A plasma reactor and a system for the conversion of reactant gas

Abstract

The present invention relates to a plasma reactor (1) for the conversion of reactant gas, the reactor (1) having a reaction chamber (2) comprising a dielectric plate (3) and a juxtaposed conductive plate (4) mounted in spaced relationship to one another so as to provide a hermetically sealed cavity (5) for plasma discharge therein and to provide a flow path (6) for reactant gas and plasma-forming gas through the reaction chamber (2), a plurality of first electrodes (7) disposed on the dielectric plate (3) and electrically connected to a high-voltage power supply unit (8), a ballast means (9) interconnected between the first electrodes (7) and the high-voltage power supply unit (8), a gas inlet (10) in fluid communication with the reaction chamber (2) for introducing the reactant gas and the plasma-forming gas thereinto and a gas outlet (11) in fluid communication with the reaction chamber (2) and configured to evacuate converted reactant gas, wherein the plurality of first electrodes (7) and the conductive plate (4) are configured to generate a plasma discharge for ionizing the reactant gas and converting thereof into resultant gas in the cavity (5) when driven by the high-voltage power supply unit (8). The present invention also relates to a system (15) for the conversion of reactant gas comprising the plasma reactor (1) and includes a recirculation pipe (16) connecting the gas inlet (10) and the gas outlet (11) of the plasma reactor (1) and a recirculating pump (17) in fluid communication with the gas outlet (11) for recirculating unconverted reactant gas back into the reaction chamber (2) via the gas inlet (10) by means of the recirculation pipe (16).

Description

[0001]

[0002] A PLASMA REACTOR AND A SYSTEM FOR THE CONVERSION OF

[0003] REACTANT GAS

[0004] FIELD OF INVENTION

[0005] The present invention relates generally to gas reactors and systems for synthesizing or decomposing a gas, and particularly relates to a plasma reactor and a system for the conversion of reactant gas based on plasma discharge.

[0006] BACKGROUND OF THE INVENTION

[0007] In recent years, emission control of carbon dioxide, which is a greenhouse gas, has been gaining motion. Consequently, progress has been made in the development and practical application of hydrogen energy technologies, which are excellently used for stationary fuel cells, hydrogen vehicles, fuel cell vehicles and others. Generally, hydrogen and hydrogen-rich gases are produced on a large scale for use in the refining industry, in the production or ammonia, methanol, liquid hydrocarbons from the “Fischer-Tropsch” process, in several petrochemical processes and hydrogenation processes of solvents, paraffins and related products used in the food industry, to name a few. To acquire it, some processes of hydrocarbon reform techniques can be used such as steam reform, partial oxidation, autothermal reform or dry reform. Presently, steam reforming of natural gases such as methane and other light hydrocarbons is the most commonly used method for the production of hydrogen on an industrial scale. In the context of greenhouse gas emissions, development has been made intensively for hydrogen storage and transportation technologies to supply hydrogen as a fuel for the stationary fuel cells, hydrogen vehicles, fuel cell vehicles and the like. As such, the development of a hydrogen station as an infrastructure for supplying hydrogen has reached its demonstration stage.

[0008] Nevertheless, the conventional processes abovementioned have parameters that can render the process expensive or impair the process itself, such as the need to purchase and manufacture, regeneration, replacement and disposal of catalysts commonly used in each reform process. Some processes, in the latter case, use atmospheric air as a source of oxygen thereby generating gas with low heat value in view of the high nitrogen content present in air. In light of gas transportation, gas conversion stations include on-site type gas conversion station in which gas is internally produced at station area and an off-site type to which gas produced outside is transported. The former generally involves a problem in that a large amount of carbon dioxide by-product such as carbon monoxide is produced in the gas conversion and a considerable amount of carbon dioxide is inevitably discharged eventually. Essentially, these collectively contributes to greenhouse emissions. Thus, it is necessary to find processes for conversion of reactant gas by reforming natural gas and light hydrocarbons or otherwise cracking of ammonia gas that can be carried out dry, without the use of catalysts or diluents, or even without the use of fossil fuels combustion for generation of resultant gas.

