Electrode with protection against electrical arcing

Abstract

The invention relates to an electrode with protection against electrical arcing, designed to generate an electric field, which comprises at least one covering of dielectric material, wherein the electrode is designed to generate an electric field in an environment in which the temperature exceeds 100°C, wherein the electrode comprises at least one metal control plate, which may be embedded in the dielectric material or be in contact with the face of the dielectric material that is within the electric field, the control plate and the electrode being connected to a control system that controls the power differential generated between the two elements and which is designed to: maintain electrical power to the electrode as long as the power differential remains above a predetermined value; and cut off electrical power to the electrode if the power differential falls below the predetermined value.

Description

[0001]

[0002] ELECTRODE WITH PROTECTION AGAINST ELECTRIC ARC

[0003] TECHNICAL SECTOR

[0004] The present invention relates to electrodes and electrode systems used for generating an electric field with industrial applications.

[0005] Specifically, the present invention describes an electrode that prevents the appearance of electric arcs between two or more facing electrodes with the objective of generating an electric field that is used in industrial applications, such as the polarization of materials or in applications where the electric field facilitates and drives the movement of a plurality of ions, in order to increase the kinetics of chemical reactions without the need to use catalysts with a very high price as occurs with Platinum or gold.

[0006] Therefore, the present invention also aims at its use in applications such as high temperature electrolysis, fuel cells, or gas separation by means of mixed ionic-electronic conduction membranes MIEC, or purely ionic membranes, which implies that it also includes a safety system that prevents a possible appearance of an electric arc, to avoid the degradation, breakage, or fire of the equipment where said electrodes are installed.

[0007] BACKGROUND OF THE INVENTION

[0008] Currently, electric fields are widely known, understood as a vector field in which a given point electric charge is affected by the electric force of the field.

[0009] Likewise, electrodes are also widely known, understood as the conductive component through which an electric current flows and which is in contact with a non-conductive medium or material. Thus, two electrodes facing each other and subjected to sufficient electric potential can generate an electric field between them, where one electrode will be positive, as it loses electrons; and the other electrode will be negative, as it gains electrons.

[0010] Within the electrode classification, we can find high-voltage electrodes, which generate local field intensities so high that they can generate a plasma by gas discharge, as occurs when generating a corona or atmospheric pressure plasma. We can also find high-frequency electrodes, which are used to excite a plasma by means of high-frequency alternating fields.

[0011] Both electric fields and electrodes are used in electrical polarization processes, or polarization, in which an electric field is applied to a material to rearrange its molecules according to the direction of the electric field. Polarization is understood to be the modification of the charge distribution that occurs in a material when a sufficiently strong electric field acts on it to deform the material's molecules.

[0012] One of the main problems that must be faced during the polarization process of a material, as in the case of piezoelectrics, lies in the risk that, during said process and due to the high voltages that must be used during the polarization process, between 1,000 and 3,000 V per mm of thickness of the material, a dielectric breakdown of the piezoelectric occurs and an electric arc is formed between the two polarization electrodes, which inevitably leads to the immediate destruction of the material to be polarized, due to the high temperature reached in the area where the dielectric breakdown occurs.

[0013] An electric arc is a highly energetic and typically very destructive phenomenon that occurs when two conductive elements, such as two electrodes separated by a certain distance and between which there is a potentially very large electrical potential difference, generate an electric field that ionizes the atoms of the material or the air between them, allowing electrons to move from the cathode to the anode. The Joule effect causes the cathode temperature to increase in microseconds, generating more ions and increasing the current between the cathode and the anode until, literally, part of the cathode melts, generating a plasma through which a current flows to the anode that can exceed 100 amps and can reach temperatures close to 10.000°C, along with a very intense luminosity, which causes the destruction of the electrodes and any elements located next to or between them.

[0014] The main cause of dielectric breakdown and the subsequent appearance of the electric arc are usually internal defects, such as the pores that comprise the materials to be polarized, and which represent a very important risk factor, especially if they contain air or some gas, and are at high temperature, as occurs during the polarization process of piezoelectrics, since the gas at high temperature is easily ionized, favoring the creation of a path for the formation of an electric arc.

[0015] When a dielectric breakdown occurs in an insulating element located between two electrodes with a very high potential difference, the insulating element becomes conductive and allows the passage of electrons, generating an electric arc in a time of the order of microseconds that is capable of generating temperatures of several thousand °C. However, the reaction time of electric arc protection devices that cut off the power supply to the equipment when they detect the problem is of the order of milliseconds, which means that although the equipment where the electrodes are installed will not suffer serious damage, both the electrodes and the elements located between them will be destroyed.

[0016] This becomes particularly important if these electrodes are to be installed in combination with devices containing highly flammable elements, such as hydrogen and oxygen, which are generated and used in electrolyzer cells and fuel cells, respectively.

[0017] On the other hand, with regard to the polarization process of piezoelectrics, the greater the thickness and dimensions of the material to be polarized, the greater the probability that in some areas there will be a higher concentration of pores with gas inside, or open pores at both ends, which facilitate the path for the formation of the electric arc during the polarization process.

[0018] One of the main applications of material polarization is the manufacture of piezoelectrics, which is carried out by mixing, grinding and synthesizing prepared powders, resulting in polycrystalline ceramics to which a pair of electrical contacts are subsequently placed.

[0019] After this procedure, the resulting elements must be polarized by applying an electric field to the ceramic electrode, where the field can be continuous, intermittent or variable, and can be periodically reversed.

[0020] This is the critical operation in piezoelectric production, as there is a clear tendency for dielectric breakdown and, therefore, the electric arc to occur. This situation is aggravated by cracks and physical defects that may have occurred during the process of synthesizing. Likewise, this dielectric breakdown also depends on the thickness, dimensions, shape, and configuration of the electrode.

[0021] One of the problems that arise during the polarization process of piezoelectrics, apart from those already mentioned above, is that to obtain good polarization, it is recommended that during the process, the piezoelectric be at a temperature slightly below the Curie temperature, which depends on the composition and type of piezoelectric in question.

[0022] In the case of the most commonly used piezoelectrics at the moment, which are the PZT type, the Curie temperature can reach up to 370°C in the case of hard PZT, which is a serious problem, since polarization is usually carried out by immersing the piezoelectric and the electrodes in a container with silicone oil that is heated to about 80°C, to minimize the risk of an electric arc occurring during the process.

[0023] Silicone oil has a high dielectric strength of 15 KV / mm at 25°C, but it has the problem that from 60°C its dielectric strength begins to decrease considerably as its temperature increases, and it is not advisable to heat it to more than 100°C, since its dielectric strength would decrease to such an extent that there would be a high probability that during the polarization process an electric arc would jump between the electrodes.

[0024] The time and voltage that must be applied to the electrodes during the polarization process decrease the closer the temperature of the piezoelectric is to the Curie temperature, so having to carry out the polarization at a temperature of 80°C instead of 350°C, the process is lengthened, and the voltage that must be applied to the electrodes is much higher, 3,000 V per mm of thickness, instead of the 1,000 V that would have to be applied if the temperature were 350°C.

[0025] On the other hand, the properties that can be obtained by polarizing piezoelectrics at a temperature close to the Curie temperature are superior because the high temperature facilitates the orientation of the dipoles of the piezoelectric when subjected to the electric field.

[0026] Therefore, to solve the above problems, an electrode system is needed that allows the generation of an electric field in a high-temperature environment without the risk of dielectric breakdown and the consequent appearance of an electric arc.

[0027] In reference to this last point, we find document W02007056027, which describes a high impedance system for generating an electric field, from two electrodes comprising a dielectric material, in which each electrode has at least one surface coated with an electrically conductive material, and in which the dielectric material forms a barrier that separates the conductive coating from a fluid in which a treatment is carried out, such as electroporation, such that the conductive material is on a surface of the electrode that is not in contact with the fluid.

[0028] Thus, the previous document proposes the use of a dielectric material placed between the electrodes and the material to be subjected to the electric field, with the aim of reducing the probability of an electric arc occurring.

[0029] However, this invention does not allow to avoid the risks assumed when working at high temperatures close to Curie temperatures, which can not only maximize the possibilities of the appearance of the electric arc, but also cause the decrease of the dielectric strength and over time, the inevitable and certain degradation and dielectric breakdown of the dielectric material installed, with the consequent appearance of the electric arc and the damage it causes.

[0030] Another application of electrodes and electric field generation is the ion engine or propulsion system, which uses an ion beam for propulsion by accelerating the ions using the advantage of the charge-to-mass ratio to accelerate them to very high speeds using an electric field.

[0031] Thanks to this, ion thrusters can achieve a high specific impulse, reducing the amount of mass required, but increasing the amount of power required compared to conventional rockets.

