Microwave-assisted plasma reactor, installation and corresponding method

Abstract

The invention relates to a microwave-assisted plasma reactor (100) that includes a disc-shaped resonant receptacle (110) connected to waveguide conduits (120) supplied by magnetrons (90), the resonant receptacle being connected to a guiding segment (140) for guiding to a reactor vessel (300) where the plasma is generated. The lengths of the wave guides (120) are designed such that the waves transported along same are in phase when they enter the cylindrical interior cavity of the resonant receptacle (110). The height of the cylindrical interior cavity is between λ / 4 and λ, and the cavity diameter is greater than 5λ / 2. Also described is an installation containing one or more of the described microwave reactors connected in series, and a method for pyrolysing or gasifying raw material, implemented in the installation.

Description

[0001]

[0002] MICROWAVE-ASSISTED PLASMA REACTOR AND CORRESPONDING INSTALLATION AND PROCEDURE

[0003] Technology sector

[0004] The present invention relates to the technical field of microwave-assisted plasma reactors. More specifically, it relates to installations or systems of one or more microwave reactors, the microwaves being generated by one or more microwave sources, and in which the creation of a plasma is required. The invention focuses more specifically on a configurable reactor that creates a plasma in a continuous and optimized manner, and on processes carried out with one or more reactors operating in series for the decomposition and transformation of materials.

[0005] State of the art

[0006] The use of microwaves as a heat source and, eventually, as a plasma source in reactors for materials processing has been documented in numerous publications and patents. Most of these cover a wide range of applications, including waste treatment (by induced pyrolysis), gas reactions (through exposure to a plasma), and other processes such as the drying or roasting (torrefaction) of biomass and organic materials.

[0007] These publications mention, for example, the use of microwaves in applications related to plasmas and gas production, including flares, low-pressure plasmas, and surface treatments. Specifically, the following can be cited: US9812295B1 describes a supply gas for generating plasma in a plasma zone of a 1.5 kW tubular reactor, converting gaseous input materials into transformed components. WO2001009031 A1 focuses on the conversion of fossil fuels into hydrogen-rich gas using microwave-generated plasma with added oxygen or air. Furthermore, WO2023150461 A1 details a plume plasma formed by directed microwave vapors in a gas reactor.On the other hand, US patent 11551910B2 claims a plasma generator for processing a raw material (hydrocarbon gas), comprising a first waveguide directed at a plasma in a first reaction zone (in which electrodes are located) that receives the raw material; and an induction coil around a second reaction zone, located after the first reaction zone, in which the waveguide energizes the plasma and propagates it into the second reaction zone. Finally, US patent 8808507B2 claims a microwave-assisted flash pyrolysis system for carrying out pyrolysis on an industrial scale. The microwave-assisted flash pyrolysis system comprises a microwave generator; a chamber comprising a raw material inlet, a baffle plate, a rotating microwave-transparent window, a microwave inlet, a wet gas outlet, and a dry end product outlet.

[0008] In the vast majority of these applications, the power and stability of the microwave signal are critical factors for generating and maintaining plasma in a reactor of this type. These parameters directly influence the efficiency, control, and quality of the processes performed within the reactor.

[0009] Power determines the amount of energy delivered to the system and affects various aspects of plasma and its applications. Sufficient power is required to ionize the gas and form the plasma. If the power is too low, the energy threshold for ionization is not reached, preventing plasma generation. Power also affects plasma density, which is the amount of charged particles (ions and electrons) present. Higher plasma density improves chemical reactivity, favoring processes such as the synthesis of advanced materials or gasification. Furthermore, higher power results in higher plasma temperatures, allowing for the processing of more resistant materials or the execution of chemical reactions that require high activation energies. Finally, the ability to adjust the power allows for controlling the plasma intensity according to the specific needs of the process.

