Methods and apparatus for producing hydrogen

Abstract

Disclosed herein is a method of generating molecular hydrogen comprising the steps of: (i) providing a plasma chamber having an inlet and an outlet; (ii) providing a feed of a hydrogen containing molecule through the inlet to a plasma in said plasma chamber wherein said plasma is exposed to at least one electromagnetic frequency whereby said hydrogen containing molecule is disassociated into a hydrogen species and at least one non-hydrogen species; (iii) removing said hydrogen species from the chamber at the outlet; and (iv) then forming molecular hydrogen from said hydrogen species.

Description

Field

[0001] The present invention is directed to a method of producing molecular hydrogen from hydrogen containing compounds in a plasma. In particular, the present invention is directed to techniques where vapor or gaseous source is exposed to at least one electromagnetic frequency to produce a plasma. The ions in the plasma are then separated and hydrogen is extracted. Background

[0002] Generating energy from renewable sources such as solar and wind is one way of addressing the energy needs of society while minimising the use of fuels that produce carbon dioxide. Due to technological advancements, these sources of energy are becoming economically more viable than fossil fuels such as coal and gas. However, because these sources are inherently variable, difficulties arise when they provide a substantial proportion of electricity to a grid ---for example, they may not provide enough electricity during down-times, they produce too much electricity than required when operational, and variations in output can destabilise the grid. In these circumstances, appropriate energy storage is required in order to have a stable grid, to take up excess electricity, and to provide electricity when the renewable sources are unavailable or are not producing sufficient energy.

[0003] Batteries are the classic example of energy storage although there are others. For example, electricity can be used in an electrolyser to separate water into molecular hydrogen and molecular oxygen, and the energy of the electricity is “stored” in the molecular hydrogen. This is because the process can be effectively reversed in a fuel cell to produce electricity and water from hydrogen and oxygen. Hydrogen is also versatile because it can be used as a flammable gas in a similar way to LPG or natural gas, and as a feedstock in various industrial processes.

[0004] Electrolysers have the disadvantage of being expensive and requiring the use of rare and expensive materials in their construction. For example, they require electrodes that use noble metals in their construction. Further, electrolysers are typically limited to producing hydrogen from water.

[0005] Water can also be disassociated into hydrogen and oxygen species in a plasma. A plasma is a distinct state of matter containing a significant number of electrically charged particles, this number being sufficient to affect its electrical properties and behaviour. In an equilibrium gas each atom contains an equal number of positive and negative charges wherein the positive charges in the nucleus are surrounded by an equal number of negatively charged electrons. Each atom in the equilibrium gas is therefore electrically "neutral."

[0006] The gas becomes a plasma when the addition of heat or other energy causes a significant number of atoms to release some or all of their electrons. The remaining parts of those atoms are left with a positive charge, and the detached negative electrons are free to move about. The positively charged atoms and free electrons constitute an electrically charged gas called a plasma.

[0007] In many cases interactions between the charged particles, free electrons, and the neutral particles are important in determining the behaviour and application use of the plasma. The type of atoms in a plasma, the ratio of ions, and electrons to neutral particles and the particle energies all result in a broad spectrum of plasma types, characteristics and behaviours. There are many ways of producing a plasma. Examples of plasma generation devices are low pressure (nonequilibrium) plasmas, penning plasma discharge, radiofrequency capacitive discharges, radiofrequency inductively coupled plasmas, microwave generated plasma, D.C. electrical discharges, and inductively coupled discharges.

[0008] Plasma methods are known to generate hydrogen and oxygen species from water. However, this is not the same as generating molecular hydrogen as the two species will readily re-combine to form water or react with other components in the plasma or the environment. In order to prepare molecular hydrogen species separation and isolation of the hydrogen and oxygen species is required. The use of a plasma to generate molecular hydrogen from water has been contemplated in, for example, US73846192, however, while this patent speculates broadly as to the conditions that might be required, it does not disclose a working model and certainly does not disclose a system that would be commercially viable. Furthermore, to the inventor’s knowledge, there are also no known commercial plasma systems for producing hydrogen from compounds other than water.

[0009] It is an object of the invention to address at least one shortcoming of the prior art and / or provide a useful alternative. Summary of Invention

[0010] In a first aspect of the invention there is provided a method of generating molecular hydrogen comprising the steps of: (i) providing a plasma chamber having an inlet and an outlet; (ii) providing a feed of a hydrogen containing molecule through the inlet to a plasma in said plasma chamber wherein said plasma is exposed to at least one electromagnetic frequency whereby said hydrogen containing molecule is disassociated into a hydrogen species and at least one non-hydrogen species; (iii) removing said hydrogen species from the chamber at the outlet; and (iv) then forming molecular hydrogen from said hydrogen species.

[0011] In an embodiment, the hydrogen containing molecule is selected from the group consisting of: water, a hydrocarbon, or ammonia.

