WO2023039043A1 - Systems and methods for processing gases - Google Patents

Abstract

The invention includes a system for transforming an inflow gas containing methane and a second inflow gas containing carbon dioxide into outflow products that contain carbon monoxide and hydrogen, where the system includes a gas delivery subsystem, a plasma reaction chamber, a microwave subsystem, and an effluent separation and disposal system, with the gas delivery subsystem in fluid communication with the plasma reaction chamber; and the microwave subsystem directs microwave energy into the plasma reaction chamber to energize the first inflow gas and the second inflow gas, thereby forming a plasma, which plasma effects the transformation of the methane and the carbon dioxide into the outflow gas products; and wherein the system further includes an effluent separation and disposal system that includes a separator for segregating the carbon monoxide and the hydrogen from the effluent gas stream.

Description

SYSTEMS AND METHODS FOR PROCESSING GASES

RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63/242,310 filed September 9, 2021. The entire teachings of the above application are incorporated herein by reference.

BACKGROUND

[0002] Methane and carbon dioxide are both greenhouse gases and targets of a global effort to reduce emissions. Methane, a particularly potent greenhouse gas, is abundant and available for industrial uses, but it is often simply consumed by combustion, generating more carbon dioxide. The abundance of natural gas is driving the search for more ways to use this material without burning it, to decrease its greenhouse gas effects and to avoid transforming it into CO2, another greenhouse gas, by simple combustion.

[0003] Besides natural gas, other mixed gas sources such as oceanic clathrates, coal mine gas, and biogas contain methane gas as well. Biogas is a naturally produced mixed gas source that is produced by the anaerobic decomposition of organic waste material in various human-created environments such as landfills, manure holding ponds, waste facilities, and the like, and in natural environments such as peat bogs, melting permafrost, and the like. The anaerobic bacteria that occur in such environments digest the organic material that accumulates there to produce a gas mixture composed mainly of carbon dioxide and methane. Biogas with a high methane content, as can be found in landfill-derived gas mixtures, can be hazardous, because methane is potentially flammable. Moreover, as mentioned, methane is a potent greenhouse gas. Currently biogas that is collected from organic decomposition (e.g., landfills, waste facilities, holding ponds, and the like, or natural regions containing decaying organic materials) is purified to remove the CO2 and other trace gases, resulting in a high concentration of methane for producing energy. However, simply burning methane-rich biogas also produces CO2, another greenhouse gas. It would be desirable to identify uses for biogas or other mixed gas sources that can exploit their energy potential without burning them, to decrease the greenhouse gas effects of methane while avoiding transforming methane into another greenhouse gas, CO2.

[0004] Techniques exist for producing useful products from methane without combustion. Steam reforming, for example, is a process that uses methane as a feedstock for forming carbon monoxide and hydrogen by contacting the methane with the steam for producing a mixture of carbon monoxide and hydrogen called syngas, according to the following equation:

EQI: CH4+H2O — CO + 3H2

[0005] The CO+H2 mixture can be used itself as a fuel, or it can be converted into other hydrocarbon products, for example via the Fischer-Tropsch process to yield liquid hydrocarbons for fuel, or via various catalytic processes to form methane derivatives such as methanol and dimethyl ether. The CO+H2 mixture can also be reacted in a second stage of steam reforming, which combines the water in the steam with the carbon monoxide to yield more hydrogen plus carbon dioxide, a reaction known as the water gas shift reaction, as set forth in the following equation:

EQ2: CO + H2O CO2 + H2

[0006] Steam reforming is carried out at high temperatures, and is energy -intensive, requiring costly materials that can withstand the harsh reaction conditions. Steam reforming uses catalysts to effect the conversion of methane to hydrogen, but the catalysts are vulnerable to poisoning by common contaminants. Furthermore, while processing methane via steam reforming is a widely-used process for generating hydrogen, it yields carbon dioxide as a byproduct. Thus, although steam reforming allows methane to be used industrially without combustion, it is not environmentally neutral.

[0007] As an alternative to steam reforming, dry reforming processes use two greenhouse gases, methane and carbon dioxide, as feedstocks, according to the following equation:

EQ3: CO2 + CH4 ^2H2+ 2CO

[0008] In the dry reforming process, methane reacts with the carbon dioxide to produce syngas at temperatures between 700°C and 900°C, although higher temperatures can be used to mitigate the coking that accompanies the process.

[0009] While dry reforming, using methane and carbon dioxide, appears to offer significant environmental benefits through its use of these two greenhouse gases as feedstocks, the technology itself faces important limitations. It is highly endothermic, requiring energy input that itself can be derived from environmentally challenging processes; in addition, the energy demands lead to high operating costs regardless of its means of production. In addition, there is a tendency for coke formation during the dry reforming process, which can deactivate the catalysts used to carry out the reactions. Furthermore, the hydrogen that is produced can react with the carbon dioxide, because the reaction shown in the equation below (EQ4) proceeds with lower activation energy than the dry reforming reaction shown in EQ3, resulting in an unfavorable yield of hydrogen, which is often the most desired reaction product:

EQ4: CO2 + H2 H2O + CO

[0010] Whether used as an intermediary for hydrogen production or as a reactant for producing other chemicals or fuels, syngas (short for “synthetic gas”) itself, comprising carbon monoxide and hydrogen gases is widely used in industry.

[0011] It would be desirable to use the abundant methane and carbon dioxide feedstock sources to convert them into this useful product. However, current techniques for forming syngas from methane and carbon dioxide have limitations. The most common process for forming syngas is coal gasification, which uses steam and oxygen to react with carbon to form hydrogen and carbon monoxide, according to the following equation:

EQ 5: 3C (from coal) + 02 H2 + 3CO

[0012] The carbon monoxide, though, can react with steam during the process via the water gas shift reaction (EQ2), producing more CO2.

[0013] Advantageously, syngas would be formed without adding more carbon dioxide to the atmosphere, and without requiring large amounts of input energy. Advantageously, a process for forming syngas could use greenhouse gases for feedstock, thus removing these substances from the atmosphere while producing a desirable product. It would be desirable to use the abundant methane and carbon dioxide feedstock sources to convert them into this useful product. While the use of methane and carbon dioxide as reactants for syngas formation has environmental benefits, the use of these feedstocks together presents practical challenges. Streams comprising carbon dioxide and methane of various compositions are hard to work with and profit from, leading to these streams being treated as waste products in some applications and are simply vented to the atmosphere. In some cases, such as offgas from a carbon dioxide scrubbing system on a natural gas line, a mostly carbon dioxide stream is vented to the atmosphere as waste while abundant natural gas (i.e., methane) is present.

[0014] There is a need in the art, therefore, for a process that can use both methane and carbon dioxide, taking advantage of the abundance of these sources to form higher value products while removing these greenhouse gases from the environment. There is a further need in the art for a process that forms syngas without imposing the burdens on the environment that occur with existing technologies. SUMMARY OF THE INVENTION

[0015] Disclosed herein, in embodiments, is a system for transforming a first inflow gas comprising methane and a second inflow gas comprising carbon dioxide into outflow gas products comprising carbon monoxide and hydrogen, comprising a gas delivery subsystem, a plasma reaction chamber, a microwave subsystem, and an effluent separation and disposal system; wherein the gas delivery subsystem is in fluid communication with the plasma reaction chamber and directs the first inflow gas and the second inflow gas into the plasma reaction chamber; and comprises a gas delivery conduit and a gas injector, wherein the gas delivery conduit is in fluid communication with the gas injector, wherein the gas delivery conduit delivers the first inflow gas and the second inflow gas to the gas injector, and wherein the gas injector delivers the first inflow gas and the second inflow gas into the plasma reaction chamber; wherein the plasma reaction chamber is in fluid communication with the effluent separation and disposal system and is disposed within an elongate reactor tube having a proximal and a distal end, wherein the elongate reactor tube is dimensionally adapted for interaction with the microwave subsystem; wherein the microwave subsystem directs microwave energy into the plasma reaction chamber to energize the first inflow gas and the second inflow gas, thereby forming a plasma in the plasma reaction chamber, and wherein the plasma effects the transformation of the methane and the carbon dioxide into the outflow gas products; and comprises an applicator for directing microwave energy towards the plasma reaction chamber, and wherein the plasma reaction chamber is disposed in the region of the elongate reactor tube that passes through the applicator and intersects it perpendicularly; and further comprises a power supply, a magnetron, and a waveguide, whereby the power supply energizes the magnetron to produce microwave energy, the microwave energy being conveyed by the waveguide to the applicator, and wherein the applicator directs the microwave energy towards the reaction chamber within the elongate reactor tube, thereby forming the plasma in the plasma reaction chamber, wherein the outflow gas products flow within the plasma reaction chamber towards the distal end of the elongate reactor tube and emerge from the distal end of the elongate reactor tube, entrained within an effluent gas stream that enters the effluent separation and disposal subsystem, and wherein the effluent separation and disposal system comprises a separator for segregating the carbon monoxide and the hydrogen from the effluent gas stream. In embodiments, the first inflow gas is derived from a first mixed gas source, which can be natural gas or a biogas. In embodiments, the first inflow gas consists essentially of methane. In embodiments, the second inflow gas is derived from a second mixed gas source. In embodiments, the gas delivery conduit delivers each of the first inflow gas and the second inflow gas into the gas injector respectively through a first and a second separate pathway. In embodiments, the gas delivery conduit can comprise an additional gas conveying circuit that delivers an additional gas into the gas injector, and the gas delivery conduit can deliver the additional gas into the gas injector through a third pathway that is separate from the first and the second separate pathway, and the additional gas can comprise hydrogen. In embodiments, the additional gas conveying circuit is a recycled gas conveying circuit that delivers a recycled gas into the gas injector, and the recycled gas comprises hydrogen. In embodiments, the gas injector comprises an injector body comprising two or more coaxially arranged and separate gas feeds, a first gas feed conveying the first inflow gas into the plasma reaction chamber through a first set of one or more nozzles, and the second gas feed conveying the second inflow gas into the plasma reaction chamber through a second set of one or more nozzles. In embodiments, at least one of the first set of one or more nozzles or at least one of the second set of one or more nozzles is oriented at an angle to a longitudinal axis of the plasma reaction chamber or at an angle to a transverse axis of the plasma reaction chamber, and the combined gas flow from the first set of nozzles and the second set of nozzles can create a vortex flow within the plasma reaction chamber. In embodiments, the gas injector conveys the first inflow gas and the second inflow gas into a proximal portion of the elongate reactor tube, and wherein the first inflow gas and the second inflow gas flow distally therefrom towards the plasma reaction chamber. In embodiments, the gas injector is positioned centrally within the proximal portion, and the first set of one or more nozzles and the second set of one or more nozzles are oriented peripherally, or vice versa. In embodiments, the elongate reactor tube is a quartz tube. In embodiments, the plasma reaction chamber is disposed approximately at the midportion of the elongate reactor tube. In embodiments, the effluent separation and disposal subsystem further comprises a hydrogen separation subsystem, which can be in fluid communication with the recycled gas conveying circuit and wherein hydrogen collected by the hydrogen separation subsystem is recycled into the recycled gas conveying circuit. In embodiments, the effluent separation and disposal subsystem further comprises a syngas separator. In embodiments, the vacuum subsystem produces a first reduced pressure environment for the outflow gas products passing through one or more components of the effluent separation and disposal subsystem, and the vacuum subsystem can, in embodiments, produce a first, second, and third reduced pressure environment, wherein pressure in at least one of the first, second, and reduced pressure environments is between about 75 and about 375 Torr, or between about 130 and about 280 Torr, or between about 150 and about 200 Torr. In embodiments, pressure in the first, second, and third reduced pressure environments is substantially similar. In embodiments, the system further comprises a cooling subsystem, and/or further comprises a data management and safety subsystem.

[0016] Further disclosed herein, in embodiments, are methods for processing a first inflow gas comprising methane and a second inflow gas comprising carbon dioxide to produce carbon monoxide and hydrogen, comprising the steps of injecting the first inflow gas and the second inflow gas into a plasma reaction chamber; energizing the first inflow gas and the second inflow gas in the plasma reaction chamber with microwave energy to create a plasma; forming outflow gas products in the plasma, wherein the outflow gas products comprise carbon monoxide and hydrogen; flowing the outflow gas products in an outflow stream to exit the plasma reaction chamber; and separating carbon monoxide and hydrogen from the outflow stream. In embodiments, the first inflow gas can be derived from a mixed gas source. In embodiments, the method further comprises injecting one or more additional gases into the plasma reaction chamber concomitant with the step of injecting the first inflow gas and the second inflow gas, wherein the one or more additional gases can comprise a recycled gas, which can be hydrogen.

