Coupling system for a device for heat treatment by microwave radiation

Abstract

The present invention relates to a device for treating a product, which device comprises: - an enclosure intended to contain the product to be treated; - a waveguide arranged between the enclosure and a generator configured to produce incident electromagnetic waves; - an impedance matching unit configured to vary an acoustic impedance in the waveguide in order to match it to the acoustic impedance in the enclosure; and - a stirring unit inside the enclosure for stirring the product contained therein, characterised in that the device further comprises a coupling unit (8) mounted between the enclosure and the waveguide, which coupling unit comprises: - a widening module (81) configured to expand the electromagnetic wave transmission surface between the waveguide (3) and the enclosure (1); and - a shut-off module (82) configured to close, in a gas-tight manner, the through-hole inlet (121).

Description

[0001] Description

[0002] Title: COUPLING SYSTEM FOR MICROWAVE RADIATION HEAT TREATMENT DEVICE

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to the general technical field of devices for treating plant biomass of any plant species known to those skilled in the art, for example parts of vines.

[0005] The biomass to be treated can be dry or wet, and its treatment can be carried out in the presence (or not) of an aqueous solvent.

[0006] Such a treatment device allows the extraction of metabolites from plant biomass, said metabolites being able to be polyphenols or any other type of secondary metabolites known to those skilled in the art.

[0007] The metabolites thus extracted can be used in different application fields, such as biocontrol applications or cosmetic applications.

[0008] In the following, the device according to the invention will be described with reference to the treatment of a dry plant biomass rich in polyphenols (such as parts of vines) in the presence of an aqueous solvent, it being understood by those skilled in the art that the device according to the invention can be used for the treatment of any type of plant biomass - dry or wet - in the presence or absence of one (or more) aqueous solvent(s).

[0009] STATE OF THE ART

[0010] 1. Presentation

[0011] Plant biomass extracts rich in polyphenols are known to those skilled in the art. Many studies have focused on the extraction of biomass to obtain an extract rich in polyphenols, all of which have several drawbacks regarding the economic viability of the processes, such as low yields or very long extraction times, or limiting their use post-extraction, and in particular the use of toxic organic solvents.

[0012] Document WO 2018 / 115296 describes a process for preparing a dry plant biomass extract, rich in polyphenols, comprising:

[0013] A step of extracting the dry biomass by bringing it into contact with an aqueous solvent, and

[0014] A step of recovery of the aqueous phase enriched in polyphenols.

[0015] During the extraction stage, the plant biomass / aqueous solvent mixture is treated, at a pressure between 50 and 950 mbar (5,000 and 95,000 Pa), by applying to the mixture:

[0016] Electromagnetic waves with a frequency between 10 MHz and 100 GHz, preferably between 433 MHz and 30 GHz, and even more preferably between 915 MHz and 28 GHz, and

[0017] From a mixing of the mixture.

[0018] The present invention aims to propose a heat treatment device allowing the implementation of the method according to WO 2018 / 115296. In particular, the present invention relates to a device for treating a product for the extraction of a substance of interest, the treatment device being configured to:

[0019] Stir the product, and

[0020] Apply to the product electromagnetic waves of frequency between 10MHz and 100GHz, preferably between 433MHz and 30GHz, and even more preferably between 915MHz and 28GHz. 2. Problems associated with the use of electromagnetic waves

[0021] 2.1 Minimizing the risks of device degradation

[0022] As illustrated in Figure 1, such a device is composed of:

[0023] From an enclosure 1 containing the product 2 to be treated,

[0024] From a brewing unit housed in the enclosure, and

[0025] From a waveguide 3 connected between the enclosure 1 and a generator 4 of electromagnetic waves.

[0026] Waveguide 3 transmits the electromagnetic waves generated by generator 4 to enclosure 1.

[0027] A part of the incident electromagnetic waves transmitted by the generator 4 (“incident waves”) via the waveguide 3 is absorbed by the product 2 to be treated, and another part of these electromagnetic waves is reflected towards the generator 4 (“reflected waves”).

[0028] If the power of the reflected waves is too high, they can damage or even destroy the generator 4. To protect the generator 4, a circulator (not shown) including a heat transfer fluid can be associated with the generator 4. This circulator converts the reflected waves into heat and dissipates this heat outside the generator 4.

