Microwave reactor for continuous treatment of a flowing fluid medium by microwaves

Description

[0001] The present invention relates to a microwave reactor for continuous microwave treatment of a flowing fluidic medium, as well as to an associated microwave installation and a method for continuous microwave treatment of a flowing fluidic medium.

[0002] The invention lies in the field of continuous microwave treatment of a flowing fluidic medium, such as a liquid medium, a viscous medium, a pasty medium, a two-phase liquid / solid or liquid / gas mixture.

[0003] The invention finds a favorite, but not limiting, application in the continuous microwave heat treatment of pumpable products, in particular agri-food products and especially homogeneous liquid products or products with regularly distributed pieces in a sufficiently carrier phase.

[0004] With reference to the figure 1 , it is known from the prior art to employ a microwave reactor RM, generally called a "downstream" reactor, comprising a flow tube TE made of microwave-transparent material, a waveguide GO connected to a microwave generator and coupled to the flow tube TE for continuous microwave treatment of the fluidic medium, and an enclosure EN inside which the flow tube TE extends at least in part, such an enclosure EN being made of a microwave-reflective material.

[0005] As seen on this figure 1 It is classic to have, on the one hand, a flow tube TE extending longitudinally along a flow axis and, on the other hand, a waveguide GO having a rectangular section with two long sides GC (i.e. sides with the largest dimension) and two short sides PC (i.e. sides with the smallest dimension), where the long sides GC of the waveguide GO are orthogonal to the flow axis, while the short sides PC of the waveguide GO are parallel to the flow axis.

[0006] Such a downstream reactor, also described, for example, in US document 2006 / 0213759, proves relatively effective for fluidic media with low absorption, that is, media with a low dielectric loss coefficient (or a low loss angle, a low loss tangent, a low delta tangent, or a low loss factor). Indeed, with a fluidic medium with low absorption, microwaves pass through the fluidic medium quite easily because the dielectric losses are low and, moreover, the absorbed field in the fluidic medium is fairly homogeneous.

[0007] On the other hand, such a "downstream" reactor proves to be relatively inefficient for absorbing, or even highly absorbing, fluidic media, i.e. having a high dielectric loss coefficient (or a high loss angle, a high loss tangent, a high delta tangent or a high loss factor), such as water-based media, certain solvents for extraction, agri-food products such as compote, certain chemicals, etc.

[0008] Indeed, as depicted on the figure 3 The electric field (Ey) in a rectangular waveguide is typically distributed parallel to the shorter sides (b) of the waveguide and is maximum at the midpoints of the longer sides (a) of the waveguide. Thus, in the case of a downstream reactor with an absorbing fluid medium, the electric field will, on the one hand, have difficulty penetrating the medium and, on the other hand, reflect the waves because the electric field will encounter a boundary and a very abrupt change in dielectric losses at the flow tube because: the electric field is parallel to the short sides PC of the GO waveguide and is therefore parallel to the flow tube TE in which the fluidic medium flows, and the electric field is maximum at the midpoints of the long sides GC of the GO waveguide, i.e. at the location of the flow tube TE.

[0009] Consequently, in a downstream reactor, the electric field acts as if it were a mirror, being largely, or at least to a significant extent, reflected back towards the microwave generator. The absorbed portion of the field is absorbed only on the side of the microwave generator, as the waves cannot penetrate the absorbing fluid medium. As a result, this downstream reactor configuration creates a localized hot spot, making heating heterogeneous and inefficient.

[0010] The state of the art can also be illustrated by the teachings of document EP 1 397 939 which discloses a microwave reactor conforming to the preamble of claim 1.

[0011] It is also known from document US2010 / 012650 to employ two applicator stages through which a flow tube passes, in which these two applicator stages have specially formed protrusions to provide different radial distributions of hot spots between the two applicator stages.

[0012] The present invention aims in particular to provide a microwave reactor for continuous microwave treatment of a flowing fluidic medium, which is particularly suitable for both low-absorbing and high-absorbing fluidic media.

[0013] One aim of the invention is to enable homogeneous or uniform heating, without localized hot spots in the fluidic medium.

[0014] To this end, it proposes a microwave reactor for continuous microwave treatment of a flowing fluidic medium, such a microwave reactor comprising: a flow tube, made of microwave-transparent material, extending longitudinally along a flow axis for the flow of the fluidic medium along said flow axis; an inlet waveguide extending along a propagation axis for microwave propagation along said propagation axis, said inlet waveguide having a rectangular cross-section with two long sides defining a major dimension and two short sides defining a minor dimension less than the major dimension, and said inlet waveguide being coupled to the flow tube for continuous microwave processing of the fluidic medium, with the flow axis orthogonal to the propagation axis; and an enclosure within which the flow tube extends at least partially, said enclosure being made of a microwave-reflective material and extending longitudinally along the flow axis;The microwave reactor according to the invention is remarkable in that: the long sides of the inlet waveguide are parallel to the flow axis, while the short sides of the inlet waveguide are orthogonal to the flow axis; the enclosure has a lateral dimension measured parallel to the short sides of the inlet waveguide, said lateral dimension being greater than the short dimension of the inlet waveguide, said inlet waveguide being fixed transversely to the enclosure, said enclosure having an inlet window surrounded by the inlet waveguide for microwave propagation through the inlet window into the enclosure; and the enclosure extends longitudinally along the flow axis over a given enclosure length between a first end and a second opposite end, said enclosure length being strictly greater than the long dimension of the inlet waveguide.

[0015] Thus, with such a reactor according to the invention, the electric field is parallel to the short sides of the inlet waveguide and is therefore orthogonal (or perpendicular) to the flow tube in which the fluidic medium flows, and thus the electric field will not see a boundary or abrupt transition to high dielectric losses because it will be able to bypass the flow tube, even in the case of absorbing fluidic media or media with high dielectric losses.

[0016] Furthermore, this coupling between the inlet waveguide and the flow tube will promote wave penetration all around the tube, thus creating more uniform heating over the flow tube cross-section.