[0017] Also disclosed herein is a system for transforming an inflow gas comprising methane and carbon dioxide into outflow gas products comprising carbon monoxide and hydrogen, comprising a gas delivery subsystem, a plasma reaction chamber, a microwave subsystem, and an effluent separation and disposal system; wherein the gas delivery subsystem is in fluid communication with the plasma reaction chamber and directs the inflow gas into the plasma reaction chamber; wherein the plasma reaction chamber is in fluid communication with the effluent separation and disposal system; and is disposed within an elongate reactor tube having a proximal and a distal end, wherein the elongate reactor tube is dimensionally adapted for interaction with the microwave subsystem; wherein the microwave subsystem directs microwave energy into the plasma reaction chamber to energize the inflow gas, thereby forming a plasma in the plasma reaction chamber, and wherein the plasma effects the transformation of the methane and the carbon dioxide into the outflow gas products; comprises an applicator for directing microwave energy towards the plasma reaction chamber, and wherein the plasma reaction chamber is disposed in the region of the elongate reactor tube that passes through the applicator and intersects it perpendicularly; and further comprises a power supply, a magnetron, and a waveguide, whereby the power supply energizes the magnetron to produce microwave energy, the microwave energy being conveyed by the waveguide to the applicator, and wherein the applicator directs the microwave energy towards the reaction chamber within the elongate reactor tube, thereby forming the plasma in the plasma reaction chamber, wherein the outflow gas products flow within the plasma reaction chamber towards the distal end of the elongate reactor tube and emerge from the distal end of the elongate reactor tube, entrained within an effluent gas stream that enters the effluent separation and disposal subsystem, and wherein the effluent separation and disposal system comprises a separator for segregating the carbon monoxide and the hydrogen from the effluent gas stream.

[0018] Also disclosed herein are methods for processing an inflow gas comprising methane and carbon dioxide to produce carbon monoxide and hydrogen, comprising the steps of injecting the inflow gas into a plasma reaction chamber; energizing the inflow gas in the plasma reaction chamber with microwave energy to create a plasma; forming outflow gas products in the plasma, wherein the outflow gas products comprise carbon monoxide and hydrogen; flowing the outflow gas products in an outflow stream to exit the plasma reaction chamber; and separating carbon monoxide and hydrogen from the outflow stream.

BRIEF DESCRIPTION OF THE FIGURES

[0019] FIG. 1 depicts schematically a plasma-based feedgas processing system and component subsystems.

[0020] FIG. 2 depicts schematically a gas delivery subsystem.

[0021] FIG. 3A and FIG. 3B illustrate embodiments of gas injectors.

[0022] FIG. 4, FIG. 5, and FIG. 6 illustrate embodiments of micro wave subsystems.

[0023] FIG. 7 is a schematic showing a vacuum subsystem integrated with other subsystems of a plasma-based feedgas processing system.

[0024] FIG. 8 is a block diagram of a plasma-based feedgas processing system and related subsystems.

[0025] FIG. 9 is a schematic diagram of a reaction chamber and its components.

[0026] FIG. 10A is a schematic diagram of a gas injector in cross-section.

[0027] FIG. 10B is a schematic diagram of a gas injector in cross-section.

[0028] FIG. 11 is a schematic diagram of a microwave subsystem.

DETAILED DESCRIPTION

[0029] Disclosed herein in more detail are systems and methods for converting a mixture of CH4 and CO2 into syngas. In embodiments, these systems and methods use non- thermal plasma produced by microwave energy to effect these conversions. In embodiments, the systems and methods disclosed herein can be optimized (“tuned”) to maximize efficient production of syngas, or of its components which can be isolated for further commercialization. As used herein, the term “syngas” refers to a gaseous mixture of hydrogen and carbon monoxide, containing, in embodiments, about 30-60% carbon monoxide, about 25-30% hydrogen, 0-5% methane, and about 5-15% carbon dioxide. In embodiments, syngas can contain other gas components, for example inert gases such as nitrogen present in amounts up to 40%, and can further contain H2O in amounts up to about 10%.

[0030] In embodiments, the systems and methods disclosed herein can harness waste carbon dioxide from other chemical and industrial applications and from difficult and complex mixtures of methane and carbon dioxide with other gaseous components, such as may be found in an industrial offgas stream, and convert them into syngas, forming a carbon-negative method to produce syngas. In embodiments, carbon dioxide to be used as a feed gas can be separated from the atmosphere in an air separation unit and reacted with natural gas to produce additional syngas and potentially also acetylene.

[0031] These systems and methods utilize a microwave-induced non-thermal plasma as the primary source of energization for the chemical reactions that convert the methane and carbon dioxide feedgases into the carbon monoxide and hydrogen components of the syngas that is produced. Because electrical energy is used to generate the microwaves and plasma as opposed to heat, no additional carbon dioxide is generated from the energization of this reaction if renewable energy is used to supply electricity. If the reactant feedgases are supplied from waste streams of methane and/or carbon dioxide that were to be vented, the overall carbon emissions and efficiency of the initial system is greatly improved while yielding additional syngas.

[0032] The system for producing the chemical reactions from the methane-containing and carbon-dioxide-containing feedgases rely on microwaves to produce the non-thermal plasma that energizes the reactions. As will be described in more detail below, a micro wave generator is connected via waveguide to a single-mode resonant cavity. A quartz tube intersects the broad face of the cavity, in which the gas is energized and reacted (“reactor tube”). The length of the microwave cavity is set such that the peak electric field in the cavity is centered in the reactor tube. Influent gas is continuously injected upstream of the microwave cavity into the reactor tube through a single channel or dual-channel or multichannel vortex flow injector. In a single-channel system, the hydrocarbon gas, carbon dioxide, and hydrogen are mixed before flowing through the gas injector and the reactor tube. In a dual-channel or multichannel injection system, the hydrocarbon gas is flowed through one set of channels and either a hydrogen-carbon dioxide mixture is flowed through the other set of channels (dual-channel) or each inflow gas is flowed through its own channel without any mixing. These channels remain separate until mixing within the reactor tube, at which point they are energized by the microwaves and formed into a plasma. In one embodiment, a lOOkW 915MHz micro wave generator is used to energize the plasma. In an embodiment, a three or four stub microwave autotuner can be used to optimize microwave power absorption into the plasma and minimize non-absorbed reflected power. Over 99.9% of microwave power can be absorbed into the plasma.

1. Overview a. Non-thermal plasmas

[0033] Plasma, the fourth state of matter, is an ionized gas: any gas can be turned into a plasma by applying enough energy to it to create a significant density of charged species, i.e., electrons and ions. Plasmas possess some of the properties of gases, but they differ from the ordinary gaseous state because they respond to both electric and magnetic fields, properties that are due to the charged species that exist in the plasma state. Despite having these properties, plasmas are electrically neutral, a characteristic termed quasineutrality. In addition to the ions and free electrons from the precursor gas that exist in the plasma, a plasma includes uncharged neutral gas species and precursor molecules that can enter into other chemical reactions. Some weakly ionized gases do not necessarily satisfy all of the conditions of a plasma but may still have many plasma-like qualities that influence their behavior. For example, many of the high-pressure plasmas used in industrial applications fall into this category.

[0034] One of the fundamental characteristics of a plasma is its temperature. Plasmas have been used in chemical and industrial applications because they can generate temperatures much greater than those obtained in traditional chemical engineering processes. In a plasma, energy is transferred to electrons, which in turn transfer energy to heavier particles through collisions. Electrons have a higher temperature than heavier particles, and an equilibrium temperature is reached that reflects the collisional frequency and radiative processes of the various particles in the plasma. Those plasmas having an electron temperature (T_e) that is close to that of the heavy particles’ translational temperature (To) are defined as thermal plasmas, with gas temperatures greater than 3,000 K. By contrast, in non- thermal plasmas, highly energetic electrons can co-exist with species having substantially lower temperatures. Therefore, the translational temperature To of the non-thermal plasma can be much lower than the electron temperature Te of the plasma - Te can be close to 11,600 K in industrial plasmas or even higher in other types of plasmas.

[0035] The energy situation in a plasma is more complex when the plasma contains molecules (such as H2, N2, or CH4) instead of just atoms. These molecules have the ability to store energy in various rotational and vibrational motions, and therefore have rotational and vibrational temperatures associated with them. These temperatures for such plasmas generally lie in between the translational and electron temperature of the plasma, and they can affect the behavior of the plasma and its associated chemistry. The techniques disclosed herein are based on the ability of a non-thermal plasma to transfer the major portion of the electrical input energy to energetic electrons in the constitutive feed gas, rather than heating the gas itself. Through electron impacts, ionization, dissociation, and excitation, charged atomic and molecular species (e.g., electrons, ions, radicals) are generated that can participate in chemical reactions.

[0036] Methane and carbon dioxide are both resistant to chemical conversion because of their stability: breaking the C-H bonds in methane requires an enthalpy change of 1664 kJ mol , while breaking the C=O bonds in carbon dioxide requires an enthalpy change of 1616 kJ mol⁴. Using the techniques described below, a non-thermal plasma can be produced and harnessed to break the bonds in these molecules, allowing the formation of carbon monoxide and hydrogen molecules with high efficiency and selectivity. b. Microwave plasma generation

[0037] In embodiments, the plasma used for these systems and methods is a microwave plasma, formed by directing microwave energy at the feed gas mixture comprising methane and carbon dioxide, as described below in more detail.

[0038] The microwave plasma process described herein is a gas phase process, using gaseous reactant precursors to form desired gaseous products. Because of the very fast oscillation frequency of the electric field relative to the molecular and electronic collision frequencies, microwave-generated plasmas are often in a high degree of non-equilibrium, meaning that electron and vibrational temperatures can be much greater than the gas temperature. In embodiments, collisions between the charged species (electrons, ions) and uncharged species (molecules, atoms, particles) in the microwave plasma transfer energy: this microwave-energized plasma supports a highly reactive chemical environment because of the energy contained in the plasma’s free electrons. Because of the high degree of ionization of the precursor gas, the chemical dissociation and ionization of intermediates, and the elevated vibrational and excitational energies in the plasma, the desired chemical reactions described below proceed rapidly and efficiently.

[0039] The plasma employed in these systems and methods is considered a nonthermal plasma, in which the rotational and translational temperatures of the gas are significantly lower than the vibrational and electronic temperatures of the plasma. Selectively energizing the electronic and vibrational modes of the plasma without equivalently raising the rotational and translational temperature of the gas allows for more efficient coupling of energy from the micro wave into the desired chemical reactions. Higher rotational and translational temperatures are also associated with increased production of carbon solids, which foul the reactor tube and are an unwanted product that must be cleaned and removed from the reactor and disposed of. Therefore, avoiding these higher rotational and translational temperatures is advantageous for minimizing the production of unwanted carbon solids.

[0040] Without being bound by theory, microwave radiation is understood to act as follows to create a plasma from a gaseous precursor. When the precursor gas mixture comprising methane and carbon and dioxide is subjected to microwave radiation that meets or exceeds the dielectric strength of the gas components, free electrons (present from background radiation or other sources) in the microwave field region are able to gain enough energy from the microwave electrical field in between collisions with neutral molecules that they can ionize other atoms or molecule. A secondary ionized electron is subsequently accelerated in a direction that is governed by the electric field of microwave radiation, and it gains energy too until it causes another ionization event. This process of ionization progresses throughout the microwave field region until a steady state is reached. The final number of electrons in the plasma is determined mainly by the electron loss processes of the plasma, such as diffusion, recombination, and attachment.

[0041] Mechanistically, the plasma used in these systems and methods is a complex reaction driver. Electrons, stripped from their molecules and energized by the electric fields of the microwaves, collide with molecules and transfer energy into the molecules’ vibrational energy states. This electronic to vibrational relaxation pathway efficiently breaks the existing covalent bonds in the molecules, transforming them into various radicals (C, C2, CH, CH2, CHs, O, H, etc.). These radicals then recombine into new molecules determined by a shifted chemical equilibrium, which is influenced by the kinetic, rotational, and translational temperature of the gas after the plasma. No carbon dioxide remains in the stream after it passes through the plasma, having been fully converted to other carbon- containing products.

[0042] A byproduct of the desired reactions that form carbon monoxide and hydrogen is the formation of acetylene. Acetylene, C2H2, is a valuable and highly reactive triplebonded short-chain hydrocarbon coproduct of the reaction that can be used as a chemical precursor for additional reactions. A gas temperature of approximately 2000K to 4000K improves hydrocarbon product selectivity to acetylene and carbon monoxide. Water, H2O, is an additional coproduct of the reaction. Acetylene and water coproduct selectivity may be modified by changing flow composition and other reaction parameters. Besides the desired reactions to form carbon monoxide and hydrogen, higher-order hydrocarbons can be formed by recombinations of plasma-generated radicals with each other and with the precursor gas. As used herein, the term “higher-order hydrocarbon” refers to any hydrocarbon having 3 or more carbon atoms, whether saturated or unsaturated, including aromatics.

[0043] In embodiments, parameters can be optimized to maximize the carbon monoxide or hydrogen component of the syngas product. Factors affecting product selectivity (e.g., allowing the preferential formation of carbon monoxide or hydrogen) include, without limitation, the identity of the reactant precursor gas, the addition of other gases to the system, the flow rate of any gases entering the system, the temperature and pressure in the reactor system, the amount of microwave power and flow geometry used to create the plasma, the energy density in the reaction zone, the arrangement of the electrical field surrounding the plasma, and reactor vessel geometry and dimensions. In embodiments, static electric and magnetic fields can be employed to influence the behavior of the plasma and hence the product selectivity. c. Precursor gases

[0044] For the systems and methods disclosed herein, methane and carbon dioxide can be used together as the feedstock, optionally in combination with other gases added to the mix. In an embodiment of these systems and methods, methane is the main precursor gas. In embodiments, it can be combined with carbon dioxide as it enters the plasma reaction chamber, forming a single gas mixture that is energized to the plasma state. In embodiments, methane enters the plasma reaction chamber through its own set of nozzles, while carbon dioxide and any other gases are added to the plasma reaction chamber separately, each through its own set or sets of nozzles. Methane can be used in a pure state, or it can be introduced into the system as a component of a commercially available gas stream, such as natural gas. [0045] Mixed gas sources such as natural gas or biogas are particularly advantageous sources of methane for use in the system disclosed herein. As used herein, the term “biogas” refers to a mixed gas produced by the anaerobic decomposition of organic waste material in various natural or manmade environments; the term “biogas” includes all those natural or man-made environments in which such gas-producing anaerobic decomposition can take place, e.g., landfills, manure holding ponds, municipal waste sites, sewage treatment facilities, agricultural waste sites, permafrost decay, and the like. Biogas as collected or retrieved from those sites can be treated or upgraded to increase its methane content and to remove impurities, so that it becomes especially suitable as a precursor gas for the systems and methods disclosed herein.

