Device for generation of plasma

Abstract

Provided herein is a device (100) for generating plasma using a flowing gas comprising: - a longitudinal electrode assembly (30) comprising: - a longitudinal electrically insulative body (38) having a proximal (10) and distal (20) end, - a proximal electrode (32) configured for contacting the gas, provided only at the distal end (20) of the insulative body (38), and disposed in fixed relation thereto; - a gas flow assembly (60) comprising: - a gas flow body (62); - a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38); - one or more gas inlets (66) in the gas flow body (62) for inlet of the gas; - one or more gas outlets (70) configured for outflow of the gas; - a helical flow guide (80) comprising one or more helical channels (88), each helical channel (88) having at least 0.5 helical turns, configured to direct the gas provided from the one or more gas inlets (66) along the one or more helical channels (88) to the one or more gas outlets (36), wherein: - the electrically insulative body (38) is mounted in the through-opening (64), and - the one or more helical channels (88) and the one or more gas outlets (36) are both disposed peripheral (P) of the through opening (64).

Description

[0001] DEVICE FOR GENERATION OF PLASMA

[0002] Field of the invention

[0003] Described herein is a plasma-generating device that is axially compact, increases residence time of gas between plasma-generating electrodes, which contains elements for increasing lifespan of the device, and which has flexible configurations.

[0004] Background to the invention

[0005] Plasma-generating devices are known to be valuable tools for many different types of application such as cutting, welding, and for electrified gas conversion applications. Many applications for plasma-based gas conversion have been emerging in recent years. Examples are plasma-based CO2 decomposition to CO and O2, ammonia (NH3) cracking to H2 and N2, nitrogen fixation of air to NO and NO2, and others. Although the results in the literature seem promising, scaling up the laboratory devices and keeping the energy efficiency of the processes has been proven challenging. An alternative method of using the laboratory set-ups in parallel requires high capital investment and further complicates the transition of the technology to industry. A further problem in plasma generation is short lifespan of components due to excessive heat generated by plasma production. The presently described device aims to overcome the problems of the art.

[0006] Summary of the invention

[0007] Provided herein is a device (100) for generating plasma using a flowing gas comprising:

[0008] - a longitudinal electrode assembly (30) comprising:

[0009] - a longitudinal electrically insulative body (38) having a proximal (10) and distal (20) end,

[0010] - a proximal electrode (32) configured for contacting the gas, provided only at the distal end (20) of the insulative body (38), and disposed in fixed relation thereto;

[0011] - a gas flow assembly (60) comprising:

[0012] - a gas flow body (62);

[0013] - a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38);

[0014] - one or more gas inlets (66) in the gas flow body (62) for inlet of the gas;

[0015] - one or more gas outlets (70) configured for outflow of the gas; - a helical flow guide (80) comprising one or more helical channels (88), each helical channel (88) having at least 0.5 helical turns, configured to direct the gas provided from the one or more gas inlets (66) along the one or more helical channels (88) to the one or more gas outlets (36), wherein:

[0016] - the electrically insulative body (38) is mounted in the through-opening (64) (allowing the longitudinal electrode assembly (30) to move (by sliding or rotation) relative to the gas flow assembly (60)), and

[0017] - the one or more helical channels (88) and the one or more gas outlets (36) are both disposed peripheral (P) of (and separated from) the through opening (64).

[0018] Provided herein is a device (100) for generating plasma using a flowing gas comprising:

[0019] - a longitudinal electrode assembly (30) comprising:

[0020] - a longitudinal electrically insulative body (38) having a proximal (10) and distal (20) end,

[0021] - a proximal electrode (32) configured for contacting the gas, attached to the distal end (20) of the insulative body (38),

[0022] - a gas flow assembly (60) comprising:

[0023] - a gas flow body (62);

[0024] - a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38);

[0025] - one or more gas inlets (66) in the gas flow body (62) for inlet of the gas;

[0026] - one or more gas outlets (70) configured for outflow of the gas;

[0027] - a helical flow guide (80) configured to direct the gas provided from the one or more gas inlets (66) along a helical path to the one or more gas outlets (36),

[0028] - wherein the one or more gas outlets (36) is disposed peripheral (P) of the through opening (64).

[0029] A transverse cross-section of the helical channel (88) preferably has an outer profile outer edge that is a closed loop.

[0030] The electrode assembly (30) may be linearly displaceable along a longitudinal axis (L-L’) relative to the gas flow assembly (60). The gas flow assembly (60) may be electrically insulated from the proximal electrode (32) at least by the longitudinal insulative body (38).

[0031] The helical flow guide (70) may comprise one or more helical channels (88), each helical channel (88) having at least 0.5 helical turns.

[0032] The helical flow guide (80) may comprise:

[0033] - an insert part (82) comprising a cylindrical or frustum body disposed with at least one outer helical groove (84),

[0034] - a receiving part (86) configured to fittingly receive the insert part (82) wherein:

[0035] - the at least one outer helical groove (84) and receiving part (86) co-operate to form the one or more helical channels (88);

[0036] - the receiving part (86) is disposed in the gas flow body;

[0037] - the insert part (82) is repeatably dismountably attachable to the receiving part (76).

[0038] The device (100) may further comprise a tunnel region (200) distal (20) of the gas flow assembly (60), wherein the tunnel region (200) comprises a tunnel wall (210) peripheral (P) to and surrounding the one or more gas outlets (70), and wherein the wall extends in a distal (20) direction.

[0039] A transverse cross-section of the tunnel wall inner surface (212) may be curved, preferably circular, and

[0040] - optionally the size of said transverse cross-section is constant along an axial (L- L’) length of the tunnel wall (210), or

[0041] - optionally the size of said transverse cross-section gradually varies along an axial (L-L’) length of the tunnel wall (210).

[0042] The one or more gas outlets (70) may be configured to direct the gas towards the tunnel wall inner surface (212), and in a net distal direction.

[0043] A distal electrode is further provided, and the device may be configured for generation of a plasma jet, a plasma arc, or glow discharge plasma. The device comprises the distal electrode (232) disposed distal (20) of the proximal electrode (32), the device may be configured for generation of glow discharge plasma within the reaction chamber (202).

[0044] A position of the distal electrode (232) may be slidable relative to a position of the tunnel region (200).

[0045] The device (100) may further comprise a catalyst bed (250) configured to:

[0046] - contain a catalyst mass;

[0047] - receive gas flowing from the reaction chamber (202);

[0048] - pass the received gas through the catalyst mass.

[0049] One or more helical channels (88) may each have a helix angle (alpha) that is greater than 0 deg and less than 90 deg, preferably a value in a range 50 deg to 87 deg.

[0050] The number of helical channels (88) may be two or more.

[0051] Figure Legends

[0052] FIG. 1 is a longitudinal cross-sectional schematic view of a device as described herein, containing a (proximal) electrode assembly and a (proximal) gas flow assembly.

[0053] FIG. 2 is a longitudinal cross-sectional schematic view of the (proximal) electrode assembly of FIG. 1 , isolated from the gas flow assembly.

[0054] FIG. 3 is a longitudinal cross-sectional schematic view of the gas flow assembly of FIG. 1 , isolated from the (proximal) electrode assembly.

[0055] FIG. 4 is a longitudinal cross-sectional schematic view of the gas flow assembly of FIG. 1 , isolated from the (proximal) electrode assembly, wherein the helical flow guide / helical guide body is two-piece; and both pieces are fittingly coupled together.

[0056] FIG. 5 shows the gas flow assembly of FIG. 4, wherein the helical flow guide / helical guide body is two-piece. The receiving part is shown in Panel A and the insert part is shown in Panel B.

[0057] FIG. 6 shows a detail of the outer helical groove in the insert part of the helical flow guide / helical guide body of FIG. 5 panel B, and co-operation with the receiving part.

[0058] FIG. 7. shows a flattened (unrolled) view of the outer groove of the insert part, with the helix angle (alpha) indicated. FIG. 8. shows a view of the outer groove of the insert part, with a downward gas exit angle (beta) indicated

[0059] FIG. 9. shows an end view of the helical flow guide gas outlet, and a peripheral (P) net direction outflow of gas.