[0012] In an embodiment, said at least one electromagnetic frequency is a radio frequency.

[0013] In an embodiment, said plasma is exposed to an electromagnetic frequency in the range of from about 20 kHz to about. 13,56 MHz. Preferably, the frequency is from about 40 kHz. More preferably, the frequency is from about 100 kHz. Even more preferably, the frequency is from about 200 kHz. Most, preferably, the frequency is from about 300 kHz. Alternatively, or additionally, the frequency is up to about 700 kHz. More preferably, up to about 600 kHz. Most preferably, up to about 500 kHz.

[0014] In one form of the above embodiment, said plasma is exposed to a single electromagnetic frequency.

[0015] In an embodiment, said plasma is exposed to at least two different electromagnetic frequencies wherein the first frequency has a higher magnitude than the second frequency. Preferably, said hydrogen species and said non-hydrogen species are at least partially separated by their different responses to the two electromagnetic frequencies.

[0016] In one form of the above embodiment, said chamber further comprises a permeable grid that separates the chamber into a first space and a second space, and wherein said method further comprises separating the hydrogen species into the first space and the non-hydrogen species into the second space.

[0017] In one form of the above embodiment, said first frequency is from about 100 kHz up to about 800kHz and said second frequency is from about 20kHz up to about 80 kHz.

[0018] It is preferred that the first frequency is from about 150 kHz. More preferably, about 250 kHz. Most preferably about 350 kHz. Alternatively, or additionally, the first frequency is up to about 700 kHz. More preferably, up to about 600 kHz. Even more preferably, up to about 500 kHz. Most preferably, up to about 450 kHz.

[0019] It is preferred that the second frequency is from about 25 kHz. More preferably, from about 30 kHz. Most preferably, about 35 kHz. Alternatively, or additionally, the second frequency is up to about 70 kHz. More preferably, up to about 60 kHz. Most preferably, up to about 50 kHz.

[0020] An exemplary / first and second frequency is about 400 kHz and about 40 kHz + / - 10% respectively.

[0021] In an embodiment, the method further comprises providing a magnetic separator located at or downstream of the outlet of the chamber, and wherein the method further comprises magnetically separating at least a portion of the hydrogen species from the non-hydrogen species.

[0022] In one form of the above embodiment, said magnetic separator forms part of a laval nozzle, and the step of magnetically separating at least the portion of the hydrogen species from the non-hydrogen species comprises concentrating the hydrogen species toward a centre of the nozzle and the non-hydrogen species toward an outer portion of the nozzle at an exit of the outlet.

[0023] In one form of the above embodiment, the magnet separator differentially deflects the hydrogen species and the non-hydrogen species as they exit the outlet to separate at least a portion of the hydrogen species from the non-hydrogen species.

[0024] In an embodiment, the method further comprises providing a catalyst located separate from the plasma, and the method further comprises contacting the catalyst with the hydrogen species and / or the non-hydrogen species to form molecular hydrogen and or a non-hydrogen containing molecule respectively. Preferably, the catalyst is located external to the plasma chamber.

[0025] In an embodiment, the method further comprises removing hydrogen species in a hydrogen rich stream and removing the non-hydrogen species in a hydrogen-poor stream. In one or more forms of this embodiment, the hydrogen-poor stream comprises residual hydrogen containing molecule, and the method further comprises recycling at least a portion of the hydrogen-poor stream as a feed or a feed component to the inlet.

[0026] In a second aspect of the invention, there is provided an apparatus for generating molecular hydrogen from a hydrogen containing molecule, the apparatus comprising: a plasma chamber having an inlet, e.g. for receiving a feed of a hydrogen containing molecule and an outlet e.g. for outputting a hydrogen species and a non-hydrogen species from plasma mediated dissociation of the hydrogen containing molecule; and an electromagnetic radiation generator configured to generate one or more frequencies of electromagnetic radiation within the plasma chamber between the inlet and the outlet.

[0027] In an embodiment, the electromagnetic radiation generator is a radio frequency generator.

[0028] In an embodiment, the electromagnetic radiation generator is configured to generate electromagnetic radiation at two different frequencies, a first high frequency and a second low frequency. Preferably, said first frequency is about 400kHz and said second frequency is about 40kHz.

[0029] In one form of the above embodiment, the apparatus further comprises one or more signal generators to generate signals for the first high frequency and second low frequency, and a multiplexer to provide a multiplexed signal of the first, high frequency and second low frequency, and wherein the electromagnetic radiation generator receives the multiplexed signal.

[0030] In an embodiment, the plasma chamber is cooled using the feed upstream of the inlet.

[0031] In an embodiment, said chamber further comprises a permeable grid that separates the chamber into a first space and a second space.

[0032] In an embodiment, the apparatus further comprises a magnetic separator located at or downstream of the outlet of the chamber.