[0029] However, the interactions between the incident waves (emitted by generator 4) and the reflected waves (reverberated by enclosure 1) create a phenomenon called a "standing wave" in waveguide 3, with a local increase in the intensity of the electric field.

[0030] In the case of high-power electromagnetic waves, this increase in the intensity of the electric field can be significant and reach a value that triggers an electric arc.

[0031] Such an electric arc can cause deterioration (or even destruction) of the treatment device. To limit the risks of deterioration of the treatment device, it has already been proposed to integrate an impedance matching unit 5 into the waveguide 3 (for example adjustable elements such as metal plungers integrated into the waveguide 3).

[0032] Indeed, the quantity of reflected waves depends on the difference between the input impedance in enclosure 1, and the impedance of the power transmission line (for example waveguide 3): when the input impedance of enclosure 1 is equal to the impedance of the power transmission line (waveguide 3 for example), the quantity of reflected waves is substantially zero.

[0033] However, the input impedance of speaker 1 varies depending in particular on:

[0034] Dielectric characteristics of product 2 to be treated,

[0035] From the quantity of product 2,

[0036] From the temperature of product 2,

[0037] But also the physical or chemical evolution of product 2 during treatment.

[0038] Thus, the input impedance of enclosure 1 can not only vary from one product to another, from one quantity of product to another, but also over time during the processing of a given quantity of a given product.

[0039] The impedance matching unit 5 allows an operator to locally adjust the impedance to match the input impedance of the enclosure 1. The quantity of waves reflected towards the generator 4 is thus minimized from the plane where the impedance matching unit 5 is placed. To take into account the variation in input impedance of the enclosure 1 during the processing of a product, the generator 4 is equipped with a measuring sensor (not shown) of a parameter representative of the quantity of reflected waves. Based on the reflected power indication of the generator 4 and by acting on adjustment means of the impedance matching unit 5, the operator can locally correct the impedance to match the impedance of the transmission line located upstream of the impedance matching unit 5.

[0040] The impedance matching unit 5 acts, in a way, as a "non-return valve" for the reflected wave created at the input of enclosure 1. The impedance matching unit 5 does not "destroy" the reflected wave but sends it back to enclosure 1. Under these conditions, a standing wave phenomenon is established between the matching unit 5 and the input of enclosure 1. The level of standing wave will be all the more intense as the difference in input impedance of enclosure 1 and the impedance of the power transmission line is significant. The greater this difference in impedance, the greater the risks of arcs and energy losses in the section of transmission line located between the input of enclosure 1 and the impedance matching unit 5 will be. This phenomenon will then limit the transmission power level of generator 4 to avoid arcs and energy losses.

[0041] To achieve a high power level (especially greater than 30kW) transmitted in enclosure 1 and thus ensure the expected productivity of the device, it is necessary to work on the input elements of enclosure 1. The objective is to determine geometric parameters of the arrival zone of the electromagnetic waves in the input plane of enclosure 1 so that the value of the input impedance (enclosure loaded with the product to be treated) is as close as possible to that of the transmission line. Under these conditions, the power level can be maximized. The role of the impedance matching unit 5 remains limited to impedance corrections related to variations in temperature, volume, and evolution of the product during treatment, even in conditions where the product to be treated has only low dielectric losses.

[0042] An aim of the present invention is to propose a solution for limiting, at high powers, the risks of degradation of the treatment device due to the untimely generation of an electric arc, in particular when the device is associated with a generator with a power greater than 30kW.

[0043] 2.2 Minimization of electromagnetic leakage levels

[0044] The use of electromagnetic waves for industrial, scientific and medical applications is subject to compliance with several standards for the protection of people and the protection of communications networks:

[0045] The EN 50413 standard for human exposure,

[0046] EN 50499 standard for worker exposure, EN 55011 standard for the protection of telecommunications networks.

[0047] The use, on an industrial scale, of electromagnetic waves with a frequency equal to 915 MHz requires in particular compliance with standard NE 55011. This stipulates that the electromagnetic radiation emitted towards the outside, by a device generating electromagnetic waves with a frequency equal to 915 MHz, must be lower than a threshold value of - 40 dB microvolt per meter, at 30 m from said device.

[0048] This helps to avoid disruptions to telecommunications networks.

[0049] Any exceeding of this threshold value may be sanctioned, without notice, by the immediate shutdown of the device deemed to be faulty.