[0009] Plasma processes are a relatively reliable substitute for the conversion of reactant gas whereby the basic objective of plasma reactors in the region of thermal arc, also known as thermal plasma, is the effective transformation of electrical energy into thermal energy, which would ideally make the reform and cracking processes feasible. Plasma reactors generally include a discharge chamber provided with at least two electrodes which are spaced apart at which a voltage difference is applied to the electrodes and an electric field is established therebetween. A stream of plasma-forming gas is then introduced to the space between the electrodes such that it passes through the electric field whereby exposure thereto generally ionizes the gas to create a plasma. Gases such as methane, light hydrocarbons and ammonia are then injected into the chamber where high-energy electrons and ions in the plasma collide with the gas molecules, breaking the bonds thus producing hydrogen and various intermediate species. The energetic environment ensures that these intermediates quickly combine to form stable hydrogen molecules mixed with other gaseous species. Once the gas mixture exits the reactor, the gases can be separated membrane separation to obtain pure hydrogen. Alternatively, depending on the conditions in the reactor, several reactant gases such as hydrogen gas and nitrogen gas can be recombined to form ammonia gas, for example. Nevertheless, any resultant gases can be produced depending on the types of reactant gases used for the recombination technique in the reactor.

[0010] Technologies related to plasma reactors for conversion of gas are known in the art. For example, a well-known plasma reactor for thermal cracking of hydrocarbons is disclosed in United States of America Patent No. US3622493A where plasma is generated in a discharge chamber equipped with an anode and a cathode between which an electrical arc is formed. The discharge chamber is connected with a mixing chamber where all the necessary reagents forming the initial hydrocarbon reaction mixture are fed. The reaction mixture heated to several thousand degrees Celcius is introduced directly into the discharge chamber where the desired product is formed. The disclosed plasma reactor is bulky, have complicated design and are expensive. In addition, the service life of electrodes in the discharge chamber is rather short because of the erosion caused by high voltage, strong currents and plasma particle bombardment of the surface which necessitates their frequent replacing requiring too many shutdowns of the reactors. United States of America Patent No. US5993761Aand US6007742A disclose processes for the conversion of light hydrocarbons to hydrogen-rich gas using arc electric discharges in the presence of water vapour with carbon dioxide and oxygen, respectively. In the two processes, two electrodes having flat sheet geometry are arranged for arc ignition and subsequently gliding of the arc at which distance between the anode and cathode gradually increases to a point that no longer supports the gliding arc. As a result, the gliding arc disappears at one end of the electrodes, creating a pulsed plasma. Collectively, the aforementioned plasma reactors are held back by relatively low discharge current density contributed by the poorly designed electrode configuration with substantially smaller total surface area in the chamber for distribution of current. Furthermore, the overall geometry of the plasma reactors including the shape of the chamber leads to lower reactor volume thus reducing yield of hydrogen gas.

[0011] Accordingly, there exists a need for a plasma reactor having an appropriate chamber and electrodes configuration which provides higher discharge current density and higher reactor volume for efficient reactant gas conversion. The present invention provides such a solution.

[0012] SUMMARY OF INVENTION

[0013] One aspect of the invention is to provide a plasma reactor generally constructed of a dielectric plate and a juxtaposed conductive plate which arrangement forms a cavity for plasma discharge therein and a flow path for reactant gas to be cracked or recombined into a resultant gas when driven by a high-voltage power supply unit. Advantageously, the cavity is defined by a serpentine pathway, thereby utilizing as much real estate as possible for maximizing volume of the cavity for cracking or recombination of reactant gas, thereby increasing yield of the resultant gas.

[0014] Another aspect of the invention is to provide a system for the conversion of reactant gas which includes the aforementioned plasma reactor and a recirculation mechanism for recirculating unconverted reactant gas back into the plasma reactor for further processing and collection of the resultant gas.

[0015] At least one of the preceding objects is met, in whole or in part, in which the embodiment of the present invention describes a plasma reactor for the conversion of reactant gas, the reactor having a reaction chamber comprising a dielectric plate and a juxtaposed conductive plate mounted in spaced relationship to one another so as to provide a hermetically sealed cavity for plasma discharge therein and to provide a flow path for reactant gas and plasma-forming gas through the reaction chamber, a plurality of first electrodes disposed on the dielectric plate and electrically connected to a high- voltage power supply unit, a ballast means interconnected between the first electrodes and the high-voltage power supply unit, a gas inlet in fluid communication with the reaction chamber for introducing the reactant gas and the plasma-forming gas thereinto and a gas outlet in fluid communication with the reaction chamber and configured to evacuate converted reactant gas, wherein the plurality of first electrodes and the conductive plate are configured to generate a plasma discharge for ionizing the reactant gas and converting thereof into a resultant gas in the cavity when driven by the high- voltage power supply unit.

[0016] Preferably, the ballast means is a pulse-forming network.