[0046] Biogas, produced from raw materials such as municipal waste, agricultural waste, plant material, sewage, manure, food waste or other natural or manmade organic sources, is typically formed in a closed system via the anaerobic digestion or fermentation of the organic material. The first stage of this process is hydrolysis, in which the insoluble organic polymers are broken down into sugars and amino acids that serve as substrates for the activity of the anaerobic acidogenic bacteria. In a second stage, these bacteria convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids; the acidogenic bacteria further convert the organic acids into acetic acid, ammonia and carbon dioxide. As a third stage, a separate population of anaerobic bacteria, the methanogens, convert these fermentation products into methane and carbon dioxide. Biogas, containing a mixture of methane and carbon dioxide along with gaseous byproducts such as hydrogen sulfide, can be collected and treated to remove hydrogen sulfide and any other undesirable gaseous products, leaving a gaseous mixture with a high concentration of methane and carbon dioxide that is suitable for use in the system and methods disclosed herein. Methane in biogas can be concentrated using a process of biogas upgrading, resulting in a feedstock component having similar performance characteristics as the methane-containing, fossil- derived natural gas.

[0047] Processes such as water washing, adsorption, membrane separation, amine gas treatment, and the like, can be used for biogas upgrading. Upgrading processes can advantageously be carried out to remove oxygen from the biogas before it is used as a gas source. Oxygen in the feed gas can render it vulnerable to combustion; moreover, oxygen can corrode equipment used in the plasma-based feedgas processing system as disclosed herein. Furthermore, under certain circumstances, oxygen removal may be necessary to meet regulatory standards or other purity requirements. A number of oxygen removal technologies are suitable for use with biogas. As an example, oxygen can be reacted with a reduced metal species, thus oxidizing the metal and consuming the oxygen. The oxidized metal species will then be regenerated back to the active form by reducing the metal species by passing a hydrogen or carbon monoxide containing gas stream over the metal species, generating water or carbon dioxide, respectively. Metal species such as palladium or nickel could be used to catalytically combust oxygen at >500°F with hydrocarbon species mixed with the O2. As another approach, solid scavengers can be used in a disposable fashion to trap oxygen. For example, Fe2S3 can react with three molar equivalents of molecular oxygen to form rust and elemental sulfur. As yet another approach, oxygen can be separated from other gases by molecular sieves, such as 5 A or 13X molecular sieve, similar to the technology seen in air separation units (ASUs). Other upgrading processes for biogas would be available to skilled artisans using no more than routine experimentation. Upgraded biogas can reach a purity and quality similar to the natural gas in U.S. pipelines, and can be used for the same purposes.

[0048] Natural gas as extracted from the earth is predominantly methane, making it a useful source of precursor gas for these systems and methods. Typically, it also includes higher-order hydrocarbons such as ethane, propane, butane, and pentane, along with nonhydrocarbon impurities. The table below (Table 1) illustrates an exemplary composition of natural gas.

S ource : http : //naturalgas . org/ 0 verview/background [0049] Natural gas is generally processed to remove most of the non-methane components before it is made available for commercial or residential use, so that it is almost pure methane when it is reaches the consumer. As an example, natural gas available commercially can include about 96% methane. While an extensive system of pipelines exists in the United States to bring natural gas to consumer markets after it has been stripped of its impurities, much natural gas is found in areas that are far from these markets and far from the pipeline infrastructure (often termed remote or “stranded” natural gas). In embodiments, the systems and methods disclosed herein can be used in situ, for example at the location of the stranded natural gas, with the stranded natural gas being combined with carbon dioxide on site to produce syngas. These systems and methods accordingly offer a cost-effective way to utilize this stranded natural gas as a resource.

[0050] Besides the methane-containing and carbon-dioxide-containing feedgases, other gases can be added as precursor gases. For example, hydrogen can be added as an influent in this system to reduce reaction product selectivity to carbon solids. In embodiments, gas flow compositions can include natural gas from about 10% to about 99%, hydrogen gas from 10 to 99%, and carbon dioxide from about 10% to 99%.

2. Systems and subsystems

[0051] In embodiments, the plasma-based system for producing syngas as disclosed herein can comprise six subsystems: 1) a gas delivery subsystem, 2) a microwave subsystem, 3) a vacuum subsystem, 4) a cooling subsystem, 5) an effluent separation and disposal subsystem, and 6) a data management and safety subsystem. As an overview, the reactant gases are delivered into the reactor by the gas delivery subsystem. The plasma in the reactor is produced by the microwave subsystem. The plasma is also operated and held at vacuum by a continuously running vacuum pump in a vacuum subsystem. In some embodiments, the reactor is operated at vacuum pressures between 50 mbara and 300 mbara. Vacuum pressures and hydrogen contribute to the non-thermal equilibrium between the various plasma temperatures, improving efficiency, selectivity, and reaction stability. The temperatures in the various subsystems are monitored and regulated by a cooling subsystem. After the reactants are converted into the products in the reactor, the hydrogen, carbon monoxide, and acetylene can be separated and purified to continue into downstream processes. Depending on end-customer needs, purification systems can vary. Adsorbent beds or process driers can be added to remove moisture and water from the process stream, membrane system may be used to partially separate hydrogen from the product stream to adjust the H2/CO ratio of the syngas product. A pressure swing adsorber can be used to separate and purify a hydrogen product stream of 99.97% purity from the reaction products, if desired. If acetylene is desired as an end product, a solvent absorber and stripper column system may be used to separate and purify any acetylene in the product stream to 99.7% purity.

[0052] These subsystems are described in more detail below. The integration of these subsystems is shown schematically on FIG. 1.

[0053] As shown schematically in FIG. 1, a plasma-based feedgas processing system 100 provides for the conversion of one or more inflow gases 102, 104, and 108 into a mixture of gaseous products contained in an outflow stream 112 emerging from a plasma reaction chamber 114 (or “reactor”), where the plasma reaction chamber contains the plasma that has been generated by a micro wave subsystem 118. In the depicted embodiment, a methane-containing inflow gas 102 enters the plasma reaction chamber 114 separately from the carbon-dioxide-containing inflow gas 104. An optional auxiliary gas 108 such as hydrogen can be introduced separately, or it can be derived from a recycling of a certain fraction of the outflow stream 112 as shown. Other auxiliary gases such as nitrogen can also be added in addition to the one depicted in the Figure. The various inflow gas streams and their direction into the plasma reaction chamber 114 are encompassed by the gas delivery subsystem 110. The gas delivery subsystem 110 is responsible for producing the appropriate proportions of inflow gases and controlling their flow rates. Once the inflow gases enter the plasma reaction chamber 114, they are energized by micro waves produced by the micro wave subsystem 118, which creates a plasma state within the plasma reaction chamber 114. An outflow stream 112 carries outflow (or “produced”) gas products including carbon monoxide, acetylene, hydrogen, and a mixture of unreacted methane, residual inert gases, and higher-order hydrocarbons. Carbon solids can be entrained by the outflow gas stream 112. An effluent separation and disposal subsystem 120 allows for the separation of waste components from the outflow stream 112 so that they can be disposed of, and further allows for the separation of desirable components into discrete streams as necessary for further commercialization or for reintroduction into the plasma reaction chamber 114 as an inflow gas 208. For example, a desirable product such as syngas or acetylene 124 can be separated from the outflow stream 112 by the separation/disposal subsystem 120, for further commercial purposes. In embodiments, the carbon solids entrained by the outflow gas stream 112 can be removed by the separation/disposal subsystem 120 as a discrete product 124 or waste material 122. In the depicted embodiment, a recycled stream 128 that is predominately hydrogen emerges from the separation/disposal subsystem and is recycled back into the plasma reaction chamber 114 as an inflow gas 108. In other embodiments, a portion or the entirety of hydrogen produced by the reactor can be separated from the outflow stream 112 and commercialized separately as a desirable product 124. The separation/disposal subsystem can be configured to segregate single gases or gas mixtures in accordance with specific gas processing goals. As shown schematically in FIG. 1, a vacuum subsystem 130 surrounds certain system components to maintain them at a low pressure. A cooling subsystem (not shown) provides appropriate cooling for each system component. a. Gas delivery subsystem

[0054] In embodiments, a gas delivery subsystem is constructed to direct inflow gases into the plasma reaction chamber. The gas delivery subsystem comprises two components, the delivery conduit and the gas injector. Included in the description of this subsystem are further descriptions of (i) gases fed into the reactor (inflow gases); (ii) the delivery conduit for conveying inflow gases into the plasma reaction chamber, where the delivery conduit includes one or more separate circuits (or “conveying circuits”) for gas flow, and where the conveying circuits can include a methane feedgas conveying circuit, a carbon dioxide feedgas conveying circuit, one or more auxiliary gas conveying circuits for additional gases besides the main feed gases, and/or a recycled gas conveying circuit to allow return of one or more produced gases (e.g., hydrogen) to be used as inflow gases for subsequent reactions, and (iii) the gas injector assembly in fluid communication with the delivery conduit and its component conveying circuits that introduces component inflow gases into the plasma reaction chamber itself. In embodiments, each of the conveying circuits is shown to enter the plasma reaction chamber through its own inflow path. In other embodiments, two or more of the conveying circuits can be commingled, so that a mixed gas flow comprising one main feedgas (either carbon dioxide or methane) enters the plasma reaction chamber through one inflow path, while the other main feedgas (either methane or carbon dioxide) enters the plasma reaction chamber through its own inflow path. For example, carbon dioxide and hydrogen can be combined in a single inflow path to enter the plasma reaction chamber, while methane or the methane-containing feedgas enters the plasma reaction chamber separately through its own inflow path. i. Inflow gases

[0055] Inflow gases can comprise the precursor reactant gases methane and carbon dioxide, with nitrogen optionally included as an inert gas, especially if found in one of the reactant gas sources. In certain embodiments, hydrogen can be included with methane and carbon dioxide as reactants. The proportions of reactant gases, along with the optional nitrogen additive, can be varied empirically to optimize the product profile and yield.

[0056] Inflow gases used by the plasma-based feedgas processing system can be supplied directly from feed tanks, feed lines, and/or through recycling. As used herein, the term “inflow gas” means any gas that is added to plasma reaction chamber within which the plasma is formed. An inflow gas can be a reactant gas such as methane or carbon dioxide, which is transformed by the plasma state into various products, including carbon monoxide and hydrogen. An inflow gas can be an auxiliary additive gas such as nitrogen or hydrogen. An inflow gas can be supplied from external gas sources called “feed lines,” or from intrasystem recycling, wherein a gas such as hydrogen that is produced by the system is reintroduced, in whole or in part, into the plasma reaction chamber for subsequent reactions.

[0057] An inflow gas entering the system via an external gas source or feed line can be derived from a gas reservoir such as a storage tank, or it can be derived from an extrinsically situated flowing gas lines such as a mixed gas source line (e.g., a natural gas line or biogas line). In embodiments, the inflow gas contains solely (or substantially only) the reactants methane and carbon dioxide, with no deliberately added additional gaseous additives. The methane in the inflow gas can be obtained as a component of a more complex flowing gas mixture such as natural gas or biogas. In embodiments, methane and optionally nitrogen, are fed in from feed lines (i.e., storage tanks or flowing gas lines), while carbon dioxide can be fed in from a storage tank or from a feed line. Hydrogen to be used in the system can be fed in from a storage tank or it can be recycled from the product stream and directed back into the reactor.

[0058] A recycled gas stream used for intrasystem recycling is an effluent (i.e., outflow gas) from the plasma reaction chamber, optionally separated into various component gases, with some or all of this gas or these gases reintroduced into the plasma reaction chamber. In embodiments, the hydrogen in the outflow gas products stream is separated from other gases and is recycled in a purified form. In embodiments, a methane-containing inflow gas is introduced into the plasma reaction chamber via a flowing gas feed line, for example a natural gas line or biogas line, along with a carbon-dioxide-containing inflow gas introduced from a flowing gas feed line or a storage tank, while hydrogen is introduced into the plasma reaction chamber separately from the methane and carbon dioxide inflow or commingled with the carbon dioxide; this hydrogen can be derived, in whole or in part, from a recycled gas stream. [0059] In embodiments, the recycled gas can comprise a hydrogen-rich reactant gas, wherein hydrogen is the main component, with some hydrocarbons also present that are capable of reactions. In embodiments, the recycled gas comprises a non-reactant gas such as nitrogen in addition to the hydrogen-rich reactant gas. In embodiments, the remainder of the recycled gas apart from the hydrogen-rich reactant gas is nitrogen. In other embodiments, nitrogen is added as a separate auxiliary gas, apart from its presence or absence in the recycled gas.