[0050] One of the aims of the present invention is to propose a device for heat treatment using electromagnetic waves which makes it possible not to exceed the levels of electromagnetic leakage imposed by standard EN 55011.

[0051] SUMMARY

[0052] To this end, the invention proposes a device for treating plant biomass, the treatment device comprising:

[0053] An enclosure intended to contain the plant biomass to be treated, the enclosure comprising a lower partition, an upper partition and at least one side partition extending between the upper and lower partitions, at least one of the partitions including a through inlet,

[0054] A waveguide connected to the through-inlet for the circulation, towards the interior of the enclosure, of incident electromagnetic waves produced by a generator, An impedance matching unit configured to vary an impedance in the waveguide in order to match said impedance in the waveguide to an input impedance of the enclosure,

[0055] A stirring unit for stirring the plant biomass contained in the enclosure, characterized in that the device further comprises a coupling unit, mounted between the enclosure and the waveguide, said coupling unit comprising:

[0056] An expansion module configured to expand the electromagnetic wave transmission surface between the waveguide and the enclosure, and

[0057] A sealing module configured to close the through inlet in a gas-tight manner.

[0058] In the context of the present invention, the term "connected to" means a first element directly connected to a second element, or indirectly connected to the second element, in particular by means of a third element arranged between the first and second elements.

[0059] Preferred, but not limiting, aspects of the present invention include:

[0060] The widening module may comprise: o A conduit connected to the waveguide, and o A pyramidal structure with a truncated top connected to the closure module, said structure extending in the extension of the rectangular conduit;

[0061] The pyramidal structure may comprise: o Four trapezoidal-shaped side walls defining a truncated pyramid with a polygonal base, in particular rectangular, o A separating blade extending between internal faces of a pair of opposite walls among the four side walls, o A cylindrical crosspiece extending between the internal faces of the pair of opposite walls;

[0062] The four side walls define: o A small rectangular base fixed to the end of the conduit, and o A large rectangular base intended to come opposite the closure module, the length of the large rectangular base being equal to the length of the small rectangular base, and the width of the large rectangular base being greater than the width of the small rectangular base;

[0063] The conduit may comprise: o A hollow tube with a rectangular profile made of a non-magnetic electrically conductive material, such as stainless steel or aluminum, o A rectangular flange at one end of the tube opposite the truncated pyramid, the flange being connected to the waveguide;

[0064] The closure module may comprise: o A cylindrical box fixed to the enclosure by a first end and fixed to the widening module by a second end, said box being made of a non-magnetic electrically conductive material, such as stainless steel or aluminum, and o A plate fixed to the first end of the cylindrical box, and mounted in a gas-tight manner on the through-inlet mouth, said plate being made of a material transparent to electromagnetic waves such as Teflon®;

[0065] The shutter module may further comprise a movable lens housed in the cylindrical box, said lens being capable of moving in translation along an axis of revolution of the cylindrical box between two extreme positions to vary the distance separating the plate from the movable lens.

[0066] DETAILED DESCRIPTION OF THE INVENTION

[0067] An example of a device for processing a product will now be described with reference to the figures. In these different figures, equivalent elements are designated by the same numerical reference.

[0068] 1. General The treatment device described below allows the preparation of an extract rich in metabolites (polyphenols and / or other secondary metabolite(s)) by extraction of a dry (or wet) biomass with (or without) an aqueous solvent.

[0069] According to the invention, the term "aqueous solvent" means water or an aliphatic alcohol / water mixture, in particular ethanol / water.

[0070] The plant biomass may, for example, be a biomass containing polyphenols, in particular trans-resveratrol, trans-s-viniferin, trans-piceatannol and trans-vitisin. The person skilled in the art is familiar with this biomass originating from plants known to contain these polyphenols, used alone or in mixtures, generally dicotyledonous plants such as vines, tea or even Japanese knotweed, more particularly vines.

[0071] When the biomass is dry, that is to say obtained by drying the aforementioned plants, it may consist of dry parts of plants of the genus Vitis, in particular Vitis vinifera Vitis labrusca, Vitis riparia, Vitis rupestris, Vitis berlandieri, Vitis amurensis, Vitis coignetiae, Vitis vulpina, Vitis acerifolia, Vitis aestivalis, Vitis rotundifolia and more particularly Vitis vinifera. According to an advantageous embodiment of the invention, the dry biomass comprises or consists of vine shoots.