[0017] In a preferred embodiment of the present invention, it is disclosed that the first electrodes are connected to the ballast means adapted to supply high-voltage power in order to generate plasma discharge in the cavity of the reaction chamber.

[0018] Preferably, each first electrode is electrically connected to the ballast means comprising one or more of a resistor, a capacitor or an inductor.

[0019] In another preferred embodiment of the present invention, it is disclosed that the conductive plate is further provided with a plurality of second electrodes.

[0020] Preferably, the first and second electrodes are pin electrodes arranged in an array.

[0021] In another preferred embodiment of the present invention, the flow path in the reaction chamber comprises a serpentine pathway through at least the conductive plate.

[0022] Preferably, the reactant gas and the plasma-forming gas are supplied into the reaction chamber at an operating pressure ranging from 100 mbar to 3000 mbar.

[0023] Preferably, the high-voltage power supply unit is configured to supply a power voltage at a level ranging from 5000 volts to 30000 volts.

[0024] It is preferred that the reaction chamber is provided with a sealing means sandwiched between the dielectric plate and the conductive plate for hermetically sealing the cavity.

[0025] It is also preferred that the reaction chamber comprises a fastening means for fastening the dielectric plate to the conductive plate.

[0026] Further embodiment of the present invention discloses a system for the conversion of gas, which system comprises the abovementioned plasma reactor, the system including a recirculation pipe connecting the gas inlet and the gas outlet of the plasma reactor and a recirculating pump in fluid communication with the gas outlet for recirculating unconverted reactant gas back into the reaction chamber via the gas inlet by means of the recirculation pipe.

[0027] In a preferred embodiment of the present invention, it is disclosed that the system further comprises a gas filtration means provided downstream of the recirculating pump for separating a mixture of unconverted reactant gas and resultant gas.

[0028] Preferably, the gas filtration means is a gas separation membrane.

[0029] In another preferred embodiment of the present invention, it is disclosed that the system further comprises one or more gas sources coupled to the recirculation pipe and upstream of the gas inlet of the plasma reactor for supplying reactant gas and plasmaforming gas into the reaction chamber.

[0030] Preferably, the one or more gas sources are configured to supply the reactant gas and the plasma-forming into the reaction chamber at an operating pressure ranging from 100 mbarto 3000 mbar.

[0031] In another preferred embodiment of the present invention, it is disclosed that the system further comprises a valve means provided downstream of the gas filtration means and the one or more gas sources for controlling supply of the reactant gas and the plasmaforming gas into the reaction chamber.

[0032] In another preferred embodiment of the present invention, it is disclosed that the system further comprises a gas buffer tank in fluid communication with the gas filtration means for storing the resultant gas.

[0033] One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiment described herein is not intended as limitations on the scope of the invention.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated.

[0036] FIG. 1 illustrates a perspective view of the plasma reactor according to the present invention.

[0037] FIG. 2 illustrates a cross-sectional view of the plasma reactor according to the present invention, taken along the line A-A of FIG. 1.

[0038] FIG. 3 illustrates a cross-sectional view of the plasma reactor according to the present invention, taken along the line B-B of FIG. 2.

[0039] FIG. 4 depicts the electrical connection between a high-voltage power supply unit and the plasma reactor according to the present invention.

[0040] FIG. 5 illustrates an enlarged cross-sectional view of Section C of FIG. 3 depicting a configuration of the first electrodes in the plasma reactor according to the present invention.

[0041] FIG. 6 illustrates an enlarged cross-sectional view of Section C of FIG. 3 depicting an alternative configuration of the first and second electrodes in the plasma reactor according to the present invention.

[0042] FIG. 7 illustrates a schematic diagram of a system for the conversion of reactant gas which includes the plasma reactor shown in FIG. 1 according to the present invention.

[0043] DETAILED DESCRIPTION OF THE INVENTION

[0044] Hereinafter, the invention shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description and drawings. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

[0045] The present invention relates generally to a device and a system for conversion of reactant gas into a resultant gas using high-energy environments created by plasma discharge for ionization of the reactant gas molecules. Depending on the resultant gas to be produced, the present invention may employ a cracking process to break the chemical bonds between reactant gas molecules into smaller, simpler gas molecules such as hydrogen gas, oxygen gas, nitrogen gas and the like. Alternatively, the present invention may also be employed to recombine simpler gas molecules to form new compounds. In the context of the present invention, the term “reactant gas” may be referred to light hydrocarbons such as Ci to C4 hydrocarbons which may be saturated or unsaturated, branched or unbranched, substituted or unsubstituted with one or more oxygen, nitrogen or sulphur atoms, ammonia gas (NH3), silane gas (Si H4) or any other reactive hydrogen-containing gases which are adapted for gas cracking processes. In addition, the term “reactant gas” may also be referred to simpler gas molecules such as hydrogen gas, oxygen gas, nitrogen gas and others for the purpose of gas recombination processes. The term “resultant gas” as used herein refers to end products produced from the aforementioned gas cracking or gas recombination processes in the present invention.

