WO2023194951A1

WO2023194951A1 - Method and system for improving an impedance matching between a microwave cavity and a microwave source

Info

Publication number: WO2023194951A1
Application number: PCT/IB2023/053533
Authority: WO
Inventors: Jocelyn Doucet; Jean-Philippe Laviolette; Benoit Sevigny; Navid ELAHIPANAH
Original assignee: Pyrowave Inc.
Priority date: 2022-04-06
Filing date: 2023-04-06
Publication date: 2023-10-12

Abstract

There is described methods and system for improving the impedance matching within a microwave system comprising at least a microwave source and a microwave cavity for performing a microwave-assisted treatment on a substance.

Description

METHOD AND SYSTEM FOR IMPROVING AN IMPEDANCE MATCHING

BETWEEN A MICROWAVE CAVITY AND A MICROWAVE SOURCE

FIELD

[0001 j The present technology pertains to the field of microwave-assisted treatments, and more particularly to methods and systems for improving the impedance matching between a microwave cavity and a microwave source during a microwave- assisted treatment.

BACKGROUND

[0002] A microwave reactor consists of a fluid-containing vessel where a reaction is occurring and is usually sustained in steady state. A microwave reactor is coupled to a microwave source or generator for propagating microwaves into the microwave reactor. During the operation of the microwave reactor and the microwave source, the microwaves generate heat within the microwave reactor and the substances contained in the micro wave reactor react to form products.

[0003] One issue with microwave reactor systems is directed to how the microwave power is propagated inside the reactor, i.e., the ability to perform an optimal electromagnetic coupling between the microwave source and the microwave reactor. The optimal electromagnetic coupling is achieved by matching the impedance of the circuit formed of the microwave source and all components between the microwave source and the microwave reactor (such as a microwave waveguide, a microwave coupler and/or the like) with the impedance of the microwave reactor.

[0004] The impedance matching is usually performed using an iris or a stub tuner. An iris is a perforated plate and its impedance is a function of the hole size, depth and geometry. Since the hole size, depth and geometry are fixed, an iris is therefore a static impedance matching system and its impedance fixed and may not be changed in realtime during microwave injection into the reactor. [0005] The reflection coefficient T relates the incoming and reflected waves and is defined as:

where V is the voltage from the reflected wave and V⁺ is the voltage from the incoming wave.

[0006] Voltage standing wave ratio (VSWR) is related to the magnitude of the voltage reflection coefficient T and is defined as:

An ideal system has a VSWR of 1. When reflection occurs, the VSWR is higher than 1. Higher values of VSWR correlates with reduced transmission line (and therefore overall transmitter) efficiency.

[0007] VSWR can be measured directly with a standing wave ratio (SWR) meter. A radio-frequency (RF) test instrument such as a vector network analyzer (VNA) can be used to measure the reflection coefficients of the input port (scattering parameter Si l) and the output port (scattering parameter S22). Si l and S22 are equivalent to T at the input and output port, respectively. The VNAs with math modes can also directly calculate and display the resulting VSWR value.

[0008] A stub tuner is an adjustable impedance matching system that help increasing the transmission of a system. A typical stub tuner consists of a waveguide section provided with stubs or plungers that are inserted orthogonally therealong. Most conventional stub tuners have three spaced apart stubs commonly disposed in a casing attached to the waveguide wall. The insertion depth into the waveguide section can be varied to change the characteristic impedance of the stub tuner. A stub tuner usually allows for the changing of each individual stub's insertion depth in real-time during microwave injection so as to adjust impedance matching to minimize reflected power. Such a stub tuner is therefore a dynamic impedance matching system. However, some problems exist for at least some of the stub tuners. [0009] First, a stub tuner will tend to heat up which can lead to potential damage if the impedance mismatch is too high. When inserted in the microwave field within the waveguide, the stubs are subject to an electrical and magnetic field, which induces an electrical current on the stub surface. Since the stub material has a non-zero electrical resistance (stubs are usually made of aluminum or copper), resistive heat losses occur on the stubs. Some resistive losses also occur on the waveguide wall, but these are negligible compared to the losses on the stubs. Due to those resistive losses on the stubs, the stubs heat up and their operating temperature increases. As stub temperatures increase, stubs undergo thermal expansion such that their length and diameter increase. Because of the thermal expansion, the stubs may get squeezed inside the stub casing and screw drives may no longer be moved in and out of the tuner. The system then loses its ability to change the tuner's impedance. Furthermore, forcing the stub to move or out may cause mechanical damage to the stub, stub casing, screw drives and/or actuators. Also, when higher levels of mismatch are observed the phenomenon worsens and traditional systems start to further heat up and even create recurrent arcing inside the body of the stub tuner assembly. Most existing tuners have either no cooling mechanism to control the stub temperature or they feature a liquid (water, glycol) cooling circuit in the tuner casing. In both cases, the temperature of the stubs, which are the main source of heat are not controlled and this limits the existing tuners’ use to low impedance mismatch applications (e.g., applications forwhichthe voltage standing wave ratio (VSWR) is less than 10: 1).

[0010] There is a need for an impedance matching system that allows to compensate for a broader range of impedance mismatch without upper limitation (typically any VSWR higher than 1: 1) between a microwave generator and a reactor resonant cavity at high power (e.g., 100 kW at 915 MHz and 2450 MHz).

[001 1 ] Second, the use of a stub tuner or iris in the waveguide upstream of the microwave reactor leads to an increase in the reflected power downstream of its position, that is between the cavity and the tuner. This gives rise to a standing wave downstream of the tuner into the waveguide, microwave reactor interface and the microwave reactor. The standing wave results in increased electrical field intensity leading to higher risk of electrical discharge, arcing and localized hot spots resulting in equipment damage. [0012] Therefore, there is a need for an improved method and system for improving the impedance matching within a microwave system.

SUMMARY

[0 13] According to a first broad aspect, there is provided a method for improving an impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave-assisted treatment, the method comprising: injecting an initial substance into the microwave cavity; propagating microwaves from the microwave source into the cavity to perform a microwave- assisted treatment of the initial substance; determining a parameter of the microwave system; and adjusting an impedance of the microwave system based on the determined parameter.

[0014] According to a second broad aspect, there is provided a microwave system comprising: a microwave cavity configured for receiving an initial substance therein, the microwave cavity being operatively connectable to a microwave source for receiving microwaves therefrom to perform a microwave-assisted treatment on the initial substance; a body inserted into the microwave cavity, the body being at least partially made of a material that interacts with the microwaves; a microwave determining unit for determining a parameter of the microwave system; and a control unit operatively connected to the movable body, the control unit being configured for changing the body from a first configuration to a second configuration within the microwave cavity based on the determined parameter, the second configuration being chosen to improve an impedance matching between the microwave cavity and the microwave source.

[0015] In one embodiment, the parameter comprises one of a first amount of the microwaves reflected by the microwave cavity towards the microwave source and a second amount of the microwaves transmitted into the microwave cavity, and the second configuration is chosen to one of reduce the first amount and increase the second amount. [0016] In one embodiment, the control unit is configured for modifying the body from a first size to a second size, the second size being chosen to one of reduce the first amount and increase the second amount.

[0017] In one embodiment, the control unit is configured for modifying the body from a first shape to a second shape, the second shape being chosen to one of reduce the first amount and increase the second amount.

[0018] In one embodiment, the body is moveable within the microwave cavity and the control unit is configured for moving the body from a first position to a second position within the microwave cavity, the second position being chosen to one of reduce the first amount and increase the second amount.

[0019] In one embodiment, the control unit comprises a motion device operatively connected to the body for moving the body within the microwave cavity, and a controller in communication with the motion device, the controller being configured for determining the second position for the body and controlling the motion device to move the body to the second position.

[0020] In one embodiment, the body comprises a movable plate.

[0021 ] In one embodiment, the microwave cavity extends along a longitudinal axis, the movable plate extends substantially orthogonal to the longitudinal axis and the motion device is configured for translating the movable plate along the longitudinal axis.

[0022] In one embodiment, the movable plate comprises at least one aperture extending through a thickness thereof.

[0023] In one embodiment, the system further comprises a fixed plate extending substantially orthogonally to the longitudinal axis and having a fixed position relative to the longitudinal axis, wherein the microwave cavity comprises an opening for injecting the microwaves therein, the opening being located between the fixed plate and a given longitudinal end of the microwave cavity, and the movable plate is movable between the given end and the fixed plate. [0024] In one embodiment, the microwave determining unit comprises a sensor configured for measuring the first amount of the microwaves reflected by the microwave cavity.

[0025] In one embodiment, the microwave determining unit comprises a sensor configured for measuring a complex reflection coefficient of a microwave assembly comprising the microwave cavity and at least the microwave source.

[0026] In one embodiment, the sensor comprises one of a reflectometer and a network analyzer.

[0027] In one embodiment, the sensor is configured for measuring the complex reflection coefficient at an interface between the microwave cavity and the microwave source.

[0028] v the microwave assembly further comprises a coupler installed between the microwave source the microwave cavity, the sensor being configured for measuring the complex reflection coefficient at an interface between the microwave cavity and the coupler.

[0029] In one embodiment, the microwave determining unit comprises a sensor for measuring the second amount of the microwaves transmitted into the microwave cavity.

[0030] In one embodiment, the sensor comprises a temperature sensor configured for measuring a temperature of a reference element within the microwave cavity.

[0031 ] According to a third broad aspect, there is provided a method for improving an impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave-assisted treatment, the method comprising: injecting an initial substance into the microwave cavity; propagating microwaves from the microwave source into the microwave cavity to perform a microwave-assisted treatment of the initial substance, a body being inserted into the microwave cavity and the body being at least partially made of a material that interacts with the microwaves; determining a parameter of the microwave system; and changing the body from a first configuration to a second configuration within the microwave cavity based on the determined parameter, the second configuration being chosen to improve an impedance matching between the microwave cavity and the microwave source.

[0032] In one embodiment, the step of determining the parameter comprises determining one of a first amount of the microwaves reflected by the microwave cavity towards the microwave source and a second amount of the microwaves transmitted into the microwave cavity, the second configuration being chosen to one of reduce the first amount and increase the second amount.

[0033] In one embodiment, the step of changing the body comprises modifying the body from a first size to a second size, the second size being chosen to one of reduce the first amount and increase the second amount.

[0034] In one embodiment, the step of changing the body comprises modifying the body from a first shape to a second shape, the second shape being chosen to one of reduce the first amount and increase the second amount.

[0035] In one embodiment, the step of changing the body comprises moving the body from a first position to a second position within the microwave cavity, the second position being chosen to one of reduce the first amount and increase the second amount.

[0036] In one embodiment, the step of moving the body comprises moving a movable plate.

[0037] In one embodiment, the step of moving the movable plate comprises translating the movable plate along a longitudinal axis of the microwave cavity, the movable plate extending substantially orthogonally to the longitudinal axis.

[0038] In one embodiment, the movable plate comprises at least one aperture extending through a thickness thereof.

[0039] In one embodiment, the microwave cavity is further provided with a fixed plate extending substantially orthogonally to the longitudinal axis and having a fixed position relative to the longitudinal axis, the microwave cavity comprising an opening for injecting the microwaves therein, the opening being located between the fixed plate and a given longitudinal end of the microwave cavity, wherein said moving the movable plate comprises moving the movable plate between the given longitudinal end and the fixed plate.

[0040] In one embodiment, the step of determining the amount of the microwaves being reflected comprises measuring the amount of microwaves propagating from the microwave cavity towards the micro wave source.

[0041] In one embodiment, the step of determining the amount of the microwaves being reflected comprises measuring a complex reflection coefficient of a microwave system comprising the microwave cavity and at least the microwave source.

[0042] In one embodiment, the step of measuring the complex reflection coefficient is performed using one of a reflectometer and a network analyzer.

[0043] In one embodiment, the step of measuring the complex reflection coefficient is performed at an interface between the microwave cavity and the microwave source.

[0044] In one embodiment, the microwave system further comprises a coupler installed between the microwave source the microwave cavity, said measuring the complex reflection coefficient being performed at an interface between the microwave cavity and the coupler.