[0032] Another state-of-the-art technology that the inventor considers relevant to the development of the invention lies in high-temperature electrolyzers, understood as an alternative to generating energy from fossil fuels, without the need to resort to their combustion, which reduces emissions of greenhouse gases and other toxic pollutants that pose a danger to the life or integrity of living beings.

[0033] Within this technology, we find an electrochemical cell, composed of a cathode and an anode, separated by an electrolyte, where the cathode and anode are electrical conductors, and are made of a porous material; and where the electrolyte is gas-tight, electrically insulating and ion-conducting, particularly, the electrolyte is a conductor of O ions. 2 '. These systems work by transmitting O ions 2' for the generation of electricity or pure hydrogen, using the dissociation of ions from a stream of H2O.

[0034] These electrolyzers are currently the most efficient, although the main problem is the rapid degradation of the anode due to delamination, which considerably reduces the lifespan of electrochemical cells and is the biggest challenge facing high-temperature electrolyzers.

[0035] Delamination is a phenomenon that occurs in the inferíase between the electrolyte and the anode of the cells, due to a high increase in the partial pressures of oxygen in some areas of the inferíase, due to the accumulation of diatomic oxygen that cannot escape, and which ends up causing micro-cracks in the anode, which over time ends up degrading and becoming separated from the electrolyte.

[0036] Furthermore, for the cells to function properly, the cathode must be supplied with water vapor at a temperature close to 800°C, which limits the type and number of installations where the waste heat from an industrial process, such as cement manufacturing, can be used to install electrolyzers of this type and achieve high efficiency.

[0037] Another problem is the limited current density per cm 2 of the electrodes due to their internal resistance, which limits the conduction of electrons, which in turn limits the production of hydrogen and oxygen.

[0038] At this point, in order to increase current density and therefore hydrogen and oxygen production, it is necessary to increase the cells' operating voltage, which implies greater energy consumption and a decrease in efficiency.

[0039] All of this means that this technology has not, for the time being, replaced the other technologies currently in use, which are less efficient.

[0040] In order to increase current density, it is necessary to increase the working voltage of the cells, which implies greater energy consumption and a decrease in efficiency.

[0041] This is why one of the objectives pursued with this technology focuses on increasing the current density in the cells, without the need to increase the potential difference applied to the electrodes, as well as minimizing or eliminating the problem of anode delamination, and reducing the operating temperature of the cathode, without losing efficiency.

[0042] It is important to note that by increasing the current density, the increased heat generated by the Joule effect at the cathode during electrolysis would reduce the amount of heat required to operate the process and, therefore, allow working with water vapor at lower temperatures, improving efficiency and increasing the type and number of companies and industrial processes where electrolyzers for green hydrogen production could be installed.

[0043] Another state-of-the-art technology that the inventor considers relevant to the development of the invention lies in the ceramic membranes used for gas separation, especially oxygen. Pure oxygen has countless industrial applications, and this type of membrane allows for the separation of oxygen from air much more efficiently than cryogenic distillation, the most widely used system currently.

[0044] This type of membrane can also be used to separate other gases such as nitrogen, hydrogen, or carbon dioxide, especially in processes related to oxy-combustion, given that they must operate at temperatures ranging from 500 to 1000°C.

[0045] These membranes are also used in catalytic reactors where reactions such as the non-oxidative coupling of methane and its aromatization, hydrocarbon reforming and the water gas shift reaction occur, all of these reactions having in common that they occur at high temperatures, which constitutes the appropriate framework for the use of the electrodes object of this invention, with the objective of generating electric fields that with minimum energy consumption, accelerate the chemical reactions that occur in the processes that use this type of ceramic membranes, in order to increase their efficiency and the processing volume in said processes in a safe manner, by minimizing the probability that at some point an electric arc will be generated that could cause a fire, or damage to the equipment used to carry out this type of processes.

[0046] EXPLANATION OF THE INVENTION

[0047] The electrode with protection against electric arc and the associated operating procedure that the invention proposes is therefore configured as a notable novelty within its field of application, since, according to its implementation and in a taxative manner, the objectives indicated below are achieved, the characterizing details that make it possible and that distinguish them being conveniently included in the final claims that accompany this description.

[0048] Specifically, the present invention aims to achieve an electrode that prevents the appearance of an electric arc between two electrodes subjected to a very high potential difference, which in the case of polarization of piezoelectrics, involves the destruction of the piezoelectric, while allowing its use in processes that are developed at high temperatures, such as high temperature electrolysis or the separation of oxygen and other gases by means of ceramic membranes.

[0049] Furthermore, another priority objective of the present invention is to make the appearance of an electric arc between the electrodes almost impossible indefinitely over time, something that the electrodes known in the state of the art cannot achieve, taking into account that high electric fields together with high temperatures, and the passage of time, inevitably degrade all dielectrics and cause at some point their dielectric breakdown, which sooner or later will cause the formation of an electric arc that will damage both the element subjected to the electric field and the equipment where the electrodes are placed.

[0050] It is also intended to improve the efficiency of devices or processes in which these electrodes are involved, for example, in the case of high-temperature electrolysis or the separation of oxygen and other gases, by increasing the speed at which electrochemical reactions occur, thanks to the acceleration of ions under the influence of the generated electric field, and with minimal energy consumption used for the generation of said electric field.

[0051] To achieve the first objective, that is, to prevent the occurrence of an electric arc, the present invention describes the design of an electrode that, regardless of the nature and physical properties of the materials subjected to the electric field, the temperature, and the time of exposure to the electric field, prevents the formation of an electric arc when it is generating an electric field.

[0052] In particular, the invention proposes to coat the electrodes with a material that has a dielectric constant as low as possible, so that the electric field is not affected in a relevant manner, but that at the same time has a dielectric strength as high as possible, in order to be able to apply very high voltages, minimizing the risk that due to the dielectric breakdown of said coating, an electric arc is formed between the electrodes, which also has a very high resistance to the passage of electrons, to reduce leakage currents and therefore the heat and power dissipated in the electrode, and that is capable of maintaining in a more or less stable manner, the values ​​of its dielectric constant, its dielectric strength and its resistance at high temperatures.

[0053] One material that the inventor has found advantageous is polytetrafluoroethylene (PTFE), better known as Teflon®, which includes the following characteristics:

[0054] It is worth noting that the values ​​of the dielectric constant and dielectric strength remain practically unchanged up to 300°C.

[0055] Furthermore, as previously mentioned, another problem that the invention seeks to solve is that of maximizing safety against the inevitable degradation and dielectric breakdown of dielectric materials, since this would cause damage both to the element subjected to the electric field and to the equipment where the electrodes are placed. To this end, the invention proposes the use of a metal control plate that can be embedded in the dielectric material, below and at a certain distance from the electrode, or in contact with the face of the dielectric that remains within the electric field, the control plate and the electrode being connected to a control system that constantly monitors and controls the potential difference generated between both elements by the action of the electric field.

[0056] If, due to the degradation of the dielectric located between the electrode and the control plate, its dielectric breakdown occurs, by becoming conductive, the potential difference between the electrode and the control plate will drop to practically zero volts, and it will be detected by the control system, which, in a matter of milliseconds, will cut off the power supply to the electrode and warn of the fault, preventing the electric arc from occurring, since it is practically impossible for the dielectric breakdown of the dielectrics covering the two electrodes that are generating the electric field to occur at exactly the same time, giving the control system time to cut off the power supply to the electrodes, before an electric arc can form between them.

[0057] In this way, the control system will keep the power supply connected to the electrode as long as the voltage between the electrode and the control board remains above a predetermined value; while it will immediately cut off the power supply if the voltage falls below a predetermined value.

[0058] In this way, we achieve, firstly, almost eliminating the possibility of an electric arc occurring between the electrodes, and secondly, avoiding damage to the element subjected to the electric field or any other element in the event of an electric arc occurring, since the control system will cut off the power supply in a matter of milliseconds. Based on the above, the invention describes an electrode of those existing in the state of the art that, together with another electrode facing it, when connected to an external electrical source, generate an electric field between them, in which a material to be polarized when subjected to the electric field is placed, and which is commonly in direct contact with the electrodes, configuring a sandwich-type structure, electrode - material - electrode.

[0059] In this way, it is possible to carry out the critical operation in the production of piezoelectrics, allowing polarization at high temperatures without the risk of electric arcing.

[0060] In particular, as previously mentioned, the polarization of hard PZT piezoelectrics would be desirable to be carried out at a temperature close to 350°C, and the electrodes must be in direct contact with the piezoelectric.

[0061] These temperatures would be transferred mainly, by thermal conduction, to the element in direct contact with the material to be polarized, which are normally the electrodes, but in the case of the invention described it is the dielectric material.