[0010] Signal stability is equally essential, as it ensures a uniform and controlled plasma throughout the entire process. A stable signal prevents fluctuations in plasma density and temperature, maintaining process uniformity (which is key in applications such as thin-film deposition or surface treatment where inconsistencies can lead to defects). Similarly, in chemical processes like hydrocarbon reforming or gasification, signal stability guarantees that reactions occur in a controlled and predictable manner. Furthermore, an unstable signal can result in energy losses, reducing system efficiency, or in power or frequency fluctuations that can damage reactor components.

[0011] It is therefore advantageous, according to the present invention, to provide a microwave reactor with plasma formation and an installation including one or more such reactors, in which high power levels are achieved and sufficiently stable plasma is generated to carry out the target processes (reforming and gas conversions), while simultaneously providing significant performance and safety. Some of the advantages that will be derived from the characteristics described in the following sections of this document are cited below. The reactor and installation disclosed in the present invention allow for the efficient use of several magnetrons to generate a stable plasma induced on a microwave susceptor, making the system highly versatile for the simultaneous execution of pyrolysis / gasification and reforming with reactive gases.At the same time, this allows for control of the outgoing gas composition to achieve different target compositions, including synthesis gas (syngas), depending on the initial materials and incoming gas flows. Furthermore, as will be demonstrated by the technical characteristics detailed later, the reactor or reactors allow for the selection of combinations and quantities based on the material being processed (gases, solids, and liquids: biomass, biochar, plastic waste, and mixtures thereof). The system is also scalable and, at least in some of its implementations, is easily transportable in a container and can be placed in waste processing areas or wherever, for example, the generation of H₂O or synthesis gas is required.

[0012] Object of the invention

[0013] According to one aspect of the invention, a microwave-assisted plasma reactor is provided, comprising at least one microwave source whose waves are confined and guided from each microwave source (preferably a magnetron) through a waveguide duct corresponding to each magnetron, to a disk-shaped resonant receptacle configured to break the waveguide and transition to a radiation wave propagation mode, the resonant receptacle being connected at its outlet to a guidance segment that guides and focuses the microwaves to a reactor vessel where a microwave susceptor to be processed for plasma formation is disposed, the reactor comprising a processed gas outlet and a processed solid material outlet.Furthermore, the lengths of the waveguide channels are multiples of A / 2, ensuring that the microwaves from the magnetrons arrive in phase at the resonant vessel. These waveguide channels are distributed along their connection to the resonant vessel, forming a uniformly distributed array. In this regard, the height of the resonant vessel's interior cavity ranges from A / 4 to A, and the diameter of this cavity is equal to or greater than 5A / 2, where A is the wavelength of the standard waveguide used. For example, a WR340 waveguide is suitable for a recommended frequency range of 2.2 to 3.3 GHz, with A = 172 mm, while a WR975 waveguide is suitable for a frequency range around 915 MHz, for which the wavelength is A = 327.64 mm. This design achieves efficient energy concentration in the plasma generation zone of the reactor vessel.

[0014] The microwaves from the magnetrons are guided to the discoidal resonant receptacle where their guidance mode is broken and they propagate as radiated electromagnetic waves, and are subsequently guided to the reactor vessel or cavity through the guidance segment preferably in the shape of a cylinder.

[0015] Thanks to this microwave-induced plasma reactor configuration, the waves from the different magnetrons overlap and increase their amplitude, acting with greater power. This generates, through absorption by a selected microwave susceptor, a confined and stable plasma that allows for very high pyrolysis / gasification and reforming yields with reactive gases for the production of syngas (H2 / CO) and H2 (enriched syngas), with reduced proportions of secondary gases such as CO2 and CH4, thanks to the high localized temperatures in the plasma (> 1200 °C). The temperature necessary to generate a plasma that allows for the rapid decomposition and gasification of biomass or plastic waste is efficiently reached through a stable and controlled radiation pattern, achieving a high degree of conversion / gasification of the processed materials compared to conventional pyrolysis gasification.

[0016] This reactor is more energy-efficient than known solutions that use dielectric arc breaking for gas ionization. This technology allows the use of plasma for catalyst production, activated carbon production and regeneration, and graphitization of carbonaceous materials. Solid, liquid, or gaseous materials can be processed, including biochars with high volatile content, either alone or mixed with plastics, biomass, or organic liquids (waste oils, pyrolysis liquids).