[0060] FIG. 10 is a longitudinal cross-sectional schematic view of a device described herein comprising the (proximal) electrode assembly of FIG. 1 , further comprising a tunnel region. FIG. 11 is a longitudinal cross-sectional schematic view of the (proximal) electrode assembly of FIG. 1. In Panel A the proximal electrode (32) is disposed flush with distal end of the gas flow body (62). In Panel B the proximal electrode (32) is disposed protruding from the distal end (20) of the gas flow body (62).

[0061] FIG. 12 is a longitudinal cross-sectional schematic view of a device described herein comprising the electrode assembly of FIG. 1 , provided with a distal electrode and reaction chamber. The distal half of the device (longitudinal electrode assembly, gas flow assembly) is similar to the proximal half (with the exception of the helical flow guide) and the positions of both proximal and distal electrodes are adjustable.

[0062] FIG. 13 is a longitudinal cross-sectional schematic view of the device of FIG. 12, further provided with a distal catalyst bed.

[0063] FIG. 14 is a longitudinal cross-sectional schematic view of a device described herein comprising the electrode assembly of FIG. 1 , provided with a distal electrode and reaction chamber. The position of proximal electrode is adjustable, the position of distal electrode is non-adjustable

[0064] FIG. 15 is a longitudinal cross-sectional schematic view of the device of FIG. 14, further provided with a distal catalyst bed.

[0065] FIG. 16 graph showing experimental data from the Example; energy cost for conversion of fix N2 from the air into NO and NO2 using the present device, at different currents, for different flow rates.

[0066] FIG. 17 graph showing experimental data from the Example; production rate for conversion of fix N2 from the air into NO and NO2 using the present device, at different currents, for different flow rates.

[0067] FIG. 18 three-dimensional schematic view of an insert part of a helical flow guide as described herein, having three helical channels, and disposed with fixation element.

[0068] FIG. 19 is a longitudinal cross-sectional schematic view of a device described herein, wherein the insert part is provided with a distal fixation element (threaded part) which is configured to compress an O-ring for gas sealing / frictional locking. FIG. 20 is a longitudinal cross-sectional schematic view of a device described herein comprising the electrode assembly of FIG. 1 , provided with a reaction chamber. The position of proximal electrode is adjustable.

[0069] FIG. 21 is a longitudinal cross-sectional schematic view of the device of FIG. 20, further provided with a distal catalyst bed.

[0070] FIG. 22 Panels A and B show a longitudinal cross-sectional schematic view of the gas flow assembly as shown in FIGs. 3 and 4 respectively, wherein the transverse crosssection of the helical channel is circled and enlarged in Panel C.

[0071] Detailed description of invention

[0072] Before the present system and method of the invention are described, it is to be understood that this invention is not limited to particular systems and methods or combinations described, since such systems and methods and combinations may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

[0073] As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise.

[0074] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of', "consists" and "consists of".

[0075] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

[0076] The term "about" or “approximately” as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / -10% or less, preferably + / -5% or less, more preferably + / -1 % or less, and still more preferably + / -0.1 % or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" or “approximately” refers is itself also specifically, and preferably, disclosed. Whereas the terms “one or more” or “at least one”, such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members.

[0077] All references cited in the present specification are hereby incorporated by reference in their entirety. In particular, the teachings of all references herein specifically referred to are incorporated by reference.

[0078] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0079] In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0080] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination. In the present description of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration only of specific embodiments in which the invention may be practiced. Parenthesized or emboldened reference numerals affixed to respective elements merely exemplify the elements by way of example, with which it is not intended to limit the respective elements. Unless otherwise indicated, all figures and drawings in this document are not to scale and are chosen for the purpose of illustrating different embodiments of the invention. In particular the dimensions of the various components are depicted in illustrative terms only, and no relationship between the dimensions of the various components should be inferred from the drawings, unless so indicated.

[0081] It is to be understood that other embodiments may be utilised and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0082] Presently described, and as exemplified in FIG. 1 , is a device (100) for electrically generating plasma using a flowing gas. The device (100) is typically longitudinal and has a proximal (10) and distal (20) end. The device comprises a longitudinal electrode assembly (30) (shown isolated from the device exemplarily in FIG. 2). The electrode assembly (30) comprises a longitudinal electrically insulative body (38) having a proximal end (10) and distal (20) end. The electrode assembly (30) comprises a proximal electrode (32) (of one polarity) configured for contacting the gas for generation of the plasma, disposed at the distal end (20) of the insulative body (38).

[0083] The longitudinal electrode assembly (30) may also be known as a proximal electrode assembly (30), or just electrode assembly (30). The term proximal electrode assembly (30) may be used to distinguish it from a distal electrode assembly (230) where present as described later below.

[0084] The device further comprises a gas flow assembly (60) (shown isolated from the device exemplarily in FIG. 3). The gas flow assembly (60) comprises a gas flow body (62), and a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38). In a preferred embodiment, the (electrically) insulative body (38) is mounted in the through-opening (64), allowing the longitudinal electrode assembly (30) to move, for example by sliding or rotation, relative to the gas flow assembly (60). The gas flow assembly (60) further comprises one or more gas inlets (66) in the gas flow body (62) for inlet of the gas (supply), and one or more gas outlets (70) configured for outflow of the gas. The gas flow assembly (60) further comprises a helical flow guide (80) configured to direct the gas provided from the one or more gas inlets (66) along a helical path to the one or more gas outlets (70). The one or more gas outlets (70) is disposed peripheral (P) of the longitudinal insulative body (38).

[0085] Gas entering the one or more gas inlets (66) passes through the helical flow guide (80), in which the gas flow takes a helical path, and passes out through the one or more gas outlets (70). During passage through the helical flow guide (80), the gas is directed at a helical angle (alpha) around a periphery of a longitudinal portion of the insulative body (38).

[0086] As a result of the helical path, the present device has an axially compact structure. A size reduction is a crucial goal for any device, and impacts at many different levels. From manufacturing point of view, a more compact structure takes less time to manufacture (e.g. by CNC milling), there is a reduced consumption of material, less waste, thereby reducing costs. For shipping and storage, such reactors are lighter and occupy less space and need less packaging. In operation, such reactors occupy less space, allowing other systems to be present and / or the device be placed in a smaller enclosure which reduces operating costs.

[0087] As a result of the extended flow path afforded by the helical path, the gas flow angular velocity and uniformity of the flow direction are increased by the time the gas passes through the gas outlet (70). The helical path allows the gas flow to strike a surface (e.g. tunnel region (200)) more radially tangentially (e.g. at a gas helix angle (beta) close to 89 deg in FIG. 8). This has an effect of increasing the time it takes for gas to travel distal (20) of the proximal electrode (32) as a function longitudinal (L-L’) distance, meaning that the gas is able to spend longer in contact with both electrodes. The longer residence time allows creation of very long arc / glow discharges.

[0088] The helical path also thermally insulates any external surface (e.g. tunnel region) which increases lifespan of components of the device. The device allows flow rates to be higher, since gas leaving the outlet has been guided over a longer distance by the helical flow guide and still maintains a uniform flow direction compared with typical fin-based flow guides that cause flow spread. Flow rates achieved may be in the region of e.g. 100 to 300 In / min.

[0089] Stable plasma is characterised by the amount of chaotic behaviour in the plasma motion. From the voltage-current characteristics, we can see how often the plasma detaches and reattaches to the reactor. If this motion is quasiperiodic or constant (no movement) it is known as stable plasma. When the plasma is oscillating, there is a non-uniform heating of the gas, resulting in requiring higher voltage to keep the same gas temperature. When the plasma is stable, the heating is uniform so less power is needed to heat the gas to the same temperature. With the present high-propulsion helical flow pattern, the plasma can operate in a stable manner at lower voltages. In other words, the helical flow pattern increases the plasma stability.

[0090] The term "proximal" or “proximal to” are used throughout the specification to mean towards a proximal end of the device. The proximal end (10) of the device is the end of the longitudinal electrode assembly (30, FIG. 1) opposing the end of the longitudinal electrode assembly that is disposed with the electrode (32). Thus, "proximal" or “proximal to” means towards the proximal end of the device.