[0062] At that temperature in the particular example of polytetrafluoroethylene, it would melt, with the added problem that its dielectric strength begins to decrease from 300°C.

[0063] This is why the invention proposes the use of cooling devices, through which a coolant liquid circulates, and which totally or partially surround the dielectric material, so as to maintain its temperature within the working limits, which in the case of Teflon® is below 260°C, during the periods of generation of an electric field.

[0064] It is important to note that the solution to this problem must prevent any element placed between the polytetrafluoroethylene coating the electrode and the element to be polarized, for example, the coolant or a thermal insulator, from interfering with the electric field and weakening it, especially if the fluid or insulator has a high dielectric constant.

[0065] To solve this second problem, the invention proposes a solution based on the Faraday Cage principle, which is the effect according to which the electromagnetic field inside a conductor in equilibrium is zero, canceling out the effect of external electric fields, because the conductor is polarized, generating an electric field equal in magnitude but opposite in direction to the electromagnetic field, such that the sum of both fields inside the conductor is equal to zero. Therefore, the solution proposed by the present invention consists of the inclusion between two interconnected metal plates of a cooling device between the dielectric material and the material to be polarized, which is responsible for evacuating the heat by means of a cooling fluid that circulates through the interior of the cooling device, maintaining the temperature of the dielectric material below a certain limit.Following the example embodiment, the cooling device will ensure that the temperature of the Teflon® face with which it is in contact is less than 200°C.

[0066] Likewise, the present invention also includes the possibility of using additional thermal insulators, with the aim of avoiding temperature losses or gains in the different elements.

[0067] For example, it is advantageous to maintain a high temperature in the material to be polarized, in order to facilitate the process and optimize performance, so it would be desirable to place a thermal insulator between the cooling device and the material to be polarized.

[0068] In this way, a particular embodiment includes a conductive metal cooling device, in direct contact with the metal plate which in turn is in direct contact with the polytetrafluoroethylene, while on the inside of the other metal plate which is in contact with the material to be polarized, there will be a thermal insulator to minimize the cooling of the material to be polarized during said process.

[0069] The fact that both metal plates are electrically interconnected and therefore electrically at the same potential means that, according to the Faraday Cage principle, everything inside them is not affected by the electric field and vice versa, so neither the dielectric constant of the cooling fluid nor the thermal insulator will affect the intensity of the electric field generated by the electrodes.

[0070] Likewise, the present invention allows the possibility of including multiple cooling devices as needed, with the objective of avoiding the influence of temperatures on the efficiency of the polarization process.

[0071] In the present invention, the electrode may also incorporate a heating system located between the two electrically connected plates that make up the Faraday cage, comprising at least one refractory ceramic plate and at least one electrical resistor, for the purpose of heating the metal plate that is in direct contact with the material to be polarized in order to raise its temperature. Furthermore, the present invention also describes an electrode system according to the previous description, which is located inside a housing, formed by at least two parts, and which comprises all the elements necessary for the correct operation of the system.That is, it includes the means of electrical supply, thermal insulation, and necessary electronic control, as well as any other element required for the operation of the device, such as all fluid inlet and outlet holes, electrical connection means, etc.

[0072] Specifically, the upper portion comprises one electrode, and the lower portion includes the other electrode, and one of the portions may be able to move relative to the other portion, allowing them to be separated so that the material to be polarized can be placed in the middle portion. For example, a pivoting joint may be used to allow the upper portion to rotate relative to the lower portion.

[0073] In this way, a single device is generated that comprises all the means for the correct operation and protection of the electrode system described in the present invention.

[0074] Furthermore, regarding the topic of high-temperature electrolyzers, the present invention can significantly contribute to the implementation and expansion of this technology within the electrolyzer and hydrogen generation market, given that it is the most efficient.

[0075] However, this technology has a series of limitations and problems that are hindering its implementation, and thanks to the present invention, these would be minimized, or even some of them completely resolved.

[0076] In this case, unlike the previous application in which two facing electrodes are used to polarize materials, the electrochemical cells used to dissociate water into hydrogen and oxygen are configured by two ceramic electrodes between which there is a solid electrolyte, also ceramic, which only allows the passage of oxygen ions in the case of ionic electrochemical cells, or hydrogen in the case of protonic ones, which offers the possibility of using a single electrode like the one described in the present invention to generate the electric field between it and the cathode of the electrochemical cell, or using two facing electrodes, leaving the complete electrochemical cell between both.

[0077] In the first case, the electrode object of the invention will be located after the anode of the electrochemical cell, and will be connected to the positive pole of an auxiliary power supply, while the cathode of the electrochemical cell will be connected to the negative pole of said power supply, which will generate a potential difference sufficient between them, to generate an electric field that will accelerate the movement of the dissociated oxygen ions towards the anode and will increase both the kinetics and the efficiency of the electrolytic process.

[0078] Thanks to the electrode object of the present invention, the main problem that high temperature electrolyzers have can be eliminated, which is the delamination of the anode that considerably reduces the useful life of the electrochemical cells, because in some areas of the interface between the electrolyte and the anode of the electrochemical cells, there is a high increase in the partial pressures of oxygen, due to the accumulation of diatomic oxygen that cannot escape, and which ends up causing micro-cracks in the anode, which over time ends up degrading and becoming separated from the electrolyte.

[0079] Considering that gaseous ions can move through vacuum and air, if they are propelled by an electric field, as occurs with the ion thrusters installed in space satellites, thanks to the electric field generated between the electrode object of the present invention and the cathode of the electrochemical cell, it is possible to slightly separate the anode from the electrolyte, which allows diatomic oxygen to escape and prevents delamination of the anode.

[0080] On the other hand, the speed at which oxygen ions move through the electrolyte and therefore the kinetics of the process, depends on the oxygen vacancies in the electrolyte and the potential difference between the anode and the cathode of the electrochemical cell, which is usually close to 1.5 V.

[0081] Since the voltage of the auxiliary power supply that will generate the potential difference between the electrode of the invention and the cathode will be much greater than 1.5 V, the electric field generated will greatly increase the speed of the oxygen ions, which will increase the kinetics of the process, increasing the production of hydrogen and oxygen and improving the efficiency of the process.

[0082] This is because, to achieve high efficiency, the cathode must be fed with water vapor at a temperature close to 800°C, which limits the type and number of facilities where waste heat from an industrial process, such as cement manufacturing, can be used to install electrolyzers of this type.

[0083] As the ion travel speed increases, the current flowing between the anode and cathode will increase. This, due to the Joule effect, will increase the cathode temperature, facilitating the dissociation of the water vapor molecules. This would significantly lower the temperature of the water vapor supplied to the electrochemical cells. The efficiency of the process will be improved because the energy consumed to generate the electric field will be very small, thanks to the high resistivity of Teflon. This will imply a very small leakage current, on the order of microamps, which means that the power dissipated in the electrode would be on the order of milliwatts.

[0084] Another very important aspect related to electrochemical cells for the production of hydrogen and oxygen is the protection against electric arcs that, as previously mentioned, is incorporated in the electrode that is the subject of this patent.

[0085] Thanks to the metallic control plate embedded in the dielectric material, at a certain distance from the electrode which is also embedded in the dielectric material, it is possible to monitor, by means of a control system, the potential differences generated between the electrode and the control plate, and between the control plate and the anode, so that when a dielectric breakdown occurs between any of these elements, the control system will cut off the power supply to the electrode in milliseconds, preventing an electric arc from being generated, or the two power supplies from being connected in parallel, which would generate a very high current from the higher voltage source to the lower voltage source, which could cause a fire, taking into account the flammable nature of hydrogen and oxygen.

[0086] As for the use of MIEC or ionic ceramic membranes for the separation of oxygen and other gases, which also operate at very high temperatures, between 500-1000°C, they do not need a power source to operate, because what is used to move the oxygen ions through the ceramic membrane and separate it from the air is the pressure difference at the inlet, which will be high, compared to the oxygen pressure on the other side of the membrane, which will be low.

[0087] In order to improve the efficiency and flow in the separation of oxygen through the ceramic membrane, the present invention proposes placing one or two electrodes such as those that are the object of this patent facing the ceramic membrane, and slightly separated from it, which fed by a power source, will create an electric field with sufficient intensity to facilitate the diffusion and transport of oxygen ions through the ceramic membrane, which would allow increasing the oxygen flow at the outlet, with a pressure and temperature of the air at the inlet noticeably lower, and therefore with an increase in the efficiency of the process, taking into account that thanks to the high resistivity of the dielectric material that covers the electrodes, the leakage current in the electrodes will be very small and therefore the energy consumed to generate the electric field will be very low,compared to the energy saved by reducing both the pressure and temperature of the air or gas mixture at the inlet of the ceramic separator.

