System and method for producing nitric oxide (NO)-enriched gas mixture, method of filtering and filter assembly to be applied therein

Abstract

The present invention relates to the field of producing nitric oxide (NO)-enriched gas mixtures. In the general aspect, the invention may be directed to a system for producing a nitric oxide (NO)-enriched gas mixture. The system may include: a first gas mixture supply unit configured to supply a first gas mixture, said first gas mixture comprising N2 and O2, wherein a volume ratio between N2 and O2 may be between 49:1 and 9:1; and at least one plasma reactor unit in fluid communication with the first gas mixture supply unit, wherein the at least one plasma reactor unit may be configured to receive the first gas mixture and to create an electric discharge to induce a plasma chemical conversion of at least a portion of the first gas mixture into NO, to produce the NO-enriched gas mixture.

Description

SYSTEM AND METHOD FOR PRODUCING NITRIC OXIDE (NO)- ENRICHED GAS MIXTURE, METHOD OF FIE TERING AND FILTER ASSEMBLY TO BE APPLIED THEREINCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 617,435, filed January 4, 2024; and U.S. Provisional Patent Application No. 63 / 666,175, filed June 30, 2024, the contents of which are all incorporated herein by reference in their entirety.FIELD OF THE INVENTION

[0002] The present invention relates to the field of producing nitric oxide (NO)-enriched gas mixtures. In particular, the present invention relates to the sub-field of producing NO and nitrogen (N2) gas mixtures for the treatment of medical conditions. Specifically, the system, assembly and methods of the present invention enable on-demand production of a pharmaceutical-grade NO and N2 gas mixture which is generated from air, and e.g., can be further pumped into one or more gas tanks, to be stored, transported, and used for inhalation when needed.BACKGROUND OF THE INVENTION

[0003] As known in the art, nitric oxide (NO) gas, and specifically mixtures of nitrogen (N2) and NO gas, are crucial to many biological systems and can be used to treat various medical conditions via pulmonary delivery. In particular, research has shown that nitric oxide therapy may aid in the treatment of pulmonary arterial hypertension (PAH). PAH is a potentially fatal condition characterized by increased blood pressure in the lungs caused by obstructions in lung arteries. Pharmacological treatment of PAH has not shown sufficient efficiency (about 50% of patients die in 2-5 years depending on the disease state). While the precise mechanisms of disease progression are not entirely clear, several factors were discovered as being implicated in the pathology of PAH. To wit, one of the most important mediators is Nitric Oxide (NO), a lack of which has been found to contribute to pulmonary artery vasoconstriction, vascular remodeling, and right ventricular failure associated with PAH pathology.

[0004] The vasodilator and anti-proliferative actions of NO (and mixtures of NO and N2) make it an attractive tool for pharmacological treatment of PAH. Administration of NO gasby inhalation has been shown to be beneficial to patients with PAH, particularly in children with congenital heart diseases. However, inhaled NO therapies are hampered by high costs, technical difficulties, and inconsistent patient response. Rapid withdrawal of inhaled NO therapy can also have deleterious effects with levels of oxygenation and pulmonary hypertension returning to levels worse than those seen prior to the commencement of therapy.

[0005] Nitric oxide has other possible applications, e.g., in gene therapy. Currently, genebased therapy is considered a powerful approach for treating pulmonary arterial hypertension. Genetic manipulation may be supplemental to standard pharmacotherapy or be used as a stand-alone treatment. However, genetic material must be transferred into cells and expressed at a desired level to provide therapeutic effect. NO, in turn, may play an important role in improving gene transduction in gene therapies for treating PAH.

[0006] Generation of NO, as well as mixtures of NO and N2 for medical applications, must be done within a stable and reliable process, in order to create mixtures that contain the gases of interest precisely in desired concentrations.

[0007] There are many known solutions for NO generation, in particular, appliable for medical purposes. These solutions may in general be divided into two groups: on-demand solutions, wherein the desired mixture is generated in advance and stored in a high-pressure gas tank; and on-site ones, wherein the desired mixture is generated from room air right before the usage. In both approaches, NO is commonly generated by using a controlled electric discharge to generate high-temperature plasma, thereby inducing a plasma chemical conversion, where oxygen and nitrogen in the input mixture react to produce nitric oxide.

[0008] Medical mixtures of NO and N2 are typically manufactured by mixing N2 with pure NO. Compliance with medical requirements for high purity of the final NO and N2 mixtures is considered to be technologically challenging and can result in complex and expensive techniques and methodologies. One of the major problems lies in that nitric oxide may be readily combined with oxygen (O2), e.g., from air, thereby forming toxic and cancerogenic nitrogen oxides gases such as nitrogen dioxide (NO2). NO2 has a very low limit of permissible concentration in inhalable gas, so it should be precisely controlled. Hence, it is crucial to reduce oxygen and NO2 content during the production of NO and N2 mixtures and / or to separate or filter it out therefrom afterwards.

[0009] The known solutions tend to fail to provide the stable NO concentration required for medical applications using plasma chemical conversion methods. Fluctuations in plasma power and air flow lead to changes in energy input and resultant NO concentration in the output flow. Another disadvantage lies in an excessive induction of “parasitic” chemical reactions, resulting in incidence of undesired side-components, like NO2 and O2, in the output mixture.SUMMARY OF THE INVENTION

[0010] Accordingly, there is a need for a system and method of producing NO-enriched gas mixture which would provide an improvement of the respective technological field by mitigating induction of parasitic chemical reactions and reducing the fraction of undesired side-components, such as NO2 and O2, in the NO-enriched gas mixture obtained by plasma chemical conversion, thereby resulting in further effective elimination of said sidecomponents in order to obtain a product gas mixture. Furthermore, there is a need for an effective method of selective filtering such undesired side-components from an NO-enriched gas mixture, as well as for a filter assembly to enable the said method.

[0011] In the general aspect, the invention may be directed to a system for producing a nitric oxide (NO)-enriched gas mixture. The system may include: a first gas mixture supply unit configured to supply a first gas mixture, said first gas mixture comprising N2 and O2, wherein a volume ratio between N2 and 02 may be between 49:1 and 9:1; and at least one plasma reactor unit in fluid communication with the first gas mixture supply unit, wherein the at least one plasma reactor unit may be configured to receive the first gas mixture and to create an electric discharge to induce a plasma chemical conversion of at least a portion of the first gas mixture into NO, to produce the NO-enriched gas mixture.

[0012] In another general aspect, the invention may be directed to a method of producing a nitric oxide (NO)-enriched gas mixture. The method may include: receiving, from a first gas mixture supply unit, a first gas mixture comprising N2 and O2, wherein a volume ratio between N2 and O2 is between 49:1 and 9:1; and transferring the first gas mixture through at least one plasma reactor unit, while generating an arc discharge therein to induce a plasma chemical conversion of at least a portion of the first gas mixture into NO, thereby producing the NO-enriched gas mixture.

[0013] In yet another general aspect, the invention may be directed to a filter assembly. The filter assembly may include at least one filtering module, including: a filtering modulehousing which defines an inner cavity therein; a pair of inlet and outlet channels coupled to the filtering module housing and being in fluid communication with each other via the inner cavity; and a cartridge disposed within the inner cavity, said cartridge including a filtering material that includes a metal catalyst. The filter assembly may further include at least one heating element configured to heat the cartridge; at least one sensor in operative communication with the outlet channel, said at least one sensor being configured to determine a concentration of at least one oxygen and / or gaseous oxide-containing component in a gas mixture flowing through the outlet channel; and at least one controller being in operative communication with said at least one heating element and with said at least one sensor, and configured to operate the heating element to set an operational temperature of the cartridge, based on the determined concentration of said at least one oxygen and / or gaseous oxide-containing component.

[0014] In yet another general aspect, the invention may be directed to a method of filtering a gas mixture. Said method of filtering may include: receiving a gas mixture comprising at least one oxygen and / or gaseous oxide-containing component (e.g., O2 and / or NO2); and passing the gas mixture through the filter assembly as defined in another aspect of the present invention, to reduce the content of said at least one oxygen and / or gaseous oxide-containing component in the passing gas mixture, thereby obtaining the filtered gas mixture.

[0015] In some embodiments, the plasma reactor unit may include: a reaction chamber having an inlet channel and an outlet channel; a variable power supply in operative connection with a plurality of electrodes installed within the reaction chamber and configured to create an electric discharge thereacross upon application of a voltage by the power supply; wherein the plasma reactor unit may be configured to generate a gas flow of the first gas mixture through the reaction chamber via the inlet channel and the outlet channel to transfer the first gas mixture through a gap between the plurality of electrodes, while generating, by the variable power supply, the electric discharge thereacross, thereby producing the NO-enriched gas mixture. In some embodiments, transferring the first gas mixture through said at least one plasma reactor unit may further include generating a gas flow of the first gas mixture through the reaction chamber via the inlet channel and the outlet channel to transfer the first gas mixture through a gap between the plurality of electrodes, while generating, by the variable power supply, the electric discharge thereacross, thereby producing the NO-enriched gas mixture.

[0016] In some embodiments, the plasma reactor unit may further include a circulation blower in fluid communication with said inlet and outlet channels of the reaction chamber, thereby forming together with the reaction chamber a circulating contour; wherein the plasma reactor unit may be further configured to produce the NO-enriched gas mixture further by transferring at least a portion of the first gas mixture through the circulating contour. In some embodiments, transferring the first gas mixture through said at least one plasma reactor unit may further include transferring at least a portion of the first gas mixture through the circulating contour.

[0017] In some embodiments, said first gas mixture may include between about 90 and about 98% of N2; and between about 2 and about 10% of O2.

[0018] In some embodiments, the NO-enriched gas mixture may include between about 1000 and about 5000 ppm of NO.

[0019] In some embodiments, the NO-enriched gas mixture may further include about 89.95% N2 or more.

[0020] In some embodiments, the NO-enriched gas mixture may further include between about 350 and about 1000 ppm of NO2; and between about 0.45% and about 9.95% of O2.

[0021] In some embodiments, the system may further include a filter unit configured to receive the NO-enriched gas mixture and to remove at least a fraction of NO2 and / or O2 from the NO-enriched gas mixture flowing therethrough, thereby producing a product NO- enriched gas mixture.

[0022] In some embodiments, the method of producing NO-enriched gas mixture may further include transferring the NO-enriched gas mixture through the filter unit to remove at least a fraction of NO2 and / or O2 from the NO-enriched gas mixture flowing therethrough, thereby producing the product NO-enriched gas mixture.

[0023] In some embodiments, the product NO-enriched gas mixture may include about 98% N2 or more and between about 100 and about 200 ppm of NO.

[0024] In some embodiments, the filter unit may include at least one filtering module, including: a filtering module housing which defines an inner cavity therein; a pair of inlet and outlet channels coupled to the filtering module housing and configured so as to enable the NO-enriched gas mixture flow through the inner cavity, e.g., by being in fluid communication with each other via the inner cavity; and a cartridge disposed within the inner cavity, said cartridge comprising a filtering material including a metal catalyst configuredfor reducing NO2 to NO and undergoing oxidation upon exposure to O2 to form a metal oxide. The filter unit may further include at least one heating element configured to heat the cartridge up to an operational temperature.

[0025] In some embodiments, transferring the NO-enriched gas mixture through the filter unit may include: heating the cartridge up to an operational temperature by the at least one heating element; and transferring the NO-enriched gas mixture via the inlet and outlet channels through the heated cartridge.

[0026] In some embodiments, the operational temperature may be selected from the range of about 400-850 °C.

[0027] In some embodiments, the metal catalyst may include elemental copper or copper alloy.