[0017] To promote a gradual penetration of the waves along the flow tube, the latter is surrounded by an enclosure forming a cavity extending on each side of the inlet waveguide, and thus the wave will remain gradual and be absorbed almost entirely before reaching the ends of the flow tube.

[0018] Depending on one possibility, the enclosure length is between 1.5 times and 6 times greater than the large dimension of the input waveguide.

[0019] This characteristic ensures progressive absorption of microwaves by an absorbing fluidic medium, and avoids the appearance of a resonance phenomenon inside the enclosure: when this enclosure has a length less than or equal to the large dimension of the inlet waveguide, the absorption of microwaves is not progressive along the flow axis, thus favoring the formation of hot spots inside the fluidic medium, leading to heterogeneous heating of the latter.

[0020] In an advantageous design, the enclosure has a circular cross-section with a diameter corresponding to the lateral dimension.

[0021] According to one possibility, the inlet window is bounded by two longitudinal edges parallel to the long sides of the inlet waveguide and by two lateral edges parallel to the short sides of the inlet waveguide, where the longitudinal edges have a length less than or equal to the long dimension and the lateral edges have a length less than or equal to the short dimension.

[0022] Thus, the input window has a rectangular cross-section equivalent to or smaller than the rectangular cross-section of the input waveguide.

[0023] Advantageously, the longitudinal edges of the entrance window have a length less than the larger dimension and the lateral edges of the entrance window have a length equal to the smaller dimension, so that the entrance window forms an entrance iris.

[0024] Thus, the inlet waveguide is attached to the enclosure by an inlet window characterized by longitudinal edges smaller than the longer sides of the inlet waveguide, thereby forming an inlet iris. This inlet iris is an important parameter that the user can manipulate in modeling to adapt to the flowing fluidic medium for the purpose of optimizing the processing.

[0025] In particular, the iris shape of the inlet window causes a change in the modulus of microwaves passing through such an inlet iris, allowing for improved penetration of these microwaves into the fluidic medium flowing in the flow tube.

[0026] Thus, thanks to the presence of an inlet iris, it is possible to optimize the sizing of a microwave reactor according to the invention by adapting, for example, the size of this inlet iris to a particular product intended to flow in the flow tube.

[0027] However, if the longitudinal edges of the entrance window have a length equivalent to the longest dimension, then the entrance window does not form an entrance iris.

[0028] According to one possibility, the enclosure has no internal elements arranged between the inlet window and the flow tube.

[0029] In other words, the portion of the enclosure located between the inlet window and the flow tube is unoccupied and in particular does not contain any element likely to modify or hinder the propagation of microwaves from the inlet window to the flow tube.

[0030] In particular, the enclosure does not include any device for circulating a cooling fluid around said flow tube, allowing control of the temperature of the fluidic medium flowing in the latter.

[0031] Indeed, it is known from the prior art to circulate such a cooling fluid in a helical tube surrounding the flow tube: this helical tube is then positioned parallel to the short sides of the inlet waveguide (and therefore parallel to the electric field of the microwaves circulating in it) and prevents the propagation of microwaves in the flow tube.

[0032] Thus, by not interposing any element in the cavity defined by the enclosure between the inlet window and the flow tube, it is possible to guarantee better penetration of microwaves into the fluidic medium inside the flow tube.

[0033] In a particular embodiment, the microwave reactor includes an output waveguide fixed transversely to the enclosure in a manner diametrically opposite to the input waveguide, where: said output waveguide extends along the propagation axis and has a rectangular cross-section with two long sides defining a long dimension and two short sides defining a short dimension smaller than the long dimension, the long sides of the output waveguide being parallel to the flow axis, while the short sides of the output waveguide are orthogonal to the flow axis, the long dimension of the output waveguide being equivalent to the long dimension of the input waveguide and the short dimension of the output waveguide being equivalent to the short dimension of the input waveguide; said enclosure has an output window diametrically opposite to the input window and surrounded by the output waveguide for microwave propagation through the output window.

[0034] According to one possibility, the output window is bounded by two longitudinal edges parallel to the long sides of the output waveguide and by two lateral edges parallel to the short sides of the output waveguide, where the longitudinal edges have a length less than or equal to the long dimension and the lateral edges have a length less than or equal to the short dimension.

[0035] Thus, the output window has a rectangular cross-section equivalent to or smaller than the rectangular cross-section of the output waveguide.

[0036] In a particular embodiment, the longitudinal edges of the exit window have a length less than the larger dimension and the lateral edges of the exit window have a length equal to the smaller dimension, so that the exit window forms an exit iris.

[0037] Thus, the output waveguide is fixed to the enclosure by an output window having longitudinal edges smaller than the long sides of the output waveguide, thus forming an output iris.

[0038] However, if the longitudinal edges of the exit window have a length equivalent to the larger dimension, then the exit window does not form an exit iris.

[0039] It can therefore be planned to have only one input iris (as described above), or to have only one output iris, or to have an input iris and an output iris.

[0040] Advantageously, the microwave reactor further includes a short-circuit device fixed on the output waveguide, said short-circuit device being either of the piston short-circuit type adjustable along the propagation axis, or of the static short-circuit type.

[0041] Alternatively, the enclosure is closed with respect to the input waveguide and thus provides a curved reflective surface located diametrically opposite to the input waveguide.

[0042] According to one characteristic, the input waveguide is fixed transversely to the enclosure: either at a distance from the first end between 0.4 and 0.6 times the enclosure length (therefore substantially in the middle of the enclosure); or at a distance from the first end between 0.1 and 0.4 times the enclosure length (therefore substantially closer to one end of the enclosure).

[0043] According to another characteristic, the flow axis is a vertical axis so that the flow tube and enclosure extend vertically, and the propagation axis is a horizontal axis so that the input waveguide extends horizontally.

[0044] Advantageously, the speaker rests high on a support base, such as a support base with several support feet, so that the speaker is raised off the ground by means of the support base.

[0045] In a particular embodiment, the enclosure includes covers provided on the first end and the second end, said covers being provided with connecting sleeves to connect a first end and a second end of the flow tube respectively to a first pipe and a second pipe of a flow system for a flow of the fluidic medium.