[0088] If a single electrode is ultimately used, it will be placed on the output side of the ceramic membrane, connected to the positive pole of the power supply, and will act as the anode, while the ceramic membrane will be connected to the negative pole of the power supply and will act as the cathode. If two electrodes are used, the other electrode will act as the cathode.

[0089] Thanks to the characteristics and configuration of the electrode, it is possible to use it in this application as well as in those mentioned above, to improve both the efficiency of the processes, as well as the flow and quantity of material or elements obtained as a result of said processes, without the risk of an electric arc being generated during the process that could cause a fire or damage the equipment where the electrodes are installed.

[0090] The electrode system with protection against electric arc, the associated operating procedure, and the set of elements described represent an innovation with previously unknown structural and constitutive characteristics, reasons which, combined with its practical usefulness, provide sufficient grounds for obtaining the exclusive privilege requested.

[0091] BRIEF DESCRIPTION OF THE DRAWINGS

[0092] To complement the description being made and in order to help better understand the characteristics of the invention, a set of drawings is attached as an integral part of said description, in which the following has been represented for illustrative and non-limiting purposes:

[0093] Figure 1.- Section of the electrode object of the present invention.

[0094] Figure 2.- Detail of the electrode section.

[0095] Figure 3.- Section of an electrode system with material that is intended to be polarized in its central area.

[0096] Figure 4.- General exterior view of an electrode system.

[0097] Figure 5.- General exterior view of an electrode system with an outer casing, with a section in the central area to allow viewing of the interior.

[0098] Figure 6.- Diagram and equivalent circuit of an electrode system with material to be polarized

[0099] Figure 7.- Diagram and equivalent circuit of an electrochemical cell with an electric field electrode.

[0100] Figure 8.- Schematic and equivalent circuit of an electrochemical cell with an electric field electrode comprising a cooling device

[0101] Figure 9.- Diagram and equivalent circuit of an electrochemical cell with an electric field electrode system.

[0102] Figure 10.- Explanation of dielectric breakdown in the electrode system, and operation of the electric arc protection system.

[0103] Figure 11.- Explanation of dielectric breakdown in an electrochemical cell with an electric field electrode, without a metal control plate, and consequences.

[0104] Figure 12.- Explanation of dielectric breakdown in an electrochemical cell with an electric field electrode with a metal control plate, and operation of the electric arc protection system.

[0105] Figure 13.- Diagram of a gas separator with a ceramic membrane and an electric field electrode comprising a cooling device.

[0106] Figure 14.- Diagram of a gas separator with a ceramic membrane and an electric field electrode system.

[0107] List of references and figures:

[0108] 1. Electrode

[0109] 2. Dielectric material

[0110] 3. Metal control plate

[0111] 4. Control system

[0112] 5. Cooling device

[0113] 6. First metal plate connected to the second to form the Faraday Cage

[0114] 7. Second plate connected to form the Faraday Cage

[0115] 8. Element of thermal insulating material

[0116] 9. Refractory ceramic plate

[0117] 10. Ceramic resistance

[0118] 11. Outer casing

[0119] 12. Electrical connection input of the electrode together with the input and output of the cooling fluid

[0120] 13. Control board connection cable entry

[0121] 14. Cathode

[0122] 15. Anode

[0123] 16. Electrolyte

[0124] 17. Upper element of the electrode system 18. Lower element of the electrode system

[0125] 19. Material to be polarized

[0126] 20. Top of the polarization device

[0127] 21. Bottom of the polarization device

[0128] 22. Ceramic membrane

[0129] 23. Metal discharge plate

[0130] 24. Heating system connection cable entry

[0131] PREFERRED EMBODIMENT OF THE INVENTION

[0132] In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part of this specification, and in which specific preferred embodiments in which the invention may be carried out are shown by way of illustration.

[0133] These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that structural, mechanical, electrical, and / or chemical changes may be made without departing from the scope of the invention. To avoid unnecessary detail and to enable those skilled in the art to carry out the detailed description, the following embodiments should not, therefore, be taken in a limiting sense.

[0134] FIRST PREFERRED IMPLEMENTATION - SINGLE ELECTRODE

[0135] Specifically, the present invention describes an electrode (1) with protection against electric arc and to operate in high temperature environments, configured to generate an electric field, comprising at least one coating of dielectric material (2), which must be capable of maintaining its properties as a dielectric when subjected to temperatures above 100°C, where the electrode is configured to generate an electric field in an environment where the temperature exceeds 100°C.

[0136] Through this technical characteristic of including the coating of dielectric material (2), the invention manages to reduce the possibilities of an electric arc occurring when the electrode is used to generate an electric field in applications or environments where the temperature is high, since high temperatures facilitate the ionization of materials and gases subjected to an electric field, which favors the appearance of electric arcs.In particular, the invention is characterized in that it comprises at least one metallic control plate (3) located after and at a certain distance from the electrode (1), on the side where the electric field is generated, and which can be embedded in the dielectric material (2), or in contact with the face of the dielectric (2) that remains within the electric field, the electrode (1) and the metallic control plate (3) being connected to a control system (4) that monitors the potential difference that appears between the electrode (1) and the control plate (3), when the electrode is connected to an electric power supply and generating an electric field.

[0137] Where the control system (4) is capable of monitoring the potential difference existing between the control metal plate (3) and the electrode (1), being configured to:

[0138] • maintain the electrical supply to the electrode (1) as long as the potential difference remains above a previously determined value;

[0139] • cut off the power supply to the electrode (1) if the potential difference falls below the previously determined value.

[0140] Additionally, the control system (4) can be configured to activate a light signal on a control panel or send a message to a screen, along with an acoustic signal, to warn that the power supply to the electrode (1) has been cut off.

[0141] With this technical feature, it is controlled that, in the event of a possible dielectric breakdown of the dielectric material (2) that surrounds the electrode (1), the control system (4) cuts off the supply of electrical energy, avoiding the deterioration or destruction of the electrode (1) and / or the rest of the elements that form part of it.

[0142] In this way, in accordance with the objectives of the invention, it is possible, on the one hand, to minimize the possibilities of the appearance of an electric arc, and on the other hand, to cut off the electrical supply almost instantaneously in the event of an electric arc caused by the dielectric breakdown of the dielectric material coating (2) due to its degradation due to time, high temperature, and the effect of the electric fields on the material, protecting the entire system.

[0143] In a preferred embodiment, the inventor has found the use of polytetrafluoroethylene (PTFE), commonly known as Teflon®, to be advantageous since, according to the calculations shown below, considering that its dielectric strength is 60 KV / mm, and assuming that the electrode is covered by a 6 mm layer of Teflon®, a voltage of 360 KV would be required between the electrodes for an electric arc to form. It is important to bear in mind that the Teflon® layer covering the electrode is affected by the generated electric field and will therefore undergo polarization that will generate a voltage drop between the electrode and the metal control plate. Therefore, if we have two facing electrodes as described in this invention generating an electric field between them, the supply voltage will have to be increased to compensate for the voltage drop produced by the polarization of the Teflon®.

[0144] Below is a table with the calculations performed:

[0145] In a preferred embodiment, the electrode (1) additionally comprises at least one cooling device (5), preferably made of a conductive material, which partially or completely covers the coating of dielectric material (2), and through which a cooling fluid circulates.

[0146] This implementation responds to the need to reduce the temperature of the dielectric material coating (2), which could lose its integrity if the temperature exceeds a certain value, in addition to the consequent decrease in its dielectric strength, which would cause the electric arc to appear more easily. Continuing with the example of Teflon®, we find that its dielectric strength decreases from 300°C.

[0147] In a preferred embodiment, the cooling device (5) is located between two electrically connected metal plates (6,7), which implies that their electrical potential with respect to ground will be the same, and that they form a Faraday cage.

[0148] This embodiment responds to the need to prevent the cooling device (5), and any other element located after the dielectric material (2), for example, the cooling fluid, or a thermal insulator, from interfering with the generated electric field and weakening it, especially if the fluid or the insulator has a high dielectric constant.

[0149] In a preferred embodiment of the above, with the aim of minimising the amount of elements used in the electrode object of the present invention, one of the electrically connected metal plates (6,7) acts as a control metal plate (3), such that it will be the plate connected to the control circuit (4), together with the electrode (1).

[0150] According to the previous embodiments, referring to the cooling device or devices (5), and to the inclusion of the metal plates (6,7) that configure a Faraday cage, the inventor has found advantageous the particular embodiment in which the electrode comprises two cooling devices (5) connected to configure a single circuit for the cooling fluid: • a first cooling device (5) located between the two metal plates (6,7) that configure the Faraday cage, that is, by the part in which the electric field is generated;

[0151] • and a second cooling device (5) located on the outside of the assembly formed by the electrode (1) and the dielectric material (2), that is, on the part where the electric field is not generated.