[0091] The term "distal" or “distal to” are used throughout the specification to mean towards a distal end of the device, which is the longitudinal end of the device longitudinally opposing the proximal end (10) of the device. The distal end (20) is indicated in FIG. 1 . Thus, "distal" or “distal to” means towards the distal end of the device.

[0092] The components of device (100) such as the electrode assembly (30), insulative body (38), conductor (36), proximal electrode (32), gas flow assembly (60), helical flow guide (80), tunnel region (200) also each have a proximal end (10) and a distal end (20); the proximal and distal end of each component corresponds with distal and proximal ends of the device (100).

[0093] A peripheral (P) disposition or direction is in a direction away from the central longitudinal axis (L-L’) of the device (100), in particular of the insulative body (38). The central longitudinal axis (L-L’) of the insulative body (38) may extend proximally (10) and / or distally (20) beyond the insulative body (38). For instance, a first object that is peripheral of a second object may be disposed radially further away from the central longitudinal axis (L- L’) than the first object; the second object may be disposed axially within a longitudinal span of the first object or may be disposed axially outside or overlapping with the longitudinal span of the first object.

[0094] A central (C) disposition or direction is in a direction towards the central elongational axis (L- L’) of the device (100), in particular of the insulative body (38). For instance, a first object that is central of a second object may be disposed radially closer to the central longitudinal axis (L-L’) than the first object; the second object may be disposed axially within a longitudinal span of the first object or may be disposed axially outside or overlapping with the longitudinal span of the first object.

[0095] A transverse cross-section refers to a cross-section taken perpendicular to a longitudinal axis or path. The longitudinal axis may be straight (e.g. central longitudinal axis (L-L’)) or helical in the case of a groove transverse-cross section. More in particular, the transverse cross-section of the helical channel (88) is a cross-section of the helical channel across a plane parallel to and contacting a helical axis of the helical channel.

[0096] A longitudinal cross-section refers to a cross-section taken parallel to a longitudinal axis or path. The longitudinal axis may be straight (e.g. central longitudinal axis (L-L’)).

[0097] “In / min” refers to a flow rate that is litre normal per minute.

[0098] The longitudinal insulative body (38) is electrically insulative. It is electrically insulative for voltages typically used in the generation of plasma e.g. 5 kV up to around 50 kV.

[0099] The longitudinal insulative body (38) may be known as the proximal longitudinal insulative body (38) or just longitudinal insulative body. The term proximal longitudinal insulative body (38) may be used to distinguish it from a distal longitudinal insulative body (238) where present as described later below.

[0100] The longitudinal insulative body (38) electrically insulates all of the proximal electrode (32) in a peripheral (P) (radial) direction of the proximal electrode (32) along a full length of the longitudinal axis (L-L’) of the proximal electrode (32). The longitudinal insulative body (38) electrically insulates the conductor (36) in a peripheral (P) (radial) direction of the conductor (36) along a longitudinal axis (L-L’) of the conductor (36).

[0101] The insulative body may have a circular, oval, polygonal or other shaped transverse crosssection. The insulative body is preferably rigid. The insulative body may or may not be cooled (e.g. using a liquid coolant).

[0102] The insulative body is formed from an electrically non-conductive material. Examples include ceramic, but also glass, alumina, zirconia, plastic, wood or natural stone. Preferably the insulative body is made from ceramic (e.g. a ceramic material containing on silicon nitride or boron nitride).

[0103] The insulative body is configured to separate the proximal electrode (32) from the connector (34) (where present).

[0104] The proximal electrode (32) is provided at the distal end (20) of the insulative body (38). Preferably, the proximal electrode (32) is provided at only the distal end (20) of the insulative body (38). Preferably, the proximal electrode (32) is disposed in a fixed relation insulative body (38). The proximal electrode (32) may have any suitable shape of transverse cross-section including, for example, rounded (circular, oval), polygonal (regular or irregular).

[0105] A longitudinal length of the proximal electrode (32) may occupy 1 % to 10 % of a total longitudinal length of the (insulative body (38) + proximal electrode (32)).

[0106] As a result of the proximal electrode (32) provided at only the distal end (20) of the insulative body (38), and is disposed in a fixed relation thereto, the present device has offers the advantage of ensuring a more predictable and consistent positioning of the plasma arc. This arrangement limits the plasma arc’s formation to a specific location, primarily towards the distal tip of the device. Consequently, this restriction enhances reproducibility of the plasma arc formation, particularly at lower gas flow rates where plasma arc instability and erratic positioning are common. By limiting the position of the proximal electrode, the plasma reactions become more consistent and reproducible, contributing to improved control and product quality. A further advantage of the proximal electrode (32) provided at only the distal end (20) of the insulative body (38), is that a shorter proximal electrode can be utilized which offers cost savings, especially when the electrode is crafted from rare metals such as lanthanated tungsten. This facilitates more economical replacement and production, making it interchangeable and enabling a variety of electrode options.

[0107] The proximal electrode (32) may have a flat, rounded or pointed gas-contacting surface. A typical diameter of a proximal electrode (32) having a circular transverse cross-section may be in the range of 5 mm to 40 mm.

[0108] The proximal electrode (32) is preferably repeatably dismountably attached to the insulative body (38) and / or to the conductor (38). This allow for easy exchange, for instance, for different applications, in case or repair, or for replacement. The repeatable dismountable attachment may be realised by any fixation element(s), such as threaded fastener, clamp (e.g. friction clamp), snap fit connector, engageable stop member(s), or the like. The repeatable dismountable attachment provides an electrical connection to the conductor (38) for transmission of electrical power. The repeatable dismountable attachment provides a mechanical attachment to the insulative body (38) and / or to the conductor (38). The proximal electrode (32) may be made from any suitable electrically conductive material according to the application of the device. Examples of suitable material include lanthanum tungsten, copper, aluminium, nickel, chrome, palladium, gold, silver, platinum and the like.

[0109] Preferably, the peripheral (P) (radial) sides of the proximal electrode (32) are electrically insulated by the insulative body (38). The proximal electrode (32) is preferably disposed in a recess provided in the distal terminal end of the insulative body (38). The proximal electrode (32) may be flush with the distal terminal end of the insulative body (38). The proximal electrode (32) may be recessed with the distal terminal end of the insulative body (38). The peripheral (radial) protection afforded by the insulative body (38) allows the proximal electrode (32) to be disposed flush with or recesses with the gas flow body (62), without electrical contact between the proximal electrode (32) and gas flow body (62) (which is typically metallic and electrically grounded). The proximal electrode (32) may be an anode (negative polarity) or cathode (positive polarity), depending on the application of the device.

[0110] The longitudinal electrode assembly (30) further comprises a conductor (36) electrically connected to the proximal electrode (32), configured for transmission of electrical energy to the proximal electrode (32), and disposed within the longitudinal insulative body (38). The longitudinal electrode assembly (30) may further comprise a connector disposed at the proximal end of the insulative body (38) configured for dismountable electrical (and mechanical) connection to an electrical power supply lead.

[0111] The gas flow assembly (60) comprises a gas flow body (62) having at least one gas inlet (66) configured for inflow of gas, and at least one gas outlet (70) configured for outflow of gas. The gas flowing from the at least one gas outlet (70) comes into contact with the proximal electrode (32) for generation of the plasma. The gas flow body (62) may also known as a proximal gas flow body (62). The term gas flow body (62) may be used to distinguish it from a distal gas flow body (262), where present as described later below.

[0112] The gas flow body may contain a distribution chamber (68) for conveying gas provided by the gas inlet (66) to the helical flow guide The distribution chamber (68) may also known as a proximal distribution chamber (68). The term proximal distribution chamber (68) may be used to distinguish it from a distal distribution chamber (268) where present as described later below.

[0113] A distal side of the gas flow body (62) may be flat. A distal (20) side of the gas flow body (62) may contain a central annual protrusion protruding distally (20) containing the helical flow guide (80) and one or more helical channels (88).

[0114] The gas flow assembly (60) may be formed substantially as monoblock ( / .e. moulded or milled from a single piece of material). The monoblock gas flow assembly (60) may be made from a metal (e.g. stainless steel or copper). In embodiments, the gas flow assembly (60) may manufactured from electrically insulative material (the gas flow assembly (60) may be electrically insulative).