[0017] According to another feature of the invention, the height of the substantially cylindrical inner cavity of the resonant receptacle is more specifically located between A / 2 and 3A / 4.

[0018] According to another feature of the invention, the microwave susceptor is placed in a region between a distance A corresponding to the reactive near-field limit (Fresnel zone), and a distance A+2*D2 / A corresponds to the boundary of the far-field region with respect to the outlet of the resonant receptacle, where D is the maximum diagonal of the matrix formed by the cross-section of the guide ducts at the inlet to the resonant receptacle. With these design parameters, a plasma pattern that is as homogeneous as possible is achieved, allowing the gas or materials in the process to react very efficiently.

[0019] Preferably, according to another feature of the reactor of the invention, it also includes a feed conduit for both susceptor material and mixtures of susceptor material with the material to be processed (plastics, biomass, or liquids, absorbed onto the susceptor itself), connected to the resonant receptacle. This feed conduit is configured to introduce raw material in solid and / or liquid form, for example, for pyrolysis processes.

[0020] Preferably, in addition to said feeder conduit, it comprises a feeding system for transporting microwave susceptor and / or raw material to be treated, to the reactor vessel, such as a screw conveyor, or a rotary valve, so that continuous processing can be carried out while controlling the input material.

[0021] Preferably, according to another feature of the invention, the reactor includes a second resonant receptacle connectable to the guidance segment and to the reactor vessel. This design transitions the radiation from wave guidance to radiation transmitted in the first resonant receptacle, then to guidance by the guidance segment, and finally to radiation transmitted in the second resonant receptacle, thus conducting the energy to the reactor vessel. This alternative design achieves greater stabilization of the radiation mode depending on the material and process used.

[0022] The reactor is planned to preferably include an inlet for reactive gases to be processed for interaction with the generated plasma. Preferably, the gas inlet is located at the bottom of the reactor to increase its residence time and facilitate its interaction with the microwave susceptor and the plasma itself. This gas inlet, and alternatively vaporized water, promotes the degassing of the material and / or reactions of reactive gases with target gases. A gas mixing box is also planned for the efficient combination of the inlet gases.

[0023] According to another feature of the invention, the reactor vessel comprises a support surface of the susceptor material with a plurality of perforations that allow the passage of the gases to be processed into the plasma generated in the reactor. Thus, the gases are introduced through the bottom of the reactor and, upon reaching the plasma, are decomposed into their elemental components.

[0024] Preferably, said reactor vessel comprises a converging prismatic configuration, and more preferably, a truncated conical configuration with micro-perforations in its wall for the entry of the reactive gas, with a screw conveyor at the end of the inverted cone for lateral extraction of the treated residue (biochar, ash), to a cooled and sealed tank, allowing a continuous treatment process.

[0025] Regarding the reactor vessel, in one embodiment, the height of the support surface is adjustable, preferably by mechanical means such as gears or screws. The plasma pattern changes depending on the height, so it is advantageous to be able to regulate the susceptor height to achieve a homogeneous plasma and higher process temperatures.

[0026] Preferably, the reactor comprises a material flow system configured to generate convective motion that exposes the incoming material to the plasma. This ensures the continuity of the reaction, and furthermore, if the susceptor is saturated with energy, it moves, resulting in greater microwave absorption, higher and more homogeneous temperatures in the reacting mass and plasma, and a more efficient process. According to a further feature of the invention, in an alternative embodiment, one or more of the waveguide ducts supply recirculated microwave radiation from a zone of the reactor located downstream of the reactor vessel, for the purpose of energy recirculation and utilization. This reduces the use of magnetrons or microwave power.

[0027] According to another feature of the invention, the reactor comprises control means connected to at least one mass flow controller for controlling the inlet gas flow based on the stoichiometry of the target reaction.