[0033] In one form of the above embodiment, the magnetic separator forms part of a laval nozzle, and the magnetic separator is configured to concentrate the non-hydrogen species toward a centre of the nozzle and the hydrogen species toward an outer portion of the nozzle at an exit of the outlet.

[0034] In another form of the above embodiment, the magnet separator is configured to differentially deflect the hydrogen species and the non-hydrogen species as they exit the outlet to separate at least a portion of the hydrogen species from the non-hydrogen species.

[0035] In an embodiment, the apparatus further comprises a catalyst located separate from the plasma.

[0036] In an embodiment, the plasma chamber further comprises a first outlet for removing a hydrogen-rich stream and a second outlet for removing a hydrogen-poor outlet stream. In one or more forms of this embodiment, the plasma chamber further comprises a recycle line on the second outlet configured to return at least a portion of the hydrogen-poor outlet stream to the inlet.

[0037] In an embodiment, the plasma chamber further comprises an outlet including means for magnetic separation of an outlet stream into a hydrogen-rich stream and a hydrogen-poor stream. In one or more forms of this embodiment, the plasma chamber further comprises a recycle line configured to return at least a portion of the hydrogen-poor stream to the inlet.

[0038] In a third aspect of the invention, there is provided a system comprising at least the apparatuses of the second aspect of the invention, or embodiments or forms thereof, wherein the apparatuses comprises a plurality of plasma chambers arranged in series and / or in parallel.

[0039] In one embodiment, the plasma chambers are arranged in series, and wherein a hydrogen-poor outlet stream of an upstream plasma chamber forms a feed stream to an inlet of a downstream plasma chamber.

[0040] In a fourth aspect of the invention, there is provided the use of the apparatus of the second aspect of the invention, or embodiments or forms thereof, to generate molecular hydrogen.

[0041] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps. Brief Description of Drawings

[0042] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

[0043] Figure 1. depicts a plasma chamber when used in a preferred method of the present invention comprising a central grid and exposed to two separate radio frequencies. The oxygen, or other non-monatomic hydrogen species respond to the low frequency and the hydrogen species respond to the higher frequency so as to at least partially separate the two species. In this depiction, the frequencies are about 400 kHz and about 40 kHz respectively.

[0044] Figure 2. depicts a plasma chamber as described in Figure 1 when used in a preferred method of the present invention and exposed to two separate radiofrequencies. A bending magnet located beyond the outlet of the chamber allows separation of the oxygen and other nonhydrogen species and the hydrogen species whereby the magnetic field bends the flight path of hydrogen species from the outlet, in a smaller flight radius than the oxygen species allowing for separation of the ion species.

[0045] Figure 3. depicts a plasma chamber when used in a preferred method of the present invention and exposed to two separate radiofrequencies but without the presence of a central grid. A bending magnet, located beyond the outlet of the chamber allows further separation of the oxygen and the hydrogen species.

[0046] Figure 4. depicts a plasma chamber when used in a preferred method of the present invention and exposed to a single radiofrequency. A. bending magnet located beyond the outlet of the chamber allows separation of the oxygen or other non-hydrogen species and the hydrogen species. In this case, the frequency will be in the order of 13 MHz to 14 MHz, preferably 13.56 MHz.

[0047] Figure 5. depicts a magnetic laval nozzle arrangement for use in the present invention whereby the magnetic field bends the flight path of hydrogen species from the outlet in a smaller flight radius than the oxygen and other non-hydrogen species allowing for separation of the ionic species.

[0048] Figure 6 is an illustration of a system comprising three plasma chambers in stacked arrangement and operated in parallel.

[0049] Figure 7 is an illustration of a system comprising three plasma chambers in stacked arrangement and operated in series, whereby a hydrogen poor outlet stream of an upstream plasma chamber forms an inlet or a portion of an inlet for a downstream plasma chamber.

[0050] Figure 8 is an illustration of a system comprising three plasma chambers in linear arrangement and operated in series, whereby a hydrogen poor outlet stream of an upstream plasma chamber forms an inlet or a portion of an inlet for a downstream plasma chamber.

[0051] Figure 9 is a graph showing the proportion of hydrogen in the plasma versus the ratio of H:(0H + O) when water is treated in an apparatus and according to the methods disclosed herein to form hydrogen.

[0052] Figure 10 reports hydrogen generation from a series of experiments conducted at frequencies of 357, 401, 449, and 499 kHz. Description of Embodiments

[0053] The present invention provides a method of generating molecular hydrogen comprising the steps of: providing a plasma chamber having an inlet and an outlet; providing a feed of a hydrogen containing molecule through the inlet to a plasma in said plasma chamber wherein said plasma is exposed to at least one electromagnetic frequency whereby said hydrogen containing molecule is disassociated into a hydrogen species and at least one non-hydrogen species; removing said hydrogen species from the chamber at the outlet; and then forming molecular hydrogen from said hydrogen species.