[0046] Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring particularly to FIG. 1, a perspective view of a plasma reactor ( 1) of the present invention is depicted. The plasma reactor (1) is configured to generally receive one or more gases including a reactant gas and a plasma-forming gas and electrical stimulus as inputs. In an embodiment of the present invention, the plasma reactor (1) has a reaction chamber (2) that is broadly comprised of a dielectric plate (3), a juxtaposed conductive plate (4), first electrodes (7), second electrodes (12) which may alternately function as the conductive plate (4) and an electrical element of a ballast means (9). A high-voltage power supply unit (8) is electrically coupled to the first electrodes (7) to operate the plasma reactor (1). The plasma reactor (1) also includes a gas inlet (10) and a gas outlet (11) that are in fluid communication with the reaction chamber (2). The plasma reactor (1) may also include a sealing means (13) that is positioned at the interfaces between various components of the plasma reactor (1).

[0047] In a preferred embodiment of the present invention, the reaction chamber (2) of the plasma reactor (1) is generally constructed of a dielectric plate (3) and a conductive plate (4) that is juxtaposed to the dielectric plate (3). As shown in FIGS. 1 - 3, the dielectric plate (3) and the conductive plate (4) are mounted together in a spaced relationship to one another to form a cavity (5) for plasma discharge therein in which conversion of reactant gas into resultant gas takes place. In an embodiment of the present invention, the reaction chamber (2) further comprises a sealing means (13) that is sandwiched between the dielectric plate (3) and the conductive plate (4) to hermetically seal the cavity (5) so as to maintain vacuum or controlled atmosphere within the cavity (5) and to prevent leakage of gases out of the reaction chamber (2), or otherwise to prevent external contaminants from entering the reaction chamber (2). In context of the present invention, the sealing means (13) is preferably made of elastomers having electrical insulation properties such as fluorocarbon rubber, silicone rubber, ethylene propylene diene monomer, nitrile rubber, chloroprene rubber, polytetrafluoroethylene, just to name a few.

[0048] The reaction chamber (2) generally retains the components of the plasma reactor (1), and its shape may be adapted to a system in which it is implemented. For the purpose of the present invention, the reaction chamber (2) which includes the components such as the dielectric plate (3), the conductive plate (4) and the sealing means (13) may have a cuboid shape to maximize volume of the hermetically sealed cavity (5) for conversion of reactant gas into resultant gas, as seen in FIG. 1. In a preferred embodiment of the present invention, the hermetically sealed cavity (5) provides a flow path (6) for the reactant gas and the plasma-forming gas through the reaction chamber (2) in which is defined by a serpentine pathway through at least the conductive plate (4). The flow path (6) in the hermetically sealed cavity (5) as obstructed by the dielectric plate (3) is indicated by the broken lines as shown in FIG. 1. In the context of the present invention, the serpentine pathway of the flow path (6) is preferred so as to utilize as much real estate of the reaction chamber (2) as possible in order to increase volume of the cavity (5) thereby increasing yield of resultant gas. If desired, the reaction chamber (2) may be configured to have a cylindrical shape, a conical shape or any other polyhedron shapes, as long as they do not impede operation of the plasma reactor (1).

[0049] In an embodiment of the present invention, the reaction chamber (2) may include additional components that adapt the plasma reactor (1) to the system in which it is implemented. As best seen in FIG. 2 illustrating a cross-sectional view of the plasma reactor (1) taken along the line A-A in FIG. 1, the dielectric plate (3), the conductive plate (4) and the sealing means (13) may include aligned threaded or non -threaded holes (not shown) to allow for fastening means (14) to assemble the dielectric plate (3) to the conductive plate (4) with the sealing means (13) sandwiched therebetween. For example, the fastening means (4) may be an arrangement of a bolt (23) inserted through the aligned threaded or non-threaded holes of the dielectric plate (3), the sealing means (13) and the conductive plate (4). Thereafter, a nut (24) may be provided to fasten the bolt (23) so as to retain the components of the plasma reactor (1). In addition, the conductive plate (4) may include a gas inlet port (26) and a gas outlet port (27) which are connected to a gas inlet (10) and a gas outlet (11), respectively. In the present invention, the gas inlet (10) is configured to introduce and inject the reactant gas and plasma-forming gas into the reaction chamber (2) whereas the gas outlet (11) is configured to evacuate the unconverted reactant gas and resultant gas out of the reaction chamber (2).