[0046] It should be noted that the enclosure can have a constant diameter over its entire length, or alternatively the enclosure can have a diameter that reduces at its ends so that the enclosure can be conical or truncated at the ends.

[0047] In one embodiment, the microwave reactor includes another inlet waveguide extending parallel to the propagation axis, said other inlet waveguide having a rectangular cross-section with two long sides defining a large dimension and two short sides defining a small dimension less than the large dimension, and said other inlet waveguide being coupled to the flow tube for continuous microwave treatment of the fluidic medium; in which the larger sides of said other inlet waveguide are parallel to the flow axis, while the smaller sides of said other inlet waveguide are orthogonal to the flow axis; in which the lateral dimension of the enclosure is greater than the smaller dimension of said other inlet waveguide, said other inlet waveguide being fixed transversely to the enclosure, said enclosure having another inlet window surrounded by said other inlet waveguide for microwave propagation through said other inlet window into the enclosure, and in which the enclosure length is strictly greater than the larger dimension of said other inlet waveguide.

[0048] In other words, the microwave reactor includes, in addition to the input waveguide, another input waveguide arranged parallel to it and exhibiting similar structural and geometric characteristics.

[0049] This other inlet waveguide thus makes it possible to introduce microwaves into the enclosure via another inlet window offset from the inlet window along the flow axis.

[0050] This introduction of microwaves offset from the propagation axis of the inlet waveguide allows for better treatment of the fluidic medium flowing in the flow tube (in particular, more homogeneous treatment along the flow axis), especially when this fluidic medium is highly absorbing.

[0051] Advantageously, the other input waveguide is identical to the input waveguide, and in particular has a large dimension and a small dimension identical to those of said input waveguide.

[0052] It is also advantageous for the other input waveguide to be made of the same material as the input waveguide, so that the kinematics of microwave propagation in this other input waveguide is identical to that in the input waveguide.

[0053] According to one possibility, the inlet waveguide and the other inlet waveguide are connected to the same upstream waveguide intended for the introduction of microwaves inside each of said inlet waveguide and other inlet waveguide, said upstream waveguide having a rectangular section with two long sides defining a long dimension and two short sides defining a short dimension less than the long dimension, the long sides of said upstream waveguide being parallel to the flow axis, while the short sides of said upstream waveguide are orthogonal to the flow axis.

[0054] It is therefore possible, by connecting the upstream waveguide to a microwave generator, to achieve the propagation of microwaves simultaneously in the input waveguide and in the other input waveguide, parallel to the propagation axis.

[0055] The upstream waveguide therefore has the function of transmitting the microwaves propagating within it to each of the input waveguides and to the other input waveguides.

[0056] It is also advantageous that the large dimension of the upstream waveguide be equivalent to the large dimension of the input waveguide and the other input waveguide, and that the small dimension of the upstream waveguide be equivalent to the small dimension of the input waveguide and the other input waveguide.

[0057] Thus, the propagation of microwaves in the upstream waveguide is identical to that in the input waveguide and in the other input waveguide.

[0058] According to one feature, the microwave reactor includes another output waveguide fixed transversely to the enclosure in a manner diametrically opposite to the other input waveguide, where: said other output waveguide extends parallel to the propagation axis and has a rectangular cross-section with two long sides defining a long dimension and two short sides defining a short dimension smaller than the long dimension, the long sides of the other output waveguide being parallel to the flow axis, while the short sides of the other output waveguide are orthogonal to the flow axis, the long dimension of the other output waveguide being equivalent to the long dimension of the other input waveguide and the short dimension of the other output waveguide being equivalent to the short dimension of the other input waveguide; said enclosure has another output window diametrically opposite to the other input window and surrounded by the other output waveguide for microwave propagation through the other output window.

[0059] In other words, the microwave reactor includes another output waveguide associated with the other input waveguide, this other output waveguide having similar structural and geometric characteristics and the same function as the output waveguide associated with the input waveguide.

[0060] In particular, this other output waveguide can have the same large dimension and the same small dimension as the output waveguide and the input waveguide.

[0061] This other output waveguide can also, in the same way as the output waveguide, be equipped with a short-circuit device, for example of the piston short-circuit type adjustable parallel to the propagation axis or of the static short-circuit type.

[0062] The present invention also relates to a microwave installation for the continuous microwave treatment of a flowing fluidic medium, such a microwave installation comprising: a microwave reactor according to the invention; a microwave generator connected to the input waveguide; and a flow system connected to the flow tube upstream and downstream to ensure flow of the fluidic medium inside the flow tube.

[0063] When the microwave reactor has another input waveguide, it is advantageous for the microwave generator of the microwave installation to also be connected to this other input waveguide.

[0064] In the embodiment where the microwave reactor is as previously described and includes an upstream waveguide connected to the inlet waveguide and the other inlet waveguide, it is advantageous for the microwave generator of the microwave installation to be connected to this upstream waveguide: it is then indirectly connected to both the inlet waveguide and the other inlet waveguide.

[0065] The microwave generator generates microwaves, for example in at least one of the industrial, scientific and medical (ISM) microwave frequency bands allocated by the International Telecommunication Union (ITU), and in particular the microwave frequency bands 2.450 GHz ± 50.0 MHz, 5.800 GHz ± 75.0 MHz, 433.92 MHz ± 0.87 MHz, 896 MHz ± 10 MHz and 915 MHz ± 13 MHz.

[0066] The invention also relates to a continuous microwave treatment method for a flowing fluidic medium, such a continuous microwave treatment method comprising the following steps: generation of microwaves by means of a microwave generator connected to the inlet waveguide of a microwave reactor according to the invention; flow of a fluidic medium inside the flow tube of said microwave reactor, by means of a flow system connected to the flow tube upstream and downstream.