[0060] In embodiments, the amount of methane and carbon dioxide can be varied in order to select for more or less amounts of desired products, including carbon monoxide, hydrogen and acetylene. Increasing the amount of hydrogen entering the reactor increases the amount of this gas available for reacting with methane, thereby improving the conversion selectivity for acetylene production and decreasing the amount of undesirable soot build-up.

[0061] In embodiments, hydrogen is provided from hydrogen cylinders. In other embodiments, hydrogen can be provided by recycling hydrogen that is produced by the overall system. In certain embodiments, a recycled gas conveying circuit that conveys hydrogen as an inflow gas back into the system can be combined with a separate inflow source of hydrogen, for example from a hydrogen feed tank to tune the input of this gas. This approach can be advantageous at certain times during the production cycle, for example at system start-up when no recycled hydrogen has yet been produced, or to keep hydrogen inflow at a constant level despite variations in hydrogen produced during recycling.

[0062] In an embodiment, the gas delivery subsystem can be precharged, for example at system start-up, to balance the mixing of gases and to harmonize the gas flow with the microwave energy. First, the system can be evacuated and set at a near-vacuum pressure. Second, the system can be filled from an external source of hydrogen, either backfilled via hydrogen introduced retrograde into the recycled gas conveying circuit, or front-filled from a separate hydrogen inflow line. Third, the inflow gases methane and carbon dioxide can be added, with flows measured by flowmeters. With the system thus precharged with appropriate gases, the reactor can be energized, and the inflow gases can be processed. As the inflow gases are processed in the plasma reaction chamber, hydrogen is generated in the outflow gas products stream, along with other gas products. Hydrogen captured from the outflow gas products stream then can be recycled into the system, while at the same time the exogenous hydrogen inflow is decreased. This balancing of extrinsic and intrinsic hydrogen inflows (from external feed lines and from recycling) can facilitate a smooth start-up procedure for the overall system.

[0063] In embodiments, a hydrocarbon-containing inflow gas that contains methane as the main component can be used as a feedstock for the plasma-based feedgas processing system as described in these systems and methods, in a mixture that is tuned to form the desired product. In embodiments a 50:50 mixture of methane and carbon dioxide can be used. In embodiments, methane can be introduced from gas cylinders, from pipelines, or from an inflow of a mixed gas (e.g., natural gas or biogas) as described previously. A set of compressors can be used, so that methane is introduced at a selected pressure, for example at a feed pressure of at least about 2 atm. If natural gas or biogas is used to provide the methane feed gas, the amount of available methane can be monitored, for example by using a benchtop gas chromatograph, and the impurities in the natural gas can be identified and removed. For example, if the natural gas or biogas feed contains sulfur, it can affect the purity of the product stream; such an impurity can be removed before processing. Various impurities that are commonly found in natural gas or biogas (e.g., mercaptans, hydrogen sulfide, and the like) can be removed with a series of pre-scrubbers, where the type of scrubber selected depends on the impurity to be removed.

[0064] Desirably, a mixed gas comprising methane can include a high concentration of methane, so that it is substantially free of impurities or other gases. Natural gas derived directly from a natural source without commercial treatment can contain about 90% or greater of methane. However, natural gas that is processed to be available commercially, or equivalently treated biogas, can be substantially free of nonmethane gases and impurities. A methane-containing inflow gas from such a source is deemed to consist essentially of methane, which term refers to an inflow gas containing about 95% of methane or greater. Such a gas, consisting essentially of methane, can contain, for example, about 95% methane or greater, or about 96% methane or greater, or about 97% methane or greater, or about 98% methane or greater, or about 99% methane or greater. Gases provided from natural sources such as in situ natural gas (as found in wells prior to processing) or such as biogas can contain lesser amounts of methane, but they can be pretreated for use as a hydrocarbon-containing inflow gas so that such gases have higher concentrations of methane; in embodiments, such pretreated gases consist essentially of methane when used as hydrocarbon-containing inflow gases for these systems and methods.

[0065] In embodiments, other auxiliary gases can be used as components of the inflow gas stream, for example additives such as nitrogen, and/or other reactive or inert gases. In an embodiment, nitrogen can be optionally used as a component of the inflow feed gas; it can also be used as a sealing gas for the vacuum pumps, as described below. In an embodiment, the inflow feed gas contains about 10% nitrogen, although this amount can be varied or tuned to optimize efficiency and selectivity for syngas production; in other embodiments, nitrogen can be present in amounts ranging from about 0% to about 30%, with the nitrogen either deliberately added or extraneously present, for example as a minor component adventitiously found the feed gas. In other embodiments, no additional nitrogen is included. In addition to its use as an inflow gas component, nitrogen in gas and liquid form can be used as a part of the cooling subsystem to cool various components and provide a nitrogen “buffer” around the reactor, as described below. Other auxiliary gases can be used as inflow gases along with the reactant gases, for example helium for gas chromatography and argon. ii. Gas delivery conduit

[0066] The gas delivery conduit conveys the various inflow gases (including reactant gases, additive or auxiliary gases, and recycled gases) into the gas injector; the gas injector delivers the various inflow gases into the plasma reaction chamber. The gas delivery conduit contains conveying circuits dedicated to specific gas streams: in embodiments, each feed gas is carried within its own feed gas conveying circuit, additional gases are carried by one or more additional gas conveying circuits, recycled gas(es) (if any) are carried by one or more recycled gas conveying circuits. In embodiments, these systems and methods use a methane inflow stream and a carbon dioxide inflow stream as the main gas feeds, or can use a mixed gas stream (e.g., natural gas or biogas) instead of a pure methane stream, with each main gas feed being carried by its own feed gas conveying circuit. In embodiments, additional gas streams can also pass through the gas delivery conduit in their own conveying circuits in addition to the main gas feed, for example, allowing the addition of inert gases such as nitrogen, and/or reactants such as hydrogen as separate streams via their designated conveying circuits. Furthermore, in embodiments, a recycled gas stream can be added to the mix through a recycled gas conveying circuit, as described in more detail below; a recycled gas stream can contain hydrogen as the predominant component, along with other components such as nitrogen, small quantities of other substances found in the natural gas feed, small quantities of unreacted methane, and other hydrocarbon components produced by the plasma-based hydrocarbon processing system. In embodiments, each conveying circuit is in fluid communication with the gas injector assembly and conveys its gas separately into the gas injector assembly, for example through a dedicated nozzle, valve, or conduit.

[0067] A schematic diagram of an embodiment of a gas delivery subsystem 200 in accordance with these systems and methods is shown in FIG. 2. As shown in this Figure, a methane-containing inflow gas stream 202 is combined with a carbon-dioxide-containing inflow gas stream 204 and an optional auxiliary gas stream 208 containing an auxiliary gas such as hydrogen, with all the gas streams entering the plasma reaction chamber 210. In the depicted embodiment, the three gas streams enter through a gas injector 212 (described below in more detail) which disperses the various flows in directions and with velocities such that a vortex intermingling 214 of the three separate flows is produced within the plasma reaction chamber 210. The intermingled gases in the vortex intermingling 214 enter a reaction zone 218 of the plasma reaction chamber 210, where they are energized by the microwave energy produced in the microwave subsystem 222 to form the plasma 220 within the reaction zone 218 of the plasma reaction chamber 210. In the depicted embodiment, the inflow gases 202, 204 and 208 each enter the gas injector 212 as separate streams through separate inlets, and each enters the plasma reaction chamber 210 through its own outlet from the gas injector. The flow direction, flow velocity and flow rate from each outlet is oriented so that it produces the vortex intermingling 214 of the gases within the plasma reaction chamber 210.

[0068] Inflow gases can be introduced into the plasma reaction chamber in constant or variable flow patterns, and in continuous flow patterns or discontinuous flow patterns, and in any combination of these patterns. In embodiments, a variable flow pattern can be regular or irregular in its variability, and it can include intermittent pulses or surges of flow superimposed on an underlying wave form describing the flow pattern. A sinusoidal flow pattern would be an example of a variable flow pattern, as would a stepwise or “boxcar” flow pattern using square waves to delineate different amounts of flow. In embodiments, these variable flow patterns can include periods where there is no flow, so that the variable flow pattern would be discontinuous. In embodiments, gases can be introduced through all of the inlets simultaneously, or gases can be introduced through different inlets at different times. Gases can be introduced at different flow rates and at different flow patterns at each inlet. For example, one feed gas can be introduced continuously with a constant flow pattern, while one or more of the other feed gases can be introduced sporadically, i.e., discontinuously. Or, for example, a feed gas can be introduced discontinuously (i.e. , with interruptions in its inflow), with one or more of the other gases introduced variably and/or discontinuously so that the auxiliary gases are flowing while the feed gas is not. Or, as another example, a feed gas can be introduced continuously with a continuous flow pattern, while one or more of the other gas streams can be introduced continuously, but with a different flow pattern than the feed gas. Other combinations of continuous/discontinuous patterning and flow pattern variability can be arranged to accomplish specific gas processing goals, for example, to decrease soot formation in the plasma reaction chamber, or to increase acetylene selectivity, or to allow for intermittent cleaning of the reaction tubing interior. [0069] As previously described, gases that are energized into the plasma state undergo a spectrum of reactions, so that the feed gases methane and carbon dioxide are transformed into carbon monoxide and hydrogen. FIG. 2 shows an outflow stream 224 emerging from the plasma 220 that contains the desired hydrocarbon product or products, certain extraneous hydrocarbon products, and hydrogen gas. In the depicted embodiment, the components of the outflow stream 224 are separated from each other by means of the effluent separation/disposal system 228. iii. Gas injector

[0070] The gas injector introduces the various inflow gas streams into the plasma reaction chamber through a plurality of inlets. In embodiments, the gas injector containing the flow channels for the various inflow gas streams can be printed out of a high temperature resin, or can be 3-D printed from ceramic or metal. It can be deployed within or is disposed in fluid communication with the reactor at a variable distance from the plasma reaction chamber within the reactor, where the term “plasma reaction chamber” refers to the region within the reactor where the microwave energy encounters the feed gas streams. In an embodiment, the gas injector can be positioned at the proximal end of the reactor, permitting antegrade gas flow from proximal to distal along the long axis of the reactor. In other embodiments, the gas injector can be positioned at the distal end of the reactor, permitting retrograde gas flow from distal to proximal along the long axis of the reactor, or can be positioned at any other location along the long axis of the reactor. In embodiments, the gas injector is positioned centrally within the reactor tube, with gas flow directed peripherally. In other embodiments, the gas injector is positioned peripherally within the reactor tube, with gas flow directed centrally. Gas flow exiting the nozzles can be aimed at any angle along the long axis of the tube, so that gas can flow proximally or distally in an axial direction. The nozzles can be arranged to yield symmetric or asymmetric vortex flow.

[0071] In embodiments, the inflow gas flows can be aimed by the gas injector so as to create a spiral or vortical gas flow, which assists with mixing the various gas streams. The gas injector is configured to provide a separate nozzle or port for each inflow gas stream as it enters the reactor. The vortical flow can be produced from a gas injector device disposed centrally in the reactor with two or more nozzles or ports, where each inflow gas is separately delivered through its own subset of the one or more nozzles or ports. In an embodiment, these nozzles or ports, located centrally within the reactor, can be aimed peripherally, and can be angled to create the desired gas flow pattern. In other embodiments, vortical flow can be produced by gases flowing into the reactor through a gas injector having two or more nozzles or ports arrayed along the periphery of the reactor, where each inflow gas is separately delivered through its own discrete subset of the two or more nozzles or ports. In embodiments, the vortical flow serves to confine the plasma toward the interior region of the reactor. Additional vortex flow configurations, such as reverse vortex flow, can also be employed, as would be understood by those skilled in the art.

[0072] FIGs. 3 A and 3B depict an embodiment of a gas injector that is compatible with these systems and methods. FIG. 3A shows a transverse cross-section of the proximal part of the reaction chamber 302 of a plasma reactor 300, within which the gas injector 304 is centrally located; the approximate location of the depicted cross-section in FIG. 3A is shown as Line A in FIG. 2, but for convenience, the embodiments depicted in FIGs. 3 A and 3B show only two gas flows instead of the three shown in FIG. 2. In more detail, the gas injector 304 shown in this FIG. 3 A encases two coaxial but separate gas flows, a central gas flow 308 and a peripheral gas flow 310. The central gas flow 308 contains one gas, for example methane. The peripheral gas flow 310 contains the second gas, for example, carbon dioxide. In embodiments, this arrangement can be reversed, with the central gas flow 308 containing carbon dioxide and the peripheral gas flow 310 containing methane. In other embodiments (not illustrated), additional gas flows, such as a recycled gas flow or other auxiliary gas flows, can be maintained in separate coaxial chambers distinct from a flow channels illustrated in FIGs. 3 A and 3B, with each flow channel having its own set of one or more gas nozzles entering the plasma reaction chamber 302. [0073] For the injector design depicted in FIG. 3 A, the central gas flow 308 exits the gas injector 304 centrally through a central gas nozzle 308 aimed distally and seen here only in cross-section, while the peripheral gas flow 310 exits the gas injector 304 and enters the reaction chamber 302 through gas nozzles 312a and 312b, which are aimed peripherally. As shown in this Figure, the peripherally-directed gas nozzles 312a and 312b are arranged at an angle that allows the peripheral gas flows 314a and 314b to enter the plasma reaction chamber 302 to form a gas vortex within the reactor 300.