[0045] According to a fourth broad aspect, there is provided a microwave system comprising: a microwave cavity configured for receiving an initial substance therein, the microwave cavity being operatively connectable to a microwave source for receiving microwaves therefrom to perform a microwave-assisted treatment on the initial substance and thereby obtain a first substance being in a first phase and a second substance being a in a second and different phase; a microwave determining unit for determining a parameter of the microwave system; an injection unit fluidly connected to the microwave cavity for injecting an additional substance into the microwave cavity; an extraction unit fluidly connected to the microwave cavity for extracting at least some of the first substance from the microwave cavity; and a control unit in communication with the injection unit and the extraction unit for controlling a volume of the first substance within the microwave cavity based on the determined parameter, thereby improving an impedance matching between the microwave cavity and the microwave source. [0046] In one embodiment, the parameter comprises one of a first amount of the microwaves reflected by the microwave cavity towards the microwave source and a second amount of the microwaves transmitted into the microwave cavity, and the volume of the first substance is chosen based on one of the first amount and the second amount to one of reduce the first amount of the microwaves being reflected by the cavity towards the microwave source and increase the second amount of the microwaves transmitted into the microwave cavity.

[0047] In one embodiment, the additional substance comprises the initial substance.

[0048] In one embodiment, the additional substance comprises the first substance, the injection unit and the extraction unit being fluidly connected to propagate at least part of the first substance extracted by the extraction unit to the injection unit.

[0049] In one embodiment, the microwave determining unit comprises a sensor configured for measuring the first amount of the microwaves reflected by the microwave cavity.

[0050] In one embodiment, the microwave determining unit comprises a sensor configured for measuring a complex reflection coefficient of a microwave assembly comprising the micro wave cavity and at least the micro wave source.

[0051 ] In one embodiment, the sensor comprises one of a reflectometer and a network analyzer.

[0052] In one embodiment, the sensor is configured for measuring the complex reflection coefficient at an interface between the microwave cavity and the microwave source.

[0053] In one embodiment, the microwave assembly further comprises a coupler installed between the microwave source the microwave cavity, the sensor being configured for measuring the complex reflection coefficient at an interface between the microwave cavity and the coupler.

[0054] In one embodiment, the microwave determining unit comprises a sensor for measuring the second amount of the microwaves transmitted into the microwave cavity. [0055] In one embodiment, the sensor comprises a temperature sensor configured for measuring a temperature a reference element within the micro wave cavity.

[0056] According to another broad aspect, there is provided a method for improving an impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave-assisted treatment, the method comprising: injecting an initial substance into the microwave cavity; propagating microwaves from the microwave source into the cavity to perform a microwave- assisted treatment of the initial substance, thereby obtaining a first substance being in a first phase and a second substance being a in a second and different phase; determining a parameter of the microwave system; and controlling, based on the determined parameter, a volume of the first substance within the microwave cavity to reduce the amount of the microwaves being reflected by the cavity, thereby improving the impedance matching.

[0057] In one embodiment, said determining the parameter comprises determining one of a first amount of the microwaves reflected by the microwave cavity towards the microwave source and a second amount of the microwaves transmitted into the microwave cavity.

[0058] In one embodiment, said controlling the volume of the first substance comprises injecting an additional substance within the microwave cavity.

[0059] In one embodiment, the additional substance comprises the initial substance.

[0060] In one embodiment, the additional substance comprises the first substance.

[0061] In one embodiment, said determining the amount of the microwaves being reflected comprises measuring the amount of microwaves propagating from the microwave cavity towards the micro wave source.

[0062] In one embodiment, said determining the amount of the microwaves being reflected comprises measuring a complex reflection coefficient of a microwave system comprising the micro wave cavity and at least the micro wave source.

[0063] In one embodiment, said measuring the complex reflection coefficient is performed using one of a reflectometer and a network analyzer. [0064] In one embodiment, said measuring the complex reflection coefficient is performed at an interface between the microwave cavity and the microwave source.

[0065] In one embodiment, the microwave system further comprises a coupler installed between the microwave source the microwave cavity, said measuring the complex reflection coefficient being performed at an interface between the microwave cavity and the coupler.

[0066] According to a further broad aspect, there is provided a method for improving an impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave-assisted treatment, the method comprising: injecting an initial substance into the microwave cavity; propagating microwaves from the microwave source into the cavity to perform a microwave-assisted treatment of the initial substance, thereby obtaining a fluidized substance; determining a parameter of the microwave system; and varying, based on the determined parameter, effective electromagnetic properties of the fluidized substance contained within the microwave cavity to reduce the amount of the microwaves being reflected by the cavity, thereby improving the impedance matching.

[0067] In one embodiment, the parameter comprises one of a first amount of the microwaves reflected by the microwave cavity towards the microwave source and a second amount of the microwaves transmitted into the microwave cavity.

[0068] In one embodiment, said varying the effective electromagnetic properties of the fluidized substance comprises modifying a composition of the fluidized substance.

[0069] In one embodiment, said modifying the composition of the fluidized substance comprises varying an injection rate of the initial substance into the microwave cavity.

[0070] In one embodiment, said modifying the composition of the fluidized substance comprises varying an extraction rate of the fluidized substance.

[0071] In one embodiment, the method further comprises injecting microwave interacting particles into the microwave cavity, said modifying the composition of the fluidized substance comprising at least one of varying an injection rate of the microwave interacting particles into the microwave cavity and varying an extraction rate of the fluidized substance containing some of the microwave interacting particles.

[0072] In one embodiment, the method further comprises extracting a portion of the fluidized substance from the microwave cavity and recirculating the portion of the fluidized substance into the microwave cavity, said modifying the composition of the fluidized substance comprising varying a recirculation rate of the fluidized substance.

[0073] In one embodiment, said varying the effective electromagnetic properties of the fluidized substance comprises varying an homogeneity of the fluidized substance within the micro wave cavity.

[0074] In one embodiment, the method further comprises agitating the fluidized substance, said varying the homogeneity of the fluidized substance comprising varying an agitation speed of the fluidized substance.

[0075] In one embodiment, the method further comprises injecting gas into the fluidized substance, said varying the homogeneity of the fluidized substance comprising varying the injection of the gas into the fluidized substance.

[0076] In one embodiment, the method further comprises extracting a portion of the fluidized substance from the microwave cavity and recirculating the portion of the fluidized substance into the microwave cavity, said varying the homogeneity of the fluidized substance comprising varying a recirculation rate of the fluidized substance.

[0077] In one embodiment, said determining the amount of the microwaves being reflected comprises measuring the amount of microwaves propagating from the microwave cavity towards the micro wave source.

[0078] In one embodiment, said determining the amount of the micro waves being reflected comprises measuring a complex reflection coefficient of a microwave system comprising the micro wave cavity and at least the micro wave source.

[0079] In one embodiment, said measuring the complex reflection coefficient is performed using one of a reflectometer and a network analyzer. [0080] In one embodiment, said measuring the complex reflection coefficient is performed at an interface between the microwave cavity and the microwave source.

[0081] In one embodiment, the microwave system further comprises a coupler installed between the microwave source the microwave cavity, said measuring the complex reflection coefficient being performed at an interface between the microwave cavity and the coupler.

[0082] In the following, a microwave cavity should be understood as being a vessel made of or internally covered with a microwave-reflecting material having at least one opening for the injection of microwaves as well as other openings and/or ports for other purposes such as the connection of instruments, injection of material, exhaust of material, etc. A microwave reactor is an exemplary type of microwave cavities. Microwave cavities are generally made from highly conductive material (such as a metal) that reflects and contains the electromagnetic waves in the cavity. Microwave cavities can also contain solid objects or equipment that add boundaries inside the microwave cavity: mode stirrer, agitator, shaft, etc. Furthermore, the cavity walls and internal equipment bound an internal volume that can be either in vacuum or filled with a mixture that is single-phase or multi -phase: gas, liquid, solids or any homogeneous or heterogeneous mixture of one or several of those components.

[0083] Implementations of the present technology each have at least one of the above-mentioned objects and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein.

[0084] Additional and/or alternative features, aspects and advantages of implementations of the present technology will become apparent from the following description, the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] For a beter understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0086] Fig. 1 illustrates a microwave system for performing a microwave-assisted treatment on a substance, the microwave system comprising a microwave cavity provided with a movable body, the movable body being in a first configuration, in accordance with an embodiment;

[0087] Fig. 2 is a flow chart of a method for performing a microwave-assisted treatment on a substance using a movable body inserted into a microwave cavity, in accordance with an embodiment;

[0088] Fig. 3a illustrates the microwave system of Fig. 1 wherein the movable body is in a second configuration;

[0089] Fig. 3b illustrates the microwave system of Fig. 1 wherein the movable body is in a third configuration;

[0090] Fig. 4 is an external view of a microwave cavity provided with a movable plate, in accordance with an embodiment;

[0091] Fig. 5 is a cross-sectional view of the microwave cavity of Fig. 4;

[0092] Fig. 6 illustrates the movable plate of the microwave cavity of Fig. 4 and a fixed plate, in accordance with an embodiment;

[0093] Fig. 7 is a cross-sectional view of the movable and fixed plates of Fig. 6;

[0094] Fig. 8 is a block diagram illustrating a microwave system, according to another embodiment;

[0095] Fig. 9 is a method for performing a microwave-assisted treatment on a substance in accordance with another embodiment;

[0096] Fig. 10 is a block diagram illustrating a microwave system, according to a further embodiment; [0097] Fig. 11 is a method for performing a microwave-assisted treatment on a substance in accordance with a further embodiment;

[0098] Fig. 12 is a exemplary graph illustrating the microwave power reflected by the micro wave cavity of Fig. 4 as a function of the micro wave frequency for different position of the movable plate;

[0099] Fig. 13 is an exemplary graph illustrating the reflection coefficient measured for the microwave cavity of Fig. 4 and the theoretical reflection coefficient as a function of the movable plate position;

[0100] Fig. 14 is an exemplary graph illustrating the reflection coefficient measured for the microwave cavity of Fig. 8 over 5 minutes for different levels of liquid within the cavity; and

[0101] Fig. 15 is an exemplary graph illustrating a theoretical reflection coefficient for the microwave cavity of Fig. 8 as a function of the level of liquid within the cavity.

DETAILED DESCRIPTION

[0102] The examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the present technology and not to limit its scope to such specifically recited examples and conditions. It will be appreciated that those skilled in the art may devise various arrangements which, although not explicitly described or shown herein, nonetheless embody the principles of the present technology and are included within its spirit and scope.

[0103] Furthermore, as an aid to understanding, the following description may describe relatively simplified implementations of the present technology. As persons skilled in the art would understand, various implementations of the present technology may be of a greater complexity.

[0104] In some cases, what are believed to be helpful examples of modifications to the present technology may also be set forth. This is done merely as an aid to understanding, and, again, not to define the scope or set forth the bounds of the present technology. These modifications are not an exhaustive list, and a person skilled in the art may make other modifications while nonetheless remaining within the scope of the present technology. Further, where no examples of modifications have been set forth, it should not be interpreted that no modifications are possible and/or that what is described is the sole manner of implementing that element of the present technology.

[0105] In some embodiments, the present technology is directed towards a method for improving the impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave-assisted treatment. The method comprises the following steps: injecting an initial substance into the microwave cavity; propagating microwaves from the microwave source into the cavity to perform a microwave-assisted treatment of the initial substance; determining a parameter of the micro wave system; and adjusting the impedance of the microwave system based on the determined parameter.

[0106] As described in greater detail below, the determined parameter of the microwave system may be the amount of microwaves reflected by the microwave cavity or the amount of microwaves transmitted by the microwave cavity. However, the person skilled in the art will understand that determining the amount of reflected microwaves is equivalent to determining the amount of transmitted microwaves since the amount of transmitted microwaves can be determined from the amount of reflected microwaves and the total amount of microwaves emitted by the microwave source, and vice versa.

[0107] In some embodiments, the adjustment of the impedance of the microwave system is performed by adjusting the configuration of a microwave interacting body inserted into the microwave cavity, as described in greater detail below.

[0108] In other embodiments, the adjustment of the impedance of the microwave system is performed by adjusting the volume of the substance to be treated contained into the microwave cavity, as described in greater detail below. [0109] In still other embodiments, the adjustment of the impedance of the microwave system is performed by adjusting the effective electromagnetic properties of the fluidized substance contained within the microwave cavity, as described in greater detail below.