[0054] The present invention also relates to an apparatus for generating molecular hydrogen from a hydrogen containing molecule, the apparatus comprising: a plasma chamber having an inlet and an outlet; and an electromagnetic radiation generator configured to generate one or more frequencies of electromagnetic radiation within the plasma chamber between the inlet and the outlet.

[0055] “Disassociation” in this context means the breaking of bonds in the water and other hydrogen containing molecules to form ionised species. Typically, this may be a mixture of species including hydrogen radicals and ions, hydroxyl radicals and ions, and potentially oxygen radicals and ions and others. By “hydrogen species” is meant hydrogen radicals and ions and by “non-hydrogen species” it is meant radicals and ions that are not pure hydrogen radicals and ions. By way of example, a wide variety of different hydrogen containing molecules may be used, a non-limiting disclosure of such includes at least: water; hydrocarbons such as methane, ethane, propane, natural gas and the like; and ammonia. In such cases, the non-hydrogen species may be an “oxygen species” e.g. hydroxyl or oxygen radicals and ions (in the case of water), a “carbon species” e.g. carbon radicals and ions which may be partially protonated (in the case of a hydrocarbon), or a “nitrogen species” e.g. nitrogen radicals and ions (in the case of ammonia).

[0056] The hydrogen containing molecule is generally provided to the plasma chamber in gaseous form. For example, when the hydrogen containing molecule is water, this may be provided to the plasma chamber in the form of a water vapor. It is preferred that the hydrogen containing molecule is provided to the plasma chamber as a substantially pure stream of the hydrogen containing molecule and not entrained within a carrier liquid or gas.

[0057] In particular forms of the invention, the plasma chamber is cooled with a feed stream of the hydrogen containing molecule located upstream of the inlet to the plasma chamber. For example, the feed stream may be arranged for counter-current heat exchange with the plasma chamber. This arrangement also advantageously pre-heats the feed stream of the hydrogen containing molecule prior to being fed into the plasma chamber and thus improves the overall energy efficiency of the system by mitigating energy loss. In one example, the feed stream is water which is fed into the plasma chamber via an upstream water jacket which is in countercurrent arrangement with the plasma chamber. In this w'ay, the feed stream can be used to maintain the plasma chamber at a desired operating temperature whilst recovering heat energy . Advantageously, the flow of water, and thus the rate of hydrogen production and energy recovery / can be controlled and balanced to optimize the energy efficiency of the sy stem. In some forms, water in the feed stream is converted to steam through heat exchange prior to being fed through the inlet into the plasma chamber.

[0058] Once inside the chamber, the hydrogen containing molecule is entrained within the plasma and under high energy dissociates into a hydrogen species and a non-hydrogen species (e.g. an oxygen, carbon, nitrogen species depending on the hydrogen containing molecule of the feed stream). The plasma will consist of a quasi-equilibrium mixture of ions, electrons and neutral atoms. The plasma is defined as in a quasi-equilibrium state because of the continuous ionization and recombination rates of the species. For example, where the hydrogen containing molecule is water, the water dissociates into hydrogen ions, hydroxyl ions, oxygen ions, and electrons that, respond to the electromagnetic fields and will recombine in situ within the plasma chamber to reform neutral atoms and molecules of H2O (water), H2 (molecular hydrogen), and O2 (molecular oxygen). The extraction of the hydrogen is accomplished by guiding the charged ions with electric and magnetic fields to the extraction port. This is within the bounds of the present invention.

[0059] Ideally, the hydrogen containing molecule is fully dissociated within the plasma chamber to provide an outlet stream that comprises the hydrogen species and the non-hydrogen species in the absence of any residue of the hydrogen containing molecule of the feed. However, the skilled person will appreciate that depending on operating conditions, full dissociation may not occur and the outlet stream may contain some amount of the hydrogen containing molecule. To increase conversion efficiency, a portion of the outlet stream may be recycled to the inlet. Alternatively , or additionally, multiple units of the apparatus may be arranged in series with the outlet of one apparatus feeding into the inlet of a subsequent apparatus.

[0060] Further to the above, and as will be discussed below7, the apparatus preferably comprises separation means to produce two outlet streams a first hydrogen rich outlet stream comprising a substantially pure stream of the hydrogen species or molecular hydrogen and a second hydrogen poor outlet stream comprising non-hydrogen species (noting that some amount of hydrogen may carry over into the hydrogen poor stream). In such cases, it is preferred that the separation means also directs any residual hydrogen containing molecule into the hydrogen poor stream so that this stream can be further processed to convert residual hydrogen containing molecule by either recycling this stream to the inlet of the plasma chamber or feeding this stream into a second sequential apparatus for additional processing.

[0061] Throughput and efficiency of the system can also be enhanced by arranging multiple trains of the apparatus in parallel.

[0062] Without being bound by theory, the present inventors consider that the electromagnetic frequency destabilises covalently bonded hydrogen in the hydrogen containing molecules so that they are more likely to disassociate in the plasma.