[0028] With this real-time information, variable adjustments can be implemented to optimize the process towards the production of synthesis gas or target gases (since it can foresee the possibility of cracking organic and plastic compounds into condensable gases such as gasoline, paraffins and other compounds), through iteration software included in the control media or centralized control system.

[0029] Additionally, preferably these control means are configured for plasma energy control by controlling the radiation power by controlling the pulse frequency of the microwave radiation source and the duty cycle of the pulsed radiation.

[0030] It is also planned that the reactor will preferably include temperature sensors on the reactor walls and / or on the material support tray, and / or a cooling system for cooling the reactor vessel, the guide ducts, and / or the feed system. Preferably, the control means will regulate the temperature by regulating the total radiated power and operating a cooling system with defined operating and safety points.

[0031] This way the temperature of the reaction zone is controlled and the time during which the components are subjected to the reaction conditions is limited, by means of radiation pulses in all reactors.

[0032] According to another aspect of the invention, a microwave-assisted plasma reactor installation is provided. This installation may comprise two or more of the reactors described in the preceding paragraphs of this section, and these reactors may be connected in series such that the processed gases from the outlet of the first reactor, after pyrolysis and / or gasification of the microwave susceptor, are used as inlet gases for the second reactor for processing. As defined above, the first reactor comprises an inlet for microwave susceptor and / or raw material, preferably in the upper part of a resonant receptacle, while the second and third reactors will only have inlet gases from the processed gases of the previous reactor, and an additional inlet for gases and / or water (as reactive gases).Thus, the first reactor will be used for the pyrolysis and gasification of solid mass or gases to be processed, the second reactor being for conversion of target gas being designed for the treatment of gases, and the third or subsequent reactors being for enriching the synthesis gas and decomposing any remaining organic component, using reactive gases in stoichiometric proportions.

[0033] According to another aspect, the invention also contemplates a pyrolysis / gasification process of raw material by using a microwave-assisted plasma reactor installation.

[0034] Description of the figures

[0035] The drawings attached to this document are listed and briefly described below, by way of non-limiting example, to illustrate and facilitate the interpretation of the plasma-assisted microwave reactor and the installation disclosed by this invention.

[0036] Figure 1 is a perspective top view of an embodiment of a top portion of the plasma-assisted microwave reactor of the present invention.

[0037] Figure 2 is a plan or top view of the embodiment shown in Figure 1.

[0038] Figure 3 is a side view of the embodiment shown in Figures 1 and 2.

[0039] Figure 4 is a bottom perspective view of the embodiment shown in Figures 1 to 3.

[0040] Figure 5 is a schematic view of a preferred embodiment of a reactor according to the invention.

[0041] Figure 6 is a perspective view of a reactor part according to an alternative embodiment with two resonant receptacles.

[0042] Figure 7 is a top perspective view of a reactor vessel of the present invention.

[0043] Figure 8 is a profile view of the reactor according to the practical embodiment of Figure 6.

[0044] Figure 9 is a schematic perspective view of another alternative embodiment of the reactor of the present invention, with microwave radiation recirculation.

[0045] Figure 10 is an embodiment of a series-operated microwave reactor installation of the present invention.

[0046] Detailed description of the invention

[0047] Next, a detailed description of the invention will be carried out with reference to the figures outlined in the previous section.

[0048] Figure 1 shows an embodiment of the upper feed section of a microwave-assisted plasma reactor of the present invention. The reactor of the present invention is intended (but not limited to) the initial processing of carbonaceous materials (pyrolysis / gasification), and other microwave susceptors (such as metal carbides: SiC, WC, metal powders, and ceramics) can be used. It is primarily designed to treat solid and liquid waste (although it can also accept gases) using microwave-induced plasma technology. The upper feed section of the reactor includes a disc-shaped adapter, which we refer to here as the resonant receptacle (110). This resonant receptacle (110) serves to break the wave guidance through guide channels (120) connected to it from a microwave source, such as a magnetron.Thus, the process transitions from waveguiding to radiation transmission in the disk (110), causing the waves to overlap and increase their amplitude, resulting in greater power. The reactor comprises two or more coupled microwave generators (magnetrons adapted for microwave frequencies: between 300 MHz and 300 GHz; preferably 915 MHz, with A = 327.64 mm; or 2.45 GHz, with A = 122.36 mm). The magnetron power ranges, for 2.45 GHz, from 1 kW to 12 kW (ideally between 3 and 6 kW), and for 915 MHz, from 30 kW to 150 kW (preferably 50 kW). Preferably, the process will be carried out at atmospheric pressure, although operation under overpressure or low pressure is also considered.The radiation transmission system uses waveguide ducts (120) of specific dimensions (multiples of half the wavelength) which, for the preferred realization of the figures, have a rectangular cross-section, said ducts being connected to the resonant receptacle (110) in a zenithal matrix-shaped configuration.