[0067] Other features and advantages of the present invention will become apparent from the following detailed description, of a non-limiting example of implementation, made with reference to the accompanying figures in which: [ Fig.1 ] already described, is a schematic view of a prior art "downstream" microwave reactor; [ Fig.2 ] already described, is a schematic representation of an electric field inside a waveguide with a rectangular cross-section; [ Fig.3 ] is a schematic view of a microwave reactor according to a first embodiment of the invention; [ Fig.4 ] is a schematic cross-sectional view of the reactor of the figure 3 , according to a cross-sectional plane including the flow axis and orthogonal to the short sides of the inlet waveguide, with an illustration of the amplitude of the electric field in an example of an absorbing or high dielectric loss fluidic medium, on a logarithmic scale [ Fig.5 ] is a schematic cross-sectional view of the reactor of the figure 3 , according to a cross-sectional plane including the flow axis and orthogonal to the short sides of the inlet waveguide, with an illustration of the electric field amplitude in an example of an absorbing or high-dielectric-loss fluidic medium, on a linear scale; [ Fig.6 ] is a schematic cross-sectional view of the reactor of the figure 3 , along a cross-sectional plane orthogonal to the flow axis and passing through the middle of the inlet waveguide, with an illustration of the amplitude of the electric field in the example of an absorbing fluidic medium or one with high dielectric losses of the figures 4 And 5 , on a logarithmic scale; [ Fig.7 ] is a schematic perspective view of a microwave reactor according to the invention, with an output waveguide on which is fixed a short-circuit device of the short-circuit piston type adjustable along the propagation axis; Fig.8 ] is a schematic perspective view of a microwave reactor according to the invention, with an output waveguide on which a static short-circuit type short-circuiting device is fixed; Fig.9 ] is a schematic perspective view, from another angle, of the microwave reactor according to the figures 7 And 8, without the short-circuit device; [ Fig.10 ] is a schematic cross-sectional view of the microwave reactor according to the figures 7 And 8 , without the short-circuiting device, along a cutting plane including the flow axis and orthogonal to the short sides of the inlet waveguide; and [ Fig11 ] is a schematic perspective view of a microwave installation according to the invention, equipped at least with the microwave reactor according to the figures 7 And 8 and a microwave generator connected to the input waveguide. Fig.12 ] is another schematic perspective view of a microwave installation according to the invention, equipped at least with the microwave reactor according to the figures 7 And 8 and a microwave generator connected to the input waveguide. Fig. 13 ] is a schematic perspective view of a second embodiment of the microwave reactor according to the invention, comprising another inlet waveguide.

[0068] With reference to figures 3 And 7 à 10 , a microwave reactor 1 according to a first embodiment of the invention constitutes a reactor for continuous microwave treatment of a flowing fluidic medium, that is to say a fluidic medium which flows or which is in motion.

[0069] This microwave reactor 1 finds a favorite, but not limiting, application in the continuous microwave heat treatment of pumpable products, in particular agri-food products and especially homogeneous liquid products or products with regularly distributed pieces in a sufficiently carrier phase.

[0070] This microwave reactor 1 includes a cylindrical flow tube 2 made entirely of dielectric material transparent to microwaves, such as borosilicate glass, quartz, alumina, or polymeric material such as polytetrafluoroethylene or PTFE.

[0071] This flow tube 2 extends longitudinally along a flow axis 20 and has a first end 21 and a second end 22 that are opposite, for the flow of the fluidic medium inside the flow tube 2 along this flow axis 20 from the first end 21 to the second end 22. This flow axis 20 constitutes the central axis or axis of revolution of the cylindrical flow tube 2. In the examples of figures 7 à 12 , the flow axis 20 is a vertical axis.

[0072] This microwave reactor 1 includes an enclosure 3 within which extends the flow tube 2, where this enclosure 2 is made of a microwave-reflective material, such as a conductive material or a metallic material.

[0073] This enclosure 3 is cylindrical in shape with a given diameter DE, and it extends longitudinally along the flow axis 20 over a given enclosure length LE between a first end 31 and a second opposite end 32; this flow axis 20 constituting the central axis or axis of revolution of this cylindrical enclosure 3. Thus, the flow tube 2 and the enclosure 3 extend vertically, or alternatively they extend horizontally or at an angle with respect to a vertical or horizontal axis.

[0074] It should be noted that the diameter DE of the chamber 3 can be adjusted according to the diameter of the flow tube 2 and the properties of the fluidic medium. The internal and external diameters of the flow tube 2 can also be adjusted according to the properties of the fluidic medium.

[0075] As seen on the figures 7 à 10 , this speaker 3 can rest at a height on a support base 7 equipped with several support feet 70, possibly vertically adjustable support feet 70.

[0076] Furthermore, enclosure 3 surrounds flow tube 2 and it features: On its first end 31, a first cover 33 holds the first end 21 of the drain tube 2, and on its second end 32, a second cover 35 holds the second end 22 of the drain tube 2; a first connecting sleeve 34 is fixed to the first cover 33 and hermetically sealed to the first end 21 of the drain tube 2 in order to hermetically seal a first pipe 61 (visible on the figures 7 , 11 And 12 ) at the first end 21 of the drain pipe 2; a second connecting sleeve 36 fixed to the second cover 35 and connected in a watertight manner to the second end 22 of the drain pipe 2 in order to be able to connect in a watertight manner a second pipe 62 (visible on the figures 7 , 11 And 12 ) at the second end 22 of the flow tube 2.

[0077] Thus, the fluidic medium enters the flow tube 2 via the first pipe 61, flows from the first end 21 to the second end 22, and then exits via the second pipe 62, so that the first pipe 61 forms the upstream pipe and the second pipe 62 forms the downstream pipe. Of course, the direction of flow of the fluidic medium can be reversed in the flow tube 2, as explained below.

[0078] In the illustrated example, with a vertical chamber 3 and flow tube 2, the first end 21, connected to the first pipe 61, is positioned at the bottom, while its second end 22, connected to the second pipe 62, is positioned at the top. This allows the fluid to flow in the flow tube 2 from bottom to top, which has the advantage of reducing or even preventing the formation of bubbles or inhomogeneities in the fluid. Of course, it is also possible to have a reversed flow direction, i.e., from bottom to top.

[0079] Furthermore, in unillustrated variants, the flow axis 20 and the flow tube 2 can be horizontal, so that the fluidic medium flows horizontally. It is also possible for the flow axis 20 and the flow tube 2 to be inclined with respect to a horizontal or vertical axis at an angle of less than 90 degrees.

