forms part of the wall of the enclosure 2 and which makes it possible to fix the expansion plate 24 to the sheath 4, following the filtration stage 10. The internal wall 261 of said second crown delimits the surface S24 of the upstream face 24U of the expansion plate 24 which is wetted by the natural rubber coagulum coming from the filtration stage 10.

[0082] The hydraulic diameter Dh_24U of the upstream face 24U of the expansion plate 24, which here corresponds to the geometric diameter of the internal wall 261 of the second crown 26, will preferably be between on the one hand a minimum value which is at least equal to the diameter up to which filtration orifices 15 are actually found on the filtration plate 14, that is to say the diameter of the circle fictitious circumscribed to all the filtration orifices 15, and on the other hand a maximum value which is equal to the hydraulic diameter of the section S 14 occupied by the upstream face 14U of the filtration plate 14.

[0083] Returning to the example mentioned above, according to which, preferably following a sheath 4 with a diameter of between 300 mm and 305 mm, we find a filtration plate whose hydraulic diameter Dh_14U is 360 mm, within in which the filtration orifices 15 are distributed in a fictitious circle of diameter 340 mm, so that the filtration orifices 15 radially most distant from the main axis Z2 remain slightly radially set back from the internal wall 161 of the first crown 16, as is particularly visible in Figure 6A, then the hydraulic diameter Dh_24U of the upstream face 24U of the expansion plate 24 could be between 340 mm (fictitious circumscribed circle) and 360 mm (Dh_14U), for example equal to 350 mm .

[0084] As an indication, we observe that the residual humidity level of the natural rubber obtained after the relaxation operation according to the invention is between 2% and 8% by weight.

[0085] The number, spatial distribution and dimensions of the expansion orifices 25 are of course chosen so that, compared to the filtration plate 14 which seeks to maximize the flow rate of the natural rubber coagulum and therefore to minimize the pressure losses, the expansion plate 24 on the contrary exerts a retaining function in that said expansion plate 24 has the effect of slowing down the flow of the natural rubber coagulum by imposing a strong pressure loss on it, so that the Natural rubber coagulum retains, at the level of the upstream face 24U of the expansion plate 24, a high pressure, and therefore a significant useful potential energy, which will be used for expansion. The expansion plate 24 therefore advantageously makes it possible to maintain a strong pressure gradient between its upstream face 24U, which is exposed to the high pressure which prevails in the enclosure 2, and its downstream face 24D, which is exposed to a much lower pressure. , typically the ambient atmospheric pressure, and thus subjects the natural rubber coagulum which escapes through the expansion orifices 25 to almost instantaneous expansion and of high amplitude, in fact adiabatic, which causes the vaporization of the water contained in the natural rubber coagulum.

[0086] For this purpose, the expansion orifices 25 are arranged in such a way that on the one hand said expansion orifices 25 each have a passage section S25 which is i) strictly less than the reference section S ref of the orifices filtration 15 and ii) strictly greater than the passage section SI 1 of the filtration meshMl 1: Sl l < S25 < S_ref < S15, and that on the other hand said expansion orifices 25 define as a whole a total passage section whose minimum surface area, considered in a plane normal to the main axis, and called “cumulative relaxation section” S25_tot, is strictly less than the cumulative filtration section S15_tot: S25_tot < S15_tot

[0087] Thus, the total hollowed-out surface of the expansion plate 24, which allows the passage of the natural rubber coagulum through the expansion plate 24, in the direction of the thickness E24 of said expansion plate 24, is strictly less than the recessed surface of the filtration plate 14 as provided by the filtration orifices 15, and is composed of expansion orifices 25 smaller than said filtration orifices 15.

[0088] As an indication, the hydraulic diameter Dh_25 of the smallest passage section of each of the expansion orifices 25 is preferably less than or equal to 6 mm, preferably between 1 mm and 4 mm.