[0063] In a preferred form, the at least one electromagnetic frequency is a radiofrequency. A radiofrequency is an electromagnetic frequency between about 10 kHz to 300Ghz.

[0064] In a preferred form, said plasma is exposed to two different electromagnetic frequencies wherein the first frequency has a higher frequency than the second frequency . Preferably, said hydrogen species and said non-hydrogen species are at least partially separated by their different responses to the two electromagnetic frequencies.

[0065] The present inventors consider that, the non-hydrogen species will respond more to lower frequency electromagnetic radiation and will be more likely to concentrate in a region closer to the source of this lower frequency. By contrast, the hydrogen species will respond more to higher frequency electromagnetic radiation and will be more likely to concentrate in a region closer to the source of this higher frequency. In this way, the provision of two or more frequencies of electromagnetic radiation can be used as a separation means to facilitate a hydrogen rich outlet stream and a hydrogen poor outlet stream.

[0066] Separation of the species within the plasma chamber is useful not just because it minimises the amount of purification required of the hydrogen species and of the molecular hydrogen by removing at least a proportion of the non-hydrogen species at an early stage but also because it limits the cross-reaction of hydrogen and non-hydrogen species before they exit the outlet chamber so as to minimise reformation of the desired ionic hydrogen species with non-hydrogen species.

[0067] In this context, it may further be provided that said plasma chamber further comprises a permeable grid that separates the chamber into a first, space and a second space thus providing for further separation between the hydrogen species and the non-hydrogen species.

[0068] In a. preferred form, where the hydrogen containing molecule is water and the nonhydrogen species is an oxygen species, said first frequency is -400kHz (more precisely 397kHz) and said second frequency is -40 kHz (more precisely 37kHz). However, the skilled person will appreciate that different frequencies may be employed for other hydrogen containing molecules.

[0069] In embodiments in which multiple plasma chambers are used, either in series or in parallel, a single RF match pair and RF generator pair, one for high frequency and one for low frequency can provide the RF frequency requirements to multiple chambers to reduce the cost of the overall system.

[0070] In a preferred embodiment of the present invention, the method further comprises a magnet located beyond the outlet of the chamber which at least partially separates the hydrogen species from the non-hydrogen species.

[0071] As discussed above, separating the species is important to obtaining pure molecular hydrogen.

[0072] In one embodiment, said magnet forms part, of a laval nozzle that concentrates the hydrogen species to the periphery' of the nozzle and the non-hydrogen species at an inner portion of the nozzle as they exit the outlet.

[0073] Figure 5 displays a laval nozzle 500 for use in the present invention. In this Figure it can be seen that feeding the plasma 502 to a magnetic laval nozzle 500 with a “pinching magnetic field” accelerates separation of hydrogen and. oxygen species 504, 506. This is a refinement on the concept of a mechanical laval nozzle whereby the magnetic field is pulsed on - thus forcing the ions closer together - gaining energy and then pulsed-off- allowing relaxation of the imparted energy - forcing the smaller ionic species (e.g. the hydrogen species) to the periphery of the nozzle and thus achieving more efficient separation.

[0074] In one embodiment, said magnet forms part of an arrangement that bends the flight path of the non-hydrogen species and the hydrogen ion species differentially as they exit the outlet so that they are at least partially separated. Figure 2 displays an application of this embodiment.

[0075] This separation technique takes advantage of the differences in molecular weight and ionic charge to separate the ions with a bending magnet. The H ions will change their flight path more readily than larger ions of the non-hydrogen species and thus move into a separate exit path. The present inventors envision this as a stand-alone separation method or as an addon enhancement to the Dual-Frequency, In-situ Separation Chamber.

[0076] In another embodiment, the method further comprises a catalyst located outside the plasma which enhances formation of molecular oxygen and / or molecular hydrogen from the oxygen species or the hydrogen species respectively. Preferably, the catalyst is located beyond the outlet of the chamber.

[0077] Catalysts, located outside the plasma, can be used to selectively force either H or nonhydrogen ions to bond together preferentially thus further purifying the hydrogen species and / or the molecular hydrogen from non-hydrogen contamination.

[0078] Any suitable catalyst can be used such as platinum, salts and metals, zinc chromite, or other metal oxides, among others. Gas phase catalysts may also be employed effectively.

[0079] In a further embodiment, the present inventors contemplate a further separation technique wherein a magnet rotating at a high rate of speed on the exit shaft just outside the plasma chamber outlet that would impart a rotational effect on the ions as they leave the plasma forcing the lighter hydrogen species to the edge of the shaft and leaving the heavier nonhydrogen species in the center. This could either be the main separation or a manner of refining the separation.

[0080] As would be clear to those skilled in the art, the present invention effectively contemplates three separate embodiments for the plasma chamber.