[0028] In some embodiments, the filtering material may include one or more of granules, wires, rods, particles, mesh, fabric, and combinations thereof.

[0029] In some embodiments, the filtering material may have a specific surface area (SSA) of about 500 m2 / g.

[0030] In some embodiments, the cartridge may further include a spacing material, positioned so as to create gaps between portions of the filtering material.

[0031] In some embodiments, the spacing material may be made of an inert metal or metal alloy substantially remaining in the metal state upon exposure to O2.

[0032] In some embodiments, the inert metal or metal alloy may be stainless steel or stainless-steel alloy, respectively.

[0033] In some embodiments, the filtering module housing may have substantially cylindrical shape, the filtering material may be a mesh fabric, and the mesh fabric may be formed in a roll uniformly filling the inner cavity of the filtering module housing.

[0034] In some embodiments, the filter unit may further include a preheating module arranged inline prior to the at least one filtering module, and configured to preheat the NO- enriched gas mixture prior to passing the NO-enriched gas mixture through the at least one filtering module. In some embodiments, the method of producing NO-enriched gas mixture may further include, prior to passing the NO-enriched gas mixture through the at least one filtering module, preheating the NO-enriched gas mixture by transferring the NO-enriched gas mixture through the preheating module.

[0035] In some embodiments, the system may further include a second gas mixture supply unit configured to supply a second gas mixture, said second gas mixture may include about 90% N2 or more. The system may be further configured to dilute the NO-enriched gas mixture with said second gas mixture, prior to supplying the NO-enriched gas mixture to the filter unit. In some embodiments, the method for producing NO-enriched gas mixture may further include diluting the NO-enriched gas mixture with the second gas mixture, prior to supplying the NO-enriched gas mixture to the filter unit.

[0036] In some embodiments, the second gas mixture may further comprise about 10% of O2 or less.

[0037] In some embodiments, the first gas mixture supply unit may be a first nitrogen generator comprising a pressure swing adsorption (PSA) system and / or a membrane gas separation system. The first nitrogen generator may be configured to produce the first gas mixture from air.

[0038] In some embodiments, the method of producing NO-enriched gas mixture may further include supplying air to the first nitrogen generator to produce the first gas mixture.

[0039] In some embodiments, the second gas mixture supply unit may be a second nitrogen generator comprising a pressure swing adsorption (PSA) system and / or a membrane gas separation system. The second nitrogen generator may be configured to produce the second gas mixture from air.

[0040] In some embodiments, the method of producing NO-enriched gas mixture may further include supplying air to the second nitrogen generator to produce the second gas mixture.

[0041] In some embodiments, the system may further include: one or more sensors in operative communication with at least one of the first gas mixture supplying unit, second gas mixture supplying unit, plasma reactor unit, filter unit, or a fluid communication line therebetween, and configured to determine a concentration of at least one of NO, NO2, O2 and N2 in gas mixtures flowing therethrough; and a controller in operative communication with at least one of the first gas mixture supplying unit, second gas mixture supplying unit, plasma reactor unit, filter unit, and with said one or more sensors, wherein the controller is configured to control the operation of at least one of the first gas mixture supplying unit, second gas mixture supplying unit, plasma reactor unit, and filter unit based on an input from said one or more sensors.

[0042] In some embodiments, the one or more sensors comprise a first sensor, the first sensor being in operative communication with the plasma reactor unit and configured to determine a concentration of NO in the NO-enriched gas mixture. The controller may be configured to operate the variable power supply to change the voltage applied across the plurality of electrodes so as to keep the concentration of NO in the NO-enriched gas mixture between about 1000 and about 5000 ppm, based on the input from the first sensor.

[0043] In some embodiments, the method of producing NO-enriched gas mixture may further include receiving, by at least one controller, from at least one first sensor being in operative communication with the plasma reactor unit, a current concentration of at least one component in the NO-enriched gas mixture; and operating, by said at least one controller, the variable power supply to change the voltage applied across the plurality of electrodes so as to obtain a desired concentration of said at least one component in the NO-enriched gas mixture, based on the received current concentration. The at least one component may be selected from the list consisting of: NO, NO2, N2 and O2. The respective desired concentration may be between about 1000 and about 5000 ppm of NO, between about 350 and about 1000 ppm of NO2, about 89.95% of N2 or more, and between about 0.45 and about 9.95% of O2.

[0044] In some embodiments, said one or more sensors may include a second sensor, the second sensor being in operative communication with the filter unit and configured to determine a concentration of O2 and / or NO2 in the product NO-enriched gas mixture. The controller may be further configured to operate the heating element to increase the operational temperature when the determined concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

[0045] In some embodiments, the method of producing NO-enriched gas mixture may further include receiving, by at least one controller, from at least one second sensor being in operative communication with the filter unit, a current concentration of O2 and / or NO2 in the product NO-enriched gas mixture; and operating, by said at least one controller, the heating element to increase the operational temperature when the received current concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

[0046] In some embodiments, the filter unit may include at least two filtering modules arranged successively, and the second sensor may be in the operative communication with the filter unit and may be configured to determine a concentration of O2 and / or NO2 in a gasmixture obtained after passing the NO-enriched gas mixture through a first of at least two filtering modules. The controller may be further configured to operate the heating element to increase the operational temperature when the determined concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

[0047] In some embodiments, the method of producing NO-enriched gas mixture may further include: receiving, by at least one controller, from the at least one second sensor being in operative communication with the filter unit, e.g., in operative communication with the outlet channel of a first of said at least two filtering modules, a current concentration of O2 and / or NO2 in a gas mixture obtained after passing the NO-enriched gas mixture through the first of at least two filtering modules; and operating, by said at least one controller, the heating element to increase the operational temperature when the received current concentration of O2 and / or NO2, respectively, exceeds the predefined concentration threshold.

[0048] In some embodiments, the predefined concentration threshold may be 5 ppm for O2 and 0.1 ppm for NO2, respectively.

[0049] In some embodiments, the controller may be further configured to provide a warning indication when at least one of the following conditions is met: (a) the operational temperature has reached a predefined temperature limit; (b) a rate of change of the determined concentration of O2 and / or NO2 with respect to an increase of the operational temperature gets below a predefined rate-of-change threshold. In some embodiments, the method of producing NO-enriched gas mixture may further include providing a warning indication when at least one of the abovementioned conditions is met.

[0050] In some embodiments, the system may further include a gas tank refilling station including at least one high pressure compressor positioned inline after the filter unit, and configured to compress the product NO-enriched gas mixture. Said gas tank refilling station may include means to fill a gas tank with the compressed product NO-enriched gas mixture.

[0051] In some embodiments, the method of producing NO-enriched gas mixture may further include compressing the product NO-enriched gas mixture by said at least one high pressure compressor positioned inline after and in fluid communication with the filter unit; and filling the gas tank with the compressed product NO-enriched gas mixture.

[0052] In some embodiments of the filter assembly, the metal catalyst may be configured for reducing NO2 to NO and undergoing oxidation upon exposure to O2 to form a metal oxide.

[0053] In some embodiments of the filter assembly, the at least one controller may be further configured to operate the heating element to increase the operational temperature of the cartridge when the determined concentration of said at least one oxygen and / or gaseous oxide-containing component exceeds a predefined concentration threshold.

[0054] In some embodiments of the filter assembly, the at least one controller may be further configured to operate the preheating module to preheat a gas mixture transferred through the filter assembly.

[0055] In some embodiments, the filter assembly may further include an external housing having a thermally insulated inner space therein. In such embodiments, the filtering module housing may be thermally conductive; and the at least one filtering module and the at least one heating element may be disposed within the thermally insulated inner space.

[0056] In some embodiments of the filter assembly, the at least one controller may be further configured to provide a warning indication when at least one of the following conditions is met: (a) the operational temperature has reached a predefined temperature limit; (b) a rate of change of the determined concentration of said at least one oxygen and / or gaseous oxide- containing component with respect to an increase of the operational temperature gets below a predefined rate-of-change threshold.

[0057] In some embodiments of the filter assembly, said at least one oxygen and / or gaseous oxide-containing component may be O2 and / or NO2.BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0059] Fig. 1 is a graph depicting function from a fraction of O2 in an input gas mixture subjected to plasma chemical conversion to a fraction of NO and NO2 in the respective output mixture, according to some embodiments of the present invention;

[0060] Fig. 2A is a block diagram, depicting a system for producing NO-enriched gas mixture, according to some embodiments of the present invention;

[0061] Fig. 2B is a block diagram, depicting a plasma reactor unit of the system for producing NO-enriched gas mixture, according to some embodiments of the present invention;

[0062] Fig. 2C is a block diagram, depicting a filter unit of the system for producing NO- enriched gas mixture, according to some embodiments of the present invention;

[0063] Fig. 2D is a block diagram, depicting a cartridge regeneration unit of the system for producing NO-enriched gas mixture, according to some embodiments of the present invention;

[0064] Fig. 3A is an isometric view of the filter unit of the system for producing NO- enriched gas mixture, according to some embodiments of the present invention;

[0065] Fig. 3B is another isometric view of the filter unit of the system for producing NO- enriched gas mixture, according to some embodiments of the present invention;

[0066] Fig. 3C is a front view of the filter unit of the system for producing NO-enriched gas mixture, according to some embodiments of the present invention;

[0067] Fig. 3D is a back view of the filter unit of the system for producing NO-enriched gas mixture, according to some embodiments of the present invention;

[0068] Fig. 3E is a side view of the filter unit of the system for producing NO-enriched gas mixture, according to some embodiments of the present invention;

[0069] Fig. 3F is an isometric view with a broken-out section of the filtering module of the filtering unit, according to some embodiments of the present invention;

[0070] Fig. 3G is an isometric view with a broken-out section of the filtering module of the filtering unit (without a cartridge), according to another embodiment of the present invention;

[0071] Fig. 4A is a microscopic image of the copper oxide layer on the surface of a standard mesh fabric filtering material made of copper;

[0072] Fig. 4B is another microscopic image of the copper oxide layer on the surface of a standard mesh fabric filtering material made of copper;

[0073] Fig. 5A is a graph depicting estimation of O2 concentration in the gas mixture flowing through the cartridge, measured along the length of the cartridge, with the cartridgehaving a copper oxide layer of a certain thickness, when the operational temperature is 550 °C, according to some embodiments of the present invention;

[0074] Fig. 5B is a graph depicting estimation of O2 concentration in the gas mixture flowing through the cartridge, measured along the length of the cartridge, with the cartridge having a copper oxide layer of a certain thickness, when the operational temperature is 600 °C, according to some embodiments of the present invention;

[0075] Fig. 5C is a graph depicting estimation of O2 concentration in the gas mixture flowing through the cartridge, measured along the length of the cartridge, with the cartridge having a copper oxide layer of a certain thickness, when the operational temperature is 650 °C, according to some embodiments of the present invention;

[0076] Fig. 6A is a time graph depicting a monitored concentration of NO and NO2 in a product NO-enriched gas mixture during 10-hour operating cycle of the system for producing NO-enriched gas mixture (total operation time - 24 hours), according to some embodiments of the present invention;

[0077] Fig. 6B is a time graph depicting (i) a concentration of O2 monitored before and after filtration of the NO-enriched gas mixture; and (ii) a temperature of a preheating module, during 10-hour operating cycle of the system for producing NO-enriched gas mixture (total operation time - 24 hours), according to some embodiments of the present invention;

[0078] Fig. 6C is a time graph depicting a monitored concentration of NO and NO2 in a product NO-enriched gas mixture during 10-hour operating cycle of the system for producing NO-enriched gas mixture (total operation time - 130 hours), according to some embodiments of the present invention;

[0079] Fig. 6D is a time graph depicting (i) a concentration of O2 monitored before and after filtration of the NO-enriched gas mixture; and (ii) a temperature of a preheating module, during 10-hour operating cycle of the system for producing NO-enriched gas mixture (total operation time - 130 hours), according to some embodiments of the present invention;

[0080] Fig. 7A is a time graph depicting an operational temperature and CO2 concentration in the output of the filter unit during a cartridge regeneration cycle, according to some embodiments of the present invention;

[0081] Fig. 7B is a time graph depicting a CO2 concentration in the output of the filter unit and calculated mass of O2 and recovered Cu that were obtained after reducing copper oxideduring a cartridge regeneration cycle, according to some embodiments of the present invention;

[0082] Fig. 8A is an image depicting a comparison of a standard mesh fabric filtering material made of copper and an improved mesh fabric filtering material made of copper, according to some embodiments of the present invention;

[0083] Fig. 8B is an image depicting a microscopic 3D scan of the improved mesh fabric filtering material made of copper, according to some embodiments of the present invention;

[0084] Fig. 9 is a schematic illustration of a cartridge of a filtering module, the cartridge including a roll having alternating layers of filtering and spacing materials, according to some embodiments of the present invention;

[0085] Fig. 10A is a flow diagram depicting a method for producing NO-enriched gas mixture, according to some embodiments of the present invention.