[0110] Fig. 1 illustrates one embodiment of a microwave system 10 for performing a microwave-assisted treatment on an initial substance or material. The system 10 comprises a microwave cavity 12 operatively connectable to a microwave source 14 via a microwave waveguide 16, a reflection determining unit 18, a body 20, a configuration device 22 operatively connected to the body 20 and a controller 24. In one embodiment, the controller 24 and the configuration device 22 form together a control unit. For example, the configuration device 22 and the controller 24 may be integral to form a control unit configured to control the configuration of the body 20 within the microwave cavity 12.

[01 1 1] In one embodiment, the configuration of the body 20 refers to the position of the body 20 within the microwave cavity 12 and/or the geometry of the body 20, i.e., the shape and/or dimension of the body 20. Therefore, the configuration device 22 is adapted to change the position of the body 20 within the microwave cavity 12 and/or change the geometry of the body 20.

[ 1 12] The initial substance or material to be treated can be in a solid phase, a liquid phase and/or a gaseous phase. In one embodiment, the initial substance or material comprises a plurality of initial substances or materials which can be in the same phase or in different phases. For example, the initial material to be treated may comprise liquid polystyrene to be pyrolyzed. In another example, the initial material to be treated may comprise a piece of ceramic to be cured. In a further embodiment, the initial substance to be treated may comprise two immiscible liquid substances.

[01 13] In one embodiment, gas may be injected into the microwave cavity 12 in addition to the initial substance to be treated as part of the process.

[0114] The microwave cavity 12 comprises a hollow body 26 defining an internal chamber 28 for receiving therein the initial substance on which the microwave-assisted treatment is to be performed. The internal surface of the body 26 surrounding the internal chamber 28 is usually made from a material that reflects microwaves, as known in the art. The body 26 is provided with an opening 30 for allowing the microwaves coming from the waveguide 16 to propagate into the internal chamber 28 of the microwave cavity 12.

[01 15] It should be understood that the body 26 may comprise a plurality of additional openings for injecting the substance to be treated into the internal chamber 26, extracting the treated substance, extracting gases created during the treatment, inserting a sensor, and/or the like.

[01 16] The microwave cavity 12 is operatively connected to the microwave source 14 to receive the microwaves generated by the microwave source 14. More precisely, the microwave waveguide 16 is connected between the microwave cavity 12 and the micro wave source 14 to guide the micro waves emitted by the micro wave source 14 to the internal chamber 28 of the microwave cavity 12.

[01 17] As illustrated in Fig. 1, the body 20 is inserted in the internal chamber 28 of the microwave cavity 12 and mechanically connected to the configuration device 22. The configuration device 22 is adapted to change the configuration of body 20 within the internal chamber 28. For example, the configuration device 22 is adapted to move the body 20 within the microwave cavity 12 such as to position the body 20 at a desired position, vary the dimension of the body 20 such as to obtain to a target size or dimension for the body 20, and/or modify the shape of the body 20 such as to obtain a desired shape for the body 20. In an embodiment in which the configuration device 22 is configured to move the body 20, it should be understood that the configuration device 22 may be any adequate device that allows for moving a body within a microwave cavity. In one embodiment, the configuration device 22 may allow 2D displacements of the body 20 within the chamber 28. For example, the configuration device 22 may translate the body 20 along the longitudinal axis of the microwave cavity 12 and/or along an axis orthogonal to the longitudinal axis. In another embodiment, the configuration device 22 may allow 3D displacements of the body 20 within the chamber 28. In an embodiment in which the configuration device 22 is configured to change the geometry of the body 20, it should be understood that the configuration device 22 may be any adequate device that allows for changing the shape and/or dimension of the body 22. For example, the body 22 may be made of different pieces movably connected together and the configuration device 22 is configured to adjust the relative positions of the different pieces to change the shape of the body 22. In another example, the body 20 may be a cylindrical perforated cage of which the diameter is controllable by the configuration device 22. In a further example, the body 20 may be inflatable and the configuration is configured for injecting and extracting a fluid from the body 20 in order to adjust the shape and/or dimension of the body 20.

[011.8] The body 20 is at least partially made of with a material that interacts with microwaves. For example, the body 20 may be entirely made of a material that interacts with microwaves or be covered with a material that interacts with microwaves. For example, the body 20 may be made of a material that reflects microwaves, a material that absorbs microwaves, a material that dissipates microwaves, and/or the like. It should be understood that the body 20 may be provided with any adequate initial shape and/or size. For example, the body 20 may be provided with a plate shape, a cubic shape, a spherical shape, etc.

[ 1 19] In an embodiment in which the configuration device 22 is adapted to move the body 20, the body 20 has an asymmetrical shape and/or is inhomogeneous, i.e., the composition and/or structure of the body varies from one point of the body to another. In this case, the configuration device 22 may be adapted to rotate the body 20 from a first angular position to a second and different angular position. It should be understood that the configuration device 22 may be adapted to further translate the body 20, as described above.

[0120] The reflection determining unit 18 is configured for determining the amount of microwaves that are reflected by the microwave cavity 12 towards the microwave source 14. In one embodiment, the amount of microwaves reflected by the microwave cavity 12 corresponds to the power or amplitude of the microwaves reflected by the microwave cavity 12. In another embodiment, the amount of microwaves reflected by the microwave cavity 12 corresponds to the complex reflection coefficient of the microwave assembly comprising at least the microwave cavity 12, the microwave source 14 and the waveguide 16.

[0121] In one embodiment, the reflection determining unit 18 comprises a sensor adapted to measure the power and/or amplitude of microwaves. In this case, the system 10 may further comprise a circulator (not shown) comprising at least three ports. In one embodiment, the circulator is connected between the microwave source 14 and the waveguide 16 and the sensor is connected to the circulator. The microwave source 14 is connected to a first port of the circulator and the waveguide is connected to a second port of the circulator so that micro waves emitted by the micro wave source 14 and entering the circulator by the first port are transmitted to the waveguide 16 via the second port. The sensor is connected to the third port of the circulator so that microwaves entering the circulator via the second port from the waveguide are transmitted to the sensor via the third port. In another embodiment, the circulator is connected between the microwave cavity 12 and the waveguide 16 and the sensor is connected to the circulator. The microwave cavity 12 is connected to a first port of the circulator and the waveguide 16 is connected to a second port of the circulator so that microwaves emitted by the microwave source 14, propagating into the waveguide 16 and entering the circulator by the second port are transmitted to the microwave cavity 12 via the first port. The sensor is connected to the third port of the circulator so that microwaves reflected by the microwave cavity 12 and entering the circulator via the first port are transited to the sensor via the third port.

[01 2] In another embodiment, the reflection determining unit 18 comprises a device adapted to measure or determine the complex reflection coefficient of the microwave assembly comprising the microwave cavity 12, the microwave source 14 and the waveguide 16. In one embodiment, the reflection determining unit 18 is a reflectometer. In another embodiment, the reflection determining unit 18 is a network analyzer. In one embodiment, the reflection determining unit 18 is configured to measure the complex reflection coefficient at the interface between the microwave cavity 12 and the waveguide 16.

[0123] Referring back to Fig. 1, the system 10 further comprises a controller 24. The controller 24 is in communication with the reflection determining unit 18 for receiving the amount of reflected microwaves therefrom. The controller 24 is further in communication with the configuration device 22 for controlling the configuration of the body 20 based on the received amount of reflected microwaves. In one embodiment, the controller 24 is configured to determine a target configuration for the body 20, i.e., a target position, a target shape and/or a target size for the body 20, that improves the internal impedance of the assembly comprising the microwave cavity 12, the microwave source 14 and the waveguide 16, i.e., that improves the impedance matching between the microwave cavity 12 and the microwave source 14. It should be understood that when the amount of microwaves reflected by the microwave cavity 12 towards the microwave source 14 decreases, the net internal impedance of the assembly comprising the microwave cavity 12, the microwave source 14 and the waveguide 16 decreases and the difference between the imaginary impedance component of the microwave cavity 12 and the imaginary impedance component of the microwave source 14 decreases, thereby improving the impedance matching between the microwave cavity 12 and the microwave source 14.

[01 4] In an embodiment in which the configuration device 22 is configured to move the body 20 to a target position, the target configuration comprises a new 3D position for the body 20 within the microwave cavity 12. In an embodiment in which the body 20 has an asymmetrical shape and/or is inhomogeneous, the target position comprises a new 3D position and/or a new angular position.

[01 5] In an embodiment in which the configuration device 22 is configured to control the geometry of the body 20, the target configuration comprises a new configuration, i.e., a new shape and/or a new dimension, for the body 20.

[0126] As known in the art, the impedance Z of the assembly is composed of a real resistance term R and an imaginary reactance term X and can be expressed as:

Z = R + jX

[0127] In one embodiment and in order to improve the impedance of the assembly comprising the microwave cavity 12, the microwave source 14 and the waveguide 16 (i.e., improve the impedance matching between the microwave cavity 12 and the microwave source 14), the controller 24 is configured for determining a configuration for the body 20 that decreases the reactance X of the assembly. Decreasing the reactance X of the assembly allows for decreasing the difference between the impedance of the microwave cavity 12 and the impedance of the microwave source 14, thereby improving the impedance matching between the micro wave cavity 12 and the microwave source 14. [0128] In one embodiment, the controller 24 is configured for determining a configuration for the body 20 that reduces or minimizes the reactance X of the assembly comprising the microwave cavity 12, the microwave source 14 and the waveguide 16. Reducing or minimizing the reactance X of the assembly allows for decreasing the difference between the impedance of the microwave cavity 12 and the impedance of the microwave source 14, thereby improving the impedance matching between the micro wave cavity 12 and the micro wave source 14.

[0129] In one embodiment, the controller 24 is configured for determining a configuration for the body 20 that sets to zero the value of the reactance X of the assembly comprising the microwave cavity 12, the microwave source 14 and the waveguide 16. In this case, the difference between the reactance of the microwave cavity 12 and the reactance of the microwave source 14 is also equal to zero, which corresponds to a perfect impedance matching between the microwave cavity 12 and the microwave source 14.

[0130] In one embodiment, the controller 24 is configured for accessing a database stored in a memory and comprising predefined configurations for the body 20, such as predefined positions, shapes and/or sizes, and respective predefined amounts of reflected microwaves. In this case, the controller is configured to determine the target configuration for the body 20 by accessing the database and retrieving the predefined configuration that corresponds to the amount of reflected microwaves received from the reflection determining unit 18.

[0131 ] In another embodiment, the controller 24 is configured for applying a control loop such as a proportional-integral-derivative (PID) loop to determine the target configuration of the body 20. In this case, the reflection determining unit 18 substantially continuously determines the amount of microwaves reflected by the microwave cavity 12 and the controller 24 substantially continuously determines the configuration for the body 20 using the control loop until a given configuration for the body 20 that reduces or minimizes the amount of reflected microwaves is reached.

[0132] In an embodiment in which the microwave source 14 is tunable, i.e., the frequency or wavelength of the microwaves emitted by the microwave source 14 is adjustable, the controller 24 is further operatively connected to the microwave source 14 for controlling the frequency of the emitted microwaves. In this case, the controller 24 is further configured for adjusting the frequency to a desired value in addition to controlling the configuration of the body 20, in order to reduce or minimize the amount of reflected microwaves.

[0133] In one embodiment, the controller 24 iteratively controls the configuration of the body 20 and the frequency of the microwaves to reduce or minimize the amount of reflected microwaves. For example, the controller 24 may first adjust the configuration of the body 20 based on the actual amount of reflected microwaves received from the reflection determining unit 18 so that the amount of reflected microwaves reaches a first amount of reflected microwaves, and then adjust the frequency of the microwaves to a target frequency based on the actual amount of reflected microwaves received from the reflection determining unit 18 so that the amount of reflected microwaves reaches a second amount that is less than the first amount.

[0134] In one embodiment, the controller 24 is configured for accessing a database stored in a memory and comprising predefined frequencies and respective predefined amounts of reflected microwaves. In this case, the controller is configured for determining the target frequency by accessing the database and retrieving the frequency that corresponds to the amount of reflected microwaves received from the reflection determining unit 18.