[0115] More preferably, the gas flow assembly (60) is a multi-piece unit, the parts constituting the gas flow assembly (60) being dismountably attached to each other. A multi-piece unit allows for ease of cleaning and interchanging of parts. The multi-piece gas flow assembly (60) may be made all from the same material such as all-ceramic material (e.g. a ceramic material containing on silicon nitride or boron nitride) or all-metal (e.g. stainless steel or copper), or one or more parts may be made from metal (e.g. stainless steel or copper) and one or more parts may be made from a ceramic material (e.g. a ceramic material containing on silicon nitride or boron nitride).

[0116] The gas flow assembly (60) may also be known as a proximal gas flow assembly (60). The term proximal gas flow assembly (60) may be used to distinguish it from a distal gas flow assembly (260) where present as described later below.

[0117] The gas flow body (62) comprises through-opening (64) configured for (slidably) receiving the longitudinal insulative body (38). The through-opening is a space connecting an opening in the proximal end of the gas flow body (62) with an opening in the distal end of the gas flow body (62). The through-opening (64) may be a side-walled or non-side-walled passageway open at both ends. Where the through-opening (64) is a non-side-walled passageway, an engagement between the opening in the distal end of the gas flow body (62) and the longitudinal insulative body (38), between the opening in the proximal end of the gas flow body (62) and the longitudinal insulative body (38), preferably creates a gasseal to prevent or reduce seepage of inflowing gas from the gas flow body (62). Alternatively, the through-opening is a walled passageway, with side walls extending between both open ends that prevents or reduces seepage of inflowing gas from the gas flow body (62).

[0118] The through-opening (64) in the gas flow body is further configured for peripherally (P) (radially) constraining the longitudinal insulative body (38). The through-opening (64) may be configured for slidable and fixable displacement of the longitudinal insulative body (38) relative to the gas flow assembly (60).

[0119] The gas flow assembly (60) comprises one of more gas inlets (66). The one or more gas inlets (66) may each comprise a coupling configured for repeatable dismountable attachment to a tubing or piping or conduit for carrying the gas towards the helical flow guide (80). The gas flow assembly (60) is preferably mounted on the gas flow body (62). The gas flow assembly (60) comprises one or more gas outlets (70). The gas outlet (70) is a directional gas outlet (70) configured to direct the gas so as to induce a helical flow pattern. In particular, the helical flow pattern is induced in the tunnel region (200). As explained later below, the flow direction of gas exiting the gas outlet (70) may be defined according to a downward gas exit angle (beta). The flow direction is determined primarily by the helical flow guide (80), and the directional gas outlet (70) is an opening in the helical channel (88).

[0120] Where the quantity of gas outlets (70) is greater than one, they are preferably disposed circumferentially evenly spaced around a circle. The one or more gas outlets (36) is disposed on the helical guide body (62’). The one or more gas outlets (36) is disposed peripheral (P) of the through opening (64). The one or more gas outlets (36) is disposed central (C) of the tunnel wall (210) inner surface (212) where present. The one or more gas outlets (36) is disposed as close as possible to the tunnel wall (210) inner surface (212). The one or more gas outlets (70) is configured to direct the gas towards the tunnel wall inner surface (212)

[0121] The one or more gas outlets (36) is preferably an aperture in the distal (20) side of the gas flow body (62), connecting the one or more helical channels (88) to the exterior of the gas flow body (62). The aperture may have any shape, preferably square or oblong or annular segment shaped; it may have pointed or rounded corners.

[0122] The gas flow assembly (60) comprises a helical flow guide (80). The helical flow guide (80) is configured to direct the gas provided from the one or more gas inlets (66) along a helical path to the one or more gas outlets (70). The helical flow guide (80) comprises one or more helical channels (88) configured to convey gas, each helical channel (88) having at least 1 (preferably at least 2) helical turns.

[0123] The one or more helical channels (88) are disposed peripheral (P) the through opening (64). The one or more helical channels (88) are both disposed separated from the through opening (64). The one or more helical channels (88) are disposed within the gas flow body (62). The one or more helical channels (88) are confined to within the gas flow body (62).

[0124] A peripheral location of the one or more helical channels (88) reduces a possibility of a longitudinal flow by the gas by confining the flow of gas to a helical path within the gas flow body (62). Under higher flow rates, and where the one or more helical channels are (unlike the present disclosure) formed as part of an engaged thread with, for example, an exterior electrode, gaps between the engaged threads allow gas to flow also longitudinally. The gas flow is no longer confined to a helical path, and the longitudinal gas flow interferes with the swirling flow, particularly at high flow rates. This reduces consistency and even destroys the swirling flow path.

[0125] Preferably, a transverse cross-section of the helical channel (88) has an outer profile outer edge that is a closed loop. The closed loop geometry is caused by the helical channel (88) being disposed within the gas flow body (62). An exemplary transverse cross-section (89) of the helical channel (88) is shown in FIG. 22 panel C, and the outer profile outer edge is presented as a closed loop (91) (rectangle). It is understood that the closed loop is not present at the one or more gas inlets (66) and one or more gas outlets (36).

[0126] The quantity of helical turns of a helical channel (88) may be a fraction of one turn (e.g. 0.5 or 0.95, a fraction in the range 0.5 to 0.95), whole number of complete turns (e.g. 1 , 2, 3, an integer in the range 1 to 10 or more), or a whole number of complete turns in addition to a fraction of a turn (e.g. 1.5, 1.7, 2.5; an integer in the range 1 to 10 or more + a fraction in the range 0.05 to 0.95). The one or more helical channels (88) are disposed peripheral (P) of the insulative body (80). The one or more helical channels (88) are disposed peripheral (P) of the proximal electrode (32). The turning direction of one or more helical channels (88) in a proximal to distal direction is clockwise or anti-clockwise.

[0127] A helical channel may have a helix angle (alpha) (e.g. FIG. 7) which is an angle between the longitudinal axis (L-L’) and the helical channel (88) when the helical channel is unravelled onto a plane. In FIG. 7, the line H-H’ represent the planar-unravelled helical channel (88). The helix angle (alpha) may depend on the application of the device. The helix angle (alpha) is greater than 0 deg, and less than 90 deg. Typically, the helix angle (alpha) is preferably 50 to 87 deg. Where the quantity of helical channels (88) is two or more, the helix angle (alpha) is the same for all the helical channels (88).

[0128] A helical channel may have an axial helix height, which is an axial distance between the start and end of the helix, more in particular between the helical channel inlet (62’i) and helical channel outlet (62’o) (see later below). Where the quantity of helical channels (88) is two or more, the axial helix height is the same for all the helical channels (88). The quantity of helical channels (88) may be one, two, three or more. Where the number of helical channels is more than one, each helix is preferably displaced longitudinally from its adjacent other helix. Each helical channel (88) is fluidly connected to its own gas outlet (70). Each helical channel (88) is fluidly connected to its own helical channel inlet (62’i) at its proximal end and to its own helical channel outlet (62’o)) at its distal end. Each helical channel (88) is fluidly isolated from other helical channels (except gas inlet (66) and gas outlet (70), more in particular, except at the helical channel inlet (62’i) and helical channel outlet (62’o)).

[0129] As a non-limitative general guidance, for a gas flow rate of 300 In / min and 1 bar pressure drop, the helical flow guide (80) may comprise three helical channels (88), each helical channel (88):

[0130] - having a transverse cross-sectional oblong shape and being sized at 2 mm deep and 3 mm wide;

[0131] - having an axial height of 25 mm;

[0132] - having a helix angle (alpha) of 81.5 deg;

[0133] - having a major diameter (peripheral most diameter) of 62 mm;

[0134] - having a minor diameter (diameter across the groove) of 29 mm;

[0135] - terminating distally in a separate gas outlet (70) and being sized at 3 mm x 2 mm.

[0136] In practice, the parameters such as the quantity of helical turns, quantity of helical channels (88), helix angle (alpha), axial helix height, and helical channels (88) cross-sectional area and shape depend on the application of the device. The skilled person will understand how to configured the helical flow guide based on desired flow rate in particular.