[0089] This fineness of the expansion orifices 25 advantageously allows each expansion orifice 25 to create, between the upstream face 24U and the downstream face 24D of the expansion plate 24, and more particularly between the inlet of said expansion orifice 25 , which opens onto the pressurized enclosure 2, and the outlet of said expansion orifice 25, which communicates with the ambient atmosphere, a strong pressure gradient, conducive to effective expansion.

The expansion orifices 25 can take any appropriate geometric shape, and for example form cylindrical holes, oblong holes, rectangular slots, etc. Preferably, for convenience of construction, the expansion orifices 25 are formed by cylindrical holes with a circular base. The axes of these cylindrical holes with a circular base are preferably parallel to each other. The axes of said cylindrical holes of circular base are preferably perpendicular to the upstream 24U and downstream 24D faces of the expansion plate 24, and therefore substantially or even exactly parallel to the main axis Z2.

[0091] Particularly preferably, the majority, and more preferably all, of the expansion orifices 25 will be identical to each other, that is to say they will have the same shape and identical dimensions from an expansion orifice 25 to the other, more particularly the same diameter Dh_25 and therefore the same passage section S25 from one expansion orifice 25 to the other.

[0092] Preferably, the filtration orifices 15 are formed by cylindrical holes of circular base whose minimum diameter is equal to or greater than a predetermined reference diameter D ref, and the expansion orifices 25 are formed by cylindrical holes circular base whose minimum diameter is strictly less than said reference diameter D ref, preferably at least twice less, at least three times less, or even at least five times less, said reference diameter D ref.

[0093] The expansion orifices 25 are therefore particularly fine in comparison with the filtration orifices 15, for the reasons already detailed above according to which it is necessary for the filtration orifices 15 to interfere as little as possible with the flow of the natural rubber coagulum. while the expansion orifices 25 must slow down and contain this flow while respecting two contradictory constraints, namely on the one hand maintaining a sufficient pressure gradient across the thickness of the expansion plate 24 to obtain effective expansion and on the other hand maintain a satisfactory mass flow of natural rubber through the expansion plate 24.

[0094] By convention, the reference diameter D ref can correspond to the smallest diameter observable among the filtration orifices 15, that is to say the “low threshold” defining a filtration orifice 15. In addition, we can also define said reference diameter D ref as being the hydraulic diameter of the reference passage section S ref, and therefore the geometric diameter of said reference passage section S ref when said reference passage section S ref is circular.

[0095] As an indication, the reference diameter D ref could be chosen between 8 mm and 14 mm, and for example equal to 10 mm or 12 mm. [0096] In any case, the arrangement proposed by the invention advantageously combines an endless screw 3, a filtration stage 10 and an expansion stage 20 within the same device 1, and more precisely within of the same enclosure 2 which comprises the sheath 4 and the extensions of said sheath 4 which form the respective side walls 161, 261 of the filtration stage 10 and the expansion stage 20, up to the expansion plate 24 .

[0097] Thanks to the arrangement proposed by the invention, the endless screw 3 is advantageously capable of forcing the natural rubber coagulum to pass successively through the filtration stage 10 then through the expansion stage 20.

[0098] Advantageously, no additional pump, such as a second endless screw, a gear pump or a piston pump, is therefore necessary to force the passage of the natural rubber coagulum from the filtration stage 10 through the expansion stage 20. The device 1 is therefore advantageously devoid of a pump between these two stages of filtration 10 and expansion 20, which makes said device 1 particularly compact and relatively economical in terms of energy consumption.

[0099] Furthermore, as is visible in Figures 1A, 2 and 3, the device 1 is preferably provided with a knife 30, preferably a rotating knife 30, which produces granules ("crumbs", in English) the dehydrated natural rubber coagulum which leaves the enclosure 2 through the expansion orifices 25 of the expansion plate 24.

[00100] Said knife 30 may include one or more blades which scrape the downstream face 24D of the expansion plate to cut the natural rubber threads which spring from the expansion orifices 25, inflating and expelling their water in the form of vapor .