[0152] In a preferred embodiment, the electrode (1) comprises as many elements of thermal insulating material (8) as necessary to fully or partially cover the different elements of the cooling device (5) that are not in direct contact with the dielectric material (2).

[0153] In this way, it is prevented that the heat to which the rest of the elements that make up the electrode (1) are subjected, if for example it is installed inside an oven, can raise the temperature of the cooling device (5) and the coolant, as well as decrease the temperature of the oven, with the consequent loss of efficiency.

[0154] In a preferred embodiment, the electrode (1) comprises a heating system located between the two electrically connected plates (6, 7). Preferably, the heating system comprises at least one refractory ceramic plate (9) and at least one ceramic resistor (10).

[0155] Following the preferred embodiment in which there is a cooling device (5) located between the two metal plates (6,7) that make up the Faraday cage, the heating system is located on the opposite side of the cooling device to which the metal plate (3) is in contact with the dielectric material (2).

[0156] In a preferred embodiment, the electrode (1) comprises at least one outer casing (11), with at least one hole for the entry of an electrical connection of the electrode (12) and at least one hole (13) for the electrical connection of the metal control plate (3), which in turn is connected to the control system (4).

[0157] Preferably, the housing (11) also comprises at least inlet and / or outlet holes for the cooling fluid that circulates through the cooling devices, which may coincide with the inlet of the electrical connection of the electrode (12).

[0158] Additionally, in the event that the electrode (1) comprises a heating system, the housing (11) also comprises a hole for the entry of the connection cable of the heating system (24)

[0159] Below, based on the previous embodiments, different applications of the electrode with protection against electric arc for high temperature operation object of the present invention are presented.

[0160] FIRST APPLICATION EXAMPLE - ELECTROLYSER WITH AN ELECTRIC FIELD ELECTRODE

[0161] Another possible application of the present invention is the use of an electrode like the one initially described to generate an electric field that accelerates ions entering it, applying by analogy the technology used in ion propellants. Specifically, the invention is applied to an electrolyzer.

[0162] In the following embodiments, although reference is made to an electrochemical cell operating in electrolysis mode, it can also be extended to its use for generating electrical energy, when the electrolyzer operates in fuel cell mode.

[0163] Likewise, the following characteristics would also be applicable to a stack of electrochemical cells operating in electrolyzer mode or fuel cell mode, since this is the way they are normally used.

[0164] In this case, the electrolyzer comprises at least one electrochemical membrane comprised of a cathode (14), an anode (15) and a non-conductive electrolyte (16) located between the cathode (14) and the anode (15), such that the electrochemical cell is configured to dissociate the oxygen ions from a stream of water vapor, transport them to the anode (15) and generate a flow of hydrogen and another of oxygen.

[0165] In particular, the present invention describes the use of an electrode (1) with protection against electric arc that can operate at high temperature, configured to generate an electric field, comprising at least one dielectric material (2), and additionally comprising at least one metallic control plate (3) embedded in the dielectric material (2), and connected to at least one control system (4), capable of monitoring multiple potential differences such as that generated during operation of the electrode, between the metallic control plate (3) and the electrode (1), which is also connected to the control system (4); said control system also monitoring the potential difference existing between the metallic control plate (3) and the anode (15).Where the control system (4) is capable of monitoring at the same time the potential differences existing between the control metal plates (3), and the electrodes (1) and anodes (15) of a plurality of electrochemical cells that, being interconnected in series or in parallel, form an electrochemical cell, and where said control system (4) is configured to:.

[0166] • maintain the electrical supply to the electrode (1) of each cell while the voltage (V B ) and (V D ) remain above a previously determined value;

[0167] • and cut off the power supply to the electrode (1) of each cell in case of decrease in any of the voltages (V B ) or (V D ) below the previously determined value.

[0168] Additionally, the control system (4) can be configured to activate a light signal on a control panel or send a message to a screen, together with an acoustic signal, to warn that the power supply to one of the electrochemical cells has been cut off, including identifying the cell to which the power supply to the electrode (1) has been cut off.

[0169] In particular, the electrode (1) is connected to the positive pole of the power supply that provides the potential difference necessary to generate the electric field, while the cathode (14) of the electrochemical cell is connected to the negative pole of said power supply, applying a potential difference sufficient between them to generate an electric field that accelerates the displacement of the dissociated oxygen ions and increases both the kinetics and the efficiency of the electrolytic process.

[0170] In addition to allowing work at high temperatures and voltages, the above configuration allows the anode (15) to be slightly separated from the electrolyte (16), avoiding the delamination problems that this type of membrane suffers during its use in high temperature electrolysers, thanks to the fact that the gaseous ions can move through the air if they are driven by an electric field.

[0171] In a preferred embodiment, the inventor has found the use of polytetrafluoroethylene (PTFE), commonly referred to as Teflon®, to be advantageous.

[0172] In a preferred embodiment, the electrode (1) additionally comprises at least one cooling device (5), preferably made of a conductive material, which partially or completely covers the dielectric material (2), and through which a cooling fluid circulates.

[0173] This implementation responds to the need to reduce the temperature of the dielectric material (2), which could lose its integrity, in addition to the consequent decrease in its dielectric strength, which would cause the electric arc to appear more easily. Continuing with the Teflon® example, we find that its dielectric strength decreases from 300°C.

[0174] In Figure 7 we can see the equivalent circuit in which we find three virtual capacitors: a first capacitor formed by the electrode (1) and the control board (3); a second capacitor formed by the control board (3) and the anode (15); and a third capacitor formed by the anode (15) and the cathode (14) of the electrochemical cell.

[0175] It can also be observed how both the control metal plate (3), the electrode (1) and the anode (15), are connected to the control system (4), which controls the potential difference between the electrode (1) and the control metal plate (3), (V B ); as well as the potential difference between the control metal plate (3) and the anode (15), (V D ).

[0176] In this case, it is necessary to simultaneously monitor both potential differences (V B ) y (V D), because the objective of said control is to detect the dielectric breakdown of the dielectric material (2), due to its progressive degradation when subjected to high temperatures and the electric field, and cut off the power supply to the electrode (1) to prevent damage to both the electrochemical cells and the power supplies, and thus minimize the possibility of a fire occurring in the electrolyzing equipment due to the flammable nature of the hydrogen and oxygen generated during the electrolysis process.

[0177] Figure 11 shows what would happen if dielectric breakdown of the dielectric material (2) occurred and the metal control plate (3) did not exist between the electrode (1) and the anode (15).

[0178] As can be seen in Figure 11, the electrochemical cell is connected to two different power supplies that supply DC energy at two different voltages. The first power supply is connected to the anode and cathode of the electrochemical cell and supplies the energy required to cause the electrolysis of water vapor at a voltage close to 1.5 V and is represented by (V A ). The second power supply is connected between the cathode (14) and the electrode (1), and provides the potential difference necessary to generate the electric field that drives the O2 ions towards the anode (15), and works at a much higher voltage represented by (V c ), which is the first power supply.

[0179] If dielectric breakdown of the dielectric material (2) were to occur, it would cease to be an insulator and would become a conductor, which would mean that at that moment the two power sources would be interconnected in parallel. If this were to happen, due to the large potential difference between the two power sources, a very high current would be generated from the source that supplies energy at a higher voltage, towards the source of lower voltage. This could cause serious damage to both the electrochemical cell and the electrolyser equipment, and could even cause a fire due to the flammable nature of hydrogen and oxygen.

[0180] However, as can be seen in Figure 12, if the metallic control plate (3) is inserted in the intermediate zone of the dielectric material (2), between the anode (15) and the electrode (1), and the potential difference between the anode (15) and the control plate (3), corresponding to (V D ), and the potential difference between the control plate (3) and the electrode (1) corresponding to (V B ), taking into account that it is practically impossible for the dielectric breakdown of the two sections of the dielectric material (2) to occur due to degradation with a time margin of less than milliseconds, the probability of the parallel connection of the two power supplies occurring is practically zero, since as soon as (V D ) or (V B) fall below a certain value, the control system (4) will cut off the power supply to the electrode (1) within a few milliseconds.

[0181] SECOND APPLICATION EXAMPLE - OXYGEN SEPARATION BY CERAMIC MEMBRANES, WITH AN ELECTRIC FIELD ELECTRODE

[0182] Another possible application of the electrode object of the present invention is, as in the case of high temperature electrolysis, its use to accelerate the movement of oxygen ions through a ceramic membrane, for its separation from air or other gases.