[0072] Alternatively, the biomass can be wet. In this case, the water molecules contained in the biomass can eliminate the need for an aqueous solvent.

[0073] This device allows the implementation of a process for extracting metabolites such as polyphenols.

[0074] This process is characterized by the combination of at least two constraints applied to plant biomass (dry or wet) in the presence (or not) of an aqueous solvent:

[0075] (i) electromagnetic waves with a frequency between 10 MHz and 100 GHz, preferably between 433 MHz and 30 GHz, and even more preferably between 915 MHz and 28 GHz, and (ii) mixing, and / or

[0076] (iii) a depression or pressure of 50 to 950 mbar.

[0077] In the following, the device according to the invention will be described with reference to the treatment of a mixture composed of a dry biomass and an aqueous solvent, it being understood by those skilled in the art that this device can be used with other types of products.

[0078] 2. Processing device

[0079] Referring to Figure 2, an example of a treatment device according to the invention is illustrated. The device comprises:

[0080] - A speaker 1,

[0081] - A 3 waveguide,

[0082] - A 5 impedance matching unit,

[0083] - A 7 brewing unit, and

[0084] - A coupling unit 8.

[0085] As will become apparent below, the presence of a coupling unit 8 allows the processing device to operate at high operating powers (in particular 100 kW) with minimal risk of creating an electric arc; it is furthermore designed to limit the rise of humidity outside the enclosure 1 in the waveguide 3 and to maintain the enclosure 1 under pressure or depression.

[0086] The enclosure 1 is intended to be connected to a generator 4 via the waveguide 3, this generator 4 being able to be integrated or dissociated from the processing device.

[0087] The generator 4 is configured for the emission of electromagnetic waves with a frequency between 10 MHz and 100 GHz, preferably between 433 MHz and 30 GHz, and even more preferably between 915 MHz and 28 GHz, corresponding to waves in the microwave domain. Those skilled in the art will be able to choose the frequency most suited to the implementation of the method, in particular depending on the biomass, to optimize the extraction process. Advantageously, the frequency of the electromagnetic waves ranges from 915 MHz to 2.45 GHz. Advantageously, the frequency of the electromagnetic waves will be chosen according to known industrial devices for generating electromagnetic waves on an industrial scale, in particular generators of electromagnetic waves with frequencies below 1500 MHz, more advantageously around 915 MHz.

[0088] The person skilled in the art will also be able to choose the power of the electromagnetic waves best suited to the biomass and the extracts obtained. The power of the electromagnetic waves advantageously ranges from 300 W to 10 MW, more advantageously from 500 W to 200 kW, and even more advantageously from 1 kW to 100 kW. This power will be chosen in particular according to the volume to be treated and the time required for extraction. For example, the power of the electromagnetic waves can be chosen according to the following ratio: for 1 kg of material to be extracted, the power of the electromagnetic waves is from 1 to 10 kW, ideally 2 to 6 kW.

[0089] 2.1 Speaker

[0090] Enclosure 1 makes it possible to define an enclosed space in which it is possible to generate a depression (or an overpressure), that is to say a space in which it is possible to reduce (or increase) the pressure to a value lower (or higher) than atmospheric pressure, in particular to a pressure between 50 and 950 mbar.

[0091] Enclosure 1 is configured to withstand pressures above or below atmospheric pressure. Furthermore, Enclosure 1 is configured to resist corrosion. Finally, Enclosure 1 is configured to withstand temperatures above or equal to 200°C.

[0092] Such an enclosure 1 may have different shapes and be made from different conductive materials to ensure this function. In the embodiment illustrated in Figure 2, the enclosure 1 has a cylindrical shape, and is essentially made of stainless steel plates. This sealed enclosure 1 comprises:

[0093] A lower partition 11 forming a bottom of the enclosure 1,

[0094] A curved upper partition 12 forming a ceiling of the enclosure 1, and

[0095] One (or more) vertical side partition(s) 13 extending between the upper and lower partitions 11, 12.

[0096] The enclosure can have a volume between 0.1 m 3 and 10 m 3 The power of the electromagnetic waves generated by the treatment device advantageously allows extraction to be carried out in such enclosure volumes.