[00101] Preferably, the ratio L 10 20 / Dh lOD enters, in the numerator, the distance L_10_20, called “staging distance” L_10_20, which axially separates the upstream face 24U of the expansion plate 24 from the downstream face 14D of the filtration plate 14, and, in the denominator, the hydraulic outlet diameter Dh lOD of the filtration stage 10, as visible in Figure 6B, is between zero and 10%. We recall that the hydraulic diameter Dh of a section is the equivalent diameter as calculated by the formula: Dh = 4 x Area of the section considered / perimeter of the section considered in which the section considered corresponds here, for the calculation of the diameter hydraulic outlet of the filtration stage Dh lOD, at the section of the passage of the enclosure 2 considered in a plane which is normal to the main axis Z2 and tangent to the downstream face 14D of the filtration plate 14.

[00102] Such sizing, that is to say here such a length/diameter ratio, makes it possible in particular to limit the pressure losses during the flow of the natural rubber coagulum from the filtration stage 10 to the expansion stage 20. The natural rubber coagulum thus has, at the outlet of the filtration stage 10, then when it appears at the entrance to the expansion stage 20, a significant residual energy, and in particular a high residual pressure, which is sufficient to force the passage of said natural rubber coagulum through the expansion orifices 25 and therefore to carry out the expansion operation. Limiting pressure losses also makes it possible to maintain a suitable mass flow rate, and therefore satisfactory industrial efficiency.

[00103] In practice, the hydraulic outlet diameter of the filtration stage Dh lOD corresponds to the diameter of the annular wall of the enclosure 2 considered, and more particularly to the diameter of the radially internal annular wall 261 of the second ring 26 of the expansion plate 24 which forms the second extension of the enclosure 2 following the filtration stage 10, considered in the plane which is normal to the main axis Z2 and tangent to the downstream face 14D of the plate filtration stage 14, that is to say the diameter of the passage section of the enclosure 2 at the outlet of the filtration stage 10.

[00104] When, preferably, the passage section of the enclosure 2 remains constant from the downstream face 14D of the filtration plate 14 to the upstream face 24U of the expansion plate 24, then the hydraulic diameter of outlet of the filtration stage Dh lOD, here the geometric outlet diameter of the filtration stage 10 in a cylindrical enclosure configuration with a circular base, is equal to the hydraulic diameter Dh_24U, here the geometric diameter, of the plate of relaxation 24.

[00105] The staging distance L 10 20 corresponds in practice to the distance which axially separates the outlets of the filtration orifices 15 from the inlets of the expansion orifices 25.

[00106] Said staging distance L 10 20 is advantageously short, or even zero, so as to minimize the aforementioned ratio L 10 20 / Dh lOD, and therefore to minimize losses load during the flow of the natural rubber coagulum from the filtration stage 10 to the expansion stage 20, to maximize the energy available for the expansion operation, and maximize the flow rate of the device 1.

[00107] Preferably, the distance L_10_20, called “staging distance” L_10_20, which axially separates the upstream face 24U of the expansion plate 24 from the downstream face 14D of the filtration plate 14 is less than or equal to 50 mm, for example between 10 mm and 40 mm, preferably less than or equal to 35 mm, for example between 30 mm and 35 mm, or even less than or equal to 20 mm.

[00108] These values in fact cover in practice most situations of use of the invention, and in particular situations of use which call upon enclosures 2 whose passage section typically presents, at the level of the downstream face 14D of the filtration plate 14, a hydraulic outlet diameter Dh lOD, and more particularly a geometric outlet diameter in the preferred case of an enclosure of circular section, which is between 300 mm and 400 mm, more particularly between 340 mm and 360 mm to correspond to the diameter values Dh_24U of the expansion plate 24 mentioned above.

[00109] According to a first possible configuration, the expansion plate 24 is attached to the filtration plate 14, so that the distance L 10 20, called “staging distance” L 10 20, which axially separates the outlet of the filtration orifices 15 of the inlet of the expansion orifices 25 is zero, as illustrated in Figures 7 A and 7B.