[0074] FIG. 3B shows a longitudinal section of an embodiment of a gas injector 350, incorporating the principles illustrated in FIG. 3 A. The gas injector 350 depicted in FIG. 3B shows the coaxial arrangement of the central gas flow 352 surrounded by the peripheral gas flow 354. The gas injector 350 is positioned centrally within the reactor (not shown in the Figure), and the gas flows from the central gas flow 352 and the peripheral gas flow 354 exit the gas injector 350 to flow into the reactor. The peripheral gas nozzles 358a and 358b can be arranged at angles (as seen in FIG. 3A), so that the secondary gas exiting these nozzles is aimed to create a vortex flow. As well, the gas exiting the primary gas nozzle 360 can be directed to create or to contribute to a vortex flow. In embodiments, the vortex flow created in the reactor 300 by the gas injector 350 permits gas mixing, which in turn can optimize the exposure of the gas streams to the plasma. b. Microwave subsystem

[0075] In embodiments, the microwave subsystem comprises the various components used to generate, guide, and apply microwave power to form the nonthermal plasma that transforms the feed gas into its products.

[0076] A schematic diagram for an embodiment of a microwave subsystem is shown in FIGS. 4 and 5 below. FIG. 4 provides an overview of the subsystem’s components. As shown in FIG. 4, an embodiment of the microwave subsystem 400 includes a power supply 402, a magnetron 404, a waveguide assembly 408, and an applicator 410, with the micro wave energy produced by the magnetron 404 encountering the inflow gas in a plasma reaction chamber 412 within an elongate reactor tube 414 (seen here in cross-section) to create the plasma. The reactor tube 414 can be made of quartz, as is described below in more detail. In an embodiment, the power supply 402 requires 480 V, 150 A of AC electrical power to generate 20 kV, 5.8 A of low ripple DC power with an efficiency of 96% to energize the magnetron. In an embodiment, the magnetron 404, also rated at 100 kW, produces microwave power at 83-89% efficiency. In embodiments, the microwaves produced are in the L-band, having a frequency of 915 MHz.

[0077] As shown in this Figure, the microwaves enter a waveguide assembly 408 that directs them to the applicator 410, which in turn directs the micro waves to the plasma reaction chamber 412 in the reactor tube 414. In the depicted embodiment, the waveguide assembly 408 comprises two circulators 418 and 420, which direct the micro waves towards the applicator 410 and which prevent reflected micro wave power from coupling back into the magnetron 404 and damaging it. Each circulator 418 and 420 contains a ferrite array 416 and 426 respectively that deflects reflected microwaves in order to direct them towards the applicator 410 and plasma reaction chamber 412, as described below in more detail. Each circulator 418 and 420 has its respective water load 422 and 424 at its end to collect the reflected microwaves. As depicted, the second circulator 420 includes a power tuner 428 that steps down power using a three-stub tuner 430 in the arm that is distal to its junction with the applicator. In the arm of the second circulator 420 that interfaces with the applicator 410, a three-stub tuner 432 is arranged distal to the dual-directional coupler 434; this arrangement is intended to minimize microwave reflection and optimize the microwave energy directed into the applicator 410. A quartz window 438 is inserted between the second circulator 420 and the applicator 410 to prevent arcing. When the plasma is off and the micro waves are on, a standing wave is set up in the applicator 410 between the three-stub tuner 432 and a sliding shorting plate 440 on the end of the applicator 410 such that the electric field is sufficient to initiate breakdown of the feed gases in the reactor tube 414 that contains the plasma reaction chamber 412. The reactor tube 414 runs through the broad wall of the applicator 410 but is not in direct contact with the microwave waveguide 408. Once the initiation of the plasma state is achieved, the three-stub tuner 432 can then be adjusted to match the impedance of the incoming microwave signal to the plasma-loaded applicator 410. Microwave energy entering the applicator 410 is tuned to peak at the center of the plasma reaction chamber 412, using the shorting plate 440 as needed to change the dimensions of the cavity within which the plasma is formed.

[0078] To optimize the power for producing the plasma, it is desirable to match the impedance of the waveguide 408 to the impedance of the applicator 410 in the presence and the absence of the plasma. Plasma impedance is dynamic however, and can change based on the operating pressures, gas flows, and gas compositions in the plasma reaction chamber 412. In embodiments, the micro wave subsystem can be equipped with a standard three-stub autotuner 432, which has three metal stubs inserted into the waveguide. The depth to which each of these stubs is inserted into the waveguide alters the phase of the micro waves entering the reactor 410 and allows for power matching into the plasma. Microwave power and phase measurement in the autotuner 432 allow the autotuner 432 to modify stub depth algorithmically, so that reflected power (i.e., the power not absorbed by the plasma), is minimized. In embodiments, a dual directional coupler 434 with attached power diodes (not labeled) can be included, to measure forward and reflected power in the subsystem. The coupler 434 can be fitted with two small holes that couple microwaves with a known attenuation to the diodes, which convert the microwave into a voltage. In embodiments, reflected power is less than 1% of total micro wave power sent into the system. In embodiments, the microwave applicator 410 is a single-mode resonant cavity that couples the microwaves to the flowing gas feed in the plasma reaction chamber 412. A sliding electrical short 440 can be built into the applicator 410 to change total cavity length. In embodiments, the plasma for the 100-kW demo unit can generate upwards of lOkW of heat, which can be removed via water and gas cooling subsystems.

[0079] The plasma is created in the plasma reaction chamber 412 within the elongate reactor tube 414. In embodiments, the reactor tube 414 can comprise a long aspect ratio fused quartz tube, with an outer diameter between about 30 and about 120mm, a length of approximately 6 ft, and a thickness varying from about 2.5-6.0 mm. In an embodiment, the reactor tube can have an outer diameter of 50mm, or an outer diameter of 38 mm. In embodiments, tube sizes can have an outer diameter (OD) and corresponding inner diameter (ID) of 120/114 mm OD/ID, or 120/108mm OD/ID, or 80/75 mm OD/ID, or 50/46 mm OD/ID, or 38/35 mm OD/ID. In embodiments, the reactor tube 414 has a consistent diameter throughout its length. In other embodiments, the reactor tube 414 can have a varying diameter, with certain portions of the tube 414 having a smaller diameter, and other areas having a larger diameter. In embodiments, a tube can have an outer diameter of about 50 mm at the top and about 65 mm at the bottom. In embodiments, the tube can have a narrower diameter at a preselected portion of the tube, for example, approximately in the middle of the tube. Quartz is advantageous as a reactor tube 414 material because it has high temperature handling, thermal shock resistance, and low microwave absorption.

[0080] FIG. 5 shows, in more detail, a microwave subsystem 500, such as was depicted in FIG. 4, and the paths of microwave energy 505, 507, and 515 flowing therein; in FIG. 5, certain features of the microwave subsystem 500 are shown schematically but, for clarity, were not labeled as they were in FIG. 4. As shown in the embodiment depicted in FIG. 5, micro wave energy, generated by the magnetron 504, is directed forward along a forward energy path 505 from the magnetron 504 to the distal end of the waveguide assembly 508, from which it is reflected along an antegrade (forward) reflected path 507. The direction of the antegrade (forward) reflected path 507 is shaped by its encounter with the ferrite array 526 in the second circulator 520, which deflects the reflected microwaves 507 towards the applicator 510 and the plasma reaction chamber 512. Micro waves can also be reflected retrograde from the applicator 510 along a retrograde (reverse) reflected path 515, which passes backwards through the second circulator 520 into the first circulator 518, where the micro waves in this path 515 are collected by the water load 522 within the first circulator 518. The retrograde (reverse) reflected path 515 is deflected by the ferrite array 526 in the second circulator 520, and then by the ferrite array 516 in the first circulator 518 to establish its final direction. In an embodiment, forward power in the system is approximately 25 kW, with reflected power 1% of this or less, with the goal of 0% reflected micro wave energy. In embodiments, the forward power in the system is approximately 30kW; in other embodiments, the forward power in the system is approximately lOOkW. In yet other embodiments, forward power levels of about 8 kW, about 10 kW, or about 19-20 kW can be employed. In embodiments, the system can advantageously encompass a forward power at levels less than about lOOkW.

[0081] In an embodiment, the microwave subsystem includes a single arm pathway towards the plasma reaction chamber, as depicted in FIG. 4 and FIG.5. In other embodiments, a double-arm applicator pathway can be employed, as shown below in FIG. 6. As shown schematically in FIG. 6, a double-armed microwave subsystem 600 comprises a magnetron 604 producing microwave energy that enters the circulator assembly 603, which comprises two circulators, labeled “1” and “2.” Microwave energy passes through the circulators substantially as depicted in FIG. 5, to enter a power splitter 606 that directs the microwaves into two waveguide arms 609a and 609b, within which arms the micro waves are aimed towards their respective applicators 610a and 610b. In embodiments, the double-arm waveguide 609a and 609b plus applicators 610a and 610b can split the incident power in a 50:50 ratio, but in other embodiments, a selected ratio of power splitting can be engineered.

[0082] Certain maintenance measures within the microwave subsystem can extend the lifespan of the components and optimize the product output. In embodiments, for example, the reactor can be cleaned periodically. It is understood that carbon soot build-up can occur in the reactor tube when non-thermal plasma technology is used to convert methane and carbon dioxide to carbon monoxide and hydrogen, and the presence of soot can lead to localized areas of overheating on the quartz surface with subsequent damage to the reactor tube. In addition, soot that accumulates distal to the microwave coupling can become conductive, leading to formation of undesirable arcs. Therefore, in embodiments, regular cleaning of the reactor is undertaken in order to minimize these problems. Cleaning can be undertaken on a periodic basis, or based on the discontinuous demands for commercial operation, or in response to observable characteristics of the plasma or effluent. For cleaning purposes, several steps are typically employed: 1) de-energizing the plasma process with in the plasma reaction chamber, either by switching off the microwave power creating the plasma, or by shifting the gas inflow from the process gas to an inert cleaning gas or gas mixture (e.g., pure N2 or a combination of nitrogen with air or with other cleaning gases), or both; 2) discontinuing the feed gas inflow and introducing an inert gas mixture (e.g., nitrogen) that purges the inflow lines of the flammable feed gas; 3) filling the reactor with the cleaning gas (e.g., nitrogen mixed with air); 4) re-energizing the plasma reaction chamber with microwave energy to create a plasma state from the cleaning gas, including monitoring and adjusting the microwave energy and the pressure to permit effective cleaning; 5) reversing the process once the reactor tube is clean, with evacuation of the cleaning gas or displacement of the cleaning gas by the feed gas, leading to filling the reactor tube with the feed gas, and subsequent energizing of the feed gas to form a plasma.

[0083] In embodiments, soot deposition (and therefore the need for cleaning) can be minimized by including hydrogen as an inflow gas; this approach, however, has the drawback of decreased efficiency in hydrocarbon (e.g., methane) conversion. In other embodiments, soot deposition can be managed directly by periodic manual cleaning; this approach has the drawback of requiring physical interventions to access the internal surfaces of the reactor tubing where the soot accumulates. In yet other embodiments, a nitrogen: air mixture at a 50:4 ratio can be used, resulting in a cleaning time of about three minutes every 2-3 hours.

[0084] An embodiment of this system contains parallel microwave reactor setups multiplexed together, with a first reactor and a second reactor joined after the reactor tube and heat exchanger and isolation valves for each reactor but sharing vacuum pumps. A first reactor’s magnetron can be shut off and, and the reactor isolated by the isolation valve, then opened to an alternate vacuum system, while the second reactor is operating to energize the feedstock gas in its plasma reaction chamber. A cleaning plasma can then be utilized for the first reactor. Once the cleaning is done, the first reactor system will be evacuated of the cleaning gas mixture and purged with nitrogen, then purged again by the respective mixture of new feed gas and recycled gas used for the process, then reopened to the main vacuum system and reignited. The second reactor can be cleaned in turn, using the same sequence. In some embodiments, the total number of parallel reactors can be increased to include three or more reactors, with their cleaning cycles sequenced such that the total throughput of the multiplexed system is constant while any one reactor is undergoing cleaning. This cleaning step can therefore be cycled through the multiplexed reactor system individually or in small groups indefinitely, with cycles timed such that there is no loss in product throughput over continuous use. c. Vacuum subsystem

[0085] In embodiments, a vacuum system is arranged around all components between the gas injector providing gas inflow to the reactor and the product outflow stream distal to the reactor. In embodiments, a vacuum is maintained in the reactor, or a low-pressure environment is produced, on the order of about 30 to about 120 Torr, or 60 to about 100 Torr, or 70 to about 80 Torr. In embodiments, a low-pressure environment on the order of about 75 to about 375 Torr, or about 120 to about 280 Torr, or about 150 to about 200 Torr, or about 170 Torr.

[0086] A simplified schematic of a plasma-based feedgas processing system 700 highlighting the vacuum subsystem 702a and 702b is shown in the FIG. 7, with arrows indicating the direction of gaseous flow throughout the system 700. In embodiments, a vacuum subsystem (illustrate here at 702a and 702b) envelopes certain components of the processing system 700 to maintain a pressure in those components in the range of about 30 to about 120 Torr. Alternately, the same system can maintain a pressure in those components in the range of about 75 to about 375 Torr, or about 120 to about 280 Torr, or about 150 to about 200 Torr, or about 170 Torr.