[0135] In another embodiment, the controller 24 is configured for applying a control loop such as a PID loop to determine the target frequency. In this case, the reflection determining unit 18 substantially continuously determines the amount of microwaves reflected by the microwave cavity 12 and the controller 24 substantially continuously determines the frequency of the microwaves using the control loop until a given frequency that reduces or minimizes the amount of reflected microwaves is reached.

[0136] In another embodiment, the controller 24 concurrently controls the configuration of the body 20 and the frequency of the microwaves to reduce or minimize the amount of reflected microwaves.

[0137] In one embodiment, the controller 24 is configured for accessing a database stored in a memory and comprising predefined combinations of a configuration for the body 20 and a predefined frequency, and respective predefined amounts of reflected microwaves, i.e., for each predefined amount of reflected microwaves correspond a unique combination of body configuration and frequency. In this case, the controller is configured to determine the target configuration for the body 20 and the frequency for the microwaves by accessing the database and retrieving the predefined combination that corresponds to the amount of reflected microwaves received from the reflection determining unit 18.

[ 138] In another embodiment, the controller 24 is configured for applying a control loop to determine the target configuration of the body 20 and the frequency of the microwaves. In this case, the reflection determining unit 18 substantially continuously determines the amount of microwaves reflected by the microwave cavity 12 and the controller 24 substantially continuously determines the combination of configuration for the body 20 and frequency using the control loop until a given combination of configuration for the body 20 and frequency that reduces or minimizes the amount of reflected microwaves is reached.

[0139] Fig. 2 illustrates one exemplary method of operation of the system 10. At step 52, an initial substance to be treated using microwaves is injected into the microwave cavity 12. It should be understood that the initial substance may comprise a mixture of substances. For example, the initial substance may comprise a substance to be pyrolyzed and additional material such as ceramic particles, microwave receptors and/or the like.

[0140] In an embodiment in which two immiscible substances are present in the microwave cavity 12 during the microwave-assisted treatment (such as when a liquid and gas are present or when two immiscible liquids are present), the amount or quantity of substance injected into the microwave cavity 12 is chosen so that the top level or bed 32 of the initial substance be located on top of the aperture 30 so that all microwaves entering the internal chamber 28 of the microwave cavity 12 via the opening 30 propagate into the initial substance. It should be understood that the top level 32 represents the bed of solid particles (with gas between the particles) or the interface between a solid and gas, between a solid and a liquid, between two immiscible liquids, or between a liquid and gas, between solid particles in a liquid and an immiscible substance on top (gas or immiscible liquid, or the like. The top level 32 also represents the interface between two different phases, e.g., the interface between the initial substance being in a solid, fluidized, slurry, liquid or viscous phase and a gaseous phase comprises air, any gas injected into the microwave cavity as part of the process and/or gases generated by the microwave-assisted treatment of the initial substance.

[0141 ] At step 54, microwaves are propagated from the microwave source 14 into the internal chamber 28 of the microwave cavity 12 via the micro wave waveguide 16 and the aperture 30. The microwaves then interact with the initial substance, thereby treating the initial substance. During the treatment of the initial substance, some of the treated substance may be extracted from the microwave cavity 12 via an outlet, additional initial substance may be injected into the microwave cavity 12, components such as gases may be generated, and/or the like, which results in a change in the impedance of the microwave cavity 12, resulting in a mismatch between the impedance of the micro wave cavity 12 and the impedance of the micro wave source 14 or an increase in the impedance mismatch. Furthermore, the impedance of the microwave source 14 may also change during the microwave-assisted treatment which may also create an impedance mismatch between the microwave cavity 12 and the microwave source 14 or increase the impedance mismatch.

[0142] At step, 56, the amount microwaves reflected by the microwave cavity 12 towards the microwave source 14 is determined by the reflection determining unit 18. As described above, the mount of reflected microwaves may correspond to the amplitude or power of the microwaves reflected by the microwave cavity 12 towards the microwave source 12 measured by a microwave sensor. In another embodiment, the amount of reflected microwaves corresponds to the complex reflection coefficient of the microwave assembly comprising at least the microwave cavity 12, the microwave source 14 and the waveguide 16. The determined amount of reflected microwaves is then sent by the reflection determining unit 18 to the controller 24.

[0143] At step 58, the configuration of the body 20 is moved from a first or actual configuration to a second or target configuration that allows for reducing or minimizing the amount of reflected microwaves. In one embodiment, the received amount of reflected microwaves is compared to a threshold. If the received amount of reflected microwaves is less than a predefined threshold, the configuration of the body 20 remains unchanged. If the received amount of reflected microwaves is equal to or greater than the predefined threshold, a new configuration for the body, i.e., the target configuration, is determined and the configuration is changed to the target configuration.

[0144] As described above, the target configuration may be determined by accessing a database comprising predefined configurations and respective amounts of reflected microwaves. In another embodiment, the target configuration is achieved using a control loop.

[0145] In one embodiment, the determination of the amount of reflected microwaves and the adjustment of the configuration of the body 20 are performed iteratively in a stepwise manner. For example, they may be performed every 10 seconds.

[0146] In another embodiment, the determination of the amount of reflected microwaves and the adjustment of the configuration of the body 20 are substantially continuously performed.

[ 147] In an embodiment in which the configuration device 22 is configured to move the body 20, the displacement of the body 20 within the microwave cavity 12 is limited to the space occupied by a single phase. For example, the displacement of the body 20 may be limited to the phase occupying the bottom of the microwave cavity or the liquid or viscous phase. For example, the body 20 may be displaced from the position illustrated in Fig. 1, in which the body 20 is located within a liquid phase below the interface 32, to the position illustrated in Fig. 3a in which the body 20 is also located within a liquid phase below the interface 32 and which is adapted to reduce the amount of reflected microwaves compared to the initial position.

[0148] In another embodiment, the displacement of the body within the microwave cavity 12 is not limited to any phase and may occupy any adequate position with the internal chamber 28 of the microwave cavity 12. For example, the body 20 may be displaced from the position illustrated in Fig. 1, in which the body 20 is located within a liquid phase below the interface 32, to the position illustrated in Fig. 3b in which the body 20 is located within a gaseous phase above the interface 32 and which is adapted to reduce the amount of reflected microwaves compared to the initial position. [0149] In one embodiment, the controller 24 is further configured to control the injection rate of initial substance into the microwave cavity 12 and the extraction rate of material from the microwave cavity 12 so as to keep the height of the bed level 22 substantially constant in time.

[0150] In an embodiment in which a microwave interacting substance is injected into the microwave cavity 12 via an injection unit connected to the microwave cavity 12, the controller 24 is further configured to adjust or vary the amount of the microwave interacting substance present into the microwave cavity 12 to decrease or minimize the microwave reflected power. For example, the controller 24 may be configured for controlling the injection rate of the microwave interacting substance into the microwave cavity 12.

[0151] In one embodiment, a desired setpoint for the position or height of the interface is determined in order to reduce or minimize the reflected power. The injection rate of the initial substance is modulated in order for the interface to reach the desired setpoint. For example, a PID control method between a level transmitter and the feed pump speed may be used. If the initial material decreases at a certain rate due to a reaction or a material outlet on the reactor, the injected rate of initial material must be higher than its rate of consumption if the interface position setpoint is higher than the current interface position and inversely. Once the interface position has reached the setpoint, then the injection rate is equalled to the consumption rate and the interface position is constant. Therefore, the injection rate is based on the rate of change of the interface and on a mass balance of the material in the reactor.

[0152] In the following, there is described an example of microwave cavity that may be used in the system 10. In this embodiment, the body having a planar shape and the configuration unit is configured to control the position of the body.

[01 3] Figs 4 and 5 illustrates one embodiment of a microwave cavity 100 which comprises a vessel 102 made from a microwave reflecting material. The vessel 102 defines an internal chamber 104 in which a microwave-assisted treatment is to be performed. The vessel 102 is provided with an opening 106 for injecting microwaves into the chamber 104. It should be understood that the microwave cavity 100 is connectable to a microwave source (not shown) via a microwave waveguide (not shown). The microwave waveguide is to be positioned around the opening 106 for injecting the microwaves generated by the microwave source into the internal chamber 104.

[0154] In the illustrated embodiment, the vessel 102 further comprises a plurality of opening for injecting and/or extracting substances such as an inlet opening for injecting the substance to be treated, an outlet opening for extracting the treated substance, at least one opening for extracting gases generated during the microwave-assisted treatment, at least one opening for inserting at least one sensor into the chamber 104, etc.

[0155] The vessel 102 comprises an elongated hollow body 110, atop wall or cover 112 and a bottom or cover wall 114. In one embodiment, the top cover 112 and/or the bottom cover 114 are fixedly secured to the tubular body 110. In another embodiment, the top cover 112 and/or the bottom cover 114 are removably secured to the tubular body 110. In one embodiment, the elongated hollow body 110 comprises two hollow portions removably secured together, i.e., a top hollow portion to which the top cover 112 is secured and a bottom hollow portion to which the bottom cover 114 is secured.

[0156] While in the illustrated embodiment, the elongated hollow body 110 is provided with a tubular shape, i.e., it has a circular cross-sectional shape, it should be understood that the elongated hollow body 110 may have another adequate crosssection shape such as an oval cross-section shape.

[0157] The top cover 112 is provided with a first arm receiving aperture 120 and an optional second arm receiving aperture 122 both extending through a thickness thereof. The first and second arm receiving apertures 120 and 122 are each shaped and sized for receiving therein a respective arm or shaft, as described below.

[0158] A movable plate 130 is inserted into the internal chamber 104 of the microwave cavity 100. The movable plate 130 is made from a material that interacts with microwaves so that a displacement of the movable plate 130 within the chamber 104 changes the impedance of the microwave cavity 100. In the illustrated embodiment, the movable plate 130 is positioned so as to be substantially orthogonal to the longitudinal axis of the hollow body 110 and is translatable along the longitudinal axis of the hollow body 110 while remaining substantially orthogonal to the longitudinal axis of the hollow body 110. However, it should be understood that the position of the movable plate 130 relative to the hollow body 110 and/or the displacement of the movable plate 103 within the hollow body 110 may vary.

[0159] In the illustrated embodiment, the movable plate 130 has a disc shape and its circumference is less than that of the cross-section of the hollow body to allow the movable plate 130 translate along the hollow body 110.

[0160] As illustrated in Fig. 7, the movable plate 130 is provided with a plurality of holes 132 extending therethrough for allowing the substance being treated in the microwave cavity 100 to pass through the movable plate 130 when the movable plate 130 is translated within the microwave cavity 100. In one embodiment, the shape and size of the holes 132 are chosen based on characteristics of the substance being treated such as its viscosity for example. In one embodiment, the number and/or the size of the holes 132 is chosen to decrease or minimize the amount of microwaves that may propagate through the fixed plate 130.

[0161 ] Referring back to Figs. 4 and 5, a configuration device 140 is mounted onto the top cover 112 of the microwave cavity 100 and connected to the movable plate 130 for translating the movable plate 130 within the microwave cavity 100. The configuration device 140 comprises an arm or shaft 142 of which the length within the chamber 104 is adjustable and a motor assembly 144 for adjusting the length of the arm 142 within the chamber 104. The arm 142 extends longitudinally between a first end 146 operatively connected to the motor assembly 144 and a second end fixedly secured to the movable plate 130 and also extends through the aperture 120 located in the top cover 112 to allow the connection of the first end 146 to the motor assembly 144 located outside of the microwave cavity 100.

[0162] Upon activation of the motor assembly 144, the length of the portion of the arm 142 located within the microwave cavity 100 varies, i.e., the length portion of the arm 142 located within the chamber 104 may increase or decrease, to position the movable plate 130 at a desired position long the longitudinal axis of the microwave cavity 100. It should be understood that the configuration device 140 is controlled by a controller, such as controller 24, which determines the target position of the movable plate 130 based on the amount of microwaves reflected by the microwave cavity 100 determined by a reflection determining unit, such as reflection determining unit 18.