[0049] As can be seen in the figures, the resonant receptacle (110) is substantially disc-shaped, and the waveguide channels (120) enter it through the entrance face (112). In Figure 1 (and subsequent figures), the waveguide channels (120) are preferably represented as four channels of varying lengths to illustrate the requirement that the waves carried by each of these waveguide channels (120) enter the inner cavity of the receptacle (110) in phase, in order to break the microwave guidance mode and transition to a radiation mode in which the waves are in phase, with the consequent desired power increase.The inner cavity of the receptacle (110) has a substantially flattened cylindrical or disc shape, as indicated by the outer shape of the resonant receptacle (110). The estimated dimensions that provide suitable performance are, on the one hand, a height of said inner cavity between A / 4 and A, and on the other hand, a diameter greater than 5A / 2, which will depend on the number of guide channels (120), where A is the wavelength of the microwaves arriving at the resonant receptacle (110). More preferably, the height of the inner cavity of the resonant receptacle (110) is between A / 2 and 3A / 4.

[0050] As can be seen, the waveguide channels (120) are substantially perpendicular to the inlet face (112) of the resonant receptacle (110). Furthermore, and also protruding perpendicularly, this time from the opposite face (114) (see Figure 3 for clarity), a waveguide segment (140) is provided, which leads to the microwave susceptor positioning area. Since this embodiment is primarily intended for the processing of solid and liquid raw materials, although not exclusively, a raw material feed channel (130) is also shown in Figures 2 and 3. This feed channel (130) is preferably located in the center of the resonant receptacle (110), and the waveguides (120) are arranged around it.

[0051] Figure 7 shows a reactor vessel (300) adapted to be coupled to the guide segment (140) of the reactor embodiments 100 shown in Figures 1 to 5 or to the additional central cylindrical conduit portion 240 of Figure 6. This reactor vessel (300) comprises a flange with corresponding holes and a substantially flat end (310) or perforated tray (320) (of which only two are shown in Figure 7). These perforations (320) can be micrometric in size, allowing the passage of reactive or inert gases. The dimensions of the vessel 300 can be similar to those of the guide segment (140). The material of the vessel (300), in which the susceptor material is placed, can be metallic (e.g., stainless steel, steel, nickel, copper, and their alloys), graphite, or ceramic (including Al₂O₃, SiC, MgO, etc.).

[0052] Preferably, the height at which the tray is positioned relative to the power source is between a distance A corresponding to the reactive near-field boundary (Fresnel zone) and a distance A+2*D2 / A corresponding to the far-field boundary, where D is the maximum diagonal of the array formed by the cross-section of the guide channels (120) in the resonant receptacle (110), as shown in Figure 2. For a standard WR340 guide, with an A of 172 mm, the distance from the microwave susceptor to the outlet of the resonant receptacle will be approximately 182 mm. In a preferred embodiment of the receptacle (300), not illustrated, it can be adjusted to different heights within the reactor by means of a mechanical lifting system (screws, gears), optimizing the internal dimensions of the reactor for an optimal resonant electromagnetic field and ideal plasma generation on the microwave susceptor.