[0087] As depicted in FIG. 7, the vacuum subsystem designated by the dashed line 702a creates a first reduced-pressure environment around the around the gas delivery subsystem 704; the vacuum subsystem designated by the dashed line 702b creates a second reduced pressure environment around the reactor 710 and its outflow stream 716, and around various components downstream from the reactor 710, all as described in more detail below. For purposes of clarity, a portion of the vacuum subsystem is identified by dashed line 702a and a portion of the vacuum subsystem is identified by dashed line 702b; these two dashed lines can represent separate vacuum subsystems, or they can be considered to be merged together to represent a single vacuum subsystem. Subsystems and components shown in this Figure for clarity include: (i) the gas delivery subsystem 704 that passes the inflow gases, including a first feed gas 706a and a second feed gas 706b (e.g., feed gases containing, respectively, methane and carbon dioxide), with an optional hydrogen-containing recycled gas 712, through their respective feed gas inlets (not shown) into the reactor 710; (ii) a micro wave delivery system 708a that forms the micro waves 708b that act upon the inflow gases (i.e., the feed gases 706a and 706b, and the hydrogen-containing recycled gas 712) in the reactor 710 to effect chemical transformations in the inflow gases 706a and 706b and 712 in the plasma reaction chamber 711 region of the reactor 710, with the products of these chemical transformations exiting the reactor 710 as the outflow stream 716; (hi) an effluent separation and disposal system comprising an separator 714 for separating out the components of syngas (carbon monoxide and hydrogen) and an optional hydrogen separator 718 that separates the outflow stream 716 into component gas streams, with the remainder of the outflow stream 716 distal to the syngas separator 714 and the hydrogen separator 718 becomes the recycled gas stream 712. As mentioned previously and as shown in this Figure, certain components situated downstream from the reactor 710 are also contained within the vacuum subsystem as designated by dashed line 702a, such as a filter 720 for the outflow stream 716, a heat exchanger/separator 722, and a series of pumps 724 and 728. In this Figure, an optional cold trap 730 for removing higher order hydrocarbons is situated outside the vacuum subsystem as designated by dashed line 702a, as are the syngas separator 714 and the optional hydrogen separator 718.

[0088] The filter 720 shown in the Figure is intended to remove carbon solids from the outflow stream 716. In embodiments, the plasma process makes a small amount of carbon solids as a by-product; for example, carbon solids can be produced in the range of 0.1-0.5%. Therefore, it is desirable to filter the outflow stream 716 to remove these carbon solids in order to prevent these particles from fouling the downstream components of the system. Since the filter 720 is the first surface that the outflow stream 716 encounters after leaving the reactor 710, the gas in this stream is very hot (on the order of 400 - 1000°C). Therefore, the material for the filter 720 is selected so that it can withstand such temperatures, with or without additional cooling. In embodiments, the filter 720 can be made of ceramic materials or of stainless steel, with cooling added as needed. d. Cooling subsystem

[0089] In embodiments, a cooling subsystem can be implemented to control the operating temperatures for the various components of the gas processing system described herein. In embodiments, the plasma formed in the reactor reaches a temperature between 2000 - 3000 K (1700 - 2700°C), exiting the reactor at a temperature of about 400 - 1100°C. To protect the downstream components of the system from heat damage, cooling is provided. In addition, it is desirable to cool the reactor itself, for example to keep the outer temperature of the reactor tube below 500°C. Moreover, the reactor tube is more likely to retain heat during gas-based cleaning (as described above) vs during syngas production, so that more cooling power can be required intermittently to protect the reactor tube from heat stress. In embodiments, the cooling for the system includes two types of cooling: water cooling and gas cooling. Water cooling can be used for many of the components of the system, for example the magnetron, the power supply, the vacuum pumps, the applicator, and the like. Gas cooling can be employed for other components as appropriate, for example, the reactor tube, the reactor itself, and the various O-ring seals in the system. In embodiments, nitrogen is used for gas cooling. Nitrogen has the additional benefit of replacing atmospheric gases in enclosed parts of the system, thus enhancing safety. In an embodiment, the reactor tube and the applicator can be enclosed in a sealed, nitrogen-purged (oxygen-free) environment, where the presence of nitrogen provides cooling and also serves as a safety mechanism: by replacing the oxygen in the environment around the reactor system, the nitrogen gas coolant reduces the chance of explosion if a leak is created. e. Effluent separation and disposal subsystem

[0090] In embodiments, the outflow stream emerges from the low-pressure environment created by the vacuum subsystem, and then undergoes further management to separate the desired gaseous products from each other and from the waste products. To optimize the economics of the process and to provide a customized gas flow for recycling, a set of components is positioned distal to the vacuum subsystem to segregate certain of the gaseous components in the outflow stream from each other. [0091] In embodiments, it is envisioned that a plasma-based feedgas processing system and the methods of its use described herein convert methane in a stoichiometry that is net hydrogen positive, with 1.5 moles of hydrogen being generated for every mole of methane consumed. The outflow stream thus contains a mixture of hydrocarbons, including the desirable products that form syngas, along with a predominance of hydrogen. In embodiments, this hydrogen can be separated from the outflow stream, for example by using a membrane separator to separate the hydrogen from the remainder of the effluent. After separation, hydrogen can be purified and commercialized as a separate gas product; alternatively, or in addition, hydrogen can be, in whole or in part, recycled into the system, as illustrated in previous Figures. In other embodiments, syngas can be separated from the outflow stream via a separator instead of or in addition to hydrogen separation. In an embodiment, the outflow stream from the reactor can first be treated to remove particulate carbon and condensates, and then syngas can be removed. After the syngas is segregated from the outflow stream, the hydrogen can be optionally removed, captured, or recycled.

[0092] As the outflow stream leaves the plasma reaction chamber, it contains a combination of gases, volatilized higher-order hydrocarbons, and particulate carbon. As previously described, the particulate carbon can be filtered out immediately downstream from the reactor chamber. In embodiments, the outflow stream can subsequently be passed through a cold trap in order to remove certain higher-order hydrocarbons from the outflow stream as condensates. After passing through the cold trap, the outflow stream can be further separated. For example, other higher-order hydrocarbons can be removed from the outflow stream as described below. These compounds are typically deemed waste products, and they can be discarded or disposed of after their removal. Following or simultaneously with the removal of higher-order hydrocarbons, syngas and optionally hydrogen can be separated from the outflow stream via the effluent separation and disposal subsystem. The separation process can employ one or more separation technologies, such as adsorption technologies, absorption technologies, chemical reaction technologies such as oxidization or catalyst-mediated conversion, and the like. f. Data management and safety subsystems

[0093] Advantageously, the overall gas production system comprises interconnected data management subsystems and safety subsystems, so that the safety measures incorporated in these systems and methods are informed by data collected about the system’s performance. In embodiments, data management can include devices, procedures and algorithms for data collection and performance diagnosis, and storage facilities for recording and preserving data. In embodiments, performance diagnosis includes monitoring the state of the system within normal parameters to facilitate overall integration and control, and identifying signs of upcoming or active failure states. Optical diagnostics can be directed at surveillance of the plasma region, for example visible light cameras, mid-IR pyrometers, broadband spectrometers, and the like. Apparatus diagnostics can include pressure transducers, thermocouples, flow meters, microwave power sensors, and the like. Other diagnostic equipment can be used as appropriate, for example full-scale spectrometers and oscilloscopes. In embodiments, various diagnostic modalities can be integrated and monitored automatically and/or manually during a run.

[0094] In embodiments, the manual and automatic diagnostic procedures can be integrated with safety procedures, which can include a fault-interlock system. In an embodiment, diagnostic input can be actively monitored by hardware and software. If an anomaly is detected, a fault signal can be triggered that activates a predetermined response pattern. For those most serious faults, such as a sudden corroborated pressure spike, an immediate automated “hard” shutdown can be triggered. For faults of moderate severity, where the consequences are less serious, a slower automated shutdown can be triggered, intended to stop operations over the course of several seconds. For those faults where a parameter is outside the expected range, but no major consequences are anticipated, the operator can be alerted, so that appropriate actions are taken to rectify the situation and clear the fault without requiring a system shutdown.

3. Exemplary systems and subsystems: IQOkW-powered plasma-based hydrocarbon processing system

[0095] A plasma-based feedgas processing system using plasma technology to transform methane-containing and carbon dioxide-containing inflow gases into syngas, acetylene and hydrogen can obtain a high degree of source gas conversion in combination with a high degree of selectivity for the production of desirable products. The system described below is an embodiment of a plasma-based feedgas processing system that uses a lOOkW power supply to generate the micro waves that form the plasma and effect the chemical transformations.

[0096] The central reaction of this process takes place when methane and carbon dioxide are fed into a microwave-energized region, where they break down into a plasma. [0097] In this embodiment, the feedgas conversion process in the lOOkW-powered processing system, which may use methane as may be found in a natural gas or biogas feed or a pure methane feed, uses approx. 9.5kWhr per kg of syngas product formed; for the feed gas employed, about 90% is converted to syngas. The resulting product mix is influenced by the non-thermal nature of the plasma temperatures. The gas temperature is 3000-4000 K while the vibrational temperature and electronic temperatures are two to three times higher, pushing the reaction equilibrium to form carbon monoxide and hydrogen with a high selectivity. The reaction products can be commercialized together as syngas, or can be separated into the component gases carbon monoxide and hydrogen, or can be used as reactants together or separately for further industrial processes. a. Overall system

[0098] The lOOkW-powered plasma-based feedgas processing system comprises four subsystems: gas delivery, micro wave, vacuum, and cooling. The gas delivery subsystem contains two inflow lines. The first inflow line is a feed line conveying a mixed gas such as natural gas continuously sourced from a local utility company or such as upgraded biogas, comprising a mixture of predominantly methane, with small amounts of ethane, propane, carbon dioxide, and nitrogen (depending on the source of the raw mixed gas). This inflow can be scrubbed using conventional technologies before it enters the plasma reaction chamber, resulting in an almost pure methane stream, with other residual mixed gas components present on the order of about 100 ppm. The total flow from this inflow line is scalable with the overall microwave power of the system, with a flow of approximately about 1 to about 3 SLM methane/kW microwave power. A second inflow line conveys a gas flow comprising carbon dioxide, at a total flow of about 1 to about 3 SLM/kW microwave power, which can be scaled with the overall microwave power of the system.

[0099] Each inflow stream is sent into the plasma reaction chamber through its own inlet that injects its flow into an entry region of a quartz tube to flow through the tube to the region in which the plasma is created. The inlet for each inflow stream can be angled by a gas injector device to produce the vortex flow that mixes the streams within the quartz tube as they flow towards the reaction region, i.e., the plasma reaction chamber. The flow of gas entering through each inlet is controlled by mass flow controllers, adjusted to create a carbon dioxide to methane molar ratio between about 1:3 CO2:CH4 and about 3:1 CO2:CH4, or a carbon dioxide to methane molar ratio between about 1:1 CO2:CH4 and about 3:1 H2:CH4. In an embodiment, there is a yield of about 50% to about 90% syngas. [00100] An exemplary lOOkW-powered plasma-based feedgas processing system 800 is represented schematically by the block diagram shown in FIG. 8. As shown in this Figure, a central reactor 802, comprising an injection region 804, a reaction region 808, and an outflow region 810, receives three separate gas streams: (1) a first feed gas 812a containing methane (for example the methane in a mixed gas such as natural gas or biogas, or as a single gas, or a customized blend of C1-C4 hydrocarbons), and (2) a second feed gas 812b containing carbon dioxide; and (3) a recycled gas flow 814 that includes hydrogen, and optionally a mixed hydrocarbon-containing gas, and optionally unreactive nitrogen.

[00101] As schematically represented in the Figure, the inflow gas streams 812a, 812b, and 814 are processed in the reactor 802 to form an outflow stream 818 that contains carbon monoxide, hydrogen, and a small proportion of mixed hydrocarbons. The outflow stream 818 is then separated into its gaseous components via a gas separation system 828 (e.g., adsorption, absorption, or a combination thereof) to yield a syngas stream 820 and a hydrogen-dominant gas stream 822 that contains hydrogen 836 and a mixture of hydrocarbons 824. Thus, diverted from the main outflow stream 818 by the gas separation system 828, the syngas stream 820 can be purified via further sequestration of impurities in a purification system 826 to yield a purified syngas product 832. Once the syngas 820 has been removed from the outflow stream 818, the remaining gas stream 822 is predominantly hydrogen along with a mixture of hydrocarbon reaction products, i.e., is hydrogen-dominant. This hydrogen-dominant gas stream 822 can be subjected to further separation if desired, so that hydrogen gas is isolated as a distinct gas stream 830. The hydrogen gas product stream 830 can be further purified as necessary and sold as a product, or it can be recycled back into the reactor 802 for further reaction with the feed gas 812. In this system 800, instead of recycling the hydrogen gas product stream 830, the mixed hydrogen-dominant gas stream 822 is recycled to form the recycled gas flow 814, which is reintroduced into the reactor 802 for further reaction with the feed gases 812a and 812b. Mass flow controllers 840a, 840b, and 842 coordinate the inflow of the feed gases 812a and 812b and recycled gas 814 into the reactor 802 to create the desired ratio of hydrogen to methane (or hydrogen to other source hydrocarbon) in the reactor 802. b. Reactor

[00102] The reactor identified in FIG. 8 is shown in more detail in FIG. 9. FIG. 9 depicts schematically the reactor 902, its components, and its integration with the microwave subsystem 904. As depicted, and as outlined by the grey shadowed box, the microwave subsystem includes a power supply and magnetron complex 916 for producing the microwaves, and a waveguide assembly 920 for guiding the microwaves towards a reaction region 912 within the quartz tube where the microwave plasma 918 is formed. As shown in FIG. 9, a quartz tube 908 contains the components of the reactor 902: the injection region 910, the reaction region or reaction chamber 912, and the outflow region 914. Within the quartz tube 908, the microwave plasma 918 is generated by the microwaves (not shown) aimed at the gas flow 906 within the tube 908, thereby effecting the transformation of source hydrocarbon into hydrogen and various hydrocarbon-derived products. This quartz tube 908 is inserted through the broad wall of a microwave waveguide assembly 920. The size of the quartz tube 908 depends on the amount of microwave power used in the system. For the depicted system using 100 kW of power to produce micro waves, the quartz tube 908 has an 80mm outer diameter, a 75mm inner diameter, a length of 1700mm, and is maintained at in a low pressure environment, for example at a pressure of about 70 Torr by downstream vacuum pumps (not shown), or at a pressure of about 30 to about 120 Torr, or 60 to about 100 Torr, or 70 to about 80 Torr, or at a pressure of about 75 to about 375 Torr, or about 120 to about 280 Torr, or about 150 to about 200 Torr, or about 170 Torr.