[0163] In one embodiment such as in the illustrated embodiment, the microwave cavity 100 is further provided with a fixed plate 150 which is inserted into the chamber 104 and has a fixed position within relative to the vessel 102. The fixed plate 150 extends transversally throughout the whole cross-section of the hollow body 110 to divide the internal chamber 104 into two chamber sections 104a and 104b, i.e., the circumference of the fixed plate 150 is equal to that of the internal wall of the hollow body 110. The fixed plate 150 is provided with an arm receiving opening through which the arm 142 extends. The fixed plate 150 is made of a material that is opaque to microwaves to limit the amount of microwaves that may propagate therethrough. For example, the fixed plate 150 may be made of a microwave absorbing material such as a magnetic material. In another example, the fixed plate 150 may be made of a micro wave reflecting material such as metal.

[0164] The fixed plate 150 is located within the vessel 102 between the opening 106 and the top cover 112 so as to limit or minimize the amount of micro waves that may propagate into the chamber section 104a. As illustrated in Fig. 7, the fixed plate 150 is provided with a plurality of holes 152 extending therethrough for allowing the substance being treated in the microwave cavity 100 to pass through the fixed plate 150. In one embodiment, the shape and size of the holes 152 are chosen based on characteristics of the substance being treated such as its viscosity for example. In one embodiment, the number and/or the size of the apertures 152 is chosen to decrease or minimize the amount of micro waves that may propagate through the fixed plate 150.

[0165] In operation, the amount of initial substance injected into the microwave cavity 100 is chosen so that the fixed plate 150 be immerged into the initial substance, i.e., the top level of the initial substance is located between the fixed plate 150 and the top cover 112. Microwaves are injected into the microwave cavity 100 via the opening 106 of the vessel 102. The microwaves are substantially contained within the chamber 104b since the fixed plate 150 substantially prevent or minimizes the amount of microwaves that pass therethrough to reach the chamber section 104a. The movable plate 130 may then be moved within the chamber 104 to adjust the impedance of the microwave cavity 100 to a desired value. [0166] It should be understood that, while the above description refers to the fixed plate being immerged into the initial substance, the top level of the initial substance may be located below the fixed plate 150.

[0167] In one embodiment such as in the illustrated embodiment, the microwave cavity is further provided with an agitator device 160 for mixing the substance being treated. The agitator device 160 comprises a motor assembly 162 mounted onto the top cover 112 of the vessel 102, a shaft 164 and at least one mixing plate 166 mounted to the shaft 164. The shaft 162 longitudinally extends between a first end operatively connected to the motor assembly 162 and a second end. The shaft 164 extends through the aperture 122 of the top cover 112 to allow the connection between the first end of the shaft 164 to the motor assembly 162 and also extends through an aperture located in the bottom cover 114 so that the shaft 164 be rotatably mounted to the vessel 102, i.e. the shaft may rotate about its longitudinal axis relative upon activation of the motor assembly 162. The mixing plates 166 are fixedly secured to the shaft so that a rotation of the shaft 164 creates a rotation of the mixing plates which allows for the mixing of the substance contained in the microwave cavity 100.

[0168] Fig. 12 exemplarily illustrates the microwave power reflected by the microwave cavity 100 as a function of frequency for different positions of the movable plate 130. The curve solid curve indicates the reflected power as a function of frequency for a position of the movable plate 130 in the middle of a range of adjustability. The dashed and dotted curves indicate the reflected power as a function of frequency for a few, equally spaced positions above and below the midrange point, respectively.

[0169] Fig. 13 exemplarily illustrates the measured power reflection coefficient evaluated for several forward and reverse cycles of the movable plate 130, under operation, at a single frequency. Theoretical assessment is also added for visualization. This shows the tunability of the power reflection coefficient, at fixed frequency, with the movable plate 130.

[0170] In the following, there is described further methods and systems for improving the internal impedance of a microwave assembly comprising at least a microwave cavity and a micro wave source. [0171 ] Fig. 8 illustrates one embodiment of a microwave system 200 comprising a microwave cavity 202, a microwave source 204, a microwave waveguide 206, a reflection determining unit 208, a controller 210, an injection unit 212 for injecting an initial substance into the microwave cavity 202 and an extraction unit 214 for extracting material from the micro wave cavity 202.

[0172] The microwave cavity 202 comprises a hollow body 216 defining an internal chamber 218 for receiving therein the initial substance on which the microwave- assisted treatment is to be performed. At least the internal surface of the body 216 surrounding the internal chamber 28 is usually made from a material that reflects microwaves, as known in the art. The body 216 is provided with an opening 220 for allowing the microwaves coming from the waveguide 206 to propagate into the internal chamber 218 of the micro wave cavity 202.

[0173] The injection unit 212 is connected to the hollow body 216 for injecting the substance to be treated into the internal chamber 218 of the microwave cavity 202. Similarly, the extraction unit 214 is connected to the hollow body 216 for extracted some of the substance contained into the internal chamber 218 of the microwave cavity 202

[0174] In one embodiment, the injection unit 212 comprises a reservoir or tank containing the substance to be treated and at least one pump to inject the substance to be treated from the tank into the internal chamber 218 of the microwave cavity 202.

[0175] In one embodiment, the extraction unit 214 comprises at least one pump connected to the microwave cavity for extracting some of the substance being treated from the internal chamber 218. In one embodiment, the extraction unit 214 may further comprise a tank or reservoir for receiving therein the extracted substance.

[0176] The reflection determining unit 208 is similar to the reflection determining unit 18 described above and configured for determining the amount of microwaves that are reflected by the microwave cavity 202 towards the microwave source 204. In one embodiment, the amount of microwaves reflected by the microwave cavity 202 corresponds to the power or amplitude of the microwaves reflected by the microwave cavity 202. In another embodiment, the amount of microwaves reflected by the microwave cavity 202 corresponds to the complex reflection coefficient of the microwave assembly comprising at least the microwave cavity 202, the microwave source 204 and the waveguide 206.

[0177] In one embodiment, the reflection determining unit 208 comprises a sensor adapted to measure the power and/or amplitude of microwaves. As described above with respect to the system 10, the system 200 may further comprise a circulator (not shown) comprising at least three ports. In one embodiment, the circulator is connected between the microwave source 204 and the waveguide 206 and the sensor is connected to the circulator. The microwave source 204 is connected to a first port of the circulator and the waveguide 206 is connected to a second port of the circulator so that microwaves emitted by the microwave source 204 and entering the circulator by the first port are transmitted to the waveguide 206 via the second port. The sensor is connected to the third port of the circulator so that microwaves entering the circulator via the second port from the waveguide are transited to the sensor via the third port. In another embodiment, the circulator is connected between the microwave cavity 202 and the waveguide 206 and the sensor is connected to the circulator. The microwave cavity 202 is connected to a first port of the circulator and the waveguide 206 is connected to a second port of the circulator so that micro waves emitted by the micro wave source 204, propagating into the waveguide 206 and entering the circulator by the second port are transmitted to the microwave cavity 202 via the first port. The sensor is connected to the third port of the circulator so that microwaves reflected by the microwave cavity 202 and entering the circulator via the first port are transited to the sensor via the third port.

[0178] In another embodiment, the reflection determining unit 208 comprises a device adapted to measure or determine the complex reflection coefficient of the microwave assembly comprising the microwave cavity 202, the microwave source 204 and the waveguide 206. In one embodiment, the reflection determining unit 208 is a reflectometer. In another embodiment, the reflection determining unit 208 is a network analyzer. In one embodiment, the reflection determining unit 208 is configured to measure the complex reflection coefficient at the interface between the microwave cavity 202 and the waveguide 206.

[0179] The controller 210 is in communication with the reflection determining unit 208 for receiving the determined amount of reflected waveguides therefrom and is further in communication with the injection unit 212 and the extraction unit 214 to control the injection unit 212 and the extraction unit 214 based on the received amount of reflected microwaves in order adjust the ratio between the volume of the different phases present in the microwave cavity 202, as described in greater detail below.

[0180] Fig. 9 illustrates one exemplary method 250 for operating the system 200.

[0181] At step 252, an initial substance to be treated is injected into the internal chamber 218 of the microwave cavity 202. The controller 210 controls the injection unit 212 to inject an initial amount of substance to be treated into the chamber 218. In one embodiment, the initial amount of substance to be treated is chosen so that the bed or top level 222 of the substance within the chamber 218 be positioned on top of the opening 220, i.e. between the opening 222 and the top of the microwave cavity 202, so that all of the microwaves propagating from the waveguide 206 propagate into the initial substance.

[0182] At step 254, microwaves are injected into the microwave cavity 202. The controller 210 controls the microwave source 204 to generate an adequate amount of microwaves and the generated microwaves propagate into the internal chamber 218 of the microwave cavity 202 via the microwave waveguide 206 and the opening 220. While propagating into the internal chamber 218, the microwaves interact with the initial substance, thereby treating the initial substance.

[01 3] At step 256, the amount of microwaves reflected by the microwave cavity 202 towards the microwave source 204 is determined. As described above, the amount of reflected microwaves may correspond to the power or amplitude of the microwaves that are reflected by the microwave cavity 202. In another embodiment, the amount of reflected microwaves is estimated by determining the complex reflection coefficient of the microwave assembly comprising at least the microwave cavity 202, the microwave source 204 and the waveguide 206.

[01 4] At step 258, the ratio between the volume of the different phases present in the internal cavity 218 is adjusted based on the determined amount of reflected microwaves. While propagating in the internal cavity 218, the microwaves interact with the initial substance and at least two different phases may be created. For example, during the microwave-assisted treatment, a first substance being in a liquid or slurry phase 224 and a second substance being in a gaseous phase 226 may be created in addition to gas already present into the microwave cavity 202 prior to the injection of the microwaves into the microwave cavity 202. The slurry substance 224 is at the bottom of the internal cavity 218 while the gaseous substance 226 is at the top of the internal cavity 218. The top level of bed 222 of the slurry substance 224 represents the interface or limit between the slurry substance 224 and the gaseous substance 226. 185] Since the volume of the internal chamber 218 is fixed, varying the volume of the section of the internal chamber 218 occupied by the slurry substance 224 allows for changing the ratio between the volume of the slurry substance 224 and the volume of the gaseous substance 226, and therefore changing the height of the interface 222. The volume of the slurry substance 224 may be changed by either injecting additional substance into the internal chamber 218 or extracting some of the slurry substance from the internal cavity 218, i.e., the volume of the slurry substance 224 can be increased by injecting additional substance into the internal chamber 218 using the injecting unit 212 and the volume of the slurry substance 224 can be decreased by extracting some of the slurry substance 226 from the internal chamber 218 using the extracting unit 214. It should be understood that controlling the volume of the slurry substance 224, i.e., the volume of the section of the internal cavity 218 occupied by the slurry substance 224, is equivalent to controlling the height of the top level or bed 222 of the slurry substance within the internal cavity 218.

[0186] The controller 210 controls the injection unit 212 to inject additional substance into the chamber 218 of the microwave cavity 202 and the extraction unit 214 to extract some of the slurry substance 224 to adjust the ratio between the volume of the slurry substance 224 and the volume of the gaseous substance 226 based on the determined amount of reflected microwaves in order to adjust the impedance of the microwave cavity 202 and improve the internal impedance of the microwave assembly comprising the microwave cavity 202, the microwave source 204 and the microwave waveguide 206, i.e. in order to improve the impedance matching between the microwave cavity 202 and the microwave source 204.

[018?] For example, at step 258, the controller 210 may determine that the volume of the slurry substance 224 within the chamber 218 illustrated in Fig. 8 must be decreased to improve the impedance matching between the microwave cavity 202 and the microwave source 204. The controller 210 then activates the extraction unit 214 to remove some slurry substance 224 from the internal chamber 218 and thereby improve the impedance matching between the microwave cavity 202 and the microwave source 204. As illustrated in Fig. 10, the volume of the slurry substance 224 is reduced and the height of the top level 220 of the slurry substance 224 is decreased.