[00110] According to this first configuration, the upstream face 24U of the expansion plate 24 and the downstream face 14D of the filtration plate 14 are contiguous, so that each filtration orifice 15 communicates only with the expansion orifice(s) 25 on which said filtration orifice 15 actually opens, and therefore only with a part of the total number of expansion orifices 25 provided on the expansion plate 24. More preferably, each filtration orifice 15 thus communicates with a single expansion orifice 25 which is dedicated to said filtration orifice 15.

[00111] Preferably, the expansion plate 24 can then comprise a expansion orifice 25, and more preferably a single expansion orifice 25, facing each filtration orifice 15. Preferably said expansion orifice 25 is coaxial with said filtration orifice 15. [00112] The filtration plate 14 and the expansion plate 24 then have networks of orifices 15, 25, here cylindrical orifices 15, 25 with circular bases, which are superimposable, as is visible in Figure 7A, that is to say that the expansion orifices 25 and the filtration orifices 15 have the same spatial distribution on the passage section of the enclosure 2. In this way, it is possible to axially align each expansion orifice 25 with a and a single filtration orifice 15, and conversely, align each filtration orifice 15 with one and only one expansion orifice 25.

[00113] According to a second possible configuration, the upstream face 24U of the expansion plate 24 is axially distant from the downstream face 14D of the filtration plate 14, by a distance L 10 20 called “staging distance” L 10 20 which is non-zero, so that the filtration plate 15 and the expansion plate 25 define between them an interface chamber 35, as is visible in Figures 3 and 6B.

[00114] The interface chamber 35 thus places several, and more preferably all, of the filtration orifices 15, located at the inlet of said interface chamber 35, in communication with several, and more preferably with all, of the orifices expansion valve 25, located at the outlet of the interface chamber 35.

[00115] Said interface chamber 35 thus advantageously allows the flow of natural rubber coagulum which leaves the filtration plate 14 through the filtration orifices 15 to be distributed between the different expansion orifices 25.

[00116] Advantageously, the expansion plate 24 can then have a number of expansion orifices 25 which differs from the number of filtration orifices 15, and/or a spatial distribution of the expansion orifices 25, considered in a plane normal to the main axis Z2 and tangent to the upstream face 24U of the expansion plate 24, which differs from the spatial distribution of the filtration orifices 15 considered in a plane normal to the main axis Z2 and tangent to the downstream face 14D of the relaxation plate filtration 14.

[00117] Thus, it is possible to associate a freely chosen expansion plate 24 with a freely chosen filtration plate 14, and easily replace an expansion plate 24 having a first arrangement of expansion orifices 25 with another expansion plate 24 having a second arrangement of expansion orifices 25 different from the first arrangement, and/or replace a filtration plate 14 having a first arrangement of expansion orifices filtration 15 by another filtration plate 14 having a second arrangement of filtration orifices 15 different from the first arrangement of filtration orifices 15.

[00118] The presence of an interface chamber 35 therefore advantageously allows the user to freely define the pairs of plates 14, 24 used within the device 1, in particular depending on the nature of the natural rubber coagulum to be treated. .

[00119] The dimensioning of the interface chamber 35 will of course respect the criteria given above, in particular concerning the staging distance L 10 20, which corresponds here to the axial length of the interface chamber 35, and the ratio L 10 20 / Dh lOD, where the hydraulic filtration stage outlet diameter Dh lOD corresponds here to the hydraulic inlet diameter Dh_35 of said interface chamber 35, and more preferably to the geometric diameter, here constant, of the chamber interface 35 if we consider that said interface chamber 35 preferably has a right cylindrical shape with a circular base.

[00120] The interface chamber 35 will therefore induce relatively few pressure losses in the flow of the natural rubber coagulum, and will therefore be compatible with combining the filtration and dehydration functions within the same device. 1.