[0097] The lower partition 11 may be flat or concave towards the inside of the enclosure 1. It comprises an orifice 111 to allow an operator to access the inside of the enclosure 1. In operation, this orifice 111 is closed by a hatch (or door) 112 normally locked in a sealed manner by any technique known to those skilled in the art, for example by bolting the hatch 112 to the lower partition 11, a sealing gasket (for example made of electrically conductive rubber) being mounted between the orifice 111 and the facing hatch 112 (i.e. between the edges of the orifice and the edges of the hatch facing each other). Of course, the lower partition 11 may comprise more than one orifice 111 which can be closed by a hatch 112. Furthermore, the reader will appreciate that this (or these) orifice(s) 111 which can be closed by one or more hatch(es) 112 may be arranged in a partition 12, 13 other than the lower partition 11.

[0098] The upper partition 12 comprises a through inlet 121 at which the waveguide 3 is connected. Thus, the incident waves (electromagnetic waves produced by the generator 4) circulating in the waveguide 3 emerge in the enclosure 1 through the inlet 121. Of course, this inlet 121 can be provided in the lateral partition 13 (or in the lower partition 11) rather than the upper partition 12. The upper partition 12 also comprises a hole 122 for the passage of a shaft 71 of the mixing unit 7.

[0099] The enclosure 1 may comprise a hole to which a pump (not shown) is connected for generating a vacuum in the enclosure 1. Such an enclosure 1 being known to those skilled in the art, it will not be described in more detail below.

[0100] 2.2 Waveguide

[0101] Waveguide 3 allows the circulation of electromagnetic waves produced by the generator towards the interior of enclosure 1.

[0102] The waveguide 3 may consist of a parallelepiped tube of rectangular cross-section which can advantageously propagate electromagnetic waves in TE01 mode including:

[0103] A first end capable of being connected to the generator 4, this first end defining an opening for receiving the electromagnetic waves produced by the generator 4;

[0104] A second end capable of being connected to the enclosure 1, this second end defining an opening for diffusing electromagnetic waves inside the enclosure 1.

[0105] Such a waveguide 3 is made of a material impervious to electromagnetic waves, for example of a conductive material (non-magnetic metal) such as stainless steel or aluminum.

[0106] 2.3 Impedance Matching Unit

[0107] The impedance matching unit 5 allows the impedance in the waveguide 3 to be locally adjusted to match the input impedance in the enclosure 1. The power transfer between the generator 4 and the enclosure 1 is thus optimized.

[0108] More specifically, the impedance matching unit 5 allows impedance correction to bring the power level of the residual reflected waves (electromagnetic waves reverberated by the enclosure 1) to the lowest level. In particular, the impedance matching unit 5 allows the power level of the reflected waves to be corrected as a function of the evolution (during treatment) of the dielectric characteristics of the mixture (dry biomass + aqueous solvent) placed in the enclosure 1.

[0109] Thus, in accordance with the rules of the art in the field of power transfers, an impedance adaptation is carried out in order to avoid the return of reflected power at the input of enclosure 1 to generator 4.

[0110] This impedance adaptation can be achieved by acting on the adjustment elements of the impedance adapter 5 as a function of data transmitted by measuring probes (not shown) of the energy reflected by the enclosure 1.

[0111] These measuring probes can be integrated into generator 4.

[0112] The impedance matching unit 5 may be of any type known to those skilled in the art.

[0113] Moreover, just as in the prior art, the processing device may also comprise a circulator 9 between the waveguide 3 and the generator 4 to absorb the reflected waves which would otherwise be reinjected into the generator 4. This makes it possible to ensure protection of the magnetron (not shown) installed in the generator 4.

[0114] Such an impedance matching unit 5 being known in the prior art, it will not be described in more detail below.

[0115] 2.4 Brewing unit

[0116] The mixing unit 7 allows the biomass / solvent mixture to be mixed to be treated in order to homogenize the microwave treatment of this mixture.

[0117] The stirring unit 7 comprises a shaft and two (or four) blades at one end of the shaft, the other end of the shaft being connected to a motor M to induce rotation of the shaft and the blades. Preferably, stirring is carried out by rotating the blades at a rotation speed ranging from 3 to 20 revolutions per minute.

[0118] 2.5 Coupling Unit

[0119] To support the powers used (30 to 40 kW, or even 100 kW) in the preparation of an extract rich in polyphenols by extraction of a dry biomass with an aqueous solvent, the treatment device comprises a coupling unit 8. This coupling unit 8 is positioned between the waveguide 3 and the inlet mouth 121 located directly on the enclosure 1.