[0080] This microwave reactor 1 further includes an inlet waveguide 4 fixed transversely to the enclosure 3, that is, to its peripheral wall or perimeter. This inlet waveguide 4 is made of a microwave-reflective material, such as a conductive or metallic material. By way of non-limiting example, this inlet waveguide 4 is fixed to the enclosure 3 by welding.

[0081] This inlet waveguide 4 has a rectangular cross-section with two long sides 41 defining a long dimension GD (i.e., sides with the largest dimension) and two short sides 42 defining a short dimension PD smaller than the long dimension GD (i.e., sides with the smallest dimension); the long dimension GD corresponding to the length of the rectangular cross-section and the short dimension PD corresponding to the width of the rectangular cross-section. This inlet waveguide 4 has a free termination 43 equipped with a connecting ring or plate suitable for bolting to an upstream waveguide 8 (see figures 11 And 12 ), for connecting the input waveguide 4 with a microwave generator 9. For this purpose, this free termination 43 forming a ring or connection plate is provided with holes all around its perimeter for the passage of screws.

[0082] This input waveguide 4 extends along a propagation axis 40 for the propagation of microwaves, originating from the microwave generator 9, along said propagation axis 40; it being noted that this propagation axis 40 is orthogonal to the flow axis 20. In the examples of figures 7 à 12 , the propagation axis 40 is therefore a horizontal axis, and thus the input waveguide 4 extends horizontally.

[0083] Of course, the upstream waveguide 8 can be vertical and / or horizontal and / or have bends and / or be made up of several waveguide sections depending on the arrangement and location of the microwave generator 9 relative to the microwave reactor 1 and according to the inclinations of the flow axis 20 and the propagation axis 40.

[0084] This inlet waveguide 4 is coupled to the flow tube 2 for continuous microwave processing of the fluidic medium flowing in the flow tube 2.

[0085] To do this, the enclosure 3 has a rectangular inlet window 37, surrounded by the inlet waveguide 4 for the propagation of microwaves, originating from the microwave generator 9 and propagating in the inlet waveguide 4, through the inlet window 37 inside the enclosure 3 where the flow tube 2 is located.

[0086] It should be noted that this coupling meets the following geometric requirements: the large sides 41 of the inlet waveguide 4 are parallel to the flow axis 20, the small sides 42 of the inlet waveguide 4 are orthogonal to the flow axis 20; the diameter DE of the enclosure 3 is greater than the small dimension PD of the inlet waveguide 4.

[0087] In the example of figures 7 à 12 , the input waveguide 4 is fixed transversely on the enclosure 3 substantially in the middle (or at mid-length or mid-height) of the enclosure 3, i.e. generally at a distance from the first end 31 (or the second end 32) of between 0.4 and 0.6 times the length of the enclosure LE.

[0088] Furthermore, it should be noted that the entrance window 37, rectangular in shape or section, is delimited by: two longitudinal edges 371 parallel to the long sides 41 of the inlet waveguide 4, and therefore parallel to the flow axis 20; and by two lateral edges 372 parallel to the short sides 42 of the inlet waveguide 4 and therefore orthogonal to the flow axis 20.

[0089] Due to the cylindrical shape of the enclosure 3, the longitudinal edges 371 of the entrance window 37 are straight while the lateral edges 372 of the entrance window 37 are arched.

[0090] The inlet window 37 is surrounded by the inlet waveguide 4, and therefore its longitudinal edges 371 have a length less than or equal to the large dimension GD and its lateral edges 372 have a length less than or equal to the small dimension PD.

[0091] In the example illustrated on the figures 9 And 10 The longitudinal edges 371 of the entrance window 37 have a length less than the larger dimension GD, and the lateral edges 372 of the entrance window 37 have a length equal to the smaller dimension PD, so that the entrance window 37 forms an entrance iris. On the figure 9 , input window 37 is in the background while output window 38 is in the foreground.

[0092] It is also conceivable that the longitudinal edges 371 of the entrance window 37 have a length equal to the large dimension GD and the lateral edges 372 of the entrance window 37 have a length equal to the small dimension PD, and thus the entrance window 37 does not form an entrance iris.

[0093] It should also be noted that, as can be seen on the figure 9 In particular, the enclosure length LE is significantly greater (here, about 6 times greater) than the large dimension GD of the input waveguide 4.

[0094] This characteristic ensures homogeneous treatment, along the flow axis 20, of the fluidic medium flowing in the flow tube 2 by the microwaves from the inlet waveguide 4, without causing the appearance of a resonance phenomenon in the enclosure 3.

[0095] It should also be noted, regarding the figures 9 And 10that the microwave reactor 1 does not include any element disposed between the inlet window 37 and the flow tube 2 which is capable of disturbing or hindering the propagation of microwaves from this inlet window 37 to this flow tube 2.

[0096] The microwave reactor 1 may also include an output waveguide 5 fixed transversely to the enclosure 3 diametrically opposite the inlet waveguide 4. This output waveguide 5 is made of a microwave-reflective material, such as a conductive or metallic material. By way of non-limiting example, this output waveguide 5 is fixed by welding to the enclosure 3.

[0097] This output waveguide 5 also extends along the propagation axis 40, in alignment with the input waveguide 4.

[0098] This output waveguide 5 has a rectangular cross-section with: two large sides 51 defining a large dimension equivalent to the large dimension GD of the inlet waveguide 4, where these large sides 51 are parallel to the flow axis 20; and two small sides 52 defining a small dimension equivalent to the small dimension PD of the inlet waveguide 4, where these small sides 52 are orthogonal to the flow axis 20.

[0099] Furthermore, the enclosure 3 has an outlet window 38 diametrically opposite the rectangular inlet window 37 and surrounded by the outlet waveguide 5 for microwave propagation through the outlet window 38 between the outlet waveguide 5 and the inside of the enclosure 3. This outlet waveguide 5 has a free termination 50 equipped with a ring or connection plate suitable for allowing a bolted connection with a short-circuit device 55, 56 fixed on the outlet waveguide 5. For this purpose, this ring or connection plate is provided with holes all around its perimeter for the passage of screws.