[0183] In this case, the gas separator comprises at least one ceramic membrane (22) comprised of an inlet where a pressurized gas mixture containing oxygen is injected, and an outlet on the other side of the ceramic membrane (22) where a low-pressure carrier gas is injected, to extract the oxygen separated from the inlet gas mixture.

[0184] In particular, the present invention describes the use of an electrode (1) with protection against electric arc that can operate at high temperature, configured to generate an electric field, comprising at least one dielectric material (2), and additionally comprising at least one metallic control plate (3) embedded in the dielectric material (2), and connected to at least one control system (4), capable of monitoring multiple potential differences such as that generated during operation of the electrode, between the metallic control plate (3) and the electrode (1), which is also connected to the control system (4); said control system also monitoring the potential difference existing between the metallic control plate (3) and the ceramic membrane (22).Where the control system (4) is capable of monitoring at the same time the potential differences existing between a plurality of metallic control plates (3) and electrodes (1), and between a plurality of metallic control plates (3) and the ceramic membranes (22) which, being interconnected in series or in parallel, form a battery, and where said control system (4) is configured to:.

[0185] • maintain the electrical supply to the electrode (1) of each cell while the voltage (V B ) and (V D ) remain above a previously determined value;

[0186] • and cut off the power supply to the electrode (1) of each cell in case of decrease in any of the voltages (V B ) or (V D ) below the previously determined value.

[0187] Additionally, the control system (4) can be configured to activate a light signal on a control panel or send a message to a screen, together with an acoustic signal, to warn that the power supply to the electrode (1) of any of the ceramic membranes (22) has been cut off, including identifying the membrane and the electrode to which the power supply has been cut off.

[0188] In particular, the electrode (1) is connected to the positive pole of the power supply that provides the potential difference necessary to generate the electric field, while the ceramic membrane (22) is connected to the negative pole of said power supply, applying a potential difference sufficient between them to generate an electric field that accelerates the displacement of the dissociated oxygen ions and increases both the kinetics and the efficiency of the gas separation process.

[0189] In a preferred embodiment, the inventor has found the use of polytetrafluoroethylene (PTFE), commonly referred to as Teflon®, to be advantageous.

[0190] In a preferred embodiment, the electrode (1) additionally comprises at least one cooling device (5), preferably made of a conductive material, which partially or completely covers the dielectric material (2), and through which a cooling fluid circulates.

[0191] This implementation responds to the need to reduce the temperature of the dielectric material (2), which could lose its integrity, in addition to the consequent decrease in its dielectric strength, which would cause the electric arc to appear more easily. Continuing with the Teflon® example, we find that its dielectric strength decreases from 300°C.

[0192] In this case, as can be seen in Figure 13, it is necessary for the cooling circuit (5) to be connected to the ceramic membrane (22) so that the O2 ions that have reached the metal surface of the cooling circuit (5) do not accumulate, charging it, but rather the electrons released by the O2 ions can have a path back to the ceramic membrane (22). In the event that the electrode does not have a cooling circuit (5), not shown in the Figure, it is necessary to include a metal discharge plate (23) on the surface of the dielectric material, which will be connected to the ceramic membrane (22).

[0193] In Figure 13 we can see how both the metallic control plate (3) and the ceramic membrane (22) are connected to the control system (4), which controls the potential difference between the electrode (1) and the metallic control plate (3), (V B); as well as the potential difference between the control metal plate (3) and the ceramic membrane (22), (V D ).

[0194] In this case, it is necessary to simultaneously monitor both potential differences (V B ) and (V D ) because the objective of said control is to detect the dielectric breakdown of the dielectric material (2), due to its progressive degradation when subjected to high temperatures and the electric field, and cut off the power supply to the electrode (1) to prevent damage to both the electrochemical cells and the power supplies, and thus minimize the possibility of a fire occurring in the gas separation equipment due to the flammable nature of oxygen.

[0195] SECOND PREFERRED EMBODIMENT - ELECTRODE SYSTEM

[0196] Specifically, the present invention describes an electrode system with protection against electric arc for operation at high temperatures, configured to generate an electric field, comprising at least a first upper element (17) and a second lower element (18), where the upper element (17) and the lower element (18) are practically symmetrical, and each of them comprises at least one electrode (1) and a dielectric material (2), which must be capable of maintaining its properties as a dielectric when subjected to temperatures greater than 100°C, where the electrode or electrodes are configured to generate an electric field in an environment in which the temperature exceeds 100°C.

[0197] Through this technical feature, the invention manages to reduce the possibilities of dielectric breakdown of the dielectric material surrounding the electrode (1) due to high temperature, with the consequent appearance of the electric arc between the two electrodes.

[0198] In particular, the invention is characterized in that the upper element (17) and the lower element (18) additionally comprise a metallic control plate (3) located below and at a certain distance from the electrode (1), on the side where the electric field is generated, and which can be completely embedded in the dielectric material (2), or externally in contact with the face of the dielectric (2) that remains within the electric field, and connected to a control system (4), which monitors the potential difference generated during operation of the electrode, between the metallic control plate (3) and the electrode (1), which is also connected to the control system (4) of each of the upper (17) and lower (18) elements.

[0199] Where the control system (4) is capable of monitoring the potential difference existing between the control metal plate (3) and the electrode (1) of each of the upper (17) and lower (18) elements, being configured to:

[0200] • maintain the electrical supply to the electrodes (1), as long as the potential difference remains above a previously determined value;

[0201] • and cut off the power supply to the electrodes (1), if the potential difference decreases below the previously determined value.

[0202] Additionally, the control system (4) can be configured to activate a light signal on a control panel or send a message to a screen, together with an acoustic signal, to warn that the power supply to one of the electrodes (1) of the elements (17) or (18) has been cut off, including identifying the element to which the power supply to the electrode (1) has been cut off.

[0203] With this last technical characteristic, it is controlled that, in the event of a possible dielectric breakdown of the dielectric material (2), the control system (4) cuts off the supply of electrical energy, avoiding the deterioration or destruction of vapors from the elements that make up the assembly, so it acts as a reactive protection system against a voltage drop that occurs between the electrodes (1) and the metal control plate (3), when the dielectric breakdown of the dielectric material (2) that surrounds the electrode (1) occurs.

[0204] Taking into account that in this case, for an electric arc to be generated between the electrodes (1) of the elements (17, 18) it would be necessary for the dielectric breakdown of the dielectric material surrounding both electrodes to occur due to its degradation, and that it is practically impossible for said breakdown to occur at the same instant, or with a difference of less than a few milliseconds, the possibility of an electric arc being generated is reduced to almost zero, since the control system (4) will cut off the power supply as soon as it detects that the dielectric breakdown of the dielectric material (2) of any of the elements (17) or (18) has occurred.

[0205] In this way, in accordance with the objectives of the invention, it is possible on the one hand to initially reduce the possibilities of the appearance of an electric arc, and on the other hand, by cutting off the electrical supply very quickly in the event of dielectric breakdown of the dielectric material coating (2) due to its degradation over time, high temperature, and the effect of the electric fields on the material, the eventual appearance of an electric arc is almost completely eliminated, protecting the entire system.

[0206] In a preferred embodiment, the inventor has found the use of polytetrafluoroethylene (PTFE), commonly referred to as Teflon®, to be advantageous.

[0207] In a preferred embodiment, each upper (17) and lower (18) element additionally comprises at least one cooling device (5), preferably made of a conductive material, which partially or completely covers the dielectric material (2), and through which a cooling fluid circulates.

[0208] In a preferred embodiment, the cooling device (5) is located between two electrically connected metal plates (6,7), which implies that their electrical potential with respect to ground will be the same, and that they form a Faraday cage.

[0209] This embodiment responds to the need to prevent the cooling device (5), and any other element located after the dielectric material (2), for example, the cooling fluid, or a thermal insulator, from interfering with the generated electric field and weakening it, especially if the fluid or the insulator has a high dielectric constant.

[0210] In a preferred embodiment of the above, with the aim of minimising the amount of elements used in the electrode system object of the present invention, one of the electrically connected metal plates (6,7) acts as a control metal plate (3), such that it will be the plate connected to the control circuit (4), together with the electrode (1).

[0211] According to the previous embodiments, referring to the cooling device or devices (5), and to the inclusion of the metal plates (6,7) that configure a Faraday cage, the inventor has found advantageous the particular embodiment in which the electrode system comprises two cooling devices (5) connected to configure a single circuit for the cooling fluid:

[0212] • a first cooling device (5) located between the two metal plates (6,7) that make up the Faraday cage, that is, located between the two or more electrodes (1) generating the electric field;

[0213] • and a second cooling device (5) located on the outside of the assembly formed by the electrode (1) and the dielectric material (2), that is, on the part that is not located between the two or more electrodes generating the electric field.