[0086] Fig. 10B is a flow diagram depicting a method for producing NO-enriched gas mixture, according to some other embodiments of the present invention.

[0087] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0088] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0089] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. Some features or elementsdescribed with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated.

[0090] Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, “processing,” “computing,” “calculating,” “determining,” “establishing”, “analyzing”, “checking”, “choosing”, “selecting”, “omitting”, “monitoring” or the like, may refer to operation(s) and / or process(es) of a controller, computer, computing platform, computing system, or other electronic computing device, that manipulates and / or transforms data represented as physical (e.g., electronic) quantities within the computer’s registers and / or memories into other data similarly represented as physical quantities within the computer’s registers and / or memories or other information non-transitory storage medium that may store instructions to perform operations and / or processes.

[0091] Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. The term “set” when used herein may include one or more items.

[0092] As used herein, the term "fluid communication" refers to a path which allows fluid (e.g., a gas) to flow between two components of the system of the present invention, wherein said two components can be directly or indirectly joined to each other. Similarly, as used herein, the terms "fluidly coupled" or "fluidly connected" are interchangeable, and refer to a connection between two components that allows fluid to flow from one component to the other, wherein said connection may be direct or indirect via an intermediate components enabling fluid flow therethrough (such via one or more lines).

[0093] In the context of present invention, the terms “filter unit” and “filter assembly” shall be understood as follows.

[0094] “Filter unit” refers to the component of the system for producing NO-enriched gas mixture, wherein this component does not necessarily comprise a controller, although may be controlled by one. E.g., the system may comprise a single controller (or controlling module) that is used for controlling the operation of other units of the system as well (e.g., the operation of the plasma reactor unit).

[0095] “Filter assembly”, in turn, is considered as a stand-alone device, comprising its own controller, although such a controller may be used to apply the same program instructions as the “general” controller of the system for producing NO-enriched gas mixture. It should further be understood that, when comprising its own controller, filter unit may represent the same device as a filter assembly, hence these terms shall be configured equivalent. It should be appreciated that filter assembly, as a stand-alone solution, may be applied for filtering various types of oxygen and / or gaseous oxide-containing components other than NO2 and / or O2, from gas mixtures other than NO-enriched gas mixture, therefore, its application for filtering NO2 and / or O2 from NO-enriched gas mixtures, as described in detail below with reference to “filter unit” as to the component of the system for production of NO-enriched gas mixture, shall be considered a non-limiting example of its possible application.

[0096] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, concurrently, or iteratively and repeatedly.

[0097] The concept of the present invention is further discussed with reference to Fig. 1.

[0098] Fig. 1 is a graph depicting function from a fraction of O2 in an input gas mixture subjected to plasma chemical conversion to a fraction of NO and NO2 in the respective output mixture, according to some embodiments of the present invention.

[0099] It was determined empirically by the inventor that, using the plasma chemical conversion method, generation of NO gas from input gas mixture comprising N2 and O2, depends on the fraction of O2 in the input mixture differently than the generation of NO2. In particular, the most tangible difference can be seen when the volume ratio between N2 and O2 is kept between 49:1 and 9:1, respectively (e.g., when the input gas mixture comprises between about 90 and about 98% of N2; and between about 2 and about 10% of O2, more preferably, between about 4 and about 7% of O2), as shown in the graph of Fig. 1.

[0100] Since the main goal of NO-enriched gas mixture production is to maximize the production of the target gas - NO, while minimizing the production of any residual component, such as NO2, by providing the input mixture having O2 and N2 content in the above-indicated range, process of production NO-enriched gas mixture may be significantly improved. The effect of such an improvement is further accentuated by the significant facilitation of the subsequent stages of producing product NO-enriched gas mixture, e.g.,appliable for medical applications. In particular, this facilitation applies, among other things, to the filtering stage, where all the residual components (such as NO2 and O2) must be selectively removed from the mixture, i.e., with a minimal effect on the concentration of the desired components therein (such as NO and N2), which is considered a technologically challenging task.

[0101] The achieved effect may be premised by the following aspects of the N O and N O2 formation mechanisms. To generate NO, it is first needed to obtain single atoms of N by dissociation of N2. Dissociation of nitrogen requires comparatively high energy application (about 10 eV), hence, in practice, the obtained concentration of N atoms is quite low. To perform N + O reaction effectively, comparatively small oxygen concentration is needed, as the competitive N + N reaction is slower because of low N atom concentration. As a result, experiments demonstrate significantly higher efficiency of NO generation when O2 concentration in the input gas mixture is up to approximately 4%.

[0102] NO2 formation mechanism is different from the mechanism of NO formation. NO2 is generated by oxidation of NO, hence, NO2 concentration is influenced by O2 concentration in the input mixture starting from the very low values thereof in a much more consistent manner. Therefore, as can be seen, concentration of oxygen between 2-10% is optimal, as NO generation is still highly effective, while NO2 generation is not that effective yet.

[0103] Reference is now made to Figs. 2A-2D, depicting system 100 for producing NO- enriched gas mixture and various components thereof, according to some embodiments of the present invention.

[0104] According to some embodiments of the invention, system 100 may be implemented as a hardware module, or a combination of a hardware module and a software module, configured for controlling the operation of hardware components.

[0105] As further described in detail herein, system 100 may be adapted to perform steps of the claimed method of producing NO-enriched gas mixture.

[0106] As shown in Figs. 2A-2D, arrows may represent a flow of one or more data elements to and from system 100 and / or among modules or elements of system 100. Some arrows have been omitted in Figs. 2A-2D for the purpose of clarity.

[0107] In some embodiments of the present invention, system 100 may include a first gas mixture supply unit, configured to supply a first gas mixture, said first gas mixturecomprising N2 and O2, wherein a volume ratio between N2 and Chis between 49:1 and 9:1. In some embodiments, the first gas mixture supply unit may be first nitrogen generator 21. First nitrogen generator 21 may be configured to produce the first gas mixture from air. Air may be supplied to first nitrogen generation 21, e.g., via air intake 10.

[0108] First nitrogen generator 21 may be of any type known in the art. E.g., generator 21 may include a pressure swing adsorption (PSA) system.

[0109] PSA is a method used to separate a gas from a mixture of gases (typically air) under pressure according to the molecular characteristics of the gas and affinity for an adsorbent material. PSA systems typically operate in a cyclical process in which beds containing an adsorbent are pressurized to operating pressure with a feed gas, impurities are removed from the feed gas to obtain the first gas mixture, and the beds are regenerated to remove impurities from the PSA system.

[0110] According to some embodiments, nitrogen generator 21 (i.e., a PSA system) comprises: an inlet region for receiving the feed air gas (optionally compressed air) from air intake 10; at least one treatment zone comprising at least one adsorbent bed (e.g., zeolites, activated carbon, and the like); and at least a first outlet region for recovering the first gas mixture into an output line of generator 21. Means can be provided for controlling the pressure in the treatment zone. According to some embodiments, in the treatment zone the feed of the compressed air is passed under pressure through the adsorbent bed (which attracts nitrogen more strongly than oxygen), and therefore a fraction of the nitrogen will stay in the bed, while the gas exiting the treatment zone (via a second outlet region) will be richer in oxygen than the air entering. When the bed reaches the limit of its capacity to adsorb nitrogen, it can be regenerated by decreasing the pressure, thus releasing the adsorbed nitrogen into the first outlet region.

[0111] According to alternative embodiments, nitrogen generator 21 may include a membrane gas separation system or device as is known in the art.

[0112] In some embodiments, nitrogen generator 21 may be configured to provide the first gas mixture comprising between about 90 and about 98% of N2; and between about 2 and about 10% of O2. In some further embodiments, nitrogen generator 21 may be configured to provide the first gas mixture comprising between about 94 and about 96% of N2; and between about 4 and about 6% of O2.

[0113] In some embodiments, system 100 may further include plasma reactor unit 30. Plasma reactor unit 30 may be in fluid communication with nitrogen generator 21, thereby, be configured to receive first gas mixture. Plasma reactor unit 30 may be further configured to create an electric discharge (a controlled electric discharge (e.g., arc discharge) to induce a plasma chemical conversion (by generating high-temperature plasma) of at least a portion of the first gas mixture into NO, to produce the NO-enriched gas mixture thereby.

[0114] Referring now to Fig. 2B, the aspects of plasma reactor unit 30 are discussed in detail.

[0115] In some embodiments, plasma reactor unit 30 may include reaction chamber 31 having an inlet channel and an outlet channel; variable power supply 32 in operative connection with a plurality of electrodes 31’ installed within reaction chamber 31 and configured to create an electric discharge thereacross upon application of a voltage by power supply 32. Plasma reactor unit 30 may be further configured to generate a gas flow of the first gas mixture through reaction chamber 31 via the inlet channel and the outlet channel to transfer the first gas mixture through a gap between the plurality of electrodes 31’, while generating, by variable power supply 32, the electric discharge thereacross, thereby producing the NO-enriched gas mixture. In some embodiments, plasma reactor unit 30 may have an input blower and / or an input control valve (not shown in figures) in order to generate and control a gas flow of the first gas mixture.

[0116] In some embodiments, plasma reactor unit 30 may further include circulation blower 34 in fluid communication with said inlet and outlet channels of reaction chamber 31, thereby forming together with reaction chamber 31 circulating contour 34’. Plasma reactor unit 31 may be further configured to produce the NO-enriched gas mixture further by transferring at least a portion of the first gas mixture through circulating contour 34’. Circulating contour 34’ may further include cooler 33, positioned before blower 34 and configured to decrease the temperature of the NO-enriched gas mixture (e.g., below 45 °C), since after plasma chemical conversion the temperature of the NO-enriched gas mixture is too high (e.g., above 200°C) for being recycled to reaction chamber 31 for additional conversion.

[0117] Accordingly, by receiving as an input the first gas mixture, comprising the abovementioned fraction of N2 and O2, plasma reactor unit 30 may operate in the improved and more efficient manner, thereby producing the NO-enriched gas mixture with the highestachievable difference in content of the desired components (e.g., NO) and residual components (e.g., NO2), as discussed with reference to Fig. 1 above.