[0100] In the implementation of figures 7 , 11 And 12This short-circuit device is of the short-circuit piston type 55, adjustable along the propagation axis 40; such a short-circuit piston 55 has a conventional impedance matching function. The short-circuit piston 55 thus provides flexibility in impedance matching so that the microwave reactor 1 can respond to a wide range of dielectric characteristics in the fluidic medium.

[0101] It is also possible to do without such a short-circuit piston 55, for example and as illustrated in figure 8 , by attaching to the output waveguide 5 a static short-circuit type short-circuit device 56. Such a static short-circuit 56 can easily be disassembled (by removing the bolts) to be replaced by the short-circuit piston 55, or vice versa.

[0102] In an unillustrated variant of this static short circuit 56, the enclosure 3 can be closed with respect to the input waveguide 4 and thus provide a curved reflective surface (in place of the output window 38) located diametrically opposite to the input waveguide 4 and thus forming a static short circuit.

[0103] Furthermore, it should be noted that the output window 38, rectangular in shape or cross-section, is delimited by: two longitudinal edges 381 parallel to the long sides 51 of the outlet waveguide 5, and therefore parallel to the flow axis 20; and by two lateral edges 382 parallel to the short sides 52 of the outlet waveguide 5 and therefore orthogonal to the flow axis 20.

[0104] Due to the cylindrical shape of the enclosure 3, the longitudinal edges 381 of the exit window 38 are straight while the lateral edges 382 of the exit window 38 are arched.

[0105] The output window 38 is surrounded by the output waveguide 5, and therefore its longitudinal edges 381 have a length less than or equal to the large dimension GD and its lateral edges have a length less than or equal to the small dimension PD.

[0106] In the example shown on the figure 3 , the longitudinal edges 381 of the exit window 38 have a length less than the large dimension GD and the lateral edges 382 of the exit window 38 have a length equal to the small dimension PD, so that the exit window 38 forms an exit iris.

[0107] In the example illustrated on the figures 9 And 10, the longitudinal edges 381 of the exit window 38 have a length equal to the large dimension GD and the lateral edges 382 of the exit window 38 have a length equal to the small dimension PD, and thus the exit window 38 does not form an exit iris.

[0108] There figure 13 illustrates a second embodiment, in which a microwave reactor 1' comprises, in addition to the inlet waveguide 4 previously described, another inlet waveguide 4'.

[0109] In this second embodiment, the microwave reactor 1' has the same elements as the microwave reactor 1 illustrated in particular by the figure 7 and described above, and in particular: the enclosure 3 surrounding the flow tube 2 extending along the flow axis 20, the inlet waveguide 4, extending along the propagation axis 40 and having the large dimension GD and the small dimension PD, the large dimension GD being parallel to the flow axis 20, and the outlet waveguide 5 diametrically opposite the inlet waveguide 4 and equipped with a short-circuiting device of the short-circuit piston type 55.

[0110] The microwave reactor 1' also includes another inlet waveguide 4' fixed to the enclosure 3 and extending along another propagation axis 40', parallel to the propagation axis 40.

[0111] It will be noted that the inlet waveguide 4 is here fixed at a distance from the first end 31 approximately equal to 0.3 times the enclosure length LE, and that the other inlet waveguide 4' is fixed at a distance from the first end 31 approximately equal to 0.7 times the enclosure length LE (or, equivalently, at a distance from the second end 32 approximately equal to 0.3 times the enclosure length LE).

[0112] This other inlet waveguide 4' is otherwise in every respect similar to the inlet waveguide 4; in particular it is made of a microwave-reflective material, so as to allow microwave propagation along the other propagation axis 40', and has a rectangular section with two long sides 41' defining a large dimension GD equal to the large dimension GD of the inlet waveguide 4 and two short sides 42' defining a small dimension PD equal to the small dimension PD of the inlet waveguide 4.

[0113] This other 4' inlet waveguide also surrounds another inlet window (not visible on the figure 13 ) provided in enclosure 3 and allowing, in the same way as the inlet window 37 previously described, microwaves circulating in the other inlet waveguide 4' to enter enclosure 3.

[0114] As with the entrance window 37, it is conceivable that this other entrance window has the shape of an entrance iris, when this other entrance window has longitudinal edges of length equal to the large dimension GD and lateral edges of length equal to the small dimension PD.

[0115] The microwave reactor 1' also includes, in this second embodiment, another output waveguide 5' fixed on the enclosure 3 opposite the other input waveguide 4' and extending along the other propagation axis 40'.

[0116] This other output waveguide 5' has a structure and geometry identical to that of the output waveguide 5: it is notably made of a microwave-reflective material, so as to allow microwave propagation along the other propagation axis 40', and has a rectangular section with two long sides 51' defining a long dimension GD equal to the long dimension GD of the other input waveguide 4' (and of the output waveguide 5) and two short sides 52' defining a short dimension PD equal to the short dimension PD of the other input waveguide 4' (and of the output waveguide 5).

[0117] This other 5' output waveguide also surrounds another output window (not visible on the figure 13 ) provided in enclosure 3, diametrically opposite to the other inlet window and allowing, in the same way as the outlet window 38 previously described, the microwaves circulating in the other outlet waveguide 5' to exit enclosure 3.

[0118] As with exit window 38, it is conceivable that this other exit window has the shape of an exit iris, when this other exit window has longitudinal edges of length equal to the large dimension GD and lateral edges of length equal to the small dimension PD.

[0119] Finally, this other output waveguide 5' is attached to another piston-type short-circuit device 55' adjustable along the other propagation axis 40', identical to the piston-type short-circuit device 55 and having the same function.

[0120] The other inlet waveguide 4' therefore allows microwave propagation in the same way as the inlet waveguide 4, along the other propagation axis 40' offset from the propagation axis 40 along the flow axis 20: this other inlet waveguide 4' therefore allows treatment of the fluidic medium flowing in the flow tube 2 at the level of a second treatment zone offset along the flow axis 20 relative to a first treatment zone of the fluidic medium associated with the inlet waveguide 4.