[0120] The coupling unit 8 makes it possible to minimize - in a plane P containing the inlet mouth 121 - the power level of the reflected waves so that it remains lower than 10% max of the power of the incident waves emitted by the generator 4.

[0121] With reference to Figures 3 to 5, the coupling unit 8 comprises a widening module 81 configured to expand the transmission surface of the electromagnetic waves between the enclosure 1 and the waveguide 3, without losing the propagation mode TE01 of said electromagnetic waves. This makes it possible to limit the intensity of the electric field produced by the electromagnetic waves at this transmission surface.

[0122] The coupling unit 8 also comprises a sealing module 82 sized to withstand the depression or pressure of the enclosure 1 and prevent any rise in humidity and any risk of condensation in the waveguide 3. It also allows the pressure or depression to be maintained in the enclosure.

[0123] 2.5.1 Widening module

[0124] The 81 expansion module includes:

[0125] A rectangular conduit 811 intended to be connected to the waveguide 3, A pyramidal structure 812 with a truncated top (hereinafter referred to as a “truncated pyramid”) in the extension of the rectangular conduit 811, the structure being intended to be connected to the shutter module 82.

[0126] The dimensions (Small side A, Large side A') of the rectangular conduit 811 in cross section are identical to the dimensions of the waveguide 3 in cross section. The rectangular conduit is hollow and is made of a material impervious to electromagnetic waves, for example of an electrically conductive material (non-magnetic metal) such as stainless steel or aluminum. The conduit 811 comprises a rectangular flange 813 at its end opposite the truncated pyramid 812. This flange 813 is connected to that of the waveguide 3 by bolting.

[0127] The truncated pyramid 812 allows to enlarge the transmission surface of the electromagnetic waves while preserving their wave propagation mode (TE01) and the impedance adaptation (limitation of the power reflected in this plane). The truncated pyramid 812 includes:

[0128] Four side walls 814 defining an internal volume,

[0129] A separating blade 815 in the internal volume,

[0130] A cylindrical 816 crosspiece in the internal volume,

[0131] An 817 ring skirt.

[0132] The four side walls 814 are trapezoidal in shape and are welded together to form the truncated pyramid with a polygonal base, in particular rectangular. The opposite edges of the four side walls 814 define:

[0133] A small rectangular base 8141 mounted at the end of the conduit 811 opposite the rectangular flange 813, and

[0134] A large rectangular base 8142 intended to come opposite the shutter module 82.

[0135] The small base 8141 of the truncated pyramid is fixed to the end of the conduit 811 (opposite the rectangular flange) by welding or brazing. The large base 8142 is fixed to the annular skirt 817. This annular skirt 817 is intended to be fixed to the closure module 82 by bolting, welding and / or brazing.

[0136] The dimensions of the small base 8141 are identical to the dimensions (Small side A, Large side A') in cross-section of the conduit 811. The dimensions of the large base 8142 define a surface area (transmission surface area) larger than the surface area defined by the dimensions of the small base 8141.

[0137] In particular, if we consider that the electromagnetic waves emitted by the generator 4 propagate in a propagation plane inside the waveguide 3, then:

[0138] The length A' of the large base 8142 is equal to the length A' of the conduit 811 (and therefore of the waveguide 3), this dimension being perpendicular to the plane of propagation of the electromagnetic waves,

[0139] The width 2 A of the large base 8142 is equal to twice the width A of the conduit 811 (and therefore of the waveguide 3), this dimension being parallel to the plane of propagation of the electromagnetic waves.

[0140] The fact that the length A' is preserved makes it possible to preserve the TE01 mode of propagation of the electromagnetic waves emitted by the generator 4. The fact that the width 2A is doubled makes it possible to increase the transmission surface of the electromagnetic waves and thus to lower the electric field intensity.

[0141] The separating blade 815 extends between the internal faces of a pair of opposite side walls (the side walls defining the width of the truncated pyramid), perpendicular to the propagation plane of the electromagnetic waves. It is made of an electrically conductive material (non-magnetic metal) such as stainless steel, brass or aluminum, and may have the same thickness as the walls of the waveguide 3. This separating blade 815 subdivides the internal volume defined between the side walls into two adjacent compartments. The separating blade 815 makes it possible to split the propagation plane of the electromagnetic waves into two secondary planes inside the compartments. At the level of the large base 8142, the cross-sectional dimensions of each of the compartments are equal to the cross-sectional dimensions of the waveguide. Thus, the transmission surface of the electromagnetic waves is doubled at the level of the large base.