[0137] The net direction of gas exiting a gas outlet (70) is distal (20). The net direction of gas exiting a gas outlet (70) may be assigned a downward gas exit angle (beta), which is an angle between the longitudinal axis (L-L’) and the net flow path (72) of the gas in a linear portion before it strikes a surface (e.g. tunnel region (200)) (FIG. 8). The gas exiting each gas outlet (70) has a net direction that is dependent on the helix angle (alpha). For example, where the helix angle (alpha) is set at 80 deg, the downward gas helix angle (beta) will be on average 80 deg in close proximity to the gas outlet (70). The downward gas exit angle (beta) chosen may depend on the application of the device (100). It can be set, for instance, by adjusting the helix angle (alpha). The downward gas exit angle (beta) is greater than 0 deg, and less than 90 deg. Typically, the downward gas exit angle (beta) is preferably 50 to 85 deg.

[0138] The net direction of gas exiting a gas outlet (70) is also peripheral (P). The one or more gas outlets (70) are located as close to a striking surface (e.g. tunnel region (200), or inner surface (212)) (FIG. 9) as possible. This allows the exiting gas flow (78) to strike the surface with a maximal pressure, so that its helical flow pattern is maintained for a maximal distance in a distal direction. The peripheral (P) or radial distance between the inner surface (212) and the one or more gas outlets (70) may be adjusted by selection of the transverse cross-sectional size of the tunnel region (200). The peripheral (P) or radial distance between the inner surface (212) and the one or more gas outlets (70) may be adjusted by selection of the major and minor diameter of the helical flow guide.

[0139] The helical flow guide may be electrically conductive or electrically non-conductive. The helical flow guide may be made from any suitable material for the operating condition (e.g. temperature) such as metal or polymer. It is preferably made from stainless steel. It may be made from a 3D printable material (e.g. low temperature operations) . It may be 3D printed.

[0140] The helical flow guide (80) may comprise a helical guide body (62’) (e.g. FIG. 3). The helical guide body (62’) may be dismountable from the remainder of the gas flow body (62) (e.g. for cleaning, maintenance, changing of size). The helical guide body (62’) may be part of a multi-piece gas flow body (62). The parts of the a multi-piece gas flow body (62) may be interconnected using fixation element(s), such as threaded fastener, clamp (e.g. friction clamp), snap fit connector, engageable stop member(s), or the like.

[0141] The gas provided through the gas inlet (66) may enter (by way of the distribution chamber (68)) the helical flow guide (80) via a helical channel inlet (62’i) of the helical guide body (62’). The gas may exit the helical flow guide (80) via a helical channel outlet (62’o) of the helical guide body (62’). The gas outlet (70) and helical outlet (62’o) are preferably one and the same.

[0142] The helical guide body (62’) may be a single piece unit (e.g. FIG. 3). The single piece helical guide body (62’) (FIG. 3) may be made from a ceramic material (e.g. a ceramic material containing on silicon nitride or boron nitride) or a metal (e.g. stainless steel or copper). More preferably, the helical guide body (62’) is a multi-piece unit (e.g. FIGs. 4 to 6). comprising an insert part (82) and a receiving part (86). In embodiments, the multipiece unit is made of the same material (e.g. stainless steel) or from different materials with a similar or the same expansion coefficient. In embodiments, the multi-piece unit may be made from different materials having a similar coefficient of expansion such that no gap is formed between the parts at the operating temperature.

[0143] In embodiments, the single piece helical guide body (62’) and / or multi-piece helical guide body may be 3D printed, particularly for lower temperature range of operation.

[0144] The helical flow guide (80), in particular, the helical guide body (62’), preferably comprises:

[0145] - an insert part (82) comprising a cylindrical or frustum body disposed with at least one outer helical groove (84),

[0146] - a receiving part (86) configured to fittingly receive the insert part (82) wherein:

[0147] - the at least one outer helical groove (84) and receiving part (86) co-operate to form the one or more helical channels (88).

[0148] The receiving part (86) is preferably disposed in fixed relation to the gas flow body (62). The receiving part (86) is one piece of a multi-piece helical guide body (62’). The receiving part has a cylindrical or frustum body shaped space (90) for fittingly receiving the insert part (82), where the space (90) is defined in part by a rounded side wall configured to contact the helical flow guide (80), and which forms an occluding wall of the at least outer helical groove (84) thereby forming the one or more helical channels. The insert part (82) may be made from a ceramic material (e.g. a ceramic material containing on silicon nitride or boron nitride) or a metal (e.g. stainless steel or copper).

[0149] The insert part (82) is repeatably dismountably attachable to the receiving part (76). The dismountable attachment may be realised using any fixation element(s) (92), such as threaded fastener, clamp (e.g. friction clamp), snap fit connector, engageable stop member(s), or the like. In FIGs. 18 and 19, the fixation element(s) (92) comprises an external screw thread which engages with an internally-threaded cap (94) disposed with an O-ring (98). The fixation element (92) - cap (94) combination is configured to compress and radially expand the O-ring (by tightening of the cap on the external screw thread) and to maintain the O-ring in fixed position relative to the insert part (82). The radially expanded O-ring increases radial friction (clamping) on the insulative body (38), thereby preventing movement, especially sliding movement, of the insert part (82) relative to the insulative body (38) or longitudinal electrode assembly (30).

[0150] The receiving part (86) may be made from a ceramic material (e.g. a ceramic material containing on silicon nitride or boron nitride) or a metal (e.g. stainless steel or copper).

[0151] The insert part (82) comprising a cylindrical or frustum body is disposed with at least one outer helical groove (84) (e.g. detailed in FIGs. 5 Panel B, 6, and 18). The characteristic of the helical groove (84) are the same as or similar to those of the helical channel (88). The quantity of helical turns may be a whole number of complete turns (e.g. 1 , 2, 3) or a whole number of complete turns in addition to a fraction of a turn (e.g. 1 .5, 1 .7, 2.5). The quantity of helical grooves (84) may be one, two, three or more. Where the quantity of helical grooves (84) is more than one, each helix is preferably displaced longitudinally from its adjacent other helix. The helical groove (84) has the same helix angle (alpha) as the helical channel (88). The helical groove (84) has the same axial helix height as the helical channel (88). The helical groove (84) has the same transverse cross-sectional oblong shape and size as the helical channel (88).

[0152] The one or more helical channels (88) are formed by co-operation of insert part (82) outer helical groove (84) and receiving part (86). The one or more gas outlets (70) are formed by co-operation of the insert part (82) and receiving part (86).

[0153] The insert part (82) helical groove (84) has at one (proximal) end, a groove inlet (84i). The helical channel inlet (62’i) is formed by co-operation of insert part (82) groove inlet (84i) and receiving part (86).

[0154] The insert part (82) helical groove (84) has at one (distal) end, a groove outlet (84o). The helical channel outlet (62’o) is formed by co-operation of insert part (82) groove inlet (84i) and receiving part (86).

[0155] The proximal electrode (32) may be disposed flush with, recesses with, or protruding from a distal end (20) of the gas flow body (62) or gas flow assembly (60). FIG. 11 Panel A shows the proximal electrode (32) disposed flush with distal end of the gas flow body (62) or gas flow assembly (60). FIG. 11 Panel B shows the proximal electrode (32) disposed protruding from the distal end (20) of the gas flow body (62) or gas flow assembly (60). Linear displacement of the longitudinal electrode assembly (30) allows adjustable positional relationship with the gas flow body (62) or gas flow assembly (60).

[0156] The gas flow assembly (60) and longitude electrode assembly (30) may be disposed in fixed and non-adjustable positional relationship with each other. Preferably, the gas flow assembly (60) and longitude electrode assembly (30) are disposed in position-adjustable relationship with each other. Preferably, the gas flow assembly (60) and longitude electrode assembly (30) are disposed in slidable relationship with each other. The electrode assembly (30) may be linearly displaceable along a longitudinal axis (L-L’) relative to the gas flow assembly (60). The position of the electrode assembly (30) relative to the gas flow assembly (60) may be repeatably lockable. The repeatable lockability may be realised by any suitable element such as a clamp (e.g. friction clamp). The linear displacement may be achieved by rotation of the electrode assembly (30) (around its longitudinal (L-L’) axis)), relative to the gas flow assembly (60); in other words, gas flow assembly (60) and longitude electrode assembly (30) may be coupled using a threaded coupling.