[0118] Accordingly, in some embodiments, plasma reactor unit 30 may generate NO- enriched gas mixture, which may include between about 1000 and about 5000 ppm of NO (theoretical maximum of NO-concentration obtained by the claimed method may be around 30000 ppm (3%)). In some embodiments, a flow rate of a gas mixture transferred through plasma reactor unit 30 may be between about 0.1 and about 1.5 m3 / hour. In some embodiments, the flow rate of the gas mixture transferred through plasma reactor unit 30 may be between about 1 and about 1.2 m3 / hour. In some embodiments, the NO-enriched gas mixture may include about 89.95% N2 or more. In some further embodiments, the NO- enriched gas mixture may further include the following fraction of residual components: between about 350 and about 1000 ppm of NO2; and between about 0.45% and about 9.95% of O2.

[0119] It should be understood that the present invention is not limited to any specific configuration of plasma reactor unit 30, hence, any configuration of plasma reactor unit 30 known in the art may be applied herein, provided that the NO-enriched gas mixture generated thereby have the desired abovementioned content.

[0120] As mentioned above, the purpose of the plasma chemical conversion stage is to maximize the generation of NO, while minimizing the generation of NO2. However, for NO- enriched mixture obtained thereby, is not applicable for above-described medical applications, as the concentration of NO in it is too high and since it includes residual components.

[0121] In order to decrease the concentration of NO, it is suggested herein to admix second gas mixture, mainly consisting of N2, to previously obtained NO-enriched gas mixture, to dilute NO-enriched gas mixture so as to obtain the desired concentration of NO in it (e.g., between about 800 and about 900 ppm).

[0122] Referring now back to Fig. 2A, it is shown that, in some embodiments, system 100 may further include a second gas mixture supply unit configured to supply the second gas mixture, said second gas mixture including about 90% N2 or more. The second gas mixture may further include about 10% of O2 or less. Since Chis an undesirable component of the NO-enriched gas mixture, it may be more preferrable to have N2 content in the second gas mixture as high as possible (e.g., 99.2-99.99%) and O2 content, accordingly, as low aspossible (e.g., 0.01-0.8%). In some embodiments, the second gas mixture supply unit may be second nitrogen generator 22. Second nitrogen generator 22 may include a pressure swing adsorption (PSA) system and / or a membrane gas separation system, same as discussed with respect to first nitrogen generator 21. Accordingly, second nitrogen generator 22 may be further configured to produce the second gas mixture from air, which may be supplied via air intake 10.

[0123] It should be understood that the present invention is not limited to any specific configuration of first and / or second nitrogen generators 21 and 22, and any configuration of nitrogen generator known in the art may be applied herein, provided that the first and second gas mixtures generated thereby have the desired abovementioned content.

[0124] In some embodiments, system 100 may be further configured to dilute the NO- enriched gas mixture with said second gas mixture, prior to supplying the NO-enriched gas mixture further down the production line.

[0125] It shall be understood for the person skilled in the art that, in order to control the process of admixing the second gas mixture to the NO-enriched gas mixture, various known- in-the-art means shall be applied, e.g., additional control valves and blowers (not shown in the figures) to control the flow of second gas mixture and / or NO-enriched gas mixture, so as to obtain the desired concentration of N2 and / or NO in the resulting mixture, as discussed above.

[0126] As indicated above, to obtain the product NO-enriched gas mixture, e.g., NO- enriched gas mixture applicable for medical purposes, traces of residual components must be removed therefrom. However, to remove such residual components as NO2 selectively, while having minimal effect on the concentration of the desired component, such as NO, is considered a challenging task.

[0127] Existing methods for selective NO2 removal are based on the use of chemical reagents such as ascorbic acid carried and supported by, e.g., zeolite or silica gel. However, these methods are not applicable for the abovementioned purpose, as they are not selective enough to remove NO2 with insignificant or no effect on NO, and they furthermore do not provide for removal of O2 to the required extent.

[0128] Hence, the absence of the required solution in the art has motivated the development of a filter assembly (or unit) and method of filtering using the developed filter assembly, which would provide an improvement of the relevant technological field byincreasing efficiency of reducing oxygen and / or gaseous oxide-containing components from product mixtures. In particular, there is a need for a filter assembly (or unit) and method of filtering using the developed filter assembly, which would provide an improvement of the relevant technological field by increasing selectivity of reducing NO2 and / or O2 from the product mixture with insignificant or no effect on NO content therein.

[0129] Accordingly, in some embodiments, system 100 may further include filter unit 40, configured according to another general aspect of the present invention. Filter unit 40 may be configured to receive the NO-enriched gas mixture (e.g., the diluted NO-enriched gas mixture, as discussed above) and to remove at least a fraction of NO2 and / or O2 from the NO-enriched gas mixture flowing therethrough, thereby producing a product NO-enriched gas mixture.

[0130] Filter unit 40 is further discussed in detail with reference to Figs. 2C and 2D, which are block diagrams, depicting filter unit 40 and cartridge regeneration unit 70 of system 100, according to some embodiments of the present invention; and further with reference to Figs. 3A-3G, which are various views of a model of filter unit 40 and its components, according to some embodiments of the present invention.

[0131] In some embodiments, filter unit 40 may include at least one filtering module, more specifically, at least two filtering modules arranged successively. More specifically, filter unit 40 may include a plurality of first-stage filtering modules 42 (e.g., six first-stage filtering modules 42) in parallel connection with each other, and second- stage filtering module 42’ in successive connection with first-stage filtering modules 42, as shown in Figs. 3A-3E. Each of filtering modules 42 may include: filtering module housing 421 which defines inner cavity 421 A therein; a pair of inlet and outlet channels 422A, 422B coupled to filtering module housing 421 and configured so as to enable the NO-enriched gas mixture flow through inner cavity 421A; and cartridge 423 disposed within inner cavity 421A, said cartridge 423 comprising a filtering material comprising a metal catalyst configured for reducing NO2 to NO and undergoing oxidation upon exposure to O2 to form a metal oxide. Filter unit 40 may further include heating elements 43 configured to heat cartridges 423 of first-stage filtering modules 42 up to an operational temperature.

[0132] Second-stage filtering module 42’ may, in turn, include: filtering module housing 421, which defines inner cavity 421A’ therein; a pair of inlet and outlet channels 422A’, 422B’, coupled to filtering module housing 421’ and configured so as to enable the NO-enriched gas mixture flow through inner cavity 421A’, after passing first-stage filtering modules 42; and cartridge 423’ disposed within inner cavity 421A’, said cartridge 423’ comprising a filtering material comprising a metal catalyst configured for reducing NO2 to NO and undergoing oxidation upon exposure to O2 to form a metal oxide. Filter unit 40 may further include heating element 43’ configured to heat cartridge 423’ of second-stage filtering module 42’ up to an operational temperature.

[0133] As can be seen, filtering modules 42 and 42’ may have different configurations in respect of position of heating elements 43 and 43’, respectively.

[0134] E.g., in some embodiments, filter unit 40 may include external housing 44 having a thermally insulated inner space therein. Each of first-stage filtering modules 42 may have thermally conductive filtering module housing 421. In such embodiments, filtering modules 42 and heating elements 43 may be disposed within the thermally insulated inner space (e.g., having a layer of polymer, foam, fiberglass material and / or combinations thereof), thereby enabling the proper heating of all cartridges 423.

[0135] Second-stage filtering module 42’, in turn, may not have additional external housing. Instead, filtering module housing 421’ of filtering module 42’ may be thermally insulated (e.g., comprise thermal insulation layer 421B’), and heating element 43’ may be positioned in the inner cavity 421A’, e.g., circumferentially covering its inner surface (as shown in Fig. 3G).

[0136] It shall be understood that the provided embodiments of arrangement heating elements 43 and 43’ with respect to filtering module 42 and 42’, respectively, represent a non-exclusive example of such arrangements. Hence, the present invention is not limited in this regard. Furthermore, in some embodiments of the present invention, other known heating methods may be used herein (e.g., including usage of induction heating), hence, such embodiments should also be considered covered by the scope of the present invention.

[0137] In some embodiments, filter unit 40 may further include preheating module 41 arranged inline prior to first-stage filtering modules 42, and configured to preheat the NO- enriched gas mixture prior to passing the NO-enriched gas mixture through filtering modules 42. Preheating module 41 may include pipeline 411 covered by thermally insulated housing and having plurality of heating elements 412, configured to heat pipeline 411.

[0138] In some embodiments, the operational temperature for cartridges 423 and 423 ’ is selected from the range of about 400-850 °C.

[0139] It shall be understood that filter unit 40 may comprise a power source (not shown) in operative connection with heating elements 412, 43 and 43’ and with controller 60, and controller 60 may be configured to operate voltage and / or current of the power source to change the temperature of respective heating elements 412, 43 and 43’, thereby controlling the operational temperature of respective cartridges. It shall be understood that any appropriate types of heating elements that are known in the art may be used as heating elements 412, 43 and 43’ herein, and the present invention shall not be considered limited in this regard.

[0140] In some embodiments, the metal catalyst of cartridges 423 and 423’ may include elemental copper or copper alloy.

[0141] In some embodiments, the filtering material of cartridges 423 and 423’ may include one or more of granules, wires, rods, particles, mesh, fabric, and combinations thereof.

[0142] In some embodiments, filter unit 40 may have configuration, as indicated in Figs. 3A-3E, which is provided for clarification purposes only and shall not be considered an exclusive example of configuration. In such configuration, preheating module 41, six first- stage filtering modules 42 and second-stage filtering module 42’ are compactly arranged on the stand (not numbered). First- stage filtering modules 42 are arranged circumferentially, with six heating elements 43 respectively positioned between adjacent filtering modules 42 and extending along their full length. Preheating module 41 is positioned in the center of the circumferential arrangement of filtering modules 42, and extends in the same direction as modules 42. The entire arrangement of preheating module 41, filtering modules 42, and heating elements 43 is disposed inside the thermally insulated inner space of external housing 44. Second-stage filtering module 42’, in turn, is positioned under the external housing 44, and extends in the same direction.

[0143] Filter module 40 is arranged so as to receive the diluted NO-enriched gas mixture via an inlet of pipeline 411. Pipeline 411 enters the housing of the preheating module 41 from one side, goes through the housing where it is heated by heating elements 412, and exits preheating module 41 from the other side. Further in the flow direction, pipeline 411 is connected with six inlet channels 422A of respective first-stage filtering modules 42, to direct the gas flow through respective inner cavities 421 A. Outlet channels 422B, in turn, are connected via a pipeline with inlet channel 422A’ of second stage filtering module 42’,thereby directing the gas flow through inner cavity 421 A’ thereof. Lastly, filtered gas mixture (e.g., the product NO-enriched gas mixture) may be outputted via outlet channel 422B’, after passing through inner cavity 421 A’ of second-stage filtering module 42’.

[0144] The suggested filer module (or assembly) provides for increasing efficiency of reducing oxygen and / or gaseous oxide-containing components from the product mixture, in particular for high selectivity of reducing NO2 and / or O2 from the NO-enriched gas mixture with insignificant or no effect on NO content therein, by using reactions of metal catalyst configured for reducing NO2 to NO and undergoing oxidation upon exposure to O2 to form a metal oxide (e.g., metal catalyst can be made of or including elemental copper or copper alloy) with NO2 and / or O2 at high operational temperatures (e.g., about 400-850 °C).

[0145] E.g., hot cartridge 423 or 423’ may remove O2 and NO2 from the NO-enriched gas mixture, consisting of NO, NO2, O2 and N2 by inducing the following chemical reactions:Cu + 1 / 2 O2= CuOCu + NO2= NO + CuO

[0146] The following parasite reaction that may also take place, has higher activation energy than reactions above and thus in optimal temperature region is practically negligible:NO + Cu = N + CuO.