[0053] Once the plasma is generated, additional material to be decomposed can be added to the reactor via the feeder conduit (130), falling by gravity and fed by a continuous feeding system. The microwave susceptors will include SiC, semiconductor / metallic powders, and carbonaceous materials (activated carbons, biochar, carbon black, graphite, among others, especially the carbonaceous materials generated during the pyrolysis-gasification process). The susceptors will have a morphology and particle size selected to obtain a specific plasma morphology and distribution, as well as the appropriate reaction temperature (conditioned by the radiation pattern and mass flow rate during agitation or vibration of the reactive solid mass). The reactor is planned to include a solid / gas particle separator system (such as a cyclone or electrostatic precipitator) to prevent clogging on the microperforated support surface or tray (310).

[0054] The use of a gas / liquid condenser is also planned to separate valuable components, mainly from the pyrolysis of plastic waste (such as liquid fuels, paraffins, oils).

[0055] A gas scrubber is also planned to remove polluting acid gases from a mixed gas stream.

[0056] Figure 3 also shows the eccentric exhaust duct (150) for processed gases, located on the same face (114) of the receptacle (110) as the guide segment (140). The exhaust gases exiting through the eccentric duct (150) could be further processed, for example, to enrich synthesis gas in a reactor connected in series, as will be explained later in relation to the installation shown in Figure 10. It is envisaged that the reactor will include a compression system for clean gas (H2O synthesis gas) for storage.

[0057] Figure 6 shows an alternative embodiment of the invention in which the upper feed portion comprises, connected downstream of the conduction segment (140), a second resonant receptacle (200) connected to the first resonant receptacle (110). According to the practical embodiment, it may comprise a funnel-shaped conduit portion (210) (conical in shape or with progressive narrowing) for concentrating the microwave radiation onto the reaction zone. Following the funnel-shaped conduit portion (210), a straight, narrow conduit portion (220) is provided, corresponding to the narrowest section of the funnel-shaped portion (210). Next, an additional resonant receptacle (200), similar to the receptacle 110 described for the preceding figures, and finally, an additional central cylindrical conduit portion (240), also similar to the guide segment (140).Furthermore, in variations of the embodiments described herein, the various parts of the auxiliary resonance section can be detachable and can be provided as individual pieces in order to customize the configuration of said section.

[0058] Thus, as can be seen in Figure 5, microwaves are fed into the reactor (100) in this case from four magnetrons (90), which are guided by the guide ducts (120) to the resonant receptacle (110) where radiation transmission occurs. This radiation is then guided and focused by the guide segment (140) to the reactor vessel (300), where the microwave susceptor is deposited via the feed duct (130) from a hopper (400). As can be seen in Figure 11, for continuous feeding, a screw conveyor (131) is provided, which moves the material to be processed from the hopper (400) to the reactor vessel (300).

[0059] This microwave receptor, placed in the reactor vessel (300), absorbs microwaves until it reaches an incandescence temperature (preferably 1200°C), forming a stable plasma. This plasma allows the introduced material to decompose, exiting in solid form through the outlet conduit (160) into a storage tank (600). Gases resulting from pyrolysis / gasification also exit through the outlet conduit (150). In one practical embodiment, the outlet (160) includes a screw conveyor to facilitate the removal of these solid elements. The reactor is further provided with a gas inlet (170) at the bottom. The gases pass through the tray (310) of the reactor vessel (300) and, upon entering the plasma, decompose into their constituent elements, which also exit through the outlet conduit (150).

[0060] Figure 9 shows an example of the reactor (100) in which three of the waveguide ducts (120) take their inlet after the vessel (300) and feed back or recirculate the radiation to the inlet face (112) of the resonant receptacle (110) to increase energy efficiency. The free-flowing waveguide (120) would receive radiation from a magnetron or microwave generator. This is just one example of one of the configurations that could be installed with these reactors (100), and the number of recirculating waveguide ducts (120), as well as the number of waveguide ducts (120) connected to magnetrons, could be different from that illustrated in Figure 9. Likewise, in all the illustrated figures, a total of four waveguide ducts (120) connected to the face (112) of the resonant receptacle (110) have been selected, but this number could also be different from that illustrated.