[00121] Advantageously, and in particular thanks to the aforementioned dimensioning, the interface chamber 35 will be passive, that is to say without a pump, because the flow of the natural rubber coagulum inside said chamber d The interface 35, from the downstream face 14D of the filtration plate 14 to the upstream face 24U of the expansion plate 24, will take place under the pressure which will have been imparted by the endless screw 3, upstream of the pressure plate. filtration 14.

[00122] As is particularly visible in Figures 3 and 6B, the expansion plate 24 may include, preferably in its center, at least one prop 36 which comes to bear against the downstream face 14D of the filtration plate 14 in order to define the staging distance L 10 20 and to reinforce the filtration plate 14 against the pressure exerted by the natural rubber coagulum pushed by the endless screw 3. [00123] The periphery of the expansion plate 24, here the second crown 26, may also include a rim forming a shoulder 37 which provides a seat for the rim of the filtration plate 14 in order, here again, to fix the distance of staging L 10 20.

[00124] An exemplary embodiment of device 1 could be as follows:

- filtration plate 14 having a hydraulic diameter Dh_14U = 360 mm and a thickness E14 = 40 mm and having 466 cylindrical filtration orifices 15 offering an individual passage section with a diameter Dh_15 = 12 mm, thus generating a cumulative filtration section S15_tot = 52,703 mm ² ;

- expansion plate 24 of hydraulic diameter Dh_24U = 350 mm, thickness E24 = 30 mm and having 114 cylindrical expansion orifices of circular base offering an individual passage section of a diameter Dh_25 = 5 mm, thus generating a section of cumulative relaxation S25_tot = 2,238 mm ² ;

- staging distance L 10 20 = 10 mm, for an interface chamber diameter Dh_35= 350 mm.

[00125] This arrangement could be completed by a stack of three sieves 13, 11 and 12 offering a mesh combination chosen from: 10/20/6, 10/30/6, 10/20/10 and 10/40/6 .

[00126] Of course, the invention also relates as such to a process for treating a natural rubber coagulum.

[00127] Said method can preferably be implemented by means of a device 1 as described in the above.

[00128] During the process according to the invention, by means of the same endless screw 3, the natural rubber coagulum is forced to pass successively through at least one sieve

11, 12, 13 belonging to a filtration stage 10, in order to filter said natural rubber coagulum in accordance with the filtration mesh Mi l defined by said at least one sieve 11,

12, 13, then through expansion orifices 25, provided in an expansion stage 20 which is located downstream of the filtration stage 10, to subject the natural rubber coagulum to an expansion which causes dehydration of said rubber coagulum. natural rubber by vaporization of at least part of the water contained in said natural rubber coagulum. [00129] Preferably, the natural rubber coagulum to which the process is applied initially has, when introduced into the endless screw 3, a water content which is greater than or equal to 12% by weight, for example included between 12% by weight, or even 15% by weight, low value, and 40% by weight, high value.

[00130] The process therefore makes it possible to directly treat a coagulated latex, and if necessary washed.

[00131] Preferably, according to the process according to the invention, the natural rubber coagulum is brought to a pressure of between 70 bar and 100 bar and to a temperature of between 110°C and 190°C, and for example between 140°C and 190°C, in steady state, at the entrance to the filtration stage 10, and therefore more particularly at the level of the upstream face 14U of the filtration plate 14.

[00132] We thus work at a temperature which is higher than the temperature ranges usually used in known filtration machines using gear pumps, namely 100°C to 110°C, which advantageously makes it possible to reduce the viscosity natural rubber coagulum, and therefore allows filtration at a lower pressure than that used in said known machines using gear pumps, which is of the order of 250 bar to 300 bar.

[00133] The endless screw 3 of the device 1 according to the invention is therefore sufficient in itself to reach the required pressure, while the fluidity of the natural rubber coagulum, favored by the high temperature, facilitates the successive passage through the filtration stage 10 then the expansion stage 20.