[0050] In an embodiment of the present invention, the dielectric plate (3) is made of a dielectric material. Dielectric material is an insulator that can be polarized by an electric field, meaning it does not conduct electricity but can support electrostatic fields. Dielectric material is crucial in the construction of the plasma reactor (1) of the present invention for maintaining electrical isolation, preventing arcing and ensuring stable and efficient plasma generation. The dielectric plate (3) prevents electrical arcing between the plasma discharge and inner walls of the dielectric plate (3) and conductive plate (4) which can otherwise be damaging to the plasma reactor (1) and disrupt the plasma generation. Ideally, the dielectric plate (3) limits the current through the plasma, preventing it from becoming a full arc discharge which helps to maintain a low- temperature, non-equilibrium plasma, which is more efficient for conversion of reactant gas into resultant gas depicted in the present invention. In the present invention, the dielectric plate (3) may be made from ceramics, glass, polymers, mica or oxides with high dielectric strength.

[0051] As shown in FIGS. 1 - 3, the reaction chamber (2) comprises a plurality of first electrodes (7) that are disposed on the dielectric plate (3). As best seen in FIG. 1, the plurality of first electrodes (7) are disposed on the dielectric plate (3) in such a way that they are arranged in an array and correspond to the serpentine pathway (6) of the hermetically sealed cavity (5) in the reaction chamber (2). The first electrodes (7) may be annular or ring-shaped, although other shapes are possible, and may be constructed from electrically conductive material such as iron, nickel, gold, copper, alloys thereof, or the like. In the present invention, the plurality of first electrodes (7) are preferably pin electrodes.

[0052] Referring generally to FIGS. 2, 3 and 5, the plurality of first electrodes (7) are located in the hermetically sealed cavity (5) and are partially isolated from the reaction chamber (2) by the dielectric plate (3) whereby an end portion (28) of the first electrodes (7) protrudes into the hermetically sealed cavity (5) as can be seen in FIG. 5. Each of the first electrodes (7) is electrically connected to an external high-voltage power supply unit (8) which controls the characteristics of the electric field. In a preferred embodiment of the present invention, the high-voltage power supply unit (8) provides a plasma generating voltage at a level from 5000 volts to 30000 volts of pulsed DC, AC or other wave form used to create a plasma discharge in the hermetically sealed cavity (5). In the preferred embodiment, the first electrodes (7) are connected to the high- voltage power supply unit (8) through a cable (25).

[0053] As self-explanatory, the conductive plate (4) is made from electrically conductive material which helps to maintain the plasma discharge generated in the reaction chamber (2) by providing a pathway for the electric current needed to ionize the reactant gas. In other words, the conductive plate (4) may itself function as an electrode. For example, suitable electrically conductive material may include metals such as iron, copper, aluminium, gold, silver or the like. Alternatively, the conductive plate (4) may be further provided with a plurality of second electrodes (12) which may be shaped the same as the first electrodes (7) and are positioned to align with the first electrodes (7) within the hermetically sealed cavity (5), as shown in FIG. 6. Similarly, an end portion (29) of the second electrodes (12) protrudes into the hermetically sealed cavity (5).

[0054] As seen in FIGS. 5 and 6, the first electrodes (7) and the conductive plate (4) or the alternate second electrodes (12) disposed thereon are spaced apart from each other whereby electrical field exists therebetween. Essentially, the first electrodes (7) and the conductive plate (4) or the alternate second electrodes (12) are configured to generate a plasma discharge for ionizing the reactant gas and converting thereof into resultant gas in the hermetically sealed cavity (5) when driven by the high-voltage power supply unit (8). In order for the plasma discharge to be generated, plasma-forming gases are commonly introduced together with the reactant gas into the reaction chamber (2) of the plasma reactor (1). Without being bound by theory, when the plasma -forming gas is subjected to the electrical field confined within the hermetically sealed cavity (5), free electrons within the plasma-forming gas gain kinetic energy that can collide with the plasma-forming gas molecules, thereby ionizing them. The resulting ionized gas or plasma move towards the electrodes, thus completing the circuit and sustaining the plasma. Subsequently, the high-energy free electrons collide with the reactant gas molecules, transferring enough energy to break or recombine the chemical bonds to dissociate them into reactive radicals or recombined into new compounds due to the energetic environment in the hermetically sealed cavity (5). Ideally, the plasma-forming gas used in the present invention is preferably inert and does not chemically react with the reactant gas. For example, argon gas and helium gas may be used. In a preferred embodiment of the present invention, the reactant gas and the plasma-forming gas are supplied into the reaction chamber (2) at an operating pressure ranging from 100 mbar to 3000 mbar.