[0081] Dual-Frequency, in-situ separation

[0082] This embodiment is represented in Figure 1

[0083] Figure 1 provides an illustration of a plasma chamber 100 having an inlet 102, oxygen outlet 104, and a hydrogen outlet 106. The chamber comprises first means for generating a first source of electromagnetic radiation 108 and a second means for generating a second source of electromagnetic radiation 110 having a lower frequency than that of the first source. The chamber also includes a permeable grounded grid plane 111 which bifurcates plasma chamber 100 into first and second internal spaces 112, 114.

[0084] During operation a hydrogen containing molecule, such as water 116, is fed into plasma chamber 100 where it is subjected to the two the first and second sources of electromagnetic radiation. The water molecule is dissociated into hydrogen radicals and ions, hydroxy] radicals and ions, and potentially oxygen radicals and ions. The hydrogen species are responsive to the higher frequency and accumulate in the first internal space 112 and are removed via hydrogen outlet 106. The oxygen species are responsive to the lower frequency and accumulate in the second internal space 114 and are removed via oxygen outlet 104.

[0085] In this embodiment, the ionic species of H and O (where the hydrogen containing molecule is water) or other non-hydrogen species (in the case where the hydrogen containing molecule is not water) are formed in the plasma and then are automatically separated into separate spaces in the chamber due to their significant differences in the molecular weight and ionization charge. Specifically, the H ions selectively move into the higher frequency plasma because they have less inertia and can respond faster to the high frequency plasma. The O or other non-hydrogen ions separate into the slower frequency plasma for the exact opposite reason. The grid “forces” oxygen or other non-hydrogen plasma species to the portion of the chamber with the lower frequency and hydrogen plasma species to the portion of the chamber with the higher frequency.

[0086] Figure 2 depicts the plasma chamber 100 of Figure 1 but which includes a bending magnet 200 located beyond the outlet of the chamber to further separate oxygen and other nonhydrogen species that may be recovered from the hydrogen outlet. The magnetic field bends the flight path of hydrogen species from the outlet in a smaller flight radius than the oxygen species allowing for separation of the ion species. This process is generally illustrated in Figure 5 as discussed above.

[0087] Dual-Frequency Chamber without center ground plane

[0088] Figure 3 illustrates a plasma chamber 300 similar to that of Figure 2, but omitting the permeable grid ground plane. The apparatus comprises an inlet 302, a grounded outlet 304, first-means for generating a first source of electromagnetic radiation 306 and a second means for generating a second source of electromagnetic radiation 308 having a lower frequency than that of the first source.

[0089] The inventors are of the view that this arrangement will produce hydrogen similar to the embodiments of Figures I and 2, but that plasma chamber 300 may be less efficient and / or may require additional post-plasma treatment separation techniques. The advantage of this design is the simpler and less costly construction.

[0090] Single-Frequency Chamber

[0091] Figure 4 illustrates a plasma chamber 400 that comprises an inlet 402, a grounded outlet 404, means for generating a source of electromagnetic radiation 406, such as in the frequency range of from about 40 kHz to about 13.56 MHz, and an optional DC bias 408. Plasma chamber 400 includes no in-situ separation means, as per the plasma chambers illustrated in Figures 1 and 2, and is a simpler design. Generally, a post plasma separation process is required to obtain hydrogen.

[0092] Figures 6, 7, and 8 illustrate various embodiments of a system comprising a plurality of the aforementioned plasma chambers for generating molecular hydrogen.

[0093] Figure 6 illustrates an arrangement 600 in which three plasma chambers 602, 604, 606, are in stacked arrangement and are operated in parallel with first and second radio frequency sources 608, 610. A hydrogen containing molecule is fed into each of the chambers as a gas or vapor via inlets 612, 614, 616. Inlets 612, 614, 616 to each chamber may obtain the hydrogen containing molecule from a common gas source. Hydrogen species are removed via outlets 618, 620, 622 and oxygen species via outlets 624, 626, 628. Each chamber is grounded 630, 632, 634.

[0094] Inside the chamber, the hydrogen containing molecule is excited by the electromagnetic RF radiation and is broken down into a hydrogen species and a non-hydrogen species into a plasma state. Each chamber has its own RF supply or is connected to a common RF supply. In this embodiment, each chamber is illustrated using of two RF frequencies, a low frequency and a high frequency. As discussed previously, the non-hydrogen species will be drawn to RF#1 being the low frequency side of the chamber whereas the hydrogen species will be drawn towards RF#2 being the high frequency side of the chamber. The hydrogen species and nonhydrogen species can thus be separated into a hydrogen rich stream and a hydrogen poor stream which can be withdrawn through separate outlets of the chamber. The hydrogen poor stream may still contain some hydrogen containing molecule, in which case the hydrogen poor stream or a portion thereof may be recycled to the inlets of one or more of the chambers.

[0095] Three chambers running in parallel can process three times the input volume of gas and subsequently triple the output as compared with a single chamber.