[00103] The relationship of the quartz tube 908 and the microwave subsystem 904 is described below in more detail.

[00104] As shown in FIG. 9, the first feedgas stream 922 mixes with the second feed gas stream 924 within the injection region 99 of the reactor 902, each stream entering the injection region 910 of the reactor 902 through its own inlet (not shown). The first or the second feedgas stream comprises carbon dioxide, while the other feed gas stream comprises methane. The passage of each gas stream through the gas injector device 932 into the reactor 902 affects its direction, flow rate, and velocity. As depicted in FIG. 9, an optional gas stream or gas streams 928, comprising for example hydrogen that has been separated from the outflow gaseous stream 934 and recycled, can be directed into the injection region 910, to be blended with the first feedgas stream 922 and the second feedgas stream 924 to create a vortical gas flow 906. In other embodiments (not shown) the first feedgas stream 922 and the second feedgas stream 924 can be used together to create a vortical gas flow 906, without the need for an optional gas stream or gas streams 928. After mixing, the gases in the gas flow 906 flow distally through the quartz tube 908, to encounter microwave energy produced by the power supply and magnetron complex 916 and delivered through the waveguide assembly 920 into the reaction region 912 of the reactor 902. The interaction of the micro wave energy and the gas within the reaction region 912 of the reactor 902 produces the plasma 918. The outflow gaseous stream 934 containing the reaction products emerges from the plasma 918 to enter the outflow region 938 of the quartz tube 908, to be passed out of the reactor 902 for further separation 940. As shown in this Figure, a microwave subsystem 904 includes the power supply and magnetron complex 916 and the waveguide assembly 920; not shown in this Figure are additional elements of the microwave subsystem that are illustrated and described in other Figures.

[00105] FIG. 10A is a cross-sectional schematic view (not to scale) of an embodiment of a gas injector suitable for use with the lOOkW-powered plasma-based feedgas processing system, with flowpaths for two feed gases (e.g., carbon dioxide and methane) shown. FIG. 10A shows a gas injector 1006 situated in a reaction chamber 1002 of a plasma reactor 1000 and providing a plurality of gas flows into the reaction chamber 1002 for those gases to encounter micro wave energy as described above. As shown in this Figure, the gas injector 1006 provides flow paths for two distinct gas streams into the reactor 1002, with each gas stream directed through its own nozzle and flow path within the gas injector device 1006 and into the reactor 1002. As illustrated in FIG. 10 A, there are four injector ports, two for the first gas flow 1004a and 1004 b, and two for the second gas flow 1008a and 1008b. As described previously, one gas flow preferably comprises methane or a methane-containing mixed gas such as natural gas, while the other gas flow comprises carbon dioxide In the Figure, the two first gas flow nozzles 1004a and 1004b are in fluid communication with a first central flow channel 1010 through which the first gas stream enters the gas injector 1006 and is directed to the first gas nozzles 1004a and 1004b. Similarly, there is a second centrally-disposed channel 1012 in the gas injector 1006 for the second gas flow, where this channel is discrete from the first central flow channel 1010 for the recycled gas stream. There are two nozzles for second feed gas 1008a and 1008b, in fluid communication with the second centrally-disposed channel 1012, with these nozzles 1008a and 1008b entering the reactor 1002 at a different level than the nozzles for the first gas flow 1004a and 1004b. The nozzles for both types of gas flow are oriented in directions that are conducive for the formation of a vortex gas flow within the reactor 1002. The channel for first gas flow 1010 and the channel for the second gas flow 1012 do not intersect with each other, but rather provide separate gas streams into their respective nozzles 1004a/1004b and 1008a/1008b; neither do the nozzles intersect with each other, but rather provide their gas streams separately into the reactor 1002. The gas flow through each of the nozzles can be coordinated with the other gas flows in the other nozzles in terms of flow rate, path length, and pressure drop. The first gas flow can comprise either methane or carbon dioxide, while the second gas flow comprises the other gas, either carbon dioxide or methane, respectively. [00106] It would be understood by skilled artisans that the relative position of the two gas channels 1010 and 1012 can be rearranged, for example, as parallel channels, as helices, at different levels within the gas injector 1006, or as other arrangements besides those shown in FIG. 10A, provided that the channels for each gas are kept separate from each other in the gas injector 1006, and further provided that each distinct gas stream enters the reactor 1002 through its own discrete nozzle or nozzles. Moreover, the number, configuration, and direction of the nozzles can be varied, provided that the gas stream for each component feed gas (i.e., carbon dioxide and methane) enters the reactor through its own nozzle, without commingling with the other gas stream. Addition of a third gas flow, for example a flow of recycled hydrogen can be accomplished by adding additional channels and nozzles, so that each type of inflow gas has its own flow path.

[00107] FIG. 10B is a cross-sectional schematic view (not to scale) of another embodiment of a gas injector suitable for use with the lOOkW-powered plasma-based hydrocarbon processing system, similar to the gas injector described in FIG. 10A. FIG. 10B shows a gas injector 1056 situated in a reaction chamber 1052 of a plasma reactor 1050 and providing a plurality of gas flows into the reaction chamber 1052 for those gases to encounter micro wave energy as described above. As shown in this Figure, the gas injector 1056 provides flow paths for two distinct gas streams into the reactor 1052, with each gas stream directed through its own set of nozzles within the gas injector device 1056 and into the reactor 1052. As illustrated in FIG. 10B, there are eight injector ports or nozzles, four (1054a, 1054b, 1054c, and 1054d) for a first gas flow, for example the recycled gas flow, and four (1058a, 1058b, 1058c, and 1058d) for a second gas flow, for example a feed gas stream. In the Figure, the four nozzles for the first gas flow (1054a, 1054b, 1054c, and 1054d) are in fluid communication with a central flow channel 1062 through which the first gas stream enters the gas injector 1056 and is directed to the appropriate nozzles 1054a, 1054b, 1054c, and 1054d. The nozzles 1058a, 1058b, 1058c, and 1058d for the second gas flow are each supplied by a separate flow channel 1060a, 1060b, 1060c, and 1060d respectively. Other arrangements of the flow channels to supply the nozzles 1058a, 1058b, 1058c, and 1058d for the second gas flow can be envisioned, provided that the flow channels for the second gas flow do not permit the second gas flow to be commingled with the first gas flow. Instead, each gas flow is conveyed with its own discrete set of nozzles and its own flow channel(s). The nozzles for the first gas flow 1054a, 1054b, 1054c, and 1054d, and the nozzles for the second gas flow 1058a, 1058b, 1058c, and 1058d, are oriented in directions that are conducive for the formation of a vortex gas flow within the reactor 1052. The gas flow through each of the nozzles can be coordinated with the other gas flows in the other nozzles in terms of flow rate, path length, and pressure drop. Addition of a third gas flow, for example a flow of recycled hydrogen can be accomplished by adding additional channels and nozzles, so that each type of inflow gas has its own flow path. c. Microwave subsystem

[00108] The microwave subsystem shown in FIG. 9 is depicted schematically in FIG. 11, and in more detail. Referring to FIG. 9, a reaction region 912 of the reactor 902 can be seen intersecting with the waveguide assembly 920, wherein the microwaves are directed at the gas flow 906 as it enters the reaction region 912 to form the plasma 918. The microwave subsystem 904 is responsible for generating the microwaves and directing them towards the reactor 902.

[00109] The microwave subsystem is shown in more detail in FIG. 11. As shown in this Figure, the micro wave subsystem 1100 comprises a power supply 1108, a magnetron 1110, a waveguide assembly 1102 (which includes a waveguide 1112 and certain other standard micro wave components as described below), and an applicator 1104. The power supply 1108 converts 480V, 150A AC electrical power to 20kV21kV, 5.8A of low-ripple DC power with a conversion of 96% to energize the magnetron 1110. The magnetron 1110, rated at lOOkW, produces continuous microwave power at 83-89% efficiency. The micro waves produced are in the L-band frequency range, approximately 915 MHz. The microwaves are launched into a waveguide assembly 1102, within which a waveguide 1112 directs them through the other components of the system and to the applicator 1104, where they interact with the gas/plasma in the plasma reaction chamber 1114. The waveguide 1112 features a 90-degree bend 1116. One of the components of the waveguide is an isolator 1118 with an attached water load 1120, located distal to the magnetron 1110, to protect the magnetron 1110 from reflected (un-absorbed) microwaves by directing them with a ferritic core 1122 to the water load 1120. The other components of the waveguide assembly 1102 allow the microwaves to be guided towards the plasma reaction chamber 1114 and tuned to optimize the creation of the plasma therein. The applicator 1104 provides the interface between the micro waves and the quartz tube 1124 within which the plasma is created. Plasma is formed within the plasma reaction chamber 1114, the region of the quartz tube 1124 within which the chemical transformations take place. As shown in cross-section in FIG. 11, the quartz tube 1124 is disposed within, but is separated from, the applicator 1104 by an air gap (not labeled). [00110] When the plasma is off and the microwaves are on, a standing wave is formed in the applicator 1104 between the 3-stub tuner 1130 and a sliding shorting plate 1132 on the end of the applicator 1104, such that the electric field is sufficient to initiate breakdown of the gas molecules in the quartz tube. Microwave energy entering the applicator 1104 is tuned to peak at the center of the plasma reaction chamber 1114, using the shorting plate 1132 as needed to change the length of the plasma reaction chamber 1114 and using the 3-stub tuner 1130 to change the phase of the incoming microwaves. Once the plasma has been initiated, the stub locations in the tuner 1130 can be altered preferentially to match the microwave power to the plasma, minimizing un-absorbed power. The 3-stub tuner 1130 contains power and phase sensors (not shown) and can algorithmically adjust the motor-driven stubs to minimize un-absorbed power. A dual-directional coupler 1134, which contains two small pinholes that couple microwaves with a known attenuation, is included in the waveguide 1112 proximal to the 3-stub tuner 1130. Power meters (not shown) are connected to these pinhole ports and convert the microwave power into a voltage, outputting forward and reflected power measurements. A thin quartz window 1138 is added into the waveguide system to prevent environmental debris and dust from entering the waveguide components.

EXAMPLES

Example 1

[00111] Precursor gases, comprising 150 standard liters per minute of utility natural gas (comprising approximately 96.7% methane, 2.7% ethane, and 0.4% nitrogen), and 150 standard liters per minute of carbon dioxide and 600 standard liters per minute of 99.9% purity hydrogen, are supplied through a gas injector via individual conduits or as one or more mixed streams into a 50mm outer diameter, 45mm inner diameter quartz tube that is evacuated to 260 mbara by a vacuum pump. The precursor gases within the quartz tube are subjected to 98.3kW of incident 915MHz microwave power in a plasma reactor apparatus as similar to that depicted in FIG. 2 above. 90% of the hydrocarbons and 100% of the carbon dioxide contained in the precursor gas are converted to hydrogen, hydrocarbon products, and carbon monoxide. The reactor effluent gas composition is described in Table 1, as analyzed by a gas chromatograph.

[00112] The reactor effluent gas is passed through water-cooled heat exchangers and passed through a stainless-steel mesh filter before exiting the vacuum pump. The effluent gas then passes through a cold trap operating at 20°C and additional cartridge filter before entering the downstream system.

Example 2

[00113] Precursor gases, comprising 200 standard liters per minute of utility natural gas (comprising approximately 96.7% methane, 2.7% ethane, and 0.4% nitrogen), 100 standard liters per minute of carbon dioxide and 600 standard liters per minute of 99.9% purity hydrogen, are supplied through a gas injector via separate conduits or as one or more mixed streams into a 50mm outer diameter, 45mm inner diameter quartz tube that is evacuated to 150 mbara by a vacuum pump. The precursor gases within the quartz tube are subjected to 99.1kW of incident 915MHz microwave power in a plasma reactor apparatus as described in FIG. 2 above. 93% of the hydrocarbons and 100% of the carbon dioxide contained in the precursor gas are converted to hydrogen, hydrocarbon products, and carbon monoxide. The reactor effluent gas composition is described in Table 2, as analyzed by a gas chromatograph.