[0157] The position-adjustable relationship between the gas flow assembly (60) and longitude electrode assembly (30) provides a tuneable plasma generator that can have different distances between both proximal and distal electrodes, depending for instance, on the gas, flow rate and voltage. The same device is suited to a variety of reaction conditions, which avoids the need for exchanging components, for having a collection of components of different sizes, thereby saves time and costs. In particular, where the tunnel region (200) is a reaction volume, the effective reaction volume can adjusted without having to substitute tunnel region for a different tunnel region of a different length.

[0158] When the longitude electrode assembly (30) protrudes from the distal end of the gas flow body (62), the longitude electrode assembly (30) helps to stabilise the helical gas flow; namely the helical flow path extends further in a proximal to distal axial direction when it advances adjacent to longitude electrode assembly (30) compared with when the longitude electrode assembly (30) is flush with the distal end of gas flow body (62). Advantageously, the longitude electrode assembly (30) can be disposed in any slidable position relative to the gas flow assembly (60), and the flow of gas past the proximal electrode is maintained is a helical pattern. The position-adjustable relationship between the gas flow assembly (60) and longitude electrode assembly (30) allows the same device to be used for generation of a plasma jet (proximal electrode advanced towards distal end of the tunnel region), plasma arc (proximal electrode advanced into the tunnel region), or glow discharge plasma (proximal electrode disposed towards proximal end of the tunnel region).

[0159] The plasma is generated by passing electrical energy between the proximal electrode (32) and a distal electrode. The distal electrode may or may not be a part of the device (100). Where the device is configured to generate a plasma arc, the distal electrode is provided by a work piece; it is typically not a part of the device. Where the device is configured to generate a plasma jet, the distal electrode is provided distal (20) of the proximal electrode (32), typically as an annular ring (through which generated plasma passes); it is typically a part of the device. Where the device is configured to generate glow discharge plasma, the distal electrode (232) is provided distal (20) of the proximal electrode (32), e.g. at a distal end of a reaction chamber (202) / tunnel region (200) and / or by the reaction chamber (202) / tunnel region (200) (see elsewhere herein); it is typically a part of the device. The distal electrode may be a cathode (positive polarity) or an anode (negative polarity) depending on the application of the device. The distal electrode has an opposing polarity to the proximal electrode (32).

[0160] The distal electrode may be made from any suitable electrically conductive material according to the application of the device. Examples of suitable material include lanthanum tungsten, copper, aluminium, nickel, chrome, palladium, gold, silver, platinum and the like.

[0161] A power supply may be provided separately or as a part of the device (100), configured for the generation of electrical current for generation of plasma. Such power supplies are known in the art. Typically, a power supply is a current-controlled high-voltage power supply operating in a linear topology or a resonance switching topology or a topology which sustains stable current. By high voltage, it is meant operating at a voltage equal to or greater than 5 kV, preferably not greater than 50 kV.

[0162] The device (100) may further comprise a tunnel region (200) disposed distal (20) of the gas flow assembly (60), in particular, distal to the one or more gas outlets (70). An exemplary tunnel region (200) is shown in FIGs. 10, 12 to 15, 20, 21. The tunnel region (200) comprises a tunnel wall (210) peripheral (P) to and surrounding the one or more gas outlets (70). The wall extends in a distal (20) direction. A proximal end (10) of the tunnel contains an opening for the one or more gas outlets (70). A distal end (20) of the tunnel contains an opening for outlet of gas and / or plasma. The tunnel wall (210) peripherally surrounds a tunnel space (214); gas and plasma occupy at least a part of the a tunnel space (214).

[0163] A transverse cross-section of the inner tunnel wall is preferably circular. The tunnel wall (210) comprises an inner surface (212). The inner surface (212) is preferably curved.

[0164] A transverse cross-section of the tunnel wall inner surface (212) is curved, preferably circular. The size of said transverse cross-section may be constant along an axial (L-L’) length of the tunnel wall (210). The size of said transverse cross-section may gradually vary along an axial (L-L’) length of the tunnel wall (210); for example, the size of said transverse cross-section may gradually reduce towards a distal end (20). The tunnel wall inner surface (212) may have a frustoconical geometric form, the smaller end disposed distally (20).

[0165] The tunnel wall inner surface (212) is preferably smooth. By smooth, it is meant it is devoid of protrusions and is devoid of recesses. The tunnel wall inner surface (212) is configured to receive flow of gas exiting from the one or more gas outlets (70). The tunnel wall inner surface (212) is configured to guide the flow of the gas exiting from the one or more gas outlets (70) in a curved direction. Since gas exiting from the one or more gas outlets (70) strikes the inner curved surface (212) at a gas helix angle (beta) that is greater than 0 deg, the gas has a helical, swirling flow path that advances in a distal direction.

[0166] A transverse cross-section of the outer tunnel wall is preferably circular, however, other shapes are foreseen, such as rectangular, triangular, hexagonal or other polygonal shape.

[0167] The tunnel region (200) may be dismountably attachable to the gas flow assembly (60) (e.g. for cleaning, maintenance, changing of size). More in particular, the tunnel region (200) may be dismountably attachable to the distal end of the gas flow body (62). The tunnel region (200) may be dismountably attachable to the gas flow assembly (60) or gas flow body (62) using fixation element(s), such as threaded fastener, clamp (e.g. friction clamp), snap fit connector, engageable stop member(s), or the like. Depending on the application of the device, the tunnel region (200) may be configured in a variety of ways.

[0168] Where the device is configured to generate a plasma jet, the distal electrode is provided distal (20) of the proximal electrode (32). It may be provided as an annular ring (through which generated plasma passes) disposed on the inner surface (212) of the tunnel region (200) or distal (20) of the tunnel region (200); in such case, the tunnel region is made from an insulative material (e.g. ceramic). Alternatively, the proximal electrode (32) may be the tunnel region (200); in such case, the tunnel region (200) may be made from any conductive metal such as stainless steel, copper, or tungsten. Preferably an additional electrical insulative body is disposed peripheral of the tunnel region (200) for user safety. The plasma jet exits through the tunnel region (200) distal opening.

[0169] Where the device is configured to generate a plasma arc, the distal electrode is provided by a work piece. Hence, the inner curved surface (212) of the tunnel region (200) does not contain the distal electrode. The plasma arc passes through the tunnel region (200) distal opening. The tunnel region (200) in a plasma arc configuration may be made from a ceramic material (e.g. a ceramic material containing on silicon nitride or boron nitride) or a metal (e.g. stainless steel or copper), or a mixture of ceramic material and metal.

[0170] Where the device is configured to generate glow discharge plasma, the distal electrode (232) is provided distal of the proximal electrode (32), typically at a distal end of the tunnel region (200), and the tunnel region (200) acts as a reaction chamber (202). The tunnel region (200) / reaction chamber (202) in a glow discharge plasma configuration may be made from a conductive or non-conductive material, for instance, any ceramic or metal. Examples of devices (100) having a tunnel region (200) / reaction chamber (202) are shown in FIGs. 12 to 15, 20 and 21. Gas exits the tunnel region (200) / reaction chamber (202) via one or more exit channels (288), and optionally via catalyst bed (250) (FIGs. 13, 15 and 21) and through a product outlet (266).

[0171] The device (100) configured to generate glow discharge plasma may be disposed with one or more of the following features or elements:

[0172] The distal electrode (232) position may be fixed (non-adjustable) with respect to the tunnel region (200) / reaction chamber (202). An example of device (100) containing a fixed (non-adjustable) distal electrode (232) is shown, for example, in FIGs. 14,15, 20 and 21. In FIGs. 20 and 21 , the distal electrode is not explicitly indicated; it is positioned distal of the proximal electrode, for instance, the distal electrode may comprise the tunnel region (200) / reaction chamber (202), and / or may be disposed distal of the tunnel region (200) / reaction chamber (202).