[00134] As an indication, the inventors have observed that, at the inlet of the expansion stage 20, and more particularly at the level of the upstream face 24U of the expansion plate 24, the residual pressure reigning in the enclosure 2 was generally lower by the order of 20 bar to 30 bar, or even 40 bar, than the pressure prevailing at the inlet of the filtration stage 10, so that said residual pressure reigning at the level of the upstream face 24U of the plate relaxation 24 could be between 30 bar and 70 bar. The residual temperature at the entrance to the expansion stage 20 could be between 140°C and 190°C. [00135] Of course, the invention is in no way limited to the only alternative embodiments described in the above, the person skilled in the art being in particular able to isolate or freely combine one or the other with each other. of the aforementioned characteristics, or to substitute equivalents for them.

Claims

1. Device (1) intended to filter and then dehydrate a natural rubber coagulum, said device being characterized in that it comprises:

- an enclosure (2) which extends along and around an axis called the “main axis” (Z2),

- an endless screw (3) which is rotatably mounted within a first stage of the enclosure (2) forming a sheath (4) so as to be able to convey the natural rubber coagulum from upstream to downstream of said sheath (4), along the main axis (Z2),

- a filtration stage (10) which forms a second stage of the enclosure (2) located axially downstream of the downstream end of the endless screw (3), in the extension of the sheath (4), and which comprises on the one hand at least one sieve (11, 12, 13) which defines a filtration mesh (Mi l), so that said at least one sieve (11, 12, 13) makes it possible to filter the natural rubber coagulum when the endless screw (3) forces the passage of said natural rubber coagulum through said at least one sieve (11, 12, 13), and on the other hand a first plate (14), called “filtration plate” ( 14), which has an upstream face (14U) forming a seat which supports the at least one sieve (11, 12, 13) against the pressure that the natural rubber coagulum exerts on said sieve, said plate of filtration (14) being provided with a first set of orifices (15), called “filtration orifices” (15), which allow the natural rubber coagulum having passed through the at least one sieve (11, 12, 13) to pass through said filtration plate (14), said filtration orifices (15) being arranged in such a way that they each have a passage section (S 15) which is greater than or equal to a predetermined reference section (S ref) , which is itself strictly greater than the passage section (SU) of the filtration mesh (Mi l) defined by the at least one sieve (11, 12, 13), and said filtration orifices (15) defining as a whole a total passage section whose minimum surface area, considered in a plane normal to the main axis (Z2), is called “cumulative filtration section” (S 15_tot),

- an expansion stage (20) which forms a third stage of the enclosure (2) located axially downstream of the filtration stage (10), in the extension of said filtration stage (10), and which comprises a second plate (24), called "relaxation plate" (24), which is provided with a second set of orifices (25), called "relaxation orifices" (25), which are arranged to receive the rubber coagulum natural from the filtration stage (10) and allow said coagulum of natural rubber to pass through said expansion plate (24) and to exit the enclosure (2) undergoing an expansion which causes vaporization of at least part of the water contained in the natural rubber coagulum, said orifices expansion valve (25) being for this purpose arranged in such a way that on the one hand said expansion orifices each have a passage section (S25) which is strictly less than the reference section (S ref) of the filtration orifices (15) ) and strictly greater than the passage section of the filtration mesh (SU), and that on the other hand said relaxation orifices (25) define as a whole a total passage section whose minimum surface area, considered in a normal plane to the main axis, and called “cumulative relaxation section” (S25_tot), is strictly lower than the cumulative filtration section (S15_tot), such that the endless screw (3) is able to force the rubber coagulum natural to pass successively through the filtration stage (10) then through the expansion stage (20).

2. Device according to claim 1 characterized in that the ratio between, in the numerator, the distance (L 10 20), called “staging distance” (L 10 20) which axially separates the upstream face (24U) of the plate relaxation of the downstream face (14D) of the filtration plate, and, in the denominator, the hydraulic outlet diameter of the filtration stage (Dh lOD), is between zero and 10%, where the hydraulic diameter is the equivalent diameter as calculated by the formula:

Dh = 4 x Area of the section considered / perimeter of the section considered in which the section considered corresponds here, for the calculation of the hydraulic outlet diameter of the filtration stage (Dh lOD), to the passage section of the enclosure (2) considered in a plane which is normal to the main axis and tangent to the downstream face (14D) of the filtration plate (14).