[ 188] In an embodiment in which initial substance is continuously injected into the microwave cavity 202 and slurry substance 224 is continuously extracted from the microwave cavity 202, the controller 210 is configured for adjusting the injection rate and/or the extraction rate in order to adjust the ratio between the volume of the slurry substance 224 and the volume of the gaseous substance 226. In an embodiment in which the injection rate of initial material into the microwave cavity 202 is constant in time, the controller 210 is configured for adjusting the extraction rate of slurry substance 224 from the microwave cavity 202 in order to adjust the ratio between the volume of the slurry substance 224 and the volume of the gaseous substance 226. For example, when the volume of slurry substance 224 must be increased, the controller 210 decreases the extraction rate of the slurry substance 224. In another example in which the volume of slurry substance 224 must be decreased, the controller 210 increases the extraction rate of the slurry substance 224. In an embodiment in which the extraction rate of slurry substance from the microwave cavity 202 is constant in time, the controller 210 is configured for adjusting the injection rate of initial substance into the microwave cavity 202 in order to adjust the ratio between the volume of the slurry substance 224 and the volume of the gaseous substance 226. For example, when the volume of slurry substance 224 must be increased, the controller 210 increases the injection rate of the initial substance. In another example in which the volume of slurry substance 224 must be decreased, the controller 210 decreases the injection rate of the initial substance.

[ 1 9] In one embodiment, the controller 210 may extract slurry substance 224 from the internal chamber 218 while always maintaining the top level 220 of the slurry substance above the opening 220.

[0190] In one embodiment, the controller 210 is configured for accessing a database stored in a memory and comprising predefined volumes for the slurry substance 224 and respective amounts of reflected microwaves. In this case, the controller 210 is configured to determine the target volume for the slurry substance 224 by accessing the database and retrieving the predefined volume that corresponds to the amount of reflected microwaves received from the reflection determining unit 208. The controller 210 is further configured for determining the actual volume of the slurry substance 224 within the internal chamber 218 at any time during the microwave-assisted treatment based on the total amount of substance injected into the internal chamber 218 and the total amount of slurry substance 224 extracted from the internal chamber 218 since the beginning of the microwave-assisted treatment. Knowing the actual volume of slurry substance 224 into the internal chamber 218 and the target volume for the slurry substance 224, the controller 210 then determines the amount or volume of additional substance to be inj ected into the internal chamber 218 or the amount or volume of slurry substance to be extracted from the internal chamber 218 in order to reach the target volume of slurry substance 224.

[0191 ] In another embodiment, the controller 210 is configured for executing a control loop such as a PID loop to determine the target volume of slurry substance within the internal chamber 218. In this case, the reflection determining unit 208 substantially continuously determines the amount of microwaves reflected by the microwave cavity 202 and the controller 210 substantially continuously adjusts the volume of slurry substance 224 into the internal chamber 218 to reduce or minimize the amount of reflected microwaves by substantially continuously injecting additional substance into the internal chamber 218 using the injection unit 212 or extracting slurry substance 224 from the internal chamber 218 using the extraction unit 214.

[0192] In an embodiment in which the microwave source 204 is tunable, i.e., the frequency or wavelength of the microwaves emitted by the microwave source 204 is adjustable, the controller 210 is further operatively connected to the microwave source 204 for controlling the frequency of the emitted microwaves. In this case, the controller 210 is further configured for adjusting the frequency of the microwaves to a desired value in addition to adjusting the volume of slurry substance 224 into the internal chamber 218 to reduce or minimize the amount of reflected microwaves.

[0193] In one embodiment, the controller 210 iteratively controls the volume of slurry substance 224 into the internal chamber 218 and the frequency of the microwaves to reduce or minimize the amount of reflected microwaves. For example, the controller 210 may first adjust the volume of slurry substance 224 into the internal chamber 218 based on the actual amount of reflected microwaves received from the reflection determining unit 208 so that the amount of reflected microwaves decreases down to a first amount of reflected microwaves, and then adjust the frequency of the microwaves to a target frequency based on the actual amount of reflected microwaves received from the reflection determining unit 208 so that the amount of reflected microwaves reaches a second amount that is less than the first amount.

[0194] In one embodiment, the controller 210 is configured for accessing a database stored in a memory and comprising predefined frequencies and respective predefined amounts of reflected microwaves. In this case, the controller is configured for determining the target frequency by accessing the database and retrieving the frequency that corresponds to the amount of reflected microwaves received from the reflection determining unit 208.

[0195] In another embodiment, the controller 210 is configured for applying a control loop such as a PID loop to determine the target frequency. In this case, the reflection determining unit 208 substantially continuously determines the amount of microwaves reflected by the microwave cavity 202 and the controller 210 substantially continuously determines the frequency of the microwaves using the control loop until a given frequency that reduces or minimizes the amount of reflected microwaves is reached.

[0196] In another embodiment, the controller 210 concurrently controls the volume of slurry substance 224 into the internal chamber 218 and the frequency of the microwaves to reduce or minimize the amount of reflected microwaves.

[0197] In one embodiment, the controller 210 is configured for accessing a database stored in a memory and comprising predefined combinations of a volume of slurry substance 224 and a predefined frequency, and respective predefined amounts of reflected microwaves, i.e., for each predefined amount of reflected microwaves correspond a unique combination of volume of slurry substance 224 and frequency. In this case, the controller 210 is configured to determine the target volume of slurry substance 224 and the frequency for the microwaves by accessing the database and retrieving the predefined combination that corresponds to the amount of reflected microwaves received from the reflection determining unit 208. [0198] In another embodiment, the controller 210 is configured for applying a control loop to determine the target volume of slurry substance 224 and the frequency of the microwaves. In this case, the reflection determining unit 208 substantially continuously determines the amount of microwaves reflected by the microwave cavity 202 and the controller 210 substantially continuously determines the combination of volume of slurry substance 224 and frequency using the control loop until a given combination of volume of slurry substance 224 and frequency that reduces or minimizes the amount of reflected microwaves is reached.

[0199] It should be understood that the initial substance comprises the initial substance injected into the internal chamber by the injecting unit 212 before the propagation of the microwaves into the internal chamber 218 comprises the substance to be treated. However, the initial substance may comprise additional substances such as microwaves receptors.

[0200] It should also be understood that during the microwave-assisted treatment, the substance injected by the injection unit 212 to reduce or minimize the amount of reflected microwaves may comprise any adequate substance. The adequate substance may comprise the substance to be treated. The adequate substance may comprise a mixture of substances such as a mixture of substance to be treated and microwave receptors. In another example, the system 200 may comprise a recirculation loop connecting the injection unit 212 and the extraction unit 214 to recirculate at least part of the slurry substance 224 extracted by the extraction unit 214. In this case, the substance injected by the injection unit 212 during the microwave-assisted treatment to reduce or minimize the amount of reflected microwaves may comprise slurry substance 224 coming from the extraction unit 214, a mixture of slurry substance 224 and substance to be treated, a mixture of slurry substance 224 and microwave receptors, a mixture of slurry substance 224, substance to be treated and microwave receptors, etc.

[0201] It should be understood that varying the volume of the slurry substance 224 within the internal chamber 218 allows for changing the effective electromagnetic properties of the internal chamber 218 which induces a change in the impedance of the microwave cavity 202. [0202] It should also be understood that the method 250 may only be used if there exists a difference in electromagnetic properties between the two phases, e.g., between the slurry substance 224 and the gaseous substance 226. For example, if the slurry substance 224 is highly capacitive and the gaseous substance 226 has a lower capacitance than the slurry substance 224, the change in volume of the slurry substance 224 will change the effective impedance of the overall cavity 202. It should be understood that the greater the difference in electromagnetic properties between the slurry substance 224 and the gaseous substance 226 is, the lesser the variation in volume of the slurry substance 224 will be in order to induce an impedance variation for the microwave cavity 202.

[0203] In one embodiment, the microwave cavity 202 is provided with an agitator device such as the agitator device 160 in order to mix the slurry substance 224 during the microwave-assisted treatment.

[0204] It should be understood that once the initial substance is injected into the microwave cavity 202, two immiscible substances separated by the top level or interface 222 are present into the microwave cavity 202. As described above, the two immiscible substances may be a slurry or liquid phase such as slurry phase 224 and a gaseous phase such as gaseous phase 226. However, the person skilled in the art will understand that other configurations are possible as long as two immiscible substances separated by the interface 222 are present. For example, the substances 224 and 226 may be immiscible liquids. In another example, the substance 224 may be a solid and the substance 226 may be a gaseous phase. In another example, the substance 224 may be a suspension of solid particles in a gas such as in a fluidized bed and the substance 226 may be a gaseous phase. It should be understood that the top level or interface 222 represents the interface between a solid and gas, between a solid and a liquid, between two immiscible liquids, or between a liquid and gas.

[0205] FIG. 14 exemplarily illustrates the power reflection coefficient measured for similar stable operating conditions of the system of Fig. 8 over a period of about 5 minutes for three different levels of slurry phase, which shows the tunability with level. [0206] FIG. 15 exemplarily illustrates a theoretical estimation of reflected power for a cylindrical cavity filled with the medium up to a referenced level, the rest of the reactor is considered to be filled with Nitrogen.

[0207] In one embodiment, the controller 24, 210 comprises at least one processing unit, an internal memory and communication means to receive and/or transmit data. Instructions for executing the method 50, 250 are stored on the memory and the method 50, 250 is performed when the processing unit executes the instructions.

[0208] It should also be understood that the system 10, 200 may comprise more than one injection device for injecting more than one substance into the microwave cavity 12, 202. For example, a first injection unit may be connected to the microwave cavity 12, 202 for injecting the initial substance thereinto. A second injection unit may be connected to the microwave cavity 12, 202 for injecting a microwave interacting substance such as a microwave receptor thereinto. A third injection device may be connected to the microwave cavity 12, 202 for injecting gas thereinto.

[0209] While in the above description a microwave assembly comprises a microwave cavity, a microwave source and a microwave waveguide, it should be understood that a microwave assembly may further comprise a coupler installed between the microwave cavity and the microwave waveguide. In this case, the internal impedance of the microwave assembly refers to the internal impedance refers to the internal impedance of the microwave assembly comprising the microwave cavity, the microwave source, the microwave waveguide and the coupler.

[0210] While the above description, the system 10, 200 comprises a reflection determining unit 18, 208 to determine the amount of microwaves that are reflected by the microwave cavity 12 towards the microwave source 14, and the position of the movable object 20, in the case of the system 10, and height of the interface 222, in the case of the system 200, are varied based on the determined reflected power, the person skilled in the art would understand that the variation of the movable object 20 and/or the variation of the height of the interface 222 can be performed based on the amount of microwaves transmitted into the microwave cavity 12, 202. Since the amount of microwaves generated by the microwave source 14, 204 is known and is substantially equal to the summation of the amount of reflected microwaves and the amount of transmited microwaves, knowing the amount of reflected power is equivalent to knowing the amount of transmited power. Therefore, the adjustment of the body 20 and/or the adjustment of the height of the interface 222 can be performed based on the amount of transmited power rather than based on the amount of reflected power. In this case, the reflection determining unit 18 is replaced with a transmission determining unit in the system 10 and/or the reflection determining unit 208 is replaced with a transmission determining unit in the system 200. The transmission determining unit is configured for determining the amount of microwaves that are transmited into the microwave cavity 12, 202, such as the power or amplitude of the transmited microwaves or the complex transmission coefficient. For example, the transmission determining unit may comprise a temperature sensor, such an infrared temperature sensor, adapted to monitor the temperature of a reference element installed into the microwave and the power or amount of transmited microwaves is determined based on the sensed temperature of the reference element. In this case, it should be understood that determining the temperature of the reference element is equivalent to determining the amount or power of the transmited microwaves. It should also be understood that in this case and when the system comprises a database for determining the configuration for the body 20, the database comprises a respective body configuration for each one of predefined amounts of transmited microwaves.

[021 1 ] In one embodiment, the reference element is made of a microwave absorbing material such as silicon carbide or carbon. In one embodiment, the reference element is positioned within a region of the microwave cavity where transmission may be achieved, e.g., inside the bed 222. The reference element can be a fixed microwave receptor that is used to promote the desired microwave treatment onto the initial substance. The transmited microwave power can be measured via the fixed microwave receptor temperature that can be measured via infrared, but also with a thermocouple or resistance temperature detector (RTD) that is inserted into the fixed microwave receptor for example.