[0142] The cylindrical crosspiece 816 is mounted between the internal faces of the pair of side walls 814, on the edge of the separating blade 815 opposite the large base 8142. The crosspiece 816, and in particular its cylindrical shape, allows, when splitting the propagation plane, not to modify the propagation mode of the electromagnetic waves while protecting against the creation of an arc.

[0143] The use of a modeling tool makes it possible to establish the manufacturing dimensions of the 81 expansion module which ensure good impedance matching and optimal splitting of electromagnetic waves. These dimensions include:

[0144] The cross-sectional length and width of the conduit and truncated pyramid, as previously indicated,

[0145] The height of the truncated pyramid (distance between the small and large bases), The distance between the crosspiece and the small base of the truncated pyramid.

[0146] At the output of the widening module, a two-way structure is obtained, each propagating electromagnetic waves having a power equal to half the power of the electromagnetic waves coming from the generator 4. This makes it possible to limit the risks of electric arc formation at the inlet mouth 121.

[0147] This solution makes it possible to double, at the exit of the truncated pyramid, the height of passage of the electromagnetic waves while controlling the propagation mode. The field intensity is then significantly lowered at each of the two exits of the truncated pyramid.

[0148] 2.5.2 Shutter Module

[0149] The 82 shutter module allows:

[0150] On the one hand to make the enclosure 1 gas-tight at the inlet mouth 121, and on the other hand to adjust the impedance in the coupling unit 8 to the input impedance of the enclosure 1.

[0151] The shutter module 82 comprises a cylindrical housing 821, a plate 822, and a movable lens 823.

[0152] The cylindrical box 821 extends between the inlet mouth 121 of the enclosure 1 and the large base 8142 of the widening module 81. The material constituting the box is a material reflecting electromagnetic waves, such as an electrically conductive non-magnetic material, for example of the stainless steel or aluminum type.

[0153] The cylindrical box 821 provides metallic continuity between the widening module 81 and the enclosure 1. It allows the circulation of electromagnetic waves between the truncated pyramid 812 and the inlet mouth 121. The cylindrical box 821 is configured to contain the plate 822 and the lens 823 movable in translation. More precisely, the plate 822 extends at the end of the cylindrical box 821 in contact with the enclosure 1, and the movable lens extends 823 between the two ends of the cylindrical box 821.

[0154] The plate 822 is fixed on the inlet mouth 121 to close the enclosure 1 in order to allow the generation of a depression or a pressure in the enclosure 1. The plate 822 is non-absorbent of electromagnetic waves (or absorbs them weakly). The plate 822 comprises for example a Teflon® (or possibly quartz) disc mounted perpendicular to the direction of propagation of the electromagnetic waves.

[0155] The thickness of the plate 822 is defined as a function of the value of the depression and the pressure likely to be generated in the enclosure 1, and its diameter is a function of the dimensions of the large base 8142, the width 2A and the length A' of which have been determined by modeling.

[0156] The movable lens 823 makes it possible to adapt the impedance in the coupling unit 8 to the input impedance of the enclosure 1, taking into account the presence of the shutter 822. The risks of electric arcing at the input mouth 121 are thus limited. The movable lens 823 is made of a material that does not absorb electromagnetic waves, such as Teflon®.

[0157] The movable lens 823 is able to move in translation inside the cylindrical box 821 between two extreme positions, the movable lens 823 being closer to the plate 822 in one of the extreme positions than in the other of the extreme positions. This makes it possible to vary the distance separating the plate 822 from the movable lens 823, and thus to limit the impedance differences between the coupling unit 8 and the input of the enclosure 1.

[0158] The use of a modeling tool makes it possible to establish the manufacturing dimensions of the shutter module 81 which ensure a minimization of the quantity of electromagnetic waves reflected by the enclosure 1. These dimensions are in particular:

[0159] The thickness “e” of the movable lens 823,

[0160] The distance “d” between the movable lens 823 and the plate 822,

[0161] The height “h” and the internal diameter “D” of the cylindrical box 821.

[0162] 2.6 Conclusions

[0163] The treatment device described above has the advantage of meeting the various standards for the protection of people and communications networks, and in particular the EN 55011 standard for the protection of telecommunications networks, the criteria for which are very strict.