[0121] In this way, it is possible to treat the fluidic medium more homogeneously along the flow axis 20 and over the entire length of enclosure LE of enclosure 3.

[0122] Each of the input waveguide 4 and the other input waveguide 4' is also connected to the same upstream waveguide 8' having two portions: a straight portion 81' extending parallel to the propagation axis 40 and to the other propagation axis 40', between these two, and a junction portion 82' in the general shape of a "Y", adapted to connect said straight portion 81' to the input waveguide 4 on the one hand and to the other input waveguide 4' on the other hand.

[0123] It should also be noted that the straight portion 81 has a rectangular section identical to that of the inlet waveguide 4 and the other inlet waveguide 4', having the same large dimension GD and the same small dimension PD.

[0124] The upstream waveguide 8' is adapted to be connected, at one end 811' of the straight section 81', to a microwave generator (not shown on the figure 13 ): The microwaves thus introduced into this upstream waveguide propagate along the straight section 81' and are then separated into two: a first part of the microwaves is introduced into the inlet waveguide 4 and propagates along the propagation axis 40, and comes into contact with the fluidic medium at the level of the first treatment zone 400, and a second part of the microwaves is introduced into the other inlet waveguide 4' and propagates along the other propagation axis 40', and comes into contact with the fluidic medium at the level of the second treatment zone 400'.

[0125] It should be noted that, due to the strictly identical structure of the input waveguide 4 and the other input waveguide 4' (as well as, respectively, of the input window 37 and the other input window, the output waveguide 5 and the other output waveguide 5', the piston-type short-circuit device 55 and the other piston-type short-circuit device 55'), the electric field propagating in each of them has the same orientation and a similar intensity.

[0126] It should be noted that it is conceivable that these various elements may have a different structure and / or geometry, with a view to heterogeneous treatment of the fluidic medium along the flow axis 20.

[0127] Finally, it should be noted that the microwave reactor 1' is here placed on a support base 7', the geometry of which is specifically adapted to that of the inlet waveguide 4 and the upstream waveguide 8'

[0128] For the implementation of a continuous microwave treatment process for a flowing fluidic medium, it is necessary to use a microwave installation 10 (partially illustrated in the figures 11 And 12 ) which includes: a microwave reactor 1 as described above; a microwave generator 9 connected to the inlet waveguide 4 via an upstream waveguide 8; and a flow system 6 connected to the flow tube 2 upstream and downstream to allow flow of the fluidic medium inside the flow tube 2.

[0129] This flow system 6 includes: The first and second pipes 61, 62 mentioned previously, which are connected respectively to the first and second ends 21, 22 of the flow tube 2; a device (not illustrated) suitable for circulating the fluid medium in the first and second pipes 61, 62, such as for example a pump, a turbine, a piston device, ...

[0130] In operation, the flow system 6 is activated to flow a fluidic medium inside the flow tube 2 and the microwave generator 9 is activated to generate microwaves which are guided to the inlet waveguide 4 and through the inlet window 37 to continuously irradiate and treat the fluidic medium flowing in the flow tube 2.

[0131] Obviously, it is conceivable that the implementation of a continuous microwave treatment process of a flowing fluidic medium is carried out by means of a microwave installation comprising a microwave reactor 1' according to the second embodiment described above.

[0132] In this case, a single microwave generator can be used for microwave propagation in the inlet waveguide 4 and in the other inlet waveguide 4', via the upstream waveguide 8'.

[0133] THE figures 4 à 6 represent the amplitude of the electric field (or microwave field) calculated in the microwave reactor 1 and in the fluidic medium for a fluidic medium equivalent to mineral water and with a microwave frequency of 915 MHz.

[0134] There figure 4 clearly shows that the microwave field is gradually absorbed along the flow tube 2.

[0135] There figure 5 corresponds to the figure 4 but with a linear scale, to highlight that almost no waves remain at the ends of the flow tube.

[0136] There figure 6 shows that the electric field is rather uniform in the cross-section of the flow tube 2 and is absorbed all around its perimeter.

[0137] Thus it is clear that the fluidic medium will be heated progressively and homogeneously, avoiding hot spots, which is ideal for fluidic media that require a relatively gentle heating dynamic, even with relatively slow flow velocities.

Claims

1. A microwave reactor (1,1') for continuous microwave treatment of a flowing fluidic medium selected from a liquid medium, a viscous medium, a pasty medium, a liquid / solid or liquid / gas two-phase mixture medium, said microwave reactor (1) comprising: - a flow tube (2), made of a microwave-transparent material, extending longitudinally along a flow axis (20) and having a first end (21) and a second end (22) opposite each other for a flow of the fluidic medium along said flow axis (20); - an input waveguide (4) extending along a propagation axis (40) for microwave propagation along said propagation axis (40), said input waveguide (4) having a rectangular section with two long sides (41) defining a large dimension (GD) and two short sides (42) defining a small dimension (PD) smaller than the large dimension (GD), and said input waveguide (4) being coupled to the flow tube (2) for continuous microwave processing of the fluidic medium, with the flow axis (20) orthogonal to the propagation axis (40); and - an enclosure (3) inside which the flow tube (2) extends at least partially, said enclosure (3) being made of a microwave-reflective material and extending longitudinally along the flow axis (20) over a given enclosure length (LE) between a first end (31) and a second end (32) opposite each other, and the enclosure (3) includes no internal element disposed between the input window (37) and the flow tube (2); wherein: - the long sides (41) of the input waveguide (4) are parallel to the flow axis (20), whereas the short sides (42) of the input waveguide (4) are orthogonal to the flow axis (20); - the enclosure (3) has a lateral dimension (DE) measured parallel to the short sides (42) of the input waveguide (4), said lateral dimension (DE) being greater than the small dimension (PD) of the input waveguide (4), said input waveguide (4) being attached transversely on the enclosure (3), said enclosure (3) having an input window (37) surrounded by the input waveguide (4) for microwave propagation through the input window (37) inside the enclosure (3), and said microwave reactor (1) being characterized in that said enclosure length (LE) is strictly greater than the large dimension (GD) of the input waveguide (4) and the flow tube (2) is surrounded by the enclosure (3) forming a cavity extending on each side of the input waveguide (4); and in that the enclosure (3) includes lids (33, 35) provided on the first end (31) and the second end (32), said lids (33, 35) being provided with connecting sleeves (34, 36) for sealingly connecting the first end (21) and the second end (22) of the flow tube (2) respectively to a first pipe (61) and a second pipe (62) of a flow-establishing system (6) for causing the fluidic medium to flow from the first end (21) to the second end (22) of the flow tube (2).