3. Device according to claim 1 or 2 characterized in that the distance (L 10 20), called “staging distance” (L 10 20) which axially separates the upstream face (24U) from the expansion plate (24) of the downstream face (14D) of the filtration plate (14) is less than or equal to 50 mm, preferably less than or equal to 35 mm, or even less than or equal to 20 mm.

4. Device according to one of the preceding claims characterized in that the filtration orifices (15) are formed by cylindrical holes of circular base whose minimum diameter is equal to or greater than a predetermined reference diameter (D ref), and in that the expansion orifices (25) are formed by cylindrical holes of circular base whose minimum diameter is strictly less than said reference diameter (D ref), preferably at least twice less, at least three times less, or even at least five times lower, said reference diameter (D ref).

5. Device according to one of the preceding claims characterized in that the expansion plate (24) is attached to the filtration plate (14), so that the distance (L 10 20), called “staging distance” (L 10 20), which axially separates the outlet of the filtration orifices (15) from the inlet of the expansion orifices (25) is zero.

6. Device according to claims 4 and 5 characterized in that the expansion plate (24) comprises a relaxation orifice (25) facing each filtration orifice (15), preferably coaxial with said filtration orifice (15).

7. Device according to one of claims 1 to 4 characterized in that the upstream face (24U) of the expansion plate (24) is axially distant from the downstream face (14D) of the filtration plate (14), d a distance (L_10_20) called “staging distance” (L_10_20) which is non-zero, so that the filtration plate (14) and the expansion plate (24) define between them an interface chamber (35) .

8. Device according to claim 7 characterized in that the expansion plate (24) has a number of expansion orifices (25) which differs from the number of filtration orifices (15), and/or a spatial distribution of the expansion orifices (25), considered in a plane normal to the main axis (Z2) and tangent to the upstream face (24U) of the expansion plate (24), which differs from the spatial distribution of the filtration orifices (15) considered in a plane normal to the main axis (Z2) and tangent to the downstream face (14D) of the filtration plate (14).

9. Device according to one of the preceding claims characterized in that the hydraulic diameter (Dh_25) of the smallest passage section of each of the expansion orifices (25) is less than or equal to 6 mm, preferably between 1 mm and 4mm.

10. Device according to one of the preceding claims characterized in that the hydraulic diameter (Dh_15) of the smallest passage section of each of the filtration orifices (15) is greater than or equal to 8 mm, preferably between 10 mm and 14 mm, for example equal to 12 mm.

11. Device according to one of the preceding claims characterized in that it is provided with a knife (30), preferably a rotating knife, which cuts into granules the dehydrated natural rubber coagulum which leaves the enclosure (2 ) through the expansion holes (25) of the expansion plate (24).

12. Process for treating a natural rubber coagulum during which, by means of the same endless screw (3), the natural rubber coagulum is forced to pass successively through at least one sieve (11, 12, 13) belonging to a filtration stage (10), in order to filter said natural rubber coagulum in accordance with the filtration mesh (Ml 1) defined by said at least one sieve (11, 1, 13), then through orifices expansion stage (25), provided in an expansion stage (20) which is located downstream of the filtration stage (10), to subject the natural rubber coagulum to an expansion which causes dehydration of said natural rubber coagulum by vaporization of at least part of the water contained in said natural rubber coagulum.

13. Method according to claim 12 characterized in that the natural rubber coagulum to which the process is applied initially has, when introduced into the endless screw (3), a water content which is greater than or equal to 12 % by weight, for example between 12% and 40% by weight.

14. Method according to claim 12 or claim 13 characterized in that the natural rubber coagulum is brought to a pressure of between 70 bar and 100 bar and to a temperature of between 110°C and 190°C, for example between 140°C and 190°C, at the entrance to the filtration stage (10).