[0214] In a preferred embodiment, the electrode system comprises as many elements of thermal insulating material (8) as necessary to fully or partially cover the different elements of the cooling device (5) that are not in direct contact with the dielectric material (2).

[0215] In this way, the heat to which the rest of the elements that make up the electrode system are subjected, if for example it is installed inside an oven, is prevented from raising the temperature of the cooling device (5) and the coolant, as well as decreasing the temperature of the oven, with the consequent loss of efficiency.

[0216] In a preferred embodiment, the electrode system comprises a heating system located between the two or more electrodes (1) for generating an electric field, specifically, the heating system is located between the two electrically connected plates (6,7).

[0217] Preferably, the heating system comprises at least one refractory ceramic plate (9) and at least one electrical resistance (10), which is preferably a ceramic resistance.

[0218] Following the preferred embodiment in which there is a cooling device (5) located between the two metal plates (6,7) that make up the Faraday cage, the heating system is located on the opposite side of the cooling device (5) to which the metal plate (3) is in contact with the dielectric material (2).

[0219] In a preferred embodiment, the electrode system is located inside two outer casings (11), each of the casings (11) with its corresponding electrode (1), where at least one of the outer casings (11) comprises a hole for the entry of the electrical connection of the electrode (12) and an entry (13) for the connection cable of the control board (3) with the control system (4).

[0220] In another preferred embodiment, at least one of the housings (11) also comprises the inlet and / or outlet holes for the cooling fluid that circulates through the cooling devices, which may coincide with the inlet of the electrical connection of the electrode (12).

[0221] Additionally, in the case where the electrode system comprises a heating system, the housing (11) also comprises a hole for the entry of the heating system connection cable (24). Figure 6 shows the equivalent circuit obtained from the electrode system described above.

[0222] As can be seen, we find three virtual capacitors: one formed by the electrode (1) and the control plate (3) of the upper element (17), taking into account that in this case the control plate (3) corresponds to the metal plate (6) electrically connected to the metal plate (7); another formed by the metal plates (7) that do not act as a control plate (3) of each of the upper (17) and lower (18) elements; and a last capacitor that is symmetrical to the first, that is, it is formed by the electrode (1) and the control plate (3) of the lower element (18), taking into account that in this case the control plate (3) corresponds to the metal plate (6) electrically connected to the metal plate (7) of the element (18).

[0223] Likewise, the potential differences (V1, V2, V3) that would exist between the different elements can also be observed, being constantly monitored by the control system (4), to detect a possible dielectric breakdown of the dielectric material (2) and cut off the power supply to the electrodes if this occurs.

[0224] In this case (V1, V3) correspond to the potential differences between the electrodes (1) and the control plates (3), while (V2) corresponds to the effective potential difference, (V2) = (VT)-(V1+V3) that will generate the desired electric field, where (VT) is the supply voltage of the electrodes (1).

[0225] FIRST APPLICATION EXAMPLE - POLARIZATION DEVICE

[0226] In a first application of the invention, a polarization device is described according to figures 3, 4 and 5, according to which the electrode system is used to apply an electric field on a material to be polarized (19), and which is characterized in that it comprises at least one compartment, in which at least one pair of electrodes is housed according to the previous embodiments.

[0227] Specifically, according to figure 5, a polarization device is described that is divided into an upper part (20) and a lower part (21), where:

[0228] • the lower part (21) includes one of the electrodes (1), which is fixed;

[0229] • and the upper part (20) includes the other electrode (1), and comprises a vertical translation movement, being able to vary the distance between the electrode of the lower part (21) and the electrode of the upper part (20) to adapt to the thickness of the material to be polarized (19).

[0230] Likewise, the polarization device includes all the means necessary for the correct operation of the electrode system, such as the power supply and control means operationally connected to the different elements.

[0231] In a preferred embodiment, the upper part (20) comprises means for completely separating the upper part (20) from the lower part (21). For example, it may comprise a pivoting joint on one of its sides, which may be actuated manually or automatically, so that a relative rotation is applied between the upper part and the lower part.

[0232] Likewise, in a preferred embodiment, the polarization device comprises thermal insulation means, so as to prevent heat loss to the outside of the device.

[0233] A particular application of the polarization device lies in its use for polarizing piezoelectric electrodes which, as indicated above, must be polarized at high temperatures and with the application of high potential differences between the electrodes. This increases the risk of dielectric breakdown of the piezoelectric electrode with the consequent formation of an electric arc, which entails the destruction of the piezoelectric electrode and possible damage to both the electrodes and the polarizing equipment. This risk increases proportionally with the dimensions of the piezoelectric electrode.

[0234] Taking Figure 6 as a representation of the equivalent electrical circuit, in this case, the material that is intended to be polarized (19) would act as a dielectric in the virtual capacitor formed by the metal plates (7) that do not act as a control plate (3) of each of the upper (17) and lower (18) elements.

[0235] SECOND APPLICATION EXAMPLE - ELECTROLYSER WITH ELECTRODE SYSTEM

[0236] Another configuration of the previous application is based on the use of an electrode system to generate an electric field that accelerates the ions that penetrate it, applying by analogy the technology used in ionic propellants.

[0237] In the same way as in the previous application, the electrolyzer comprises at least one electrochemical cell comprised of a cathode (14), an anode (15) and a non-conductive electrolyte (16) located between the cathode (14) and the anode (15), such that the electrochemical cell is configured to dissociate the oxygen ions from a stream of water vapor in the cathode (14), transport them to the anode (15) and generate a flow of hydrogen and another of oxygen.

[0238] In particular, the present invention describes the use of an electrode system comprising at least two electrodes (1) configured to generate an electric field, where the electrodes (1) comprise at least one coating of dielectric material (2), and which additionally comprise at least one metallic control plate (3) embedded in the dielectric material (2), and connected to at least one control system (4), capable of monitoring multiple potential differences such as that generated during operation of the electrode, between the metallic control plate (3) and the electrode (1), which is also connected to the control system (4); said control system also monitoring the potential difference existing between the metallic control plate (3) and the anode (15).

[0239] Where the metallic discharge plate (23) that is electrically connected to the cathode (14), has the double function of facilitating the hydrogen ions that have reached it, the capture of electrons in order to form diatomic hydrogen, and on the other hand acting as a control plate to detect a possible dielectric breakdown in the section of the dielectric material existing between it and the other control plate (3).

[0240] Where the control system (4) is capable of simultaneously monitoring the potential differences existing between the control metal plates (3), and the electrodes (1) and anodes (15) of a plurality of electrochemical cells which, being interconnected in series or in parallel, make up an electrochemical cell, and where said control system (4) is configured to:

[0241] • maintain the electrical supply to the electrodes (1) of each cell, as long as the voltage remains above a previously determined value;

[0242] • and cut off the power supply to the electrodes (1) of each cell, in the event of a voltage drop below the previously determined value.

[0243] Additionally, the control system (4) can be configured to activate a light signal on a control panel or send a message to a screen, together with an acoustic signal, to warn that the power supply to the electrode (1) of one of the electrochemical cells has been cut off, including identifying the cell and the electrode to which the power supply has been cut off.

[0244] In a preferred embodiment, the inventor has found the use of polytetrafluoroethylene (PTFE), commonly known as Teflon®, to be advantageous, since given that its dielectric strength, which remains stable up to 300°C, is 60KV / mm, a very high voltage would be required between the electrodes for an electric arc to form, in addition to having a very low dielectric constant of 2.1 and its high resistivity 10 18 Q x cm contributes to the leakage current in the electrodes being very small, and therefore the power dissipated in the electrodes being very small as well.

[0245] In a preferred embodiment, each electrode (1) additionally comprises at least one cooling device (5), preferably made of a conductive material, which partially or completely covers the dielectric material (2), and through which a cooling fluid circulates.

[0246] This implementation responds to the need to reduce the temperature of the dielectric material (2), which could lose its integrity, in addition to the consequent decrease in its dielectric strength, which would cause the electric arc to appear more easily. Continuing with the example of Teflon®, we find that its dielectric strength decreases from 300°C.

[0247] In a preferred embodiment, the cooling device (5) is located between two electrically connected metal plates (6,7), forming an electrical conductor, such that they form a Faraday cage.

[0248] This embodiment responds to the need to prevent the cooling device (5), and any other element located after the dielectric material (2), for example, the cooling fluid, or a thermal insulator, from interfering with the generated electric field and weakening it, especially if the fluid or the insulator has a high dielectric constant.

[0249] In a preferred embodiment of the above, with the aim of minimising the amount of elements used in the electrode object of the present invention, one of the electrically connected metal plates (6,7) acts as a control metal plate (3), such that it will be the plate connected to the control system (4), together with the electrode (1).