[0096] Although Figure 6 illustrates an arrangement in which each chamber has its own RF supply, the skilled person will appreciate that each chamber could be connected to a common RF supply. In this arrangement, there is only a single RF generator for each of RF#1 and RF#2 and the power is multiplexed sequentially between each chamber.

[0097] Figure 7 illustrates another embodiment of a system 700 having three chambers 702, 704, 706 with inlets 708, 710, 712, hydrogen outlets 714, 716, and 718, and exhaust outlets 720, 722, 724 with first and second radio frequency sources 720, 722. Chambers 702, 704, 706 are arranged in stacked arrangement in which the exhaust of the hydrogen poor stream is provided as an inlet feed or a portion of an inlet feed for a subsequent chamber. This is useful for recovering any residual hydrogen containing molecule present in the hydrogen poor outlet stream. Each chamber is grounded 726, 728, 730.

[0098] The output of the first chamber will contain x% H gas sent to the hydrogen rich stream. (100%-x%) containing gas is collected and sent to the second chamber. The output from the second chamber will extract an additional y% of H gas species. The remaining (100%-y%-x% ) gas is collected and sent to the final chamber. In the final chamber we extract the final percentage of z% hydrogen and send the rest to exhaust.

[0100] In this example the single chamber extraction efficiency is x%. In the multiple extraction system, an additional y% and z% is collected. In principle the number of stages can increase as needed and economically viable. Final extraction efficiency is given by: 17 100% -V x(Q where n is the number of extraction chambers and x(i) is the extraction efficiency of each chamber.

[0101] Figure 8 illustrates an arrangement of three chambers 800, 802, 804 in linear arrangement and operated in series. Each chamber 800, 802, 804 has an inlet 806, 808, 810 and an outlet 812, 814, 818, with first and second radio frequency sources 820, 822. In this embodiment the exhaust gas from each chamber consisting of ionized molecules of H and remaining gaseous plasma species in the first chamber is separated by one of the aforementioned separation methods (bending magnets, laval nozzle, etc.) 824, 826, 828. Hydrogen ionized gas is separated and remaining gas molecules with molecular hydrogen species is fed forward to the next plasma chamber. In this way, by the final chamber, most (if not all) of the hydrogen containing molecules are converted to hydrogen and recovered from the system.

[0102] Although three chambers are illustrated in each embodiment, the skilled person will appreciate that additional chambers may be added to meet a target hydrogen demand or recovery. Examples

[0103] Example 1

[0104] This example reports the generation of hydrogen via a dual frequency system.

[0105] Water was fed into a chamber in a batch wise fashion by applying water droplets onto a receiving plate of an EVG810 low temperature plasma activation system. Nitrogen gas was then introduced into the chamber as a carrier gas. The chamber was then pumped down to a pressure of about 1 mbar. Dual frequency electromagnetic radiation comprising a low frequency source and a high frequency source was applied to convert water to plasma. The low frequency source was applied at a power of 50W and wavelength of 40 kHz. The high frequency source was applied at a power of 150W and frequency of 397 kHz. Optical emission spectroscopy results were obtained at 20 seconds and at 30 seconds.

[0106] The results are summarised in Tables 1 and 2 below. Table 1: Optical emission spectroscopy results at 20 seconds. Wavelength 309 315 337 357 391 427 486 656 777 844 Counts 1696 1712 1365 1019 1562 664 1225 4659 462 131 Table 2: Optical emission spectroscopy results at 30 seconds. Wavelength 309 315 337 357 391 427 486 656 777 844 Counts 1903 1618 1075 796 1264 521 1315 5436 513 145

[0107] The peak at 309 nm represents OH.

[0108] Peaks at 315, 337, 357, 391, and 427 nm represent N2.

[0109] Peaks at 486 and 656 nm represent hydrogen.

[0110] Peaks at 777 and 844 nm represent oxygen.

[0111] The results show successful conversion of water to a hydrogen containing plasma and increasing generation of hydrogen overtime.

[0112] Example 2

[0113] This example reports the generation of hydrogen via a single frequency system.

[0114] Water was fed into a chamber in a batch wise fashion by applying water droplets onto a receiving plate of an EVG810 low temperature plasma activation system. Experiments were conducted both with and without nitrogen gas as a carrier gas. The chamber was pumped down to a pressure of about 50 mbar. Electromagnetic radiation of was applied to convert water to plasma at a power of 350W. Different wavelengths were investigated from 357 kHz to 499 kHz. Optical emission spectroscopy results were obtained.

[0115] Figure 9 is a graph showing the proportion of hydrogen in the plasma versus the ratio of H:(0H + O). The graph illustrates that the proportion of hydrogen in the plasma increases with increasing generation of H ions and decreasing generation of other ions including ionized water and OH groups. That is, conditions that result in pure hydrogen ions minimize the presence of other species.