[0061] Figure 10 shows a preferred embodiment of an installation comprising three reactors 100, 100', 100” of the type disclosed in the present invention. This installation represents a pyrolysis gasification system based on a series of microwave-induced plasma (MW) reactors 100', 100”, 100’” coupled in-line for use in the gasification of biochar, biomass, and plastic waste, and comprises:

[0062] 1. A first 100' microwave reactor for the pyrolysis / gasification of solid and liquid materials.

[0063] 2. A second 100” reactor for the enrichment of the synthesis gas (Syngas) by catalytic and plasma reactions in the exhaust gases of the 100’ reactor.

[0064] 3. Optionally, a third 100'” reactor or more microwave-induced plasma reactors, coupled until the complete conversion of the evolved gases from reactor 100' into enriched synthesis gas (H2 / CO) of controlled composition.

[0065] Thus, according to an example of the plant's processing procedure, the microwave susceptor and the raw material are first processed in a first reactor (100) as described above. The processed gases from this first reactor (100), exiting through the outlet duct (150), feed the second reactor (100'), which has a processed gas inlet (151). This second reactor (100'), with similar characteristics to the first reactor (100), processes the gases exiting the first reactor (100) to enrich the target synthesis gas. To this end, the second reactor (100') is designed to include a reactive gas inlet (152) and / or a water inlet (153) to process the exhaust gases from the first reactor (100) through catalytic and plasma reactions.This installation also includes a volumetric flow meter for outgoing gases and an outgoing gas analyzer to transform them into enriched gases, which, through a centralized control system, controls the reactions to ensure a defined stoichiometry.

[0066] The same procedure is followed in the installation for the third reactor (100”), shown in Figure 10, where the exhaust gases from the second reactor (100’) are processed to produce an enriched synthesis gas (H2 / CO) of controlled composition. Thanks to its core design and industrializable process, this installation can be implemented at waste treatment sites to valorize biomass, plastic waste and mixtures thereof, as well as conventional pyrolysis biochars, natural coals (lignite, anthracite, natural graphite), black coals (furnace blacks, acetylene carbons, channel blacks, soot), carbon nanotubes (SWNT, MWNT, carbon whiskers), saturated activated carbon (AC) waste, and mixtures thereof. This system can produce synthesis gas (Syngas), H2, activated carbons, and graphitized carbons with controlled morphologies and surface chemistries.

[0067] The radiation pattern will be applied according to the following criteria:

[0068] 1. Pyrolysis / gasification reaction requirements, to produce the maximum yield of gas or pyrolysis products (valuable liquids) according to the type of waste (biomass, plastics, biochars or mixtures thereof) to be processed.

[0069] 2. Temperature range required for the target process, including: biomass gasification, plastic pyrolysis, biochar gasification / graphitization.

[0070] 3. Microwave power required to maintain a stable induced plasma.

[0071] 4. Mass flow, type of waste to be treated and target product (considering process limitations and expected reaction yields).

[0072] According to an alternative embodiment, a nitrogen injection system is provided to keep the ducts clean, as it pushes the generated gases out of the ducts and prevents them from rising. Inert gases (primarily N2, optionally CO2 and argon) can be injected, flowing in the direction of microwave radiation propagation, and directly into the reactor to purge and protect the reactor, the waveguide ducts, and the reactor windows, both in the hopper and in the reactor.

Claims

CLAIMS 1. A microwave-assisted plasma reactor (100), comprising at least one microwave source (90) whose waves are confined and guided through a corresponding waveguide duct (120) to a disc-shaped resonant receptacle (110) configured to break the guidance and transition to a radiation wave propagation mode, the resonant receptacle (110) being connected at its outlet to a guidance segment (140) that guides and focuses the microwaves to a reactor vessel (300) where a microwave susceptor to be processed for plasma formation is disposed, the reactor comprising a processed gas outlet (150) and a processed solid material outlet (160), where: - the lengths of the waveguide channels (120) are multiples of A / 2, and said waveguide channels (120) being distributed in their connection with the resonant receptacle (110) forming a uniformly distributed array, - the height of the inner cavity of the resonant receptacle (110) being between A / 4 and A, and the diameter of said inner cavity equal to or greater than 5A / 2, A being the wavelength of the standard waveguide employed.