[0164] The coupling unit 8 described above has the advantage of being self-adapted in impedance. This coupling unit 8 makes it possible to limit the risks of electric arc formation at the inlet mouth 121 of the enclosure 1. The impedance adaptation unit 5 is mainly used only to take into account the variations in impedance due to the evolution of the dielectric characteristics of the mixture (dry biomass + aqueous solvent) during the treatment of this mixture.

[0165] The reader will understand that numerous modifications can be made to the invention described above without materially departing from the new teachings and advantages presented herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0166] Other advantages and characteristics of the invention will emerge more clearly from the following description of several variant embodiments, given as non-limiting examples, from the appended drawings in which:

[0167] - Figure 1 is a general schematic representation of a device for treating a product using electromagnetic waves,

[0168] - Figure 2 is a schematic representation of a treatment device according to the invention,

[0169] - Figure 3 is a schematic representation of a coupling unit of the processing device illustrated in Figure 2,

[0170] - Figure 4a is a schematic perspective representation of an expansion module of the coupling unit illustrated in Figure 3, - Figure 4b is a schematic front representation of the expansion module illustrated in Figure 4a,

[0171] - Figure 5 is a schematic representation of a shutter module of the coupling unit illustrated in Figure 3.

Claims

CLAIMS 1. Device for treating plant biomass, the treatment device comprising: An enclosure (1) intended to contain the plant biomass to be treated, the enclosure (1) comprising a lower partition (11), an upper partition (12) and at least one lateral partition (13) extending between the upper and lower partitions (11, 12), at least one of the partitions (11, 12, 13) including a through inlet mouth (121), A waveguide (3) connected to the through inlet mouth (121) for the circulation, towards the interior of the enclosure (1), of incident electromagnetic waves produced by a generator (4), An impedance matching unit (5) configured to vary an impedance in the waveguide (3) to match said impedance in the waveguide (3) to an input impedance of the enclosure (1), A stirring unit (7) for stirring the plant biomass contained in the enclosure (1), characterized in that the device further comprises a coupling unit (8), mounted between the enclosure (1) and the waveguide (3), said coupling unit comprising: An expansion module (81) configured to expand the electromagnetic wave transmission surface between the waveguide (3) and the enclosure (1), and A sealing module (82) configured to close, in a gas-tight manner, the through inlet mouth (121).

2. Device according to claim 1, in which the widening module (81) comprises: A conduit (811) connected to the waveguide (3), and A pyramidal structure (812) with a truncated top connected to the closure module (82), said structure extending in the extension of the rectangular conduit (811).

3. Device according to claim 2, in which the pyramidal structure (812) comprises: Four side walls (814) of trapezoidal shape defining a truncated pyramid with a polygonal base, in particular rectangular, A separating blade (815) extending between inner faces of a pair of opposing walls among the four side walls (814), A cylindrical crosspiece (816) extending between the inner faces of the pair of opposing walls.

4. Device according to any one of claims 2 or 3, in which the four side walls (814) define A small rectangular base (8141) fixed to the end of the conduit (811), and A large rectangular base (8142) intended to come opposite the closure module (82), the length of the large rectangular base (8142) being equal to the length of the small rectangular base (8141), and the width of the large rectangular base (8142) being greater than the width of the small rectangular base (8141).

5. Device according to any one of claims 2 to 4, in which the conduit (811) comprises: A hollow tube with a rectangular profile made of a material that reflects electromagnetic waves, such as stainless steel or aluminum, A rectangular flange (813) at one end of the tube opposite the truncated pyramid (812), the flange (813) being connected to the waveguide (3).

6. Device according to any one of claims 1 to 5, in which the closure module (82) comprises: A cylindrical box (821) fixed to the enclosure by a first end and fixed to the widening module (81) by a second end, said box being made of a material reflecting electromagnetic waves, such as stainless steel or aluminum, and A plate (822) fixed on the first end of the cylindrical box (821), and mounted in a gas-tight manner on the through inlet mouth (121), said plate being made of a material transparent to electromagnetic waves such as Teflon®.

7. Device according to claim 6, in which the shutter module (82) further comprises a movable lens (823) housed in the cylindrical box (821), said lens being able to move in translation along an axis of revolution of the cylindrical box (821) between two extreme positions vary the distance separating the plate (822) from the movable lens (823).

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