[0055] To ensure optimum plasma dissociation or recombination of reactant gas in the hermetically sealed cavity (5), a significant amount of energy must be available to break or recombine the chemical bonds in the reactant gas molecules. As such, the high- voltage power supply unit (8) is provided in the plasma reactor (1) and electrically connected to the plurality of first electrodes (7) to enable generation of plasma discharge in the hermetically sealed cavity (5). Nevertheless, a direct connection of the plasma reactor (1) to the high-voltage power supply unit (8), despite being able to facilitate plasma discharge generation, may still lead to lower efficiency and control of energy transfer. This is because energy dissipation occurs primarily due to resistive losses in the electrical circuit components including the cable (25) connecting the first electrodes (7) and the high-voltage power supply unit (8). For example, resistance in the electrical circuit leads to Joule heating, where the electrical energy is undesirably converted into heat as current passes through resistive elements. To mitigate such occurrence, a ballast means (9) is provided to interconnect between the high-voltage power supply unit (8) and each first electrodes (7). The interconnection of the ballast means (9) between the high-voltage power supply unit (8) and each first electrodes (7) is shown in FIG. 4. For illustrative purposes, FIG. 4 depicts an exemplary plasma reactor (1) of the present invention having a dimensionally smaller reaction chamber

[0056] (2) configured with a plurality of first electrodes (7) arranged in a linear array, of which are individually connected to the high-voltage power supply unit (8) with a ballast means (9) interconnected therebetween. Nevertheless, it is to be understood that the numbers and interconnection configuration of the first electrodes (7) and ballast means (9) may differ and adjusted in accordance to the system which it is implemented with.

[0057] Generally, the ballast means (9) is used to control the amount of current flow through the circuit between the high-voltage power supply unit (8) and each first electrodes (7) which provides the necessary starting voltage and regulate the operating current to ensure stable and efficient operation of the plasma reactor (1). The plasma reactor (1) requires a high starting voltage to ionize the plasma-forming gas within the hermetically sealed cavity (5) and initiate the plasma discharge. The ballast means (9) provides this initial high voltage to start the plasma reactor ( 1 ) . Once the plasma reactor ( 1 ) is started, the ballast means (9) regulates the current flow therethrough to ensure stable and consistent operation. This helps maintain the desired plasma discharge output and prevents fluctuations in plasma discharge.

[0058] In a preferred embodiment of the present invention, the ballast means (9) is a pulseforming network which is crucial in the plasma reactor (1) for the conversion of reactant gas into resultant gas due to its ability to efficiently deliver high-voltage, high-energy pulses to the first electrodes (7). Plasma formation typically requires high energy pulses to ionize and dissociate the reactant gas efficiently. In the preferred embodiment, the pulse-forming network is adapted to store and discharge energy quickly, thereby providing the necessary high-voltage power to generate and sustain the plasma discharge in the hermetically sealed cavity (5) of the reaction chamber (2). Advantageously, the pulse-forming network of the ballast means (9) minimizes energy losses during the charging and discharging process, ensuring that a significant portion of the energy from the high-voltage power supply unit (8) is effectively utilized for plasma generation rather than wasted as heat or other forms of energy. Furthermore, the pulse-forming network of the ballast means (9) acts as a buffer between the high- voltage power supply unit (8) and the plasma reactor (1), protecting the high-voltage power supply unit (8) from voltage spikes and transients that may occur during the plasma discharge process. This helps prolong the lifespan of the high-voltage power supply unit (8). Preferably, the ballast means (9) comprises various arrangements of one or more of a resistor, a capacitor or an inductor.