[0116] Figure 10 reports data from a series of experiments conducted at frequencies of 357, 401, 449, and 499 kHz, and that, the results show that there is an improvement in the average IF to (OH' and O2') ratio at the higher frequencies, and also an improvement in the spread of that ratio. In particular, the narrow range of ratios at the 499kHz frequency implies there is less parasitic ionization and recombination of ionized groups.

[0117] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

1. A method of generating molecular hydrogen comprising the steps of:(i) providing a plasma chamber having an inlet and an outlet;(ii) providing a feed of a hydrogen containing molecule through the inlet to a plasma in said plasma chamber wherein said plasma is exposed to at least one electromagnetic frequency whereby said hydrogen containing molecule is disassociated into a hydrogen species and at least one non-hydrogen species;(iii) removing said hydrogen species from the chamber at the outlet, and(iv) then forming molecular hydrogen from said hydrogen species.

2. A method according to claim 1, wherein the hydrogen containing molecule is selected from the group consisting of: water, a hydrocarbon, or ammonia.

3. A method according to claim 1, wherein said at least one electromagnetic frequency is a radiofrequency.

4. A method according to any one of the preceding claims, wherein said plasma is exposed to two different electromagnetic frequencies wherein the first frequency has a higher magnitude than the second frequency.

5. A method according to claim 4, wherein said hydrogen species and said non-hydrogen species are at least partially separated by their different responses to the two electromagnetic frequencies.

6. A method according to claim 5 wherein said chamber further comprises a permeable grid that separates the chamber into a first space and a second space, and wherein said method further comprises separating the hydrogen species into the first space and the nonhydrogen species into the second space.

7. A method according to any one of claims 4 to 6 wherein said first frequency is about 400kHz and said second frequency is about 40kHz.

8. A method according to any one of claims 1 to 7, further comprising a magnetic separator located at or downstream of the outlet of the chamber, and wherein the method further comprises magnetically separating at least a portion of the hydrogen species from the non-hydrogen species.

9. A method according to claim 8, wherein said magnetic separator forms part of a laval nozzle, and the step of magnetically separating at least the portion of the hydrogen species from the non-hydrogen species comprises concentrating the non-hydrogen species toward a centre of the nozzle and the hydrogen species toward an outer portion of the nozzle at an exit of the outlet.

10. A method according to claim 8, wherein said magnet separator differentially deflects the hydrogen species and the non-hydrogen species as they exit the outlet to separate at least a portion of the hydrogen species from the non-hydrogen species.

11. A method according to any one of claims 1 to 10 further comprising a catalyst located separate from the plasma, and the method further comprises contacting the catalyst with the hydrogen species and / or the non-hydrogen species to form molecular hydrogen and or a nonhydrogen containing molecule respectively.

12. A method according to claim 11 wherein the catalyst is located external to the plasma chamber.

13. An apparatus for generating molecular hydrogen from a hydrogen containing molecule, the apparatus comprising:a plasma chamber having an inlet and an outlet; andan electromagnetic radiation generator configured to generate one or more frequencies of electromagnetic radiation within the plasma chamber between the inlet and the outlet.

14. An apparatus according to claim 13, wherein the electromagnetic radiation generator is a radio frequency generator.

15. The apparatus according to claim 13 or 14, wherein the electromagnetic radiation generator is configured to generate electromagnetic radiation at two different frequencies, a first high frequency and a second low' frequency.

16. The apparatus of claim 15, wherein the apparatus further comprises one or more signal generators to generate signals for the first high frequency and second low frequency, and a multiplexer to provide a multiplexed signal of the first high frequency and second low frequency, and wherein the electromagnetic radiation generator(s) receives the multiplexed signal.

17. The apparatus of any one of claims 13 to 16, wherein the plasma chamber is cooled using the feed upstream of the inlet.

18. The apparatus of any one of claims 13 to 17, wherein said chamber further comprises a permeable grid that separates the chamber into a first, space and a second space.

19. The apparatus of any one of claims 13 to 18, further comprising a magnetic separator located at or downstream of the outlet of the chamber.

20. The apparatus of any one of claims 13 to 19 further comprising a catalyst located separate from the plasma.

21. The apparatus of claim 15, wherein said first frequency is about 400kHz and said second frequency is about 40kHz.

22. The apparatus of claim 19, wherein said magnetic separator forms part of a laval nozzle, and the magnetic separator is configured to concentrate the non-hydrogen species toward a centre of the nozzle and the hydrogen species toward an outer portion of the nozzle at an exit of the outlet.

23. The apparatus of claim 19, wherein said magnet separator is configured to differentially deflect the hydrogen species and the non-hydrogen species as they exit the outlet to separate at least a portion of the hydrogen species from the non-hydrogen species.

24. A system comprising the apparatus of any one of claims 13 to 23, wherein the apparatus comprises a plurality7 of plasma chambers arranged in series.

25. A system comprising the apparatus of any one of claims 13 to 23, wherein the apparatus comprises a plurality of plasma chambers arranged in parallel.

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