2. Microwave reactor (100) according to claim 1, wherein the height of the inner cavity of the resonant receptacle (110) is between A / 2 and 3A / 4.

3. Microwave reactor (100) according to any of the preceding claims, wherein the microwave susceptor is placed in a region between a distance A corresponding to the reactive near-field limit, and a distance A+2*D 2 / A corresponding to the limit of the far field region, with respect to the outlet of the resonant receptacle (110), D being the maximum diagonal of the matrix formed by the section of the guide conduits (120) at the entrance to the resonant receptacle (110).

4. Microwave reactor (100) according to any of the preceding claims, comprising a susceptor material feeder conduit (130) connected to the resonant receptacle (110) and configured for the introduction of raw material in solid, liquid, and gaseous form.

5. Microwave reactor (100) according to any of the preceding claims, comprising a feeding system for transporting susceptor material and / or raw material to be treated, to the reactor vessel (300).

6. Microwave reactor (100) according to any of the preceding claims, comprising a second resonant receptacle (200) connectable to the guidance segment (140) and connected to the reactor vessel (300).

7. Microwave reactor (100) according to any of the preceding claims, comprising a reactive gas inlet (170) to be processed for interaction with the generated plasma.

8. Microwave reactor (100) according to any of the preceding claims, wherein the reactor vessel (300) comprises a susceptor material support surface with a plurality of perforations (320) that allow the passage of the gases to be processed to the plasma generated in the reactor (100).

9. Microwave reactor (100) according to the preceding claim, wherein the material support surface is a converging prismatic surface.

10. Microwave reactor (100) according to any one of the preceding claims, wherein the height of the support surface of the reactor vessel (300) is adjustable.

11. Microwave reactor (100) according to any of the claims, comprising a material flow system configured to generate a convective motion that exposes the inlet material to the plasma.

12. Microwave reactor (100) according to any of the preceding claims, wherein one or more of the guide ducts (120) supply recirculated microwave radiation instead of being connected to a microwave source.

13. A microwave reactor (100) according to any of the preceding claims, comprising control means connected to at least one mass flow controller for controlling the inlet gas flow based on the stoichiometry of the target reaction.

14. A microwave reactor (100) according to any of the preceding claims, comprising temperature sensors on the reactor walls and / or on the material support tray, and / or a cooling system for cooling the reactor vessel, the guide ducts, and / or the feed system.

15. Microwave-assisted plasma reactor installation comprising a first reactor (100') and at least one second reactor (100") according to any of the preceding claims connected in series such that the processed gases from the processed gas outlet of the first reactor (100') are used as inlet gases for the second reactor (100") for further processing.

16. Microwave reactor installation according to the preceding claim, wherein the at least one second reactor (100”) comprises at least one gas inlet and / or one reactive liquid inlet. 17.- Pyrolysis / gasification process of raw material by using a microwave-assisted plasma reactor installation according to claim 14 or 15, comprising introducing susceptor material into the reactor vessel (300) of the first reactor (100) where microwave energy is focused from at least one microwave power supply (90), said susceptor material absorbing the microwaves until reaching an incandescence temperature forming a plasma, such that said susceptor material decomposes and exits the first reactor (100) in the form of processed gases and / or in solid form, and optionally introducing into said first reactor (100) gases to be processed which are introduced internally until their interaction with the plasma where they decompose to exit in the form of processed gases;said set of processed gases being the input material to be processed in the second reactor (100') interacting with the plasma to decompose said processed gases which will leave the second reactor (100') in the form of elemental elements, optionally introducing into the second reactor (100') reactive gases and / or reactive liquids to favor the reaction; and / or said processed gases from the second reactor (100') being input material to be processed in at least a third reactor (100") until the desired gas conversion is achieved, optionally introducing into the at least third reactor (100') reactive gases and / or reactive liquids to favor the reaction.;

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