[0059] An exemplary embodiment of the present invention also describes a system (15) for the conversion of reactant gas which comprises the abovementioned plasma reactor (1). The main objective of the system (15) is to ultimately collect the resultant gas in the plasma reactor (1) and recirculate unconverted reactant gas back into the plasma reactor (1) for further processing. In the present invention, the basic arrangement of the system (15) includes the plasma reactor (1) as abovementioned, a recirculation pipe (16) and a recirculating pump (17) provided along the recirculation pipe (16). As seen in FIG. 7 depicting a schematic diagram of the system (15), a recirculation pipe (16) is provided for recirculating the unconverted reactant gas back into the plasma reactor (1) whilst at the same time evacuating the resultant gas to the next phase of the system (15). The black arrows along the recirculation pipe (16) in FIG. 7 indicate a direction of inflow of the reactant gas and plasma-forming gas into the plasma reactor (1) via the gas inlet (10), and outflow of the resultant gas and unconverted reactant gas out of the plasma reactor (1) via the gas outlet (11), respectively. As such, the recirculation pipe (16) connects the gas inlet (10) and the gas outlet (11) substantially outside of the plasma reactor (1). The recirculation pipe (16) is also provided with a recirculating pump (17) that is in fluid communication with the gas outlet (11) that facilitates pumping of the unconverted reactant gas back into the plasma reactor (1) or resultant gas into the next phase of the system (15). Remark that not all components of the plasma reactor (1) for reactant gas conversion are shown in FIG. 7, for example the electrical components such as the ballast means (9) and the high-voltage power supply unit (8) for generating the plasma discharge are not shown, and these components are already described in the above.

[0060] During operation of the system (15), it is ideal for the unconverted reactant gas ejected from the gas outlet (11) of the plasma reactor (1) to be recirculated via the recirculation pipe (16) so that the recirculated unconverted reactant gas reaches the gas inlet (10) of the plasma reactor (1). Nevertheless, comingling of the unconverted reactant gas and the resultant gas is inevitable once the mixture of gases is ejected from the plasma reactor (1). In order to avoid recirculating the resultant gas back into the plasma reactor (1), the system (15) further comprises a gas filtration means (18) for separating the unconverted reactant gas and the resultant gas. Recirculation of the resultant gas, of which is chemically reactive, back into the plasma reactor (1) can be unfavourable to the conversion of reactant gas into resultant gas in the cavity (5) of the plasma reactor (1) as the already produced resultant gas may further participate in chemical transformations with the reactant gas to form unwanted by-products such as carbon dioxide (CO2) and water (H2O). As depicted in FIG. 7, the gas filtration means (18) is provided downstream of the recirculating pump (17). Preferably, the gas filtration means (18) is a gas separation membrane compatible for separating resultant gas from the reactant gas. For example, the gas separation membrane may be made of polymeric materials such as polysulfone, polyimide, polyetherimide, and cellulose acetate, inorganic materials such as zeolites, silica, alumina, and metal oxides or metals and their alloys.

[0061] During operation of the system (15), in addition to recirculating the unconverted reactant gas back into the plasma reactor (1), it is ideal to introduce a fresh stream of reactant gas into the plasma reactor (1) to ensure optimum supply thereof. As such, a preferred embodiment of the present invention describes that the system (15) further comprises one or more gas sources (19) coupled to the recirculation pipe (16) and located upstream of the gas inlet (10) of the plasma reactor (1), as shown in FIG. 7. During operation, a first gas source (19A) may be provided to supply the reactant gas whilst a second gas source (19B) may be provided to supply the plasma-forming gas such as argon gas or helium gas into the reaction chamber (2) of the plasma reactor (1). In the case of gas recombination process, a third gas source ( 19C) may be provided to supply a reactant gas that is substantially different from the one supplied by the first gas source (19A). Preferably, the gas sources (19) are configured to supply the reactant gas and the plasma-forming gas into the reaction chamber (2) of the plasma reactor (1) at an operating pressure ranging from 100 mbar to 3000 mbar. In a preferred embodiment of the present invention, the system (15) further comprises a valve means (20) provided downstream of the gas filtration means (18) and the one or more gas sources (19) for controlling supply of the unconverted reactant gas, fresh reactant gas and the plasma-forming gas, respectively, into the reaction chamber (2) of the plasma reactor (1).

[0062] Following separation of the mixture of unconverted reactant gas and the resultant gas in the gas filtration means (18), the separated resultant gas may be delivered and contained into a suitable storage vessel. In a preferred embodiment of the present invention, the system (15) further comprises a gas buffer tank (21) in fluid communication with the gas filtration means (18) for storing the resultant gas. Preferably, the gas buffer tank (21) is portable to allow transportation of the resultant gas and ensure consistent supply of the resultant gas to downstream processes or applications (22).