[0147] It should be noted that, in order to high efficiency of filtering, yet another aspect is important. During active operation of filter unit 40, surface of filtering material of cartridge 423 and 423’ is getting covered with a solid layer (or even several layers) of CuO (as shown in Figs. 4A and 4B), hindering gas diffusion to metal surface, thereby affecting the further conduction of the required chemical reaction. Consequently, with progressive exhaustion of filtering capacity of cartridge 423 and / or 423’ (cartridge degradation), the concentration of undesired components (e.g., O2 and NO2) in the output gas mixture (e.g., in product NO- enriched gas mixture) starts increasing. This process is unacceptable, since if such impure gas mixture will be admixed to the mixture of a good quality that was obtained prior the cartridge degradation, it can make the product mixture unacceptable for further medical usage.

[0148] As was empirically determined by the inventors, cartridge degradation can be compensated by increasing the operational temperature of preheating module 41 and / or cartridges 423 and 423 ’ .

[0149] To estimate how filtering capacity of cartridge 423 and 423’ is affected by different oxide layer thickness, semi-empirical estimation of oxygen concentration in gas mixture flowing through the cartridge in the presence of copper oxide layer of predefined thickness thereon has been done with respect to the cartridge length. Results of the semi- empirical estimation of oxygen concentration along cartridge length for different operational temperatures and different copper oxide layer thicknesses are shown in Figs. 5A-5C, wherein Fig. 5A shows estimation for operational temperature of 550 °C, Fig. 5B - 600 °C, and Fig. 5C - 650 °C, respectively. As can be seen, thickness of copper oxide layer dramatically affects the reaction rate, as the gas diffusion has to be performed through the oxide layer. This effect can be compensated by increasing operational temperature. For example, curve for 10 pm oxide layer thickness at 650 °C almost equivalent to 0 pm (new cartridge) curve at 550 °C.

[0150] Although system 100 may be operated manually, in order to mitigate the negative effect of cartridge degradation more efficiently, as well as to increase the efficiency of the NO-enriched mixture production process overall, the usage of automatic monitoring and control may be used, which is described in detail further below.

[0151] In some embodiments, system 100 may further include sensor 61 in operative communication with first nitrogen generator 21 or a fluid communication line between first nitrogen generator 21 and plasma reactor unit 30, and configured to determine a concentration of at least one of O2 and N2 in the first gas mixture.

[0152] In some embodiments, system 100 may further include sensor 62 in operative communication with second nitrogen generator 22 or a fluid communication line between second nitrogen generator 22 and a point in fluid communication line where the second gas mixture is admixed to the first gas mixture, and configured to determine a concentration of at least one of O2 and N2 in the second gas mixture.

[0153] In some embodiments, system 100 may further include sensor 63 in operative communication with plasma reactor unit 30 or a fluid communication line between plasma reactor unit 30 and the point in fluid communication line where the second gas mixture is admixed to the first gas mixture, and configured to determine a concentration of at least one of NO, NO2, O2 and N2 in the NO-enriched gas mixture.

[0154] In some embodiments, system 100 may further include sensor 64 in operative communication with filter unit 40 or a fluid communication line between the point in fluidcommunication line where the second gas mixture is admixed to the first gas mixture and filter unit 40, and configured to determine a concentration of at least one of NO, NO2, O2 and N2 in the NO-enriched gas mixture after dilution.

[0155] In some embodiments, system 100 may further include sensor 65 in operative communication with filter unit 40 or an outlet fluid communication line thereof, and configured to determine a concentration of at least one of NO, NO2, O2 and N2 in the product NO-enriched gas mixture.

[0156] In some embodiments, system 100 may further include sensor 66 in the operative communication with filter unit 40, in particular, with fluid communication line between first- stage filtering modules 42 and second-stage filtering module 42’, and configured to determine a concentration of O2 and / or NO2 in a gas mixture obtained after passing the NO- enriched gas mixture through first- stage filtering module 42.

[0157] It should be appreciated that sensors 61-66 may be or may include any known types of sensors, configured to measure concentration of the above-indicated components in gas mixtures, e.g., electrochemical gas sensors. The present invention should not be considered limited in regard to the types of sensors used.

[0158] In some embodiments, system 100 may further include controller 60 in operative communication with first nitrogen generator 21, second nitrogen generator 22, plasma reactor unit 30, filter unit 40, and with sensors 61-66. Controller 60 may be configured to control the operation of first nitrogen generator 21, second nitrogen generator 22, plasma reactor unit 30, and filter unit 40 based on an input from respective sensors 61-66.

[0159] In some embodiments, controller 60 may be, for example, a central processing unit (CPU) processor, a chip or any suitable computing or computational device. Controller 60 (or, alternatively, one or more controllers or processors, possibly across multiple units or devices) may be configured to request, receive, analyze, calculate and produce various types of data and signals, as well as execute various portions of instruction code, in order to carry out respective steps of methods described herein.

[0160] In particular, in some embodiments, sensor 63 may be configured to determine a concentration of NO in the NO-enriched gas mixture; and controller 60 may be further configured to operate variable power supply 32 to change the voltage applied across the plurality of electrodes 31’ so as to keep the concentration of NO in the NO-enriched gas mixture between about 1000 and about 5000 ppm, based on the input from sensor 63 (thedetermined concentration), e.g., to increase the voltage when the concentration is lower than 1000 ppm and to decrease the voltage when the concentration is higher than 5000 ppm. In some additional or alternative embodiments, controller 60 may be further configured to operate blower 34 to change the flow of the NO-enriched gas mixture in circulating contour 34’, based on the input from sensor 63, e.g., to decrease the flow when the concentration is lower than 1000 ppm and to increase the flow when the concentration is higher than 5000 ppm.

[0161] In some embodiments, controller 100 may be in operative communication with the control valve (not shown) that controls the dilution of the NO-enriched gas mixture by second gas mixture (e.g., by controlling volume of the NO-enriched gas mixture and / or second gas mixture during dilution thereof). Thereby, based on the input from sensors 61, 62 and 63, controller 100 may control the process of plasma chemical conversion and the subsequent dilution of the NO-enriched gas mixture, thereby providing the desired content of the NO-enriched gas mixture prior to passing it to filter unit 40. The content of the diluted NO-enriched gas mixture before filtering may be further controlled by controller 100, based on the input from sensor 64.

[0162] In some embodiments, sensor 65 may be configured to determine a concentration of O2 and / or NO2in the product NO-enriched gas mixture; and controller 60 may be further configured to operate at least one of: (i) heating elements 43, (ii) heating element 43’, and (iii) preheating module 41 (heating elements 412) to increase the operational temperature when the determined concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

[0163] In some embodiments, controller 60 may be configured to operate at least one of: (i) heating elements 43, (ii) heating element 43’, and (iii) preheating module 41 (heating elements 412) further based on the input from sensor 66. E.g., controller 60 may be configured to increase the operational temperature of heating elements 43 and / or heating elements 412 when the determined concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold, in order to decrease the concentration of O2 and / or NO2 in the gas mixture obtained after passing the NO-enriched gas mixture through first-stage filtering module 42. Additionally or alternatively, controller 60 may be further configured to increase the operational temperature of heating element 43’, when the determined concentration of O2 and / or NO2 exceeds a predefined concentration threshold, in order toassure that the increased residual components content in in the gas mixture obtained after passing the NO-enriched gas mixture through first-stage filtering module 42 will be sufficiently reduced by second-stage filtering module 42’, thereby providing for the desired purity of the product NO-enriched gas mixture.

[0164] In some embodiments, the predefined concentration threshold may be 5 ppm for O2 and 0.1 ppm for NO2, which corresponds to the requirements for medical applications.

[0165] Controller 60 and respective heating elements may be configured to increase the operational temperature, e.g., within a range of 400-850 °C.

[0166] The two-stage filtering configuration described above (having the plurality of first-stage filtering modules 42, connected in a parallel manner, and second-stage filtering module 42’, connected in a successive manner, as well as having sensors 65 and 66 connected as indicated above, and controller 60 in operative connection with heating elements 43, 43’ and 412 and with sensors 65 and 66), provides for reliable control of the filter unit operation, thereby assuring the desired selectiveness of filtering and thus contributing to the improvement of the indicated technological field. In the indicated configuration, the major filtering capacity accounts for first-stage filtering modules 42. Hence, in some embodiments, controller 60 is configured so as to keep the concentration of the residual components in the gas mixture obtained after passing filtering modules 42 below the predefined concentration thresholds, corresponding to the requirements to the product NO-enriched mixture. Second-stage filtering module 42’, in turn, is used as an auxiliary, reserve means to further assure that no residual components will get into the product NO- enriched gas mixture, e.g., when filtering capacity of first-stage filtering modules 42 is getting exhausted.

[0167] In some further embodiments, controller 60 may be further configured to provide a warning indication (e.g., via a visual and / or audio interface) when at least one of the following conditions is met: (a) the operational temperature has reached a predefined temperature limit (e.g., 850 °C), meaning that there is no further ability to compensate cartridge degradation by increasing the operational temperature; (b) a rate of change of the determined concentration of O2 and / or NO2 with respect to an increase of the operational temperature gets below a predefined rate-of-change threshold, meaning that further increase of the operational temperature does not provide a desired effect on its filtering capacity. Such a warning indication may signal that cartridge capacity has exhausted and that cartridge 423or 423’, respectively, must be replaced or must undergo regeneration in order to be further used for filtering the NO-enriched gas mixture.

[0168] In some embodiments, said filtering capacity and the exhaustion thereof can be calculated from simple stoichiometric calculations based on known computational methods and further based on respective sensor readings, and used for providing warnings, as well as for setting the operational temperature.

[0169] In some embodiments, the product NO-enriched gas mixture may include about 98% N2 or more and between about 100 and about 2000 ppm of NO. In some embodiments, the product NO-enriched gas mixture may include about 99.9% N2 or more and between about 700 and about 900 ppm of NO.

[0170] It should be understood that, in order to obtain all the potential capacity of filtering modules having a parallel connection (e.g., as first-stage filtering modules 42), it is critically important to provide a gas flow uniformly distributed between the filtering modules. Otherwise, some filters may have their filtering capacity exhausted earlier than others, leading to the increase of residual components content in the filtered gas mixture (e.g., product NO-enriched gas mixture). This, in turn, may require halting the filtering process to replace / regenerate the degenerated cartridge(s) more frequently and, accordingly, the filtering process, as well as the process of NO-enriched gas mixture production, will have lower productivity.

[0171] The filtering unit in the described configuration has undergone multiple tests and demonstrated high efficiency and selectiveness of NO2 and O2 reduction. As can be seen in time graphs shown in Figs. 6 A and 6B (10-hour operating cycle of system 100, total operation time of filter unit 40 without changing / regenerating cartridges 423 and 423’ - 24 hours) and further in time graphs shown in Figs. 6C and 6D (10-hour operating cycle of system 100 (10-hour operating cycle of system 100, total operation time of filter unit 40 without changing / regenerating cartridges 423 and 423’ - 130 hours), system 100 and, in particular, filter unit 40 has demonstrated reliable and stable operation.

[0172] As described above, during tests, the operational temperature was controlled to compensate cartridge degradation, as described above: between 14 and 24 hours of operation, the operational temperature was set around 730-750 °C (Fig. 6B), while between 120 and 130 hours of operation, the operational temperature was set around 780-820 °C (Fig. 6D).

[0173] According to some embodiments, cartridges 423 and 423’ may be regenerated upon degradation, in order to restore their filtering capacity.

[0174] Referring now to Fig. 2D, cartridge regeneration unit 70 is described, which may be used as an optional component of system 100, according to some embodiments of the present invention.