[0212] In one embodiment, the controller 24 is configured for accessing a database stored in a memory and comprising predefined positions for the body 20 and respective amounts of transmited power microwaves in order to vary the position of the movable object 20. [0213] In another embodiment, the controller 24 is configured for applying a control loop such as a PID loop to determine the target position of the body 20. In this case, the transmission determining unit substantially continuously determines the amount of microwaves transmitted into the microwave cavity 12 and the controller 24 substantially continuously determines the position for the body 20 using the control loop until a given position for the body 20 that maximizes the amount of transmitted microwaves is reached, thereby minimizing the amount of reflected microwaves.

[0214] In one embodiment, the controller 210 is configured for accessing a database stored in a memory and comprising predefined volumes for the slurry substance 224 and respective amounts of transmitted microwaves in order to adjust the volume of the slurry substance (or the height of the interface 222) and increase the amount of transmitted microwaves, thereby decreasing the amount of reflected microwaves.

[0215] In another embodiment, the controller 210 is configured for executing a control loop such as a PID loop to determine the target volume of slurry substance within the internal chamber 218. In this case, the transmission determining unit substantially continuously determines the amount of microwaves transmitted into the microwave cavity 202 and the controller 210 substantially continuously adjusts the volume of slurry substance 224 into the internal chamber 218 adequate to increase or maximize the amount of transmitted microwaves, thereby reducing or minimizing the amount of reflected microwaves.

[0216] In the following, a further method 300 for performing a microwave-assisted treatment on an initial substance or material. The method 300 is described with reference to the microwave system of Fig. 8. However, it will be understood that the controller 210 is modified in order to execute the method 300.

[0217] At step 302, an initial substance to be treated is injected into the internal chamber of the microwave cavity 202. The controller 210 controls the injection unit 212 to inject an initial amount of substance to be treated into the chamber 218. In one embodiment, the initial amount of substance to be treated is chosen so that the bed or top level 222 of the substance within the chamber 218 be positioned on top of the opening 220, i.e. between the opening 222 and the top of the microwave cavity 202, so that all of the microwaves propagating from the waveguide 206 propagate into the initial substance.

[0218] At step 304, microwaves are injected into the microwave cavity 202. The controller 210 controls the microwave source 204 to generate an adequate amount of microwaves and the generated microwaves propagate into the internal chamber 218 of the microwave cavity 202 via the microwave waveguide 206 and the opening 220. While propagating into the internal chamber 218, the microwaves interact with the initial substance, thereby treating the initial substance to obtain a fluidized substance such as a slurry substance or phase.

[0219] At step 306, the amount of microwaves reflected by the microwave cavity 202 towards the microwave source 204 is determined. As described above, the amount of reflected microwaves may correspond to the power or amplitude of the microwaves that are reflected by the microwave cavity 202. In another embodiment, the amount of reflected microwaves is estimated by determining the complex reflection coefficient of the microwave assembly comprising at least the microwave cavity 202, the microwave source 204 and the waveguide 206.

[0220] At step 308, the effective electromagnetic properties of the fluidized substance contained in the microwave cavity 202 are adjusted in order to decrease or minimize the amount of microwaves reflected by the microwave cavity 202 and improve of maximize the impedance matching within the micro wave system.

[0221 ] In one embodiment, step 308 consists in changing the composition of the fluidized substance contained within the microwave cavity in order to improve the impedance matching within the microwave system. In this case, the controller 210 is configured for adjusting the composition of the fluidized substance based on the amount of reflected microwaves received from the reflection determining unit 208.

[0222] In one embodiment, the controller 210 is configured for accessing a database stored in a memory and comprising predefined compositions and respective amounts of reflected microwaves. In this case, the controller is configured to determine the target composition for the fluidized substance by accessing the database and retrieving the predefined composition that corresponds to the amount of reflected microwaves received from the reflection determining unit 208. [0223] In another embodiment, the controller 210 is configured for applying a control loop such as a PID loop to determine the target composition for the fluidized substance. In this case, the reflection determining unit 208 substantially continuously determines the amount of microwaves reflected by the microwave cavity 202 and the controller 210 substantially continuously adjust the composition for the fluidized substance using the control loop until a given composition for the fluidized substance that minimizes the amount of reflected microwaves is reached.

[0224] In an embodiment in which the electromagnetic properties of the initial substance are different from that of the fluidized substance, the injection rate of the initial substance is varied. In this case, the controller 210 controls the injection unit 212 to increase or decrease the amount of initial substance being injected into the microwave cavity based on the amount of reflected microwaves received from the reflection determining unit 208 in order to change the electromagnetic properties of the fluidized substance contained into the microwave cavity 202, and therefore reduce or minimize the amount of reflected microwaves..

[0225] In one embodiment, the extraction rate of the fluidized substance is varied in order to minimize the amount of reflected microwaves. In this case, the controller 210 controls the extraction unit 214 to increase or decrease the amount of fluidized substance within the microwave cavity 202 based on the amount of reflected microwaves received from the reflection determining unit 208 in order to change the electromagnetic properties of the fluidized substance contained into the microwave cavity 202, and therefore reduce or minimize the amount of reflected microwaves.

[0226] In an embodiment in which microwave interacting particles are injected into the microwave cavity 202 via a particle injection unit (not shown), the amount of microwave interacting particles within the microwave cavity 202 is adjusted in order to decrease the amount of reflected microwaves. In this case, the controller 210 is configured for controlling, based on the amount of reflected microwaves received from the reflection determining unit 208, the particle injection unit and/or the extraction unit 214 to increase or decrease the injection rate of microwave interacting particles and/or the extraction rate of fluidized substance, and therefore the extraction rate of microwave interacting particles, from the microwave cavity in order to change the electromagnetic properties of the fluidized substance contained into the microwave cavity 202, and therefore reduce or minimize the amount of reflected microwaves.

[0227] In one embodiment, the microwave system 200 is further provided with a recirculation loop that fluidly connect the extraction unit 214 to the microwave cavity 202 to recirculate at least part of the fluidized substance that has been extracted by the extraction unit 214 into the micro wave cavity 202. As known in the art, the recirculation loop comprises elements such as pipes, valves, pumps, and/or the like, and the elements of the recirculation loop are controlled by the controller 210. The controller 210 is then configured for controlling/varying the rate of recirculation of fluidized substance into the microwave cavity 202 in order to change the electromagnetic properties of the fluidized substance contained into the microwave cavity 202, and therefore reduce or minimize the amount of reflected microwaves.

[0228] In another embodiment, step 308 consists in changing the homogeneity of the fluidized substance contained within the microwave cavity in order to improve the impedance matching within the microwave system. In this case, the controller 210 is configured for adjusting the homogeneity of the fluidized substance based on the amount of reflected microwaves received from the reflection determining unit 208. As described below, the homogeneity may be controlled by controlling a parameter that affects the homogeneity of the fluidized substance, referred to as the homogeneity parameter hereinafter, such as the rotating speed of an agitator, a gas injection rate or a recirculation rate.

[0229] In an embodiment, the controller 210 is configured for accessing a database stored in a memory and comprising predefined homogeneity parameter values and respective amounts of reflected microwaves. In this case, the controller is configured to determine the target value for the homogeneity parameter by accessing the database and retrieving the predefined homogeneity parameter value that corresponds to the amount of reflected microwaves received from the reflection determining unit 208.

[0230] In one embodiment, the controller 210 is configured for applying a control loop such as a PID loop to determine the target value for the homogeneity parameter. In this case, the reflection determining unit 208 substantially continuously determines the amount of microwaves reflected by the microwave cavity 202 and the controller 210 substantially continuously adjust the value of the homogeneity parameter using the control loop until a given value that minimizes the amount of reflected microwaves is reached.

[0231 ] In an embodiment in which the microwave cavity 202 is provided with an agitator for mixing/agitating the fluidized substance therein, the controller 210 is configured for controlling the speed of the agitator based on the amount of reflected microwaves received from the reflection determining unit 208 to adjust the homogeneity of the fluidized substance and thereby reduce or minimize the amount of reflected microwaves. Such a method may be used when microwave interacting particles are injected into the microwave cavity 202. Such particles may fall at the bottom of the cavity and not be homogenously distributed within the fluidized substance, thereby affecting the effective electromagnetic properties of the fluidized substance and therefore the impedance of the microwave cavity.

[0232] In one embodiment, the microwave system may further comprise a gas unit fluidly connected to the microwave cavity 202 for injecting gas into the fluidized substance to generate eddies into the fluidized substance and thereby mix the fluidized substance. For example, the gas unit may be configured for injecting gas from the bottom of the microwave cavity 202. In this embodiment, the controller 210 is configured to control the gas unit in order to control/vary the injection of gas into the fluidized substance in order to adjust the homogeneity of the fluidized substance and thereby reduce or minimize the amount of reflected microwaves. For example, parameters such as the pressure or the injection rate of gas may be controlled.

[0233] In one embodiment, the microwave system 200 is further provided with a recirculation loop that fluidly connect the extraction unit 214 to the microwave cavity 202 to recirculate at least part of the fluidized substance that has been extracted by the extraction unit 214 into the bed of the fluidized substance. The injection of recirculated substance creates eddies into the fluidized substance and thereby modify the homogeneity of the fluidized substance. The controller 210 is then configured for controlling the rate of recirculation of fluidized substance into the microwave cavity 202 in order to change the homogeneity of the fluidized substance contained into the microwave cavity 202, and therefore reduce or minimize the amount of reflected microwaves. [0234] In one embodiment, the controller of the microwave system may be configured to execute only of the above-described method. For example, the controller may be configured to only change the configuration of a body installed into the micro wave cavity. In another example, the controller may be configured to only control the height of the bed of fluidized substance into the microwave cavity. In a further embodiment, the controller may be configured to only control the electromagnetic properties of the fluidized substance.

[0235] In another embodiment, the controller of the microwave system may be configured to execute at least two of the above-described methods such as methods 250 and 300. For example, the controller may be configured to execute a first method and if the amplitude of the reflected microwaves is not minimized, the controller then executes the second method. In this example, the methods are ranked per execution order. In another example, the controller may identify the method to be applied based on the amount of reflected microwaves. For example, if the amount of reflected microwaves is below a first threshold, a first method such as method 250 is applied. If the if the amount of reflected microwaves is between the first threshold and a second threshold, then a second method such as method 300 is executed, and if the amount of reflected microwaves is above the second threshold, then a third method such as method 50 is executed.

[0236] Modifications and improvements to the above-described implementations of the present technology may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting.

Claims

CLAIMS What is claimed is:

1. A method for improving an impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave- assisted treatment, the method comprising: injecting an initial substance into the microwave cavity; propagating micro waves from the microwave source into the micro wave cavity to perform a microwave-assisted treatment of the initial substance; determining a parameter of the microwave system; and adjusting an impedance of the microwave system based on the determined parameter.

2. A microwave system comprising: a microwave cavity configured for receiving an initial substance therein, the microwave cavity being operatively connectable to a microwave source for receiving microwaves therefrom to perform a microwave-assisted treatment on the initial substance; a body inserted into the microwave cavity, the body being at least partially made of a material that interacts with the microwaves; a microwave determining unit for determining a parameter of the microwave system; and a control unit operatively connected to the movable body, the control unit being configured for changing the body from a first configuration to a second configuration within the microwave cavity based on the determined parameter, the second configuration being chosen to improve an impedance matching between the microwave cavity and the microwave source.

3. The microwave system of claim 2, wherein the parameter comprises one of a first amount of the microwaves reflected by the microwave cavity towards the microwave source and a second amount of the microwaves transmitted into the microwave cavity, and the second configuration is chosen to one of reduce the first amount and increase the second amount.

4. The microwave system of claim 3, wherein the control unit is configured for modifying the body from a first size to a second size, the second size being chosen to one of reduce the first amount and increase the second amount.

5. The microwave system of claim 3, wherein the control unit is configured for modifying the body from a first shape to a second shape, the second shape being chosen to one of reduce the first amount and increase the second amount.

6. The microwave system of claim 3, wherein the body is moveable within the microwave cavity and the control unit is configured for moving the body from a first position to a second position within the microwave cavity, the second position being chosen to one of reduce the first amount and increase the second amount.

7. The microwave system of claim 6, wherein the control unit comprises a motion device operatively connected to the body for moving the body within the microwave cavity, and a controller in communication with the motion device, the controller being configured for determining the second position for the body and controlling the motion device to move the body to the second position.