2. The microwave reactor (1,1') according to the preceding claim, wherein the enclosure length (LE) is between 1.5 times and 6 times the large dimension (GD) of the input waveguide (4).

3. The microwave reactor (1,1') according to any one of claims 1 and 2, wherein the input window (37) is delimited by two longitudinal edges (371) parallel to the long sides (41) of the input waveguide (4) and by two lateral edges (372) parallel to the short sides (42) of the input waveguide (4), where these longitudinal edges (371) have a length less than or equal to the large dimension (GD) and the lateral edges (372) have a length less than or equal to the small dimension (PD).

4. The microwave reactor (1,1') according to claim 3, wherein the longitudinal edges (371) of the input window (37) have a length less than the large dimension (GD) and the lateral edges (372) of the input window (37) have a length equal to the small dimension (PD), so that the input window (37) forms an input iris.

5. The microwave reactor (1,1') according to any one of claims 1 to 4, comprising an output waveguide (5) attached transversely on the enclosure (3) diametrically opposite the input waveguide (4), where: - said output waveguide (5) extends along the propagation axis (40) and has a rectangular section with two long sides (51) defining a large dimension (GD) and two short sides (52) defining a small dimension (PD) smaller than the large dimension (GD), the long sides (51) of the output waveguide (5) being parallel to the flow axis (20), whereas the short sides (52) of the output waveguide (5) are orthogonal to the flow axis (20), the large dimension (GD) of the output waveguide (5) being equivalent to the large dimension (GD) of the input waveguide (4) and the small dimension (PD) of the output waveguide (5) being equivalent to the small dimension (PD) of the input waveguide (4); - said enclosure (3) has an output window (38) diametrically opposite the input window (37) and surrounded by the output waveguide (5) for microwave propagation through the output window (38).

6. The microwave reactor (1,1') according to claim 5, further comprising a short-circuit device (55; 56) attached on the output waveguide (5), said short-circuit device being either of the short-circuit piston (55) type adjustable along the propagation axis (40), or of the static short-circuit (56) type.

7. The microwave reactor (1,1') according to any one of claims 5 and 6, wherein the output window (38) is delimited by two longitudinal edges (381) parallel to the long sides (51) of the output waveguide (5) and by two lateral edges (382) parallel to the short sides (52) of the output waveguide (5), where the longitudinal edges (381) have a length less than or equal to the large dimension (GD) and the lateral edges (382) have a length less than or equal to the small dimension (PD).

8. The microwave reactor (1,1') according to claim 7, wherein the longitudinal edges (381) of the output window (38) have a length less than the large dimension (GD) and the lateral edges (382) of the output window (38) have a length equal to the small dimension (PD), so that the output window (38) forms an output iris.

9. The microwave reactor (1,1') according to any one of claims 1 to 4, wherein the enclosure (3) is closed opposite the input waveguide (4) and thus provides a curved reflective surface located diametrically opposite the input waveguide (4).

10. The microwave reactor (1,1') according to any one of claims 1 to 9, wherein the input waveguide (4) is attached transversely on the enclosure (3): - either at a distance from the first end (31) of between 0.4 and 0.6 times the enclosure length (LE); - or at a distance from the first end (31) of between 0.1 and 0.4 times the enclosure length (LE).

11. The microwave reactor (1,1') according to any one of claims 1 to 10, wherein the flow axis (20) is a vertical axis so that the flow tube (2) and the enclosure (3) extend vertically, and the propagation axis (40) is a horizontal axis so that the input waveguide (4) extends horizontally.

12. The microwave reactor (1,1') according to any one of claims 1 to 11, including another input waveguide (4') extending parallel to the propagation axis, said other input waveguide (4') having a rectangular section with two long sides (41') defining a large dimension (GD) and two short sides (42') defining a small dimension (PD) smaller than the large dimension (GD), and said other input waveguide (4') being coupled to the flow tube (2) for continuous microwave treatment of the fluidic medium; wherein the long sides (41') of said other input waveguide (4') are parallel to the flow axis (20), whereas the short sides (42') of said other input waveguide (4') are orthogonal to the flow axis (20); wherein the lateral dimension (DE) of the enclosure (3) is greater than the small dimension (PD) of said other input waveguide (4'), said other input waveguide (4') being attached transversely on the enclosure (3), said enclosure (3) having another input window surrounded by said other input waveguide (4') for microwave propagation through said other input window inside the enclosure (3), and wherein the enclosure length (LE) is strictly greater than the large dimension (GD) of said other input waveguide (4').

13. A microwave installation (10) for a continuous microwave treatment of a flowing fluidic medium selected from a liquid medium, a viscous medium, a pasty medium, a liquid / solid or liquid / gas two-phase mixture medium, said microwave installation (10) comprising: - a microwave reactor (1, 1') according to any one of claims 1 to 12; - a microwave generator (9) connected to the input waveguide (4); - a flow-establishing system (6) connected to the flow tube (2) upstream and downstream to ensure a flow of the fluidic medium inside the flow tube (2).

14. A method for continuous microwave treatment of a flowing fluidic medium selected from a liquid medium, a viscous medium, a pasty medium, a liquid / solid or liquid / gas two-phase mixture medium, said continuous microwave treatment method comprising the following steps of: - generating microwaves by means of a microwave generator connected to the input waveguide (4) of a microwave reactor (1,1') according to any one of claims 1 to 12; - causing a fluidic medium to flow inside the flow tube (2) of said microwave reactor (1), by means of a flow-establishing system (6) connected to the flow tube (2) upstream and downstream.