[0175] In some embodiments, for cartridge regeneration, methane (CFU) may be used to induce the following chemical reaction:4 CuO + CH4= 4 Cu + CO2+ 2 H2O.

[0176] Accordingly, in some embodiments, cartridge regeneration unit 70 may include CH4supply unit in fluid connection with filter unit 40. CH4 supply unit may be further configured to supply CH4 to filter unit 40, e.g., via inlet channel 422A or 422A’ of respective filtering module 42 or 42’. To induce the chemical reaction, the operational temperature of cartridges 423 or 423’, respectively, may be maintained around approximately 600 °C. It should be understood that, during the regeneration procedure, the flow of NO-enriched gas mixture to filter unit 40 should be stopped.

[0177] The output mixture obtained after regeneration, e.g., via outlet channels 422B or 422B’, respectively, may be further directed to cooler 72, to decrease temperature of the mixture and further to condenser 73, where the water can be separated from CO2. Concentration of CO in the output mixture is neglectable.

[0178] In some embodiments, cartridge regeneration unit 70 may further include sensor 67 in operative connection with controller 60, configured to determine a concentration of at least one of CO, CO2 and / or O2 in a gas mixture obtained after the water separation. Accordingly, controller 60 may be further in operative connection with, e.g., control valve controlling CH4 flow to filter unit 40. Controller 60 may be further configured to monitor and control the regeneration procedure, based on the input from sensor 67, e.g., by operating said control valve to change CH4 flow.

[0179] Figs. 7A and 7B illustrate the regeneration process that was conducted during tests. Fig 7A depicts a time graph of an operational temperature and CO2 concentration in the output of the filter unit during a cartridge regeneration cycle, as conducted according to some embodiments of the present invention. Fig. 7B depicts a time graph of an CO2 concentration in the output of the filter unit and calculated mass of O2 and recovered Cu thatwere obtained after reducing copper oxide during a cartridge regeneration cycle, as conducted according to some embodiments of the present invention.

[0180] It has been discovered by the inventors that, upon subjection to degradationregeneration cycle as discussed above, the filtering material of cartridge (e.g., cartridge 423 or 423’) undergoes significant changes in its structure, revealing new useful characteristics that positively affect its filtering capabilities.

[0181] As can be seen in Fig. 8 A depicting a comparison of a standard mesh fabric filtering material made of copper and an improved mesh fabric filtering material made of copper, diameter of copper wires after regeneration is more than two times larger than the diameter of original copper wires. As can be seen, after degradation / regeneration cycles, all physical properties of filtering material, e.g., density, specific surface, mechanical properties, dimensions have completely changed, while chemical properties of copper remain the same.

[0182] As can be further seen in Fig. 8B depicting a microscopic 3D scan (SEM image) of the improved mesh fabric filtering material made of copper, according to some embodiments of the present invention, the surface of the filtering material has become much rougher (with multiple protrusions) than it was originally, thereby having significantly higher Specific Surface Area (SSA) - up to 500 m2 / g - which is a critical parameter for filtering capacity.

[0183] Furthermore, high roughness of material surface prevents the formation of a solid oxide layer thereon, thereby further increasing filtering capacity of the cartridge (e.g., cartridge 423 or 423’ as shown in Figs. 2C and 3F). This, in turn, provides for sufficiently effective filter unit operation under lower operational temperatures than applied for cartridges containing the original material. E.g., it was empirically determined that cartridge made of the improved material demonstrates the same efficiency of filtration under the operational temperature of 400 °C, as the cartridge made of the original material under temperature of about 700 °C. Furthermore, the range in which the operational temperature should be changed in order to compensate cartridge degradation is narrower for the improved material than for the original one. E.g., in some embodiments, for the cartridge made of the improved material, the range in which the operational temperature should be changed to compensate cartridge degradation may be between about 400 and about 500 °C.

[0184] Hence, the suggested filtering material having SSA of about 500 m2 / g, and, accordingly, the filtering cartridge (e.g., cartridge 423 or 423’ as shown in Figs. 2C and 3F), filter unit or assembly and method of filtering a gas mixture (e.g., the NO-enriched gas mixture, as discussed above) using the suggested filtering material, further provide an improvement of the relevant technological field by increasing filtering capacity of said filtering material, cartridge, filter unit (assembly), respectively, as well as by reducing power consumption required to selectively filter oxygen and / or gaseous oxide-containing components (e.g., O2 and NO2) from gas mixtures.

[0185] In some embodiments, filtering module housings 421 and 421’ (as shown in Figs. 3F and 3G) may have substantially cylindrical shape, and the filtering material may be a mesh fabric. The mesh fabric may be formed in a roll uniformly filling inner cavity 421 A or 421 A’ of the filtering module housing 421 or 421’, respectively (as shown in Figs. 3F and 3G).

[0186] In cases when filtering material is a mesh fabric formed in a roll (or has other functionally similar structure), filtering material may have much higher density (narrower gaps between portions of filtering material) after regeneration, than originally, which may cause problems such as non-uniform distribution of a gas flow through the cartridge (e.g., the gas flow may bypass the cartridge and go around it instead of going through).

[0187] As shown in Fig. 9, which is a schematic illustration of a cross section of a cartridge 423, configured according to some embodiments of the present invention, cartridge 423 may further include alternating layers 423A and 423B of spacing material and filtering material, respectively. Layers 423 A of a spacing material may be positioned so as to create gaps between portions (e.g., layers 423B) of the filtering material. In some further embodiments, spacing material may have projecting portions 423C, further assuring that layers 423B are properly spaced apart.

[0188] In some embodiments, the spacing material may be made of an inert metal or metal alloy substantially remaining in the metal state upon exposure to O2, e.g., stainless steel or stainless-steel alloy.

[0189] Accordingly, since stainless steel is less expensive material than, e.g., copper, the cartridge (e.g., cartridge 423 or 423’) having alternating layers of filtering material and spacing material may represent more cost-effective solution, than cartridge entirely made of copper, since, for the same filtering efficiency, less amount of copper is required. Thereby,an additional contribution to the abovementioned technological improvement may be provided.

[0190] Advantageously, copper provides superior filtering abilities, while steel provides superior heat resistance, thus maintaining the structural integrity of the cartridge (e.g., cartridge 423 or 423’) in a high-temperature environment.

[0191] In some additional or alternative embodiments, the metal catalyst of the filtering material may include silver, silver alloys, iron and iron alloys subjective to oxidation. In some embodiments, inert metal of the spacing material may include iron alloys that are resistant to oxidation at high temperatures, titanium and or other metals resistant to corrosion at high temperatures.

[0192] Finally, the obtained product NO-enriched gas mixture may be prepared for further transferring to the consumers.

[0193] Referring back to Fig. 2A, it is shown that, in some embodiments, system 100 may include gas tank refilling station 50. Gas tank refilling station 50 may include, e.g., cooler 51 and high-pressure compressor 52 positioned inline after filter unit 40. Cooler 51 may be configured to decrease the temperature of the product NO-enriched gas mixture. Compressor 52 may be configured to compress the product NO-enriched gas mixture. Gas tank refilling station 50 may further include means for filling gas tanks with the compressed product NO-enriched gas mixture.

[0194] It should be understood that system 100 may further include additional valves, blowers, pumps, compressing units, coolers, heaters, tanks, pressure sensors, temperature sensors, flow sensors, flow compensation output lines and valves etc., connected to the production line described above, and applied as commonly known in the art (e.g., compressing unit for supplying air to the system via air intake 10, shown in Fig. 2A). For example, in some embodiments system 100 may comprise a plurality of controllable blowers in operative communication with controller 60; and controller 60 may be further configured to operate at least one of (or a respective) blowers to generate the gas mixture flow through the entire system 100 and / or through specific components thereof of the desired velocity (e.g., an output flow rate of the product NO-enriched gas mixture may be about 8 m3 / hour), so as to obtain a desired concentration of said at least one component in the NO-enriched gas mixture. E.g., air intake 10 may be fluidly coupled or comprise one or more valves configured to create negative pressure in air intake 10 to enable air flow thereto. Accordingto some embodiments, air intake 10 is fluidly coupled to at least one air input pump (not shown), configured to pump air into the system 100. According to some embodiments, system 100 enable to control the flow rate of fresh air thereinto, optionally via the activation of compressor 60 or the at least one air input pump, to achieve a stable concentration of NO in the product NO-enriched gas mixture at a desired output flow rate.

[0195] It should be further appreciated by the person skilled in the art that such additional elements may be omitted herein for the purpose of clarity, in order to facilitate understanding of essential aspects of the present invention.

[0196] According to some embodiments, the various units or components of system 100 may be in fluid communication with each other via lines such as tubes, pipes, conduits, ducts, or any other known communication appliances in the art.

[0197] Referring now to Figs. 10A and 10B, a flow diagram is presented, depicting a method for producing NO-enriched gas mixture, according to some embodiments of the present invention, according to some additional or alternative embodiments.

[0198] As shown in step S1005 (Fig. 10A), the method of producing NO-enriched gas mixture may include receiving, from a first gas mixture supply unit (e.g., first nitrogen generator, as shown in Fig. 2A), a first gas mixture comprising N2 and O2, wherein a volume ratio between N2 and O2 is between 49: 1 and 9:1.

[0199] As shown in step S1010 (Fig. 10A), the method of producing NO-enriched gas mixture may include transferring the first gas mixture through at least one plasma reactor unit (e.g., plasma reactor unit 30, as shown in Figs. 2A and 2B), while generating an electric discharge therein (e.g., using electrodes 31’ operatively connected to variable power supply 32, as shown in Fig. 2B) to induce a plasma chemical conversion of at least a portion of the first gas mixture into NO, thereby producing the NO-enriched gas mixture.

[0200] As shown in step S2005 (Fig. 10B), the method of producing NO-enriched gas mixture may include supplying air (e.g., via air intake 10, as shown in Fig. 2A) to the first nitrogen generator (e.g., first nitrogen generator, as shown in Fig. 2 A) to produce the first gas mixture.

[0201] As shown in step S2010 (Fig. 10B), the method of producing NO-enriched gas mixture may include receiving, from the first nitrogen generator (e.g., first nitrogen generator, as shown in Fig. 2A), a first gas mixture comprising N2 and O2, wherein a volume ratio between N2 and O2 is between 49:1 and 9:1.

[0202] As shown in step S2015 (Fig. 10B), the method of producing NO-enriched gas mixture may include generating a gas flow of the first gas mixture through a reaction chamber of a plasma reactor unit (e.g., reaction chamber 31 of plasma reactor unit 30, as shown in Fig. 2B) via an inlet channel and an outlet channel thereof, to transfer the first gas mixture through a gap between a plurality of electrodes installed within the reaction chamber (e.g., electrodes 31’ installed within reaction chamber 31, as shown in Fig. 2B), while generating, by a variable power supply (e.g., variable power supply 32, as shown in Fig. 2B) being in operative connection with said plurality of electrodes, the electric discharge thereacross, thereby producing the NO-enriched gas mixture.

[0203] As shown in step S2020 (Fig. 10B), the method of producing NO-enriched gas mixture may include receiving, by at least one controller (e.g., controller 60, as shown in Figs. 2A-2C), from at least one first sensor being in operative communication with the plasma reactor unit (e.g., sensor 63 and plasma reactor unit 30, as shown in Fig. 2B), a current concentration of at least one component in the NO-enriched gas mixture, wherein the at least one component is selected from the list consisting of: NO, NO2, N2 and O2.