8. The s microwave ystem of claim 7, wherein the body comprises a movable plate .

9. The micro wave system of claim 8, wherein the micro wave cavity extends along a longitudinal axis, the movable plate extends substantially orthogonal to the longitudinal axis and the motion device is configured for translating the movable plate along the longitudinal axis.

10. The microwave system of claim 9, wherein the movable plate comprises at least one aperture extending through a thickness thereof.

11. The microwave system of claim 9 or 10, further comprising a fixed plate extending substantially orthogonally to the longitudinal axis and having a fixed position relative to the longitudinal axis, wherein the microwave cavity comprises an opening for injecting the microwaves therein, the opening being located between the fixed plate and a given longitudinal end of the microwave cavity, and the movable plate is movable between the given longitudinal end and the fixed plate.

12. The microwave system of any one of claims 3 to 11, wherein the microwave determining unit comprises a sensor configured for measuring the first amount of the microwaves reflected by the microwave cavity.

13. The microwave system of any one of claims 3 to 11, wherein the microwave determining unit comprises a sensor configured for measuring a complex reflection coefficient of a microwave assembly comprising the microwave cavity and at least the microwave source.

14. The system of claim 13, wherein the sensor comprises one of a reflectometer and a network analyzer.

15. The microwave system of claim 14, wherein the sensor is configured for measuring the complex reflection coefficient at an interface between the microwave cavity and the microwave source.

16. The microwave system of claim 15, wherein the microwave assembly further comprises a coupler installed between the microwave source the microwave cavity, the sensor being configured for measuring the complex reflection coefficient at an interface between the microwave cavity and the coupler.

17. The microwave system of any one of claims 3 to 16, wherein the microwave determining unit comprises a sensor for measuring the second amount of the microwaves transmitted into the microwave cavity.

18. The microwave system of claim 17, wherein the sensor comprises a temperature sensor configured for measuring a temperature of a reference element within the micro wave cavity.

19. A method for improving an impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave- assisted treatment, the method comprising: injecting an initial substance into the microwave cavity; propagating micro waves from the microwave source into the micro wave cavity to perform a microwave-assisted treatment of the initial substance, a body being inserted into the microwave cavity and the body being at least partially made of a material that interacts with the microwaves; determining a parameter of the microwave system; and changing the body from a first configuration to a second configuration within the microwave cavity based on the determined parameter, the second configuration being chosen to improve an impedance matching between the microwave cavity and the micro wave source.

20. The method of claim 19, wherein said determining the parameter comprises determining one of a first amount of the microwaves reflected by the microwave cavity towards the micro wave source and a second amount of the micro waves transmitted into the microwave cavity, the second configuration being chosen to one of reduce the first amount and increase the second amount.

21. The method of claim 20, wherein said changing the body comprises modifying the body from a first size to a second size, the second size being chosen to one of reduce the first amount and increase the second amount.

22. The method of claim 20, wherein said changing the body comprises modifying the body from a first shape to a second shape, the second shape being chosen to one of reduce the first amount and increase the second amount.

23. The method of claim 20, wherein said changing the body comprises moving the body from a first position to a second position within the microwave cavity, the second position being chosen to one of reduce the first amount and increase the second amount.

24. The method of claim 23, wherein said moving the body comprises moving a movable plate.

25. The method of claim 24, wherein said moving the movable plate comprises translating the movable plate along a longitudinal axis of the microwave cavity, the movable plate extending substantially orthogonally to the longitudinal axis.

26. The method of claim 25, wherein the movable plate comprises at least one aperture extending through a thickness thereof.

27. The method of claim 25 or 26, wherein the microwave cavity is further provided with a fixed plate extending substantially orthogonally to the longitudinal axis and having a fixed position relative to the longitudinal axis, the microwave cavity comprising an opening for injecting the microwaves therein, the opening being located between the fixed plate and a given longitudinal end of the microwave cavity, wherein said moving the movable plate comprises moving the movable plate between the given longitudinal end and the fixed plate.

28. The method of any one of claims 20 to 27, wherein said determining the amount of the microwaves being reflected comprises measuring an amount of microwaves propagating from the microwave cavity towards the microwave source.

29. The method of any one of claims 20 to 27, wherein said determining the amount of the microwaves being reflected comprises measuring a complex reflection coefficient of a microwave system comprising the microwave cavity and at least the microwave source.

30. The method of claim 29, wherein said measuring the complex reflection coefficient is performed using one of a reflectometer and a network analyzer.

31. The method of claim 29 or 30, wherein said measuring the complex reflection coefficient is performed at an interface between the microwave cavity and the microwave source.

32. The method of claim 31, wherein the microwave system further comprises a coupler installed between the microwave source the microwave cavity, said measuring the complex reflection coefficient being performed at an interface between the microwave cavity and the coupler.

33. A microwave system comprising: a microwave cavity configured for receiving an initial substance therein, the microwave cavity being operatively connectable to a microwave source for receiving microwaves therefrom to perform a microwave-assisted treatment on the initial substance and thereby obtain a first substance being in a first phase and a second substance being a in a second and different phase; a microwave determining unit for determining a parameter of the microwave system; an injection unit fluidly connected to the microwave cavity for injecting an additional substance into the microwave cavity; an extraction unit fluidly connected to the microwave cavity for extracting at least some of the first substance from the microwave cavity; and a control unit in communication with the injection unit and the extraction unit for controlling a volume of the first substance within the microwave cavity based on the determined parameter, thereby improving an impedance matching between the microwave cavity and the micro wave source.

34. The microwave system of claim 33, wherein the parameter comprises one of a first amount of the microwaves reflected by the microwave cavity towards the microwave source and a second amount of the microwaves transmitted into the microwave cavity, and the volume of the first substance is chosen based on one of the first amount and the second amount to one of reduce the first amount of the microwaves being reflected by the microwave cavity towards the microwave source and increase the second amount of the microwaves transmitted into the microwave cavity.

35. The microwave system of claim 34, wherein the additional substance comprises the initial substance.

36. The microwave system of claim 34 or 35, wherein the additional substance comprises the first substance, the injection unit and the extraction unit being fluidly connected to propagate at least part of the first substance extracted by the extraction unit to the injection unit.

37. The microwave system of any one of claims 34 to 36, wherein the microwave determining unit comprises a sensor configured for measuring the first amount of the microwaves reflected by the microwave cavity.

38. The microwave system of any one of claims 34 to 36, wherein the microwave determining unit comprises a sensor configured for measuring a complex reflection coefficient of a microwave assembly comprising the microwave cavity and at least the microwave source.

39. The microwave system of claim 38, wherein the sensor comprises one of a reflectometer and a network analyzer.

40. The microwave system of claim 39, wherein the sensor is configured for measuring the complex reflection coefficient at an interface between the microwave cavity and the microwave source.

41. The microwave system of claim 40, wherein the microwave assembly further comprises a coupler installed between the microwave source the microwave cavity, the sensor being configured for measuring the complex reflection coefficient at an interface between the microwave cavity and the coupler.

42. The microwave system of any one of claims 34 to 36, wherein the microwave determining unit comprises a sensor for measuring the second amount of the microwaves transmitted into the microwave cavity.

43. The microwave system of claim 42, wherein the sensor comprises a temperature sensor configured for measuring a temperature a reference element within the micro wave cavity.

44. A method for improving an impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave- assisted treatment, the method comprising: injecting an initial substance into the microwave cavity; propagating micro waves from the microwave source into the micro wave cavity to perform a microwave-assisted treatment of the initial substance, thereby obtaining a first substance being in a first phase and a second substance being a in a second and different phase; determining a parameter of the microwave system; and controlling, based on the determined parameter, a volume of the first substance within the micro wave cavity to reduce the amount of the micro waves being reflected by the microwave cavity, thereby improving the impedance matching.

45. The method of claim 44, wherein said determining the parameter comprises determining one of a first amount of the microwaves reflected by the microwave cavity towards the micro wave source and a second amount of the micro waves transmitted into the micro wave cavity.

46. The method of claim 45, wherein said controlling the volume of the first substance comprises injecting an additional substance within the microwave cavity.

47. The method of claim 46, wherein the additional substance comprises the initial substance.

48. The method of claim 46 or 47, wherein the additional substance comprises the first substance.

49. The method of any one of claims 45 to 48, wherein said determining the amount of the microwaves being reflected comprises measuring an amount of microwaves propagating from the microwave cavity towards the microwave source.

50. The method of any one of claims 45 to 48, wherein said determining the amount of the microwaves being reflected comprises measuring a complex reflection coefficient of a microwave system comprising the microwave cavity and at least the microwave source.

51. The method of claim 50, wherein said measuring the complex reflection coefficient is performed using one of a reflectometer and a network analyzer.

52. The method of claim 50 or 51, wherein said measuring the complex reflection coefficient is performed at an interface between the microwave cavity and the microwave source.

53. The method of claim 52, wherein the microwave system further comprises a coupler installed between the microwave source the microwave cavity, said measuring the complex reflection coefficient being performed at an interface between the microwave cavity and the coupler.

54. A method for improving an impedance matching of a microwave system comprising at least a microwave cavity and a microwave source during a microwave- assisted treatment, the method comprising: injecting an initial substance into the microwave cavity; propagating micro waves from the micro wave source into the micro wave cavity to perform a microwave-assisted treatment of the initial substance, thereby obtaining a fluidized substance; determining a parameter of the microwave system; and varying, based on the determined parameter, effective electromagnetic properties of the fluidized substance contained within the microwave cavity to reduce the amount of the microwaves being reflected by the microwave cavity, thereby improving the impedance matching.

55. The method of claim 54, wherein the parameter comprises one of a first amount of the microwaves reflected by the microwave cavity towards the microwave source and a second amount of the micro waves transmitted into the micro wave cavity.

56. The method of claim 55, wherein said varying the effective electromagnetic properties of the fluidized substance comprises modifying a composition of the fluidized substance.

57. The method of claim 56, wherein said modifying the composition of the fluidized substance comprises varying an injection rate of the initial substance into the micro wave cavity.

58. The method of claim 56, wherein said modifying the composition of the fluidized substance comprises varying an extraction rate of the fluidized substance.

59. The method of claim 56, further comprising injecting microwave interacting particles into the microwave cavity, said modifying the composition of the fluidized substance comprising at least one of varying an injection rate of the microwave interacting particles into the microwave cavity and varying an extraction rate of the fluidized substance containing some of the microwave interacting particles.

60. The method of claim 56, further comprising extracting a portion of the fluidized substance from the microwave cavity and recirculating the portion of the fluidized substance into the microwave cavity, said modifying the composition of the fluidized substance comprising varying a recirculation rate of the fluidized substance.

61. The method of claim 55, wherein said varying the effective electromagnetic properties of the fluidized substance comprises varying an homogeneity of the fluidized substance within the microwave cavity.

62. The method of claim 61, further comprising agitating the fluidized substance, said varying the homogeneity of the fluidized substance comprising varying an agitation speed of the fluidized substance.

63. The method of claim 61, further comprising injecting gas into the fluidized substance, said varying the homogeneity of the fluidized substance comprising varying the injection of the gas into the fluidized substance.

64. The method of claim 61 , further comprising extracting a portion of the fluidized substance from the microwave cavity and recirculating the portion of the fluidized substance into the microwave cavity, said varying the homogeneity of the fluidized substance comprising varying a recirculation rate of the fluidized substance.

65. The method of any one of claims 55 to 64, wherein said determining the amount of the microwaves being reflected comprises measuring an amount of microwaves propagating from the microwave cavity towards the microwave source.

66. The method of any one of claims 55 to 64, wherein said determining the amount of the microwaves being reflected comprises measuring a complex reflection coefficient of a microwave system comprising the microwave cavity and at least the microwave source.

67. The method of claim 66, wherein said measuring the complex reflection coefficient is performed using one of a reflectometer and a network analyzer.

68. The method of claim 65 or 66, wherein said measuring the complex reflection coefficient is performed at an interface between the microwave cavity and the microwave source.

69. The method of claim 68, wherein the microwave system further comprises a coupler installed between the microwave source the microwave cavity, said measuring the complex reflection coefficient being performed at an interface between the microwave cavity and the coupler.