[00114] The reactor effluent gas is passed through water-cooled heat exchangers and passed through a stainless-steel mesh filter before exiting the vacuum pump. The effluent gas then passes through a cold trap operating at 20°C and additional cartridge filter before entering the downstream system.

Example 3

[00115] Precursor gases, comprising 100 standard liters per minute of utility natural gas, (comprising approximately 96.7% methane, 2.7% ethane, and 0.4% nitrogen) and 200 standard liters per minute of carbon dioxide and 600 standard liters per minute of 99.9% purity hydrogen, are supplied through a gas injector via separate conduits or as one or more mixed streams into a 65mm outer diameter, 60mm inner diameter quartz tube that is evacuated to 100 mbara by a vacuum pump. The precursor gases within the quartz tube are subjected to 98.7 kW of incident 915MHz microwave power in a plasma reactor apparatus as described in FIG. 2 above. 93% of the hydrocarbons and 100% of the carbon dioxide contained in the precursor gas are converted to hydrogen, hydrocarbon products, and carbon monoxide. The reactor effluent gas composition is described in Table 3, as analyzed by a gas chromatograph.

[00116] The reactor effluent gas is passed through water-cooled heat exchangers and passed through a stainless-steel mesh filter before exiting the vacuum pump. The effluent gas then passes through a cold trap operating at 20°C and additional cartridge filter before entering the downstream system.

Example 4

[00117] Precursor gases, comprising 50 standard liters per minute of utility natural gas (comprising approximately 96.7% methane, 2.7% ethane, and 0.4% nitrogen) and 300 standard liters per minute of carbon dioxide and 200 standard liters per minute of 99.9% purity hydrogen, are supplied through a gas injector via separate conduits or as one or more mixed streams into a 50mm outer diameter, 45mm inner diameter quartz tube that is evacuated to 120 mbara by a vacuum pump. The precursor gases in the quartz tube are subjected to 99.0kW of incident 915MHz microwave power in a plasma reactor apparatus as described in FIG. 2 above. 100% of the hydrocarbons and 100% of the carbon dioxide contained in the precursor gas are converted to hydrogen, carbon monoxide, and water. The reactor effluent gas composition is described in Table 4, as analyzed by a gas chromatograph.

Example 5

[00118] 57 g/h CO2 were flowed into a micro wave plasma reactor along with 2,000 g/h of mixed hydrocarbon gases comprising >95% methane, 450 g/h hydrogen, and 24 g/h nitrogen gas. This gas mixture was exposed to approximately 15 kW of microwave power under vacuum, converting the majority of the hydrocarbons into 1,400 g/h acetylene and a majority of the carbon dioxide into 62 g/h carbon monoxide along with 790 g/h hydrogen and 210 g/h remaining mixed hydrocarbon gases. The nitrogen passed through the reactor intact.

[00119] In an exemplary embodiment, the reactor effluent gas can be passed through water-cooled heat exchangers and passed through a stainless-steel mesh filter before exiting the vacuum pump. The effluent gas then can pass through a cold trap operating at 20°C and additional cartridge filter.

EQUIVALENTS

[00120] Unless otherwise indicated, all numbers expressing reaction conditions, quantities, amounts, ranges and so forth, as used in this specification and the claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that can vary depending upon the desired properties sought to be obtained by the present invention.

[00121] Furthermore, the invention encompasses all variations, combinations, and permutations in which one or more limitations, elements, clauses, and descriptive terms from one or more of the listed claims is introduced into another claim. For example, any claim that is dependent on another claim can be modified to include one or more limitations found in any other claim that is dependent on the same base claim. Where elements are presented as lists, e.g., in Markush group format, each subgroup of the elements is also disclosed, and any element(s) can be removed from the group. It should it be understood that, in general, where the invention, or aspects of the invention, is/are referred to as comprising particular elements and/or features, certain embodiments of the invention or aspects of the invention consist, or consist essentially of, such elements and/or features. For purposes of simplicity, those embodiments have not been specifically set forth in haec verba herein. It is also noted that the terms “comprising” and “containing” are intended to be open and permits the inclusion of additional elements or steps. Where ranges are given, endpoints are included. Furthermore, unless otherwise indicated or otherwise evident from the context and understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value or sub-range within the stated ranges in different embodiments of the invention, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise. [00122] While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

47

CLAIMS A system for transforming a first inflow gas comprising methane and a second inflow gas comprising carbon dioxide into outflow gas products comprising carbon monoxide and hydrogen, comprising: a gas delivery subsystem, a plasma reaction chamber, a microwave subsystem, and an effluent separation and disposal system; wherein the gas delivery subsystem: i. is in fluid communication with the plasma reaction chamber and directs the first inflow gas and the second inflow gas into the plasma reaction chamber; and ii. comprises a gas delivery conduit and a gas injector, wherein the gas delivery conduit is in fluid communication with the gas injector, wherein the gas delivery conduit delivers the first inflow gas and the second inflow gas to the gas injector, and wherein the gas injector delivers the first inflow gas and the second inflow gas into the plasma reaction chamber; wherein the plasma reaction chamber: i. is in fluid communication with the effluent separation and disposal system; and ii. is disposed within an elongate reactor tube having a proximal and a distal end, wherein the elongate reactor tube is dimensionally adapted for interaction with the microwave subsystem; wherein the microwave subsystem: i. directs microwave energy into the plasma reaction chamber to energize the first inflow gas and the second inflow gas, thereby forming a plasma in the plasma reaction chamber, and wherein the plasma effects the transformation of the methane and the carbon dioxide into the outflow gas products; ii. comprises an applicator for directing microwave energy towards the plasma reaction chamber, and wherein the plasma reaction chamber is disposed in the region of the elongate reactor tube that passes through the applicator and intersects it perpendicularly; and 48 iii. further comprises a power supply, a magnetron, and a waveguide, whereby the power supply energizes the magnetron to produce microwave energy, the microwave energy being conveyed by the waveguide to the applicator, and wherein the applicator directs the microwave energy towards the reaction chamber within the elongate reactor tube, thereby forming the plasma in the plasma reaction chamber, wherein the outflow gas products flow within the plasma reaction chamber towards the distal end of the elongate reactor tube and emerge from the distal end of the elongate reactor tube, entrained within an effluent gas stream that enters the effluent separation and disposal subsystem, and wherein the effluent separation and disposal system comprises a separator for segregating the carbon monoxide and the hydrogen from the effluent gas stream.

2. The system of claim 1, wherein the first inflow gas is derived from a first mixed gas source.

3. The system of claim 2, wherein the first mixed gas source is natural gas.

4. The system of claim 2, wherein the first mixed gas source is a biogas.

5. The system of claim 1, wherein the first inflow gas consists essentially of methane.

6. The system of claim 1, wherein the second inflow gas is derived from a second mixed gas source.

7. The system of claim 1, wherein the gas delivery conduit delivers each of the first inflow gas and the second inflow gas into the gas injector respectively through a first and a second separate pathway.

8. The system of claim 7, wherein the gas delivery conduit comprises an additional gas conveying circuit that delivers an additional gas into the gas injector. 49

9. The system of claim 8, wherein the gas delivery conduit delivers the additional gas into the gas injector through a third pathway that is separate from the first and the second separate pathway.

10. The system of claim 8, wherein the additional gas comprises hydrogen.

11. The system of claim 8, wherein the additional gas conveying circuit is a recycled gas conveying circuit that delivers a recycled gas into the gas injector.

12. The system of claim 11, wherein the recycled gas comprises hydrogen.

13. The system of claim 1, wherein the gas injector comprises an injector body comprising two or more coaxially arranged and separate gas feeds, a first gas feed conveying the first inflow gas into the plasma reaction chamber through a first set of one or more nozzles, and the second gas feed conveying the second inflow gas into the plasma reaction chamber through a second set of one or more nozzles.

14. The system of claim 13, wherein at least one of the first set of one or more nozzles or at least one of the second set of one or more nozzles is oriented at an angle to a longitudinal axis of the plasma reaction chamber or at an angle to a transverse axis of the plasma reaction chamber.

15. The system of claim 13, whereby combined gas flow from the first set of nozzles and the second set of nozzles creates a vortex flow within the plasma reaction chamber.

16. The system of claim 13, wherein the gas injector conveys the first inflow gas and the second inflow gas into a proximal portion of the elongate reactor tube, and wherein the first inflow gas and the second inflow gas flow distally therefrom towards the plasma reaction chamber.

17. The system of claim 16, wherein the gas injector is positioned centrally within the proximal portion, and the first set of one or more nozzles and the second set of one or more nozzles are oriented peripherally. 50

18. The system of claim 16, wherein the gas injector is positioned peripherally within the proximal portion, and the first set of one or more nozzles and the second set of one or more nozzles are oriented centrally.

19. The system of claim 1, wherein the elongate reactor tube is a quartz tube.

20. The system of claim 1, wherein the plasma reaction chamber is disposed approximately at the midportion of the elongate reactor tube.

21. The system of claim 1, wherein the effluent separation and disposal subsystem further comprises a hydrogen separation subsystem.

22. The system of claim 21, wherein the hydrogen separation subsystem is in fluid communication with the recycled gas conveying circuit and wherein hydrogen collected by the hydrogen separation subsystem is recycled into the recycled gas conveying circuit.

23. The system of claim 1, wherein the effluent separation and disposal subsystem further comprises a syngas separator.

24. The system of claim 1, further comprising a vacuum subsystem that produces a first reduced pressure environment for the outflow gas products passing through one or more components of the effluent separation and disposal subsystem.

25. The system of claim 24, wherein the vacuum subsystem produces a first, second, and third reduced pressure environment.

26. The system of claim 25, wherein pressure in at least one of the first, second, and reduced pressure environments is between about 75 and about 375 Torr.

27. The system of claim 26, wherein pressure in at least one of the reduced pressure environments is between about 130 and about 280 Torr. The system of claim 27, wherein pressure in at least one of the reduced pressure environments is between about 150 and about 200 Torr. The system of claim 25, wherein pressure in the first, second, and third reduced pressure environments is substantially similar. The system of claim 1, further comprising a cooling subsystem. The system of claim 1, further comprising a data management and safety subsystem. A method for processing a first inflow gas comprising methane and a second inflow gas comprising carbon dioxide to produce carbon monoxide and hydrogen comprising the steps of: injecting the first inflow gas and the second inflow gas into a plasma reaction chamber; energizing the first inflow gas and the second inflow gas in the plasma reaction chamber with microwave energy to create a plasma; forming outflow gas products in the plasma, wherein the outflow gas products comprise carbon monoxide and hydrogen; flowing the outflow gas products in an outflow stream to exit the plasma reaction chamber; and separating carbon monoxide and hydrogen from the outflow stream. The method of claim 32, wherein the first inflow gas is derived from a mixed gas source. The method of claim 33, further comprising injecting one or more additional gases into the plasma reaction chamber concomitant with the step of injecting the first inflow gas and the second inflow gas. The method of claim 34, wherein the one or more additional gases comprises a recycled gas. The method of claim 35, wherein the recycled gas consists essentially of hydrogen. A system for transforming an inflow gas comprising methane and carbon dioxide into outflow gas products comprising carbon monoxide and hydrogen, comprising: a gas delivery subsystem, a plasma reaction chamber, a microwave subsystem, and an effluent separation and disposal system; wherein the gas delivery subsystem is in fluid communication with the plasma reaction chamber and directs the inflow gas into the plasma reaction chamber; wherein the plasma reaction chamber is in fluid communication with the effluent separation and disposal system; and is disposed within an elongate reactor tube having a proximal and a distal end, wherein the elongate reactor tube is dimensionally adapted for interaction with the microwave subsystem; wherein the microwave subsystem: i. directs microwave energy into the plasma reaction chamber to energize the inflow gas, thereby forming a plasma in the plasma reaction chamber, and wherein the plasma effects the transformation of the methane and the carbon dioxide into the outflow gas products; ii. comprises an applicator for directing microwave energy towards the plasma reaction chamber, and wherein the plasma reaction chamber is disposed in the region of the elongate reactor tube that passes through the applicator and intersects it perpendicularly; and iii. further comprises a power supply, a magnetron, and a waveguide, whereby the power supply energizes the magnetron to produce microwave energy, the microwave energy being conveyed by the waveguide to the applicator, and wherein the applicator directs the microwave energy towards the reaction chamber within the elongate reactor tube, thereby forming the plasma in the plasma reaction chamber, wherein the outflow gas products flow within the plasma reaction chamber towards the distal end of the elongate reactor tube and emerge from the distal end of the elongate reactor tube, entrained within an effluent gas stream that enters the effluent separation and disposal subsystem, and wherein the effluent separation and disposal system comprises a separator for segregating the carbon monoxide and the hydrogen from the effluent gas stream. 53 A method for processing an inflow gas comprising methane and carbon dioxide to produce carbon monoxide and hydrogen, comprising the steps of: injecting the inflow gas into a plasma reaction chamber; energizing the inflow gas in the plasma reaction chamber with microwave energy to create a plasma; forming outflow gas products in the plasma, wherein the outflow gas products comprise carbon monoxide and hydrogen; flowing the outflow gas products in an outflow stream to exit the plasma reaction chamber; and separating carbon monoxide and hydrogen from the outflow stream.