[0204] As shown in step S2025 (Fig. 10B), the method of producing NO-enriched gas mixture may include operating, by said at least one controller (e.g., controller 60, as shown in Figs. 2A-2C), the variable power supply (e.g., variable power supply 32, as shown in Fig. 2B) to change the voltage applied across the plurality of electrodes (e.g., electrodes 31’ installed within reaction chamber 31, as shown in Fig. 2B) so as to obtain a desired concentration of said at least one component in the NO-enriched gas mixture, based on the received current concentration, wherein a respective desired concentration is between about 1000 and about 5000 ppm of NO, between about 350 and about 1000 ppm of NO2, about 89.95% of N2 or more, and between about 0.45 and about 9.95% of O2.

[0205] In some embodiments, transferring the first gas mixture through said at least one plasma reactor unit (e.g., plasma reactor unit 30, as shown in Figs. 2A and 2B) may further include transferring at least a portion of the first gas mixture through the circulating contour (e.g., circulating contour 34’, as shown in Fig. 2B).

[0206] In some embodiments, the method of producing NO-enriched gas mixture may further include transferring the NO-enriched gas mixture through a filter unit (e.g., filter unit 40, as shown in Figs. 2A and 2C) to remove at least a fraction of NO2 and / or 02 from theNO-enriched gas mixture flowing therethrough, thereby producing a product NO-enriched gas mixture.

[0207] In some embodiments, transferring the NO-enriched gas mixture through a filter unit (e.g., filter unit 40, as shown in Figs. 2A and 2C) comprises: heating the cartridge (e.g., cartridge 423 and / or 423’, as shown in Fig. 2C) up to an operational temperature by the at least one heating element (e.g., heating elements 43 and / or 43’, as shown in Fig. 2C); and transferring the NO-enriched gas mixture via the inlet and outlet channels (e.g., channels 422 A, 422B, 422 A’ and 422B’ as shown in Figs. 3A-3E) through the heated cartridge.

[0208] In some embodiments, the method of producing NO-enriched gas mixture may further include receiving, by at least one controller (e.g., controller 60, as shown in Figs. 2A- 2C), from at least one second sensor (e.g., sensors 64, 65 and / or 66, as shown in Figs. 2A and 2C) being in operative communication with the filter unit (e.g., filter unit 40, as shown in Figs. 2A and 2C), a current concentration of O2 and / or NO2 in the product NO-enriched gas mixture and / or a gas mixture obtained after passing the NO-enriched gas mixture through a first of at least two filtering modules (first-stage filtering modules 42 and second- stage filtering module 42’, as shown in Fig. 2C); and operating, by said at least one controller (e.g., controller 60, as shown in Figs. 2A-2C), the heating element (e.g., heating elements 43 and / or 43’, as shown in Fig. 2C) to increase the operational temperature when the received current concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

[0209] In some embodiments, the method of producing NO-enriched gas mixture may further include providing a warning indication when at least one of the following conditions is met: (a) the operational temperature has reached a predefined temperature limit; (b) a rate of change of the determined concentration of O2 and / or NO2 with respect to an increase of the operational temperature gets below a predefined rate-of-change threshold.

[0210] In some embodiments, the method of producing NO-enriched gas mixture may further include, prior to passing the NO-enriched gas mixture through the at least one filtering module (e.g., first-stage filtering modules 42 and second-stage filtering module 42’, as shown in Fig. 2C), preheating the NO-enriched gas mixture by transferring the NO- enriched gas mixture through the preheating module (e.g., preheating module 41, as shown in Figs. 2C, and 3A-3E).

[0211] In some embodiments, the method may further include diluting the NO-enriched gas mixture with a second gas mixture, prior to supplying the NO-enriched gas mixture to the filter unit (e.g., filter unit 40, as shown in Figs. 2A and 2C), the second gas mixture comprising about 90% N2 or more and supplied by a second gas mixture supply unit (e.g., second nitrogen generator 22, as shown in Fig. 2A).

[0212] In some embodiments, the method may further include compressing the product NO-enriched gas mixture by at least one high pressure compressor (e.g., compressor 52, as shown in Fig. 2A) positioned inline after and in fluid communication with the filter unit (e.g., filter unit 40, as shown in Figs. 2A and 2C); and filling a gas tank with the compressed product NO-enriched gas mixture.

[0213] As can be seen from the provided description, the claimed invention represents a system and method of producing NO-enriched gas mixture which provide an improvement of the respective technological field by mitigating induction of parasitic chemical reactions and reducing the fraction of undesired side-components, such as NO2 and O2, in the NO- enriched gas mixture obtained by plasma chemical conversion, thereby resulting in further effective elimination of said side-components in order to obtain a product gas mixture. Furthermore, the present invention represents an effective method for selective filtering such undesired side-components from an NO-enriched gas mixture, as well as a filter assembly to enable the said method of filtering.

[0214] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Furthermore, all formulas described herein are intended as examples only and other or different formulas may be used. Additionally, some of the described method embodiments or elements thereof may occur or be performed at the same point in time.

[0215] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[0216] Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.

Claims

CLAIMS1. A system for producing a nitric oxide (NO)-enriched gas mixture, the system comprising: a first gas mixture supply unit configured to supply a first gas mixture, said first gas mixture comprising N2 and O2, wherein a volume ratio between N2 and Chis between 49:1 and 9:1; at least one plasma reactor unit in fluid communication with the first gas mixture supply unit, wherein the at least one plasma reactor unit is configured to receive the first gas mixture and to create an electric discharge to induce a plasma chemical conversion of at least a portion of the first gas mixture into NO, to produce the NO-enriched gas mixture.

2. The system of claim 1, wherein the plasma reactor unit comprises: a reaction chamber having an inlet channel and an outlet channel; a variable power supply in operative connection with a plurality of electrodes installed within the reaction chamber and configured to create an electric discharge thereacross upon application of a voltage by the power supply; wherein the plasma reactor unit is configured to generate a gas flow of the first gas mixture through the reaction chamber via the inlet channel and the outlet channel to transfer the first gas mixture through a gap between the plurality of electrodes, while generating, by the variable power supply, the electric discharge thereacross, thereby producing the NO-enriched gas mixture.

3. The system of claim 2, wherein the plasma reactor unit further comprises a circulation blower in fluid communication with said inlet and outlet channels of the reaction chamber, thereby forming together with the reaction chamber a circulating contour; and wherein the plasma reactor unit is further configured to produce the NO-enriched gas mixture further by transferring at least a portion of the first gas mixture through the circulating contour.

4. The system according to any one of claims 1-3, wherein the first gas mixture supply unit is a first nitrogen generator comprising a pressure swing adsorption (PSA) system and / or a membrane gas separation system; wherein the first nitrogen generator is configured to produce the first gas mixture from air.

5. The system according to any one of claims 1-4, wherein said first gas mixture comprises between about 90 and about 98% of N2; and between about 2 and about 10% of O2.

6. The system according to any one of claims 1-5, wherein the NO-enriched gas mixture comprises between about 1000 and about 5000 ppm of NO.

7. The system according to any one of claims 1-6, wherein the NO-enriched gas mixture further comprises about 89.95% N2 or more.

8. The system according to any one of claims 1-7, wherein the NO-enriched gas mixture further comprises between about 350 and about 1000 ppm of NO2; and between about 0.45% and about 9.95% of O2.

9. The system according to any one of claims 1-8, wherein the system further comprises a filter unit configured to receive the NO-enriched gas mixture and to remove at least a fraction of NO2 and / or O2 from the NO-enriched gas mixture flowing therethrough, thereby producing a product NO-enriched gas mixture.

10. The system of claim 9, wherein the product NO-enriched gas mixture comprises about 98% N2 or more and between about 100 and about 2000 ppm of NO.

11. The system according to any one of claims 9 and 10, wherein the filter unit comprises: at least one filtering module, comprising: a filtering module housing which defines an inner cavity therein; a pair of inlet and outlet channels coupled to the filtering module housing and configured so as to enable the NO-enriched gas mixture flow through the inner cavity; and a cartridge disposed within the inner cavity, said cartridge comprising a filtering material comprising a metal catalyst configured for reducing NO2 to NO and undergoing oxidation upon exposure to O2 to form a metal oxide; and at least one heating element configured to heat the cartridge up to an operational temperature.

12. The system according to claim 11, wherein the operational temperature is selected from the range of about 400-850 °C.

13. The system according to any one of claims 11-12, wherein the metal catalyst comprises elemental copper or copper alloy.

14. The system according to any one of claims 11-13, wherein the filtering material comprises one or more of granules, wires, rods, particles, mesh, fabric, and combinations thereof.

15. The system according to any one of claims 11-14, wherein the filtering material has a specific surface area (SSA) of about 500 m2 / g.

16. The system according to any one of claims 11-15, wherein the cartridge further comprises a spacing material, positioned so as to create gaps between portions of the filtering material.

17. The system according to claim 16, wherein the spacing material is made of an inert metal or metal alloy substantially remaining in the metal state upon exposure to O2.

18. The system according to claim 17, wherein the inert metal or metal alloy are stainless steel or stainless-steel alloy, respectively.

19. The system according to any one of claims 11-18, wherein the filtering module housing has substantially cylindrical shape, wherein the filtering material is a mesh fabric, and wherein the mesh fabric is formed in a roll uniformly filling the inner cavity of the filtering module housing.

20. The system according to any one of claims 11-19, wherein the filter unit further comprises a preheating module arranged inline prior to the at least one filtering module, and configured to preheat the NO-enriched gas mixture prior to passing the NO-enriched gas mixture through the at least one filtering module.

21. The system according to any one of claims 1-20, further comprising a second gas mixture supply unit configured to supply a second gas mixture, said second gas mixture comprising about 90% N2 or more; wherein the system is further configured to dilute the NO-enriched gas mixture with said second gas mixture, prior to supplying the NO-enriched gas mixture to the filter unit.

22. The system of claim 21, wherein the second gas mixture further comprises about 10% of O2 or less.

23. The system according to any one of claims 21 and 22, the second gas mixture supply unit is a second nitrogen generator comprising a pressure swing adsorption (PSA) system and / or a membrane gas separation system; wherein the second nitrogen generator is configured to produce the second gas mixture from air.

24. The system according to any one of claims 1-23, further comprising: one or more sensors in operative communication with at least one of the first gas mixture supplying unit, second gas mixture supplying unit, plasma reactor unit, filter unit, or a fluid communication line therebetween, and configured to determine a concentration of at least one of NO, NO2, O2 and N2 in gas mixtures flowing therethrough; and a controller in operative communication with at least one of the first gas mixture supplying unit, second gas mixture supplying unit, plasma reactor unit, filter unit, and with said one or more sensors, wherein the controller is configured to control the operation of at least one of the first gas mixture supplying unit, second gas mixture supplying unit, plasma reactor unit, and filter unit based on an input from said one or more sensors.

25. The system of claim 24, wherein said one or more sensors comprise a first sensor, the first sensor being in operative communication with the plasma reactor unit and configured to determine a concentration of NO in the NO-enriched gas mixture; and wherein the controller is configured to operate the variable power supply to change the voltage applied across the plurality of electrodes so as to keep the concentration of NO in the NO-enriched gas mixture between about 1000 and about 5000 ppm, based on the input from the first sensor.

26. The system according to any one of claims 24 and 25, wherein said one or more sensors comprise a second sensor, the second sensor being in operative communication with the filter unit and configured to determine a concentration of O2 and / or NO2 in the product NO-enriched gas mixture; and wherein the controller is further configured to operate the heating element to increase the operational temperature when the determined concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

27. The system according to any one of claims 24 and 25, wherein the filter unit comprises at least two filtering modules arranged successively; wherein the second sensor is in the operative communication with the filter unit and is configured to determine a concentration of O2 and / or NO2 in a gas mixture obtained after passing the NO-enriched gas mixture through a first of at least two filtering modules;and wherein the controller is further configured to operate the heating element to increase the operational temperature when the determined concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

28. The system according to any one of claims 26 and 27, wherein the controller is further configured to provide a warning indication when at least one of the following conditions is met: (a) the operational temperature has reached a predefined temperature limit; (b) a rate of change of the determined concentration of O2 and / or NO2 with respect to an increase of the operational temperature gets below a predefined rate-of-change threshold.