[0173] The distal electrode (232) position may be adjustable with respect to the tunnel region (200) / reaction chamber (202). Preferably, distal electrode (232) is slidable along a longitudinal axis (L-L’) relative to the tunnel region (200) / reaction chamber (202). An example of device (100) containing a position-adjustable distal electrode (232) is shown, for example, in FIGs. 12 and 13.

[0174] The distal electrode (232) may be provided on a distal longitudinal electrode assembly (230), which is similar or identical to the proximal longitudinal electrode assembly (30) as described elsewhere herein. An example of device (100) containing a proximal longitudinal electrode assembly (30) and a distal longitudinal electrode assembly (230) is shown, for example, in FIGs. 12 and 13.

[0175] The device (100) may further comprise a distal gas flow assembly (260) which is similar to the proximal gas flow assembly (60) described elsewhere herein. The distal gas flow assembly (260) may or may not contain a helical flow guide; the one or more exit channels (288) may have a linear path.

[0176] The distal gas flow assembly (260) may comprise a distal gas flow body (262) having one or more exit channels (288) through which gas from tunnel region (200) / reaction chamber (202) exits, and one or more product outlets (266) configured for outflow of the reaction product.

[0177] The gas flow body (262) may contain a distribution chamber (268) for conveying gas exiting the one or more exit channels (288) to the one or more product outlets (266) (FIGs. 12 to 15, 20 and 21), optionally via a catalyst bed (250) (FIGs. 13,15, and 21).

[0178] The device (100) may further comprise a catalyst bed (250) configured to contain catalyst mass and receive gas flowing from the tunnel region (200) / reaction chamber (202). The catalyst bed (250) contains one or more catalyst bed gas inlets or openings and one or more catalyst bed gas outlets (254), and a chamber (252) for holding the catalyst mass. The catalyst bed (250) is configured to pass the received gas through the catalyst mass and out through the one or more bed gas outlets (254). The catalyst bed (250) is preferably provided within the distribution chamber (268) of the distal gas flow body (262) of the distal gas flow assembly (260). An example of device (100) containing a catalyst bed (250) is shown, for instance, in FIGs. 13,15, and 21.

[0179] The device (100) may further comprise an aerodynamic quenching device disposed distal (20) of the tunnel region (200) / reaction chamber (202). Where the catalyst bed (250) is present, the aerodynamic quenching device may be provided distal (20) of or proximal (10) of the catalyst bed (250). Aerodynamic quenching devices are known in the art, for instance, from Chiappetta and Colket, Design Considerations for Aerodynamically Quenching Gas Sampling Probes, J. Heat Transfer. May 1984, 106(2): 460-466. An aerodynamic quenching device typically contains a passive flow control section (e.g. converging-diverging, converging- straight-diverging). An aerodynamic quenching device may optionally be water cooled. Aerodynamic quenching devices can also operate on the principle of the de Laval nozzle.

[0180] As mentioned elsewhere herein, the device may be configured to generate glow discharge plasma, the tunnel region (200) acting as a reaction chamber.

[0181] The present device configured to generate glow discharge plasma may be used for an electrified conversion of a gas. Examples of gases and their conversion products using the present device include:

[0182] CO2, which decomposes into CO and O2;

[0183] NH3, which can be cracked into H2 and N2;

[0184] - Air (containing N2), wherein the N2 can be fixed into NO and NO2;

[0185] CH4, which can be converted to higher hydrocarbons, solid carbon and H2.

[0186] Electrified conversion of a gas is typically not energy efficient in the prior art when scaling up for industrial applications. Using the present device, the residence time of the gas within the tunnel region (200) / reaction chamber (202) is increased as a result of the helical flow guide. The helical flow guide also created a thermally insulative gas cushion between the tunnel region (200) / reaction chamber wall and the generated plasma, which reduces the temperatures of the wall and increases lifetime of the device. The conversion of gas into product is maintained even at high flow rates of gas, for instance, the range of 100 - 300 In / min, meaning that the reactor allows production to be scaled up. Provided is a use of the present device for generation of a plasma jet, a plasma arc, or glow discharge plasma.

[0187] Provided is a use of the present device for plasma-induced decomposition of CO2 into CO and O2.

[0188] Provided is a use of the present device for plasma-induced cracking of NH3 into H2 and N2.

[0189] Provided is a use of the present device for plasma-induced fixing of air sourced N2 into NO and NO2.

[0190] Provided is a use of the present device for plasma-induced conversion of CH4 into graphene and H2.

[0191] Example

[0192] A device as presently described configured to generate glow discharge plasma was used to fix N2 from the air into NO and NO2. An air compressor was connected to a control valve which in turn was connected to the gas inlet of the present device through a mass flow meter (MFM) IFM SD6500. The voltage was measured with a high voltage probe (HV) Tektronix P6015A and the current was obtained by measuring the voltage drop across a shunt resistor with 2 Q resistance. Both signals are recorded with a two channel oscilloscope Keysight InfiniiVision DSOX1102A. The DC current as supplied with a current-controlled power supply unit (PSU) Technix SR12KV-10KW with negative output polarity. The current was varied between 0.15 A and 1.1 A, and the flow rate of air between 100 In / min and 300 In / min. The NO and NO2 concentrations are measured by non- dispersive ultraviolet spectroscopy (NDLIV) using WiTec ULTRA-Sens NOx AK100 TBH gas analyzer. The NOx concentration was measured after the reaction had achieved steady state. In addition, each of the experiments was also conducted 3 times in order to reduce the uncertainty. Distance between the electrodes was 14 cm. The results are shown in FIGs. 16 and 17.

[0193] Combining low currents with high pressure and flow rate can lead to very low energy costs and significantly increase the production rate. Due to the high flow rates, the production rate of NOx is increased despite the low concentrations. The production rate as function of the current for different flow rates is presented in FIG. 17. The production rate is significantly increased reaching nearly 37 g / h at a current value of 1100 mA and flow rate of 300 In / min. With concentrations as low as 0.11 % at 150 mA, the production rate reaches a value of 25 g / h. The energy cost (EC) as a function of the current for different flow rates is presented in FIG. 16. The EC decreases with the increase in the flow rate, but remains essentially the same with increasing current. This means that the reactor can operate stably at lower currents, thus allowing lower EC. This stability is caused by the helical flow guide which increase the gas flow residence time in the reaction chamber.

Claims

Claims1. A device (100) for generating plasma using a flowing gas comprising:- a longitudinal electrode assembly (30) comprising:- a longitudinal electrically insulative body (38) having a proximal (10) and distal (20) end,- a proximal electrode (32) configured for contacting the gas, provided only at the distal end (20) of the insulative body (38), and disposed in fixed relation thereto;- a gas flow assembly (60) comprising:- a gas flow body (62);- a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38);- one or more gas inlets (66) in the gas flow body (62) for inlet of the gas;- one or more gas outlets (70) configured for outflow of the gas;- a helical flow guide (80) comprising one or more helical channels (88), each helical channel (88) having at least 0.5 helical turns, configured to direct the gas provided from the one or more gas inlets (66) along the one or more helical channels (88) to the one or more gas outlets (36), wherein:- the electrically insulative body (38) is mounted in the through-opening (64), and- the one or more helical channels (88) and the one or more gas outlets (36) are both disposed peripheral (P) of the through opening (64).

2. The device (100) according to claim 1 , wherein a transverse cross-section of the helical channel (88) has an outer profile outer edge that is a closed loop.

3. The device (100) according to claim 1 or 2, wherein the electrode assembly (30) is linearly displaceable along a longitudinal axis (L-L’) relative to the gas flow assembly (60).

4. The device (100) according to any one of claims 1 to 3, wherein the gas flow assembly (60) is electrically insulated from the proximal electrode (32) at least by the longitudinal insulative body (38).

5. The device (100) according to any one of claims 1 to 4, wherein the helical flow guide (80) comprises:- an insert part (82) comprising a cylindrical or frustum body disposed with at least one outer helical groove (84),- a receiving part (86) configured to fittingly receive the insert part (82) wherein:- the at least one outer helical groove (84) and receiving part (86) co-operate to form the one or more helical channels (88);- the receiving part (86) is disposed in the gas flow body;- the insert part (82) is repeatably dismountably attachable to the receiving part (76).