[0063] The present disclosure includes as contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a degree of particularly, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangements of parts may be resorted to without departing from the scope of the invention.

Claims

CLAIMS1. A plasma reactor ( 1 ) for the conversion of reactant gas, the reactor ( 1 ) having a reaction chamber (2) comprising: a dielectric plate (3) and a juxtaposed conductive plate (4) mounted in spaced relationship to one another so as to provide a hermetically sealed cavity (5) for plasma discharge therein and to provide a flow path (6) for reactant gas and plasma-forming gas through the reaction chamber (2); a plurality of first electrodes (7) disposed on the dielectric plate (3) and electrically connected to a high-voltage power supply unit (8); a ballast means (9) interconnected between the first electrodes (7) and the high- voltage power supply unit (8); a gas inlet (10) in fluid communication with the reaction chamber (2) for introducing the reactant gas and the plasma-forming gas thereinto; and a gas outlet (11) in fluid communication with the reaction chamber (2) and configured to evacuate converted reactant gas, wherein the plurality of first electrodes (7) and the conductive plate (4) are configured to generate a plasma discharge for ionizing the reactant gas and converting thereof into resultant gas in the cavity (5) when driven by the high- voltage power supply unit (8).

2. The plasma reactor according to Claim 1, wherein the ballast means (9) is a pulse-forming network.

3. The plasma reactor according to Claim 1 or 2, wherein the first electrodes (7) are connected to the ballast means (9) adapted to supply high-voltage power in order to generate plasma discharge in the cavity (5) of the reaction chamber (2).

4. The plasma reactor according to any one of Claims 1 to 3, wherein each first electrode (7) is electrically connected to the ballast means (9) comprising oneor more of a resistor, a capacitor or an inductor.

5. The plasma reactor according to Claim 1, wherein the conductive plate (4) is further provided with a plurality of second electrodes (12).

6. The plasma reactor according to Claim 1 or 5, wherein the first (7) and second (12) electrodes are pin electrodes arranged in an array.

7. The plasma reactor according to Claim 1, wherein the flow path (6) in the reaction chamber (2) comprises a serpentine pathway through at least the conductive plate (4).

8. The plasma reactor according to Claim 1, wherein the reactant gas and the plasma-forming gas are supplied into the reaction chamber (2) at an operating pressure ranging from 100 mbar to 3000 mbar.

9. The plasma reactor according to Claim 1, wherein the high-voltage power supply unit (8) is configured to supply a power voltage at a level ranging from 5000 volts to 30000 volts.

10. The plasma reactor according to Claim 1, wherein the reaction chamber (2) is provided with a sealing means (13) sandwiched between the dielectric plate (3) and the conductive plate (4) for hermetically sealing the cavity (5).

11. The plasma reactor according to Claim 1, wherein the reaction chamber (2) comprises a fastening means (14) for fastening the dielectric plate (3) to the conductive plate (4).

12. A system (15) for the conversion of reactant gas, which system (15) comprises a plasma reactor (1) according to any one of Claims 1 to 11, the system (5) including: a recirculation pipe (16) connecting the gas inlet (10) and the gas outlet (11) ofthe plasma reactor (1); and a recirculating pump (17) in fluid communication with the gas outlet (11) for recirculating unconverted reactant gas back into the reaction chamber (2) via the gas inlet (10) by means of the recirculation pipe (16).

13. The system according to Claim 12 further comprising a gas filtration means (18) provided downstream of the recirculating pump (17) for separating a mixture of unconverted reactant gas and resultant gas.

14. The system according to Claim 13, wherein the gas filtration means (18) is a gas separation membrane.

15. The system according to Claim 12 further comprising one or more gas sources (19) coupled to the recirculation pipe (16) and upstream of the gas inlet (10) of the plasma reactor (1) for supplying reactant gas and plasma-forming gas into the reaction chamber (2).

16. The system according to Claim 15, wherein the one or more gas sources (19) are configured to supply the reactant gas and the plasma-forming into the reaction chamber (2) at an operating pressure ranging from 100 mbar to 3000 mbar.

17. The system according to any one of Claims 12 to 16 further comprising a valve means (20) provided downstream of the gas filtration means (18) and the one or more gas sources (19) for controlling supply of the reactant gas and the plasmaforming gas into the reaction chamber (2).

18. The system according to any one of Claims 12 to 14 further comprising a gas buffer tank (21) in fluid communication with the gas filtration means (18) for storing the resultant gas.

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