29. The system according to any one of claims 9-28, further comprising a gas tank refilling station comprising at least one high pressure compressor positioned inline after the filter unit, and configured to compress the product NO-enriched gas mixture; wherein said gas tank refilling station comprises means to fill a gas tank with the compressed product NO-enriched gas mixture.

30. A method of producing a nitric oxide (NO)-enriched gas mixture, the method comprising: receiving, from a first gas mixture supply unit, a first gas mixture comprising N2 and O2, wherein a volume ratio between N2 and O2is between 49:1 and 9:1; transferring the first gas mixture through at least one plasma reactor unit, while generating an electric discharge therein to induce a plasma chemical conversion of at least a portion of the first gas mixture into NO, thereby producing the NO-enriched gas mixture.

31. The method of claim 30, wherein said first gas mixture comprises between about 90 and about 98% of N2; and between about 2 and about 10% of O2.

32. The method according to any one of claims 30 and 31, wherein the first gas mixture supply unit is a first nitrogen generator comprising a pressure swing adsorption (PSA) system and / or a membrane gas separation system; and wherein the method further comprises supplying air to the first nitrogen generator to produce the first gas mixture.

33. The method according to any one of claims 30-32, wherein the plasma reactor unit comprises: a reaction chamber having an inlet channel and an outlet channel;a variable power supply in operative connection with a plurality of electrodes installed within the reaction chamber; and wherein transferring the first gas mixture through said at least one plasma reactor unit comprises: generating a gas flow of the first gas mixture through the reaction chamber via the inlet channel and the outlet channel to transfer the first gas mixture through a gap between the plurality of electrodes, while generating, by the variable power supply, the electric discharge thereacross, thereby producing the NO-enriched gas mixture.

34. The method of claim 33, wherein the plasma reactor unit further comprises a circulation blower in fluid communication with said inlet and outlet channels of the reaction chamber, thereby forming, together with the reaction chamber, a circulating contour; and wherein transferring the first gas mixture through said at least one plasma reactor unit further comprises transferring at least a portion of the first gas mixture through the circulating contour.

35. The method according to any one of claims 33 and 34, further comprising: receiving, by at least one controller, from at least one first sensor being in operative communication with the plasma reactor unit, a current concentration of at least one component in the NO-enriched gas mixture; and operating, by said at least one controller, the variable power supply to change the voltage applied across the plurality of electrodes so as to obtain a desired concentration of said at least one component in the NO-enriched gas mixture, based on the received current concentration; wherein the at least one component is selected from the list consisting of: NO, NO2, N2 and O2; and wherein a respective desired concentration is between about 1000 and about 5000 ppm of NO, between about 350 and about 1000 ppm of NO2, about 89.95% of N2 or more, and between about 0.45 and about 9.95% of O2.

36. The method according to any one of claims 30-35, further comprising transferring the NO-enriched gas mixture through a filter unit to remove at least a fraction of NO2and / or O2 from the NO-enriched gas mixture flowing therethrough, thereby producing a product NO-enriched gas mixture.

37. The method according to claim 36, wherein the filter unit comprises: at least one filtering module, comprising: a filtering module housing which defines an inner cavity therein; a pair of inlet and outlet channels coupled to the filtering module housing and being in fluid communication with each other via the inner cavity; and a cartridge disposed within the inner cavity, said cartridge comprising a filtering material comprising a metal catalyst configured for reducing NO2 to NO and undergoing oxidation upon exposure to O2 to form a metal oxide, respectively; and at least one heating element; and wherein transferring the NO-enriched gas mixture through a filter unit comprises: heating the cartridge up to an operational temperature by the at least one heating element; and transferring the NO-enriched gas mixture via the inlet and outlet channels through the heated cartridge.

38. The method according to any one of claims 36-37, further comprising: receiving, by at least one controller, from at least one second sensor being in operative communication with the filter unit, a current concentration of O2 and / or NO2 in the product NO-enriched gas mixture; and operating, by said at least one controller, the heating element to increase the operational temperature when the received current concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

39. The method according to any one of claims 36-37, wherein the filter unit comprises at least two filtering modules arranged successively; and wherein the method further comprises: receiving, by at least one controller, from at least one second sensor being in operative communication with the filter unit, a current concentration of O2 and / or NO2 in a gas mixture obtained after passing the NO-enriched gas mixture through a first of at least two filtering modules; andoperating, by said at least one controller, the heating element to increase the operational temperature when the received current concentration of O2 and / or NO2, respectively, exceeds a predefined concentration threshold.

40. The method according to any one of claims 38 and 39, further comprising providing a warning indication when at least one of the following conditions is met: (a) the operational temperature has reached a predefined temperature limit; (b) a rate of change of the determined concentration of O2 and / or NO2 with respect to an increase of the operational temperature gets below a predefined rate-of-change threshold.

41. The method according to any one of claims 38-40, wherein the predefined concentration threshold is 5 ppm for O2 and 0.1 ppm for NO2, respectively.

42. The method according to any one of claims 36-41, wherein the product NO- enriched gas mixture comprises about 98% N2 or more and between about 100 and about 2000 ppm of NO.

43. The method according to any one of claims 37-42, wherein the operational temperature is selected from the range of about 400-850 °C.

44. The method according to any one of claims 37-43, wherein the metal catalyst comprises elemental copper or copper alloy.

45. The method according to any one of claims 37-44, wherein the filtering material comprises one or more of granules, wires, rods, particles, mesh, fabric, and combinations thereof.

46. The method according to any one of claims 37-45, wherein the filtering material has a specific surface area (SSA) of about 500 m2 / g.

47. The method according to any one of claims 37-46, wherein the cartridge further comprises a spacing material, positioned so as to create gaps between portions of the filtering material.

48. The method of claim 47, wherein the spacing material is made of an inert metal or metal alloy substantially remaining in the metal state upon exposure to O2.

49. The method of claim 48, wherein the inert metal or metal alloy are stainless steel or stainless-steel alloy, respectively.

50. The method according to any one of claims 37-49, wherein the filtering module housing has substantially cylindrical shape, wherein the filtering material is a mesh fabric,and wherein the mesh fabric is formed in a roll uniformly filling the inner cavity of the filtering module housing.

51. The method according to any one of claims 37-50, wherein the filter unit further comprises a preheating module; and wherein the method further comprises, prior to passing the NO-enriched gas mixture through the at least one filtering module, preheating the NO-enriched gas mixture by transferring the NO-enriched gas mixture through the preheating module.

52. The method according to any one of claims 36-51, further comprising diluting the NO-enriched gas mixture with a second gas mixture, prior to supplying the NO-enriched gas mixture to the filter unit, the second gas mixture comprising about 90% N2 or more and supplied by a second gas mixture supply unit.

53. The method of claim 52, wherein the second gas mixture further comprises about 10% of O2 or less.

54. The method according to any one of claims 52 and 53, wherein the second gas mixture supply unit is a second nitrogen generator comprising a pressure swing adsorption (PSA) system and / or a membrane gas separation system; and wherein the method further comprises supplying air to the second nitrogen generator to produce the second gas mixture.

55. The method according to any one of claims 36-54, further comprising compressing the product NO-enriched gas mixture by at least one high pressure compressor positioned inline after and in fluid communication with the filter unit; and filling a gas tank with the compressed product NO-enriched gas mixture.

56. A filter assembly comprising: at least one filtering module, comprising: a filtering module housing which defines an inner cavity therein; a pair of inlet and outlet channels coupled to the filtering module housing and being in fluid communication with each other via the inner cavity; and a cartridge disposed within the inner cavity, said cartridge comprising a filtering material comprising a metal catalyst; at least one heating element configured to heat the cartridge; at least one sensor in operative communication with the outlet channel, said at least one sensor being configured to determine a concentration of at least one oxygenand / or gaseous oxide-containing component in a gas mixture flowing through the outlet channel; and at least one controller being in operative communication with said at least one heating element and with said at least one sensor, and configured to operate the heating element to set an operational temperature of the cartridge, based on the determined concentration of said at least one oxygen and / or gaseous oxide-containing component.

57. The filter assembly of claim 56, wherein the metal catalyst is configured for reducing NO2 to NO and undergoing oxidation upon exposure to O2 to form a metal oxide.

58. The filter assembly according to any one of claims 56 and 57, wherein the controller is further configured to operate the heating element to increase the operational temperature of the cartridge when the determined concentration of said at least one oxygen and / or gaseous oxide-containing component exceeds a predefined concentration threshold.

59. The filter assembly according to any one of claims 56-58, wherein the operational temperature is selected from a range of about 400-850 °C.

60. The filter assembly according to any one of claims 56-59, wherein the metal catalyst comprises elemental copper or copper alloy.

61. The filter assembly according to any one of claims 56-60, wherein the filtering material is formed by at least one of granules, wires, rods, particles, mesh, fabric, and combinations thereof.

62. The filter assembly according to any one of claims 56-61, wherein the filtering material has a specific surface area (SSA) of to 500 m2 / g.

63. The filter assembly according to any one of claims 56-62, wherein the cartridge further comprises a spacing material, positioned so as to create gaps between portions of the filtering material.

64. The filter assembly according to any one of claims 56-63, wherein the spacing material is made of an inert metal or metal alloy substantially remaining in the metal state upon exposure to O2.

65. The filter assembly according to any one of claims 56-64, wherein the non- catalytic metal or metal alloy are stainless steel or stainless-steel alloy, respectively.

66. The filter assembly according to any one of claims 56-65, wherein the filtering module housing has substantially cylindrical shape, wherein the filtering material is amesh fabric, and wherein the mesh fabric is formed in a roll uniformly filling the inner cavity of the filtering module housing.

67. The filter assembly according to any one of claims 56-66, wherein the filter unit further comprises a preheating module arranged inline prior to the at least one filtering module, and wherein the at least one controller is further configured to operate the preheating module to preheat a gas mixture transferred through the filter assembly.

68. The filter assembly according to any one of claims 56-67, further comprising at least two filtering modules arranged successively; and wherein said at least one sensor is in operative communication with the outlet channel of a first of said at least two filtering modules.

69. The filter assembly according to any one of claims 56-68, further comprising: an external housing having a thermally insulated inner space therein; wherein the filtering module housing is thermally conductive; and wherein the at least one filtering module and the at least one heating element are disposed within the thermally insulated inner space.

70. The filter assembly according to any one of claims 56-69, wherein the at least one controller is further configured to provide a warning indication when at least one of the following conditions is met: (a) the operational temperature has reached a predefined temperature limit; (b) a rate of change of the determined concentration of said at least one oxygen and / or gaseous oxide-containing component with respect to an increase of the operational temperature gets below a predefined rate-of-change threshold.

71. The filter assembly according to any one of claims 56-70, wherein said at least one oxygen and / or gaseous oxide-containing component is O2 and / or NO2.

72. A method of filtering a gas mixture, comprising: receiving a gas mixture comprising at least one oxygen and / or gaseous oxide- containing component; passing the gas mixture through the filter assembly corresponding to any one of claims 56-71, to reduce the content of said at least one oxygen and / or gaseous oxide- containing component therein, thereby obtaining the filtered gas mixture.

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