6. The device (100) according to any one of claims 1 to 5, further comprising a tunnel region (200) distal (20) of the gas flow assembly (60), wherein the tunnel region (200) comprises a tunnel wall (210) peripheral (P) to and surrounding the one or more gas outlets (70), and wherein the wall extends in a distal (20) direction.

7. The device (100) according to claim 6, wherein a transverse cross-section of the tunnel wall inner surface (212) is curved, preferably circular, and- optionally the size of said transverse cross-section is constant along an axial (L-L’) length of the tunnel wall (210), or- optionally the size of said transverse cross-section gradually varies along an axial (L-L’) length of the tunnel wall (210).

8. The device (100) according to claim 7, wherein the one or more gas outlets (70) is configured to direct the gas towards the tunnel wall inner surface (212), and in a net distal direction.

9. The device (100) according to any claim 6 to 8, wherein:- a distal electrode is further provided, and- the device is configured for generation of a plasma jet, a plasma arc, or glow discharge plasma.

10. The device (100) according to any one of the claims 6 to 9, wherein::- the device comprises the distal electrode (232) disposed distal (20) of the proximal electrode (32);wherein the device is configured for generation of glow discharge plasma within the reaction chamber (202).

11. The device (100) according to claim 10, wherein a position of the distal electrode (232) is slidable relative to a position of the tunnel region (200).

12. The device (100) according to claim 10 or 11, further comprising a catalyst bed (250) configured to:- contain a catalyst mass;- receive gas flowing from the reaction chamber (202);- pass the received gas through the catalyst mass.

13. The device (100) according to any one of claims 1 to 12, wherein one or more helical channels (88) each has a helix angle (alpha) that is greater than 0 deg and less than 90 deg, preferably a value in a range 50 deg to 87 deg.

14. The device (100) according to any one of claims 1 to 13, wherein the number of helical channels (88) is two or more.

15. A device (100) for generating plasma using a flowing gas comprising:- a longitudinal electrode assembly (30) comprising:- a longitudinal electrically insulative body (38) having a proximal (10) and distal(20) end,- a proximal electrode (32) configured for contacting the gas, attached to the distal end (20) of the insulative body (38),- a gas flow assembly (60) comprising:- a gas flow body (62);- a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38);- one or more gas inlets (66) in the gas flow body (62) for inlet of the gas;- one or more gas outlets (70) configured for outflow of the gas;- a helical flow guide (80) configured to direct the gas provided from the one or more gas inlets (66) along a helical path to the one or more gas outlets (36); wherein:the one or more gas outlets (36) is disposed peripheral (P) of the through opening (64); and the helical flow guide (80) comprises:- an insert part (82) comprising a cylindrical or frustum body disposed with at least one outer helical groove (84);- a receiving part (86) configured to fittingly receive the insert part (82) wherein:- the at least one outer helical groove (84) and receiving part (86) co-operate to form the one or more helical channels (88);- the receiving part (86) is disposed in the gas flow body;- the insert part (82) is repeatably dismountably attachable to the receiving part (76).

16. The device (100) according to claim 15, wherein the helical flow guide (80) comprises one or more helical channels (88), each helical channel (88) having at least 0.5 helical turns17. The device (100) according to claim 15 or 16, incorporating subject matter of any one of claims 2 to 4, and 6 to 14.

18. A device (100) for generating plasma using a flowing gas comprising:- a longitudinal electrode assembly (30) comprising:- a longitudinal electrically insulative body (38) having a proximal (10) and distal(20) end,- a proximal electrode (32) configured for contacting the gas, attached to the distal end (20) of the insulative body (38),- a gas flow assembly (60) comprising:- a gas flow body (62);- a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38);- one or more gas inlets (66) in the gas flow body (62) for inlet of the gas;- one or more gas outlets (70) configured for outflow of the gas;- a helical flow guide (80) configured to direct the gas provided from the one or more gas inlets (66) along a helical path to the one or more gas outlets (36);- a tunnel region (200) distal (20) of the gas flow assembly (60), wherein the tunnel region (200) comprises a tunnel wall (210) peripheral (P) to and surrounding the one or more gas outlets (70), and wherein the wall extends in a distal (20) direction, wherein a transverse cross-section of the tunnel wall inner surface (212) is curved, preferably circular, and- optionally the size of said transverse cross-section is constant along an axial (L- L’) length of the tunnel wall (210), or- optionally the size of said transverse cross-section gradually varies along an axial (L-L’) length of the tunnel wall (210); wherein:- the one or more gas outlets (36) is disposed peripheral (P) of the through opening (64); and- the one or more gas outlets (70) is configured to direct the gas towards the tunnel wall inner surface (212), and in a net distal direction.

19. The device (100) according to claim 18, wherein the helical flow guide (80) comprises one or more helical channels (88), each helical channel (88) having at least 0.5 helical turns20. The device (100) according to claim 18 or 19, incorporating subject matter of any one of claims 2 to 5, and 9 to 14.

21. A device (100) for generating plasma using a flowing gas comprising:- a longitudinal electrode assembly (30) comprising:- a longitudinal electrically insulative body (38) having a proximal (10) and distal (20) end,- a proximal electrode (32) configured for contacting the gas, attached to the distal end (20) of the insulative body (38),- a gas flow assembly (60) comprising:- a gas flow body (62);- a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38);- one or more gas inlets (66) in the gas flow body (62) for inlet of the gas;- one or more gas outlets (70) configured for outflow of the gas;- a helical flow guide (80) configured to direct the gas provided from the one or more gas inlets (66) along a helical path to the one or more gas outlets (36);- a tunnel region (200) distal (20) of the gas flow assembly (60), wherein the tunnel region (200) comprises a tunnel wall (210) peripheral (P) to and surrounding the one or more gas outlets (70), and wherein the wall extends in a distal (20) direction; wherein:- the one or more gas outlets (36) is disposed peripheral (P) of the through opening (64);- the device comprises the distal electrode (232) disposed distal (20) of the proximal electrode (32);- the device is configured for generation of glow discharge plasma within the reaction chamber (202); and- a position of the distal electrode (232) is slidable relative to a position of the tunnel region (200).

22. The device (100) according to claim 21 , wherein the helical flow guide (80) comprises one or more helical channels (88), each helical channel (88) having at least 0.5 helical turns.

23. The device (100) according to claim 21 or 22, incorporating subject matter of any one of claims 2 to 5, 7 to 9, and 11 to 14.

24. A device (100) for generating plasma using a flowing gas comprising:- a longitudinal electrode assembly (30) comprising:- a longitudinal electrically insulative body (38) having a proximal (10) and distal (20) end,- a proximal electrode (32) configured for contacting the gas, attached to the distal end (20) of the insulative body (38),- a gas flow assembly (60) comprising:- a gas flow body (62);- a through-opening (64) in the gas flow body configured for receiving the longitudinal insulative body (38);- one or more gas inlets (66) in the gas flow body (62) for inlet of the gas;- one or more gas outlets (70) configured for outflow of the gas;- a helical flow guide (80) configured to direct the gas provided from the one or more gas inlets (66) along a helical path to the one or more gas outlets (36);- a tunnel region (200) distal (20) of the gas flow assembly (60), wherein the tunnel region (200) comprises a tunnel wall (210) peripheral (P) to and surrounding the one or more gas outlets (70), and wherein the wall extends in a distal (20) direction;- a catalyst bed (250) configured to:- contain a catalyst mass;- receive gas flowing from the reaction chamber (202);- pass the received gas through the catalyst mass, wherein:- the one or more gas outlets (36) is disposed peripheral (P) of the through opening (64);- the device comprises the distal electrode (232) disposed distal (20) of the proximal electrode (32); and- the device is configured for generation of glow discharge plasma within the reaction chamber (202).

25. The device (100) according to claim 24, wherein the helical flow guide (80) comprises one or more helical channels (88), each helical channel (88) having at least 0.5 helical turns.

26. The device (100) according to claim 24 or 25, incorporating subject matter of any one of claims 2 to 5, and 7 to 9, 11 , 13, 14.

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