[0250] According to the previous embodiments, referring to the cooling device or devices (5), and to the inclusion of the metal plates that configure a Faraday cage, the inventor has found advantageous the particular embodiment in which the electrode system comprises two cooling devices (5) connected to configure a single circuit for the cooling fluid:

[0251] • a first cooling device (5) located between the two metal plates (6,7) that make up the Faraday cage, that is, located between the two or more electrodes generating the electric field;

[0252] • and a second cooling device (5) located on the outside of the assembly formed by the electrode (1) and the dielectric material (2), that is, on the part that is not located between the two or more electrodes generating the electric field.

[0253] In a preferred embodiment, the electrode system comprises as many elements of thermal insulating material (8) as necessary to fully or partially cover the different elements of the cooling device (5) that are not in direct contact with the dielectric material (2).

[0254] In this way, the cathode (14) and anode (15) are prevented from cooling, and also from raising the temperature of the cooling device (5) and the coolant, with the consequent loss of efficiency.

[0255] THIRD APPLICATION EXAMPLE - OXYGEN SEPARATION USING CERAMIC MEMBRANES, WITH ELECTRODE SYSTEM

[0256] Another possible application of the electrode system according to the previous embodiments is, as in the case of high-temperature electrolysis, its use to accelerate the movement of oxygen ions through a ceramic membrane, for its separation from air or other gases.

[0257] In the same way as in the previous application, the gas separator comprises at least one ceramic membrane (22) comprised of an inlet where a mixture of pressurized gases containing oxygen is injected, and an outlet on the other side of the ceramic membrane (22) where a low-pressure carrier gas is injected to extract the oxygen separated from the mixture of gases at the inlet.

[0258] In particular, the present invention describes the use of an electrode system comprising at least two electrodes (1) configured to generate an electric field, where the electrodes (1) comprise at least one coating of dielectric material (2), and which additionally comprise at least one metallic control plate (3) embedded in the dielectric material (2), and connected to at least one control system (4), capable of monitoring multiple potential differences such as that generated during operation of the electrode, between the metallic control plate (3) and the electrode (1), which is also connected to the control system (4); said control system also monitoring the potential difference existing between the metallic control plate (3) and the ceramic membrane (22)

[0259] Where the control system (4) is capable of monitoring at the same time the potential differences existing between a plurality of metallic control plates (3) and electrodes (1), and between a plurality of metallic control plates (3) and the ceramic membranes (22) which, being interconnected in series or in parallel, form a battery, and where said control system (4) is configured to:

[0260] • maintain the electrical supply to the electrodes (1) of each cell, while the potential differences remain above a previously determined value;

[0261] • and cut off the power supply to the electrodes (1) of each cell, if the potential differences decrease below the previously determined value.

[0262] Additionally, the control system (4) can be configured to activate a light signal on a control panel or send a message to a screen, together with an acoustic signal, to warn that the power supply to the electrode (1) of any of the ceramic membranes (22) has been cut off, including identifying the membrane and the electrode to which the power supply has been cut off.

[0263] In a preferred embodiment, the inventor has found the use of polytetrafluoroethylene (PTFE), commonly known as Teflon®, to be advantageous, since given that its dielectric strength, which remains stable up to 300°C, is 60KV / mm, a very high voltage would be required between the electrodes for an electric arc to form, in addition to having a very low dielectric constant of 2.1 and its high resistivity 10 18Q x cm contributes to the leakage current in the electrodes being very small, and therefore the power dissipated in the electrodes being very small as well.

[0264] In a preferred embodiment, each electrode (1) additionally comprises at least one cooling device (5), preferably made of a conductive material, which partially or completely covers the dielectric material (2), and through which a cooling fluid circulates.

[0265] This implementation responds to the need to reduce the temperature of the dielectric material (2), which could lose its integrity, in addition to the consequent decrease in its dielectric strength, which would cause the electric arc to appear more easily. Continuing with the example of Teflon®, we find that its dielectric strength decreases from 300°C.

[0266] In this case, it is necessary that the cooling circuit (5) be connected to the ceramic membrane (22), so that the O2 ions that have reached the metallic surface of the cooling circuit (5) do not accumulate, charging it, but rather the electrons released by the O2 ions can have a path back to the ceramic membrane (22). In the event that the electrode does not integrate a cooling circuit (5), as can be seen in Figure 14, it is necessary to include a metallic discharge plate (23) on the surface of the dielectric material, which will be connected to the ceramic membrane (22). In Figure 14 we can see how both the metallic control plate (3) and the ceramic membrane (22) are connected to the control system (4), which controls the potential difference between the electrode (1) and the metallic control plate (3), (V B , V E); as well as the potential difference between the control metal plate (3) and the ceramic membrane (22), (V D , V F ).

[0267] In this case, it is necessary to simultaneously monitor all potential differences (V B , VE) and (V D , V F ) because the objective of said control is to detect the dielectric breakdown of the dielectric material (2), due to its progressive degradation when subjected to high temperatures and the electric field, and cut off the power supply to the electrode (1) to prevent damage to both the electrochemical cells and the power supplies, and thus minimize the possibility of a fire occurring in the gas separation equipment due to the flammable nature of oxygen.

Claims

CLAIMS 1. An electric arc protection electrode for high temperature operation for generating an electric field, comprising at least one coating of a dielectric material (2); characterized in that it comprises at least one metal control plate (3) located downstream and at a distance from the electrode (1), on the side where the electric field is generated, and which may be embedded in the dielectric material (2), or in contact with the side of the dielectric (2) that lies within the electric field, the electrode (1) and the metal control plate (3) being connected to a control system (4) that monitors the potential difference that appears between the electrode (1) and the control plate (3), when the electrode is connected to an electrical power supply and generating an electric field, where the control system (4) is configured to: • maintain the electrical supply to the electrode (1) as long as the potential difference remains above a previously determined value; • cut off the power supply to the electrode (1) if the potential difference falls below the previously determined value.

2. Electrode according to the preceding claim, characterized in that the dielectric material (2) is polytetrafluoroethylene.

3. Electrode according to any of the preceding claims, characterized in that it comprises at least one cooling device (5) that partially or totally covers the dielectric material (2), through which a cooling fluid circulates.

4. Electrode according to the preceding claim, characterized in that the cooling device (5) is located between two electrically connected metal plates (6,7).

5. Electrode according to the preceding claim, characterized in that at least one of the plates (6,7) acts as a metallic control plate (3) together with the electrode (1), so that the control system (4) can monitor the potential difference between them.

6. Electrode according to any of claims 4 or 5, characterized in that it comprises a heating system located between the two electrically connected metal plates (6,7).

7. Electrode according to the preceding claim, characterized in that the heating system comprises at least one refractory ceramic plate (9) and a ceramic resistance (10).

8. Electrode according to any of the preceding claims, characterized in that it comprises elements of thermal insulating material (8) totally or partially covering the parts of the cooling device (5) that are not in direct contact with the dielectric material (2).

9. Electrode according to any of the preceding claims, characterized in that it comprises an outer casing (11) with at least one hole for the entry of an electrical connection of the electrode (12) and at least one hole (13) for the connection cable of the control board (3) with the control system (4).

10. Electrode according to the preceding claim, characterized in that the outer casing comprises inlet and / or outlet holes for the cooling fluid that circulates through the cooling device (5) and / or an inlet hole for the connection cable of the heating system (24).

11. Electrode according to any of the preceding claims, characterized in that it comprises light indication means and / or acoustic indication means and / or display indication means.

12. Electrode system for generating an electric field, with protection against electric arc for high temperature operation, comprising at least a first upper element (17) and a second lower element (18), each comprising at least one electrode (1) and a dielectric material (2);characterized in that the upper element (17) and the lower element (18) comprise at least one control metal plate (3) located below and at a certain distance from the electrode (1), on the side where the electric field is generated, and which can be embedded in the dielectric material (2), or in contact with the face of the dielectric (2) that remains within the electric field, the electrode (1) and the control metal plate (3) being connected to a control system (4) that monitors the potential difference that appears between the electrode (1) and the control plate (3) of each of the upper (17) and lower (18) elements, when the electrodes (1) are connected to an electrical power supply and generating an electric field, where the control system (4) is configured to:; • maintain the electrical supply to the electrodes (1) as long as the potential difference remains above a previously determined value; • cut off the power supply to the electrodes (1) if the potential difference falls below the previously determined value.

13. Electrode system according to the preceding claim, characterized in that the dielectric material (2) is polytetrafluoroethylene.

14. Electrode system according to the preceding claim, characterized in that each upper (17) and lower (18) element comprises at least one cooling device (5) that partially or totally covers the dielectric material (2), through which a cooling fluid circulates.

15. Electrode system according to any of the preceding claims, characterized in that the cooling device (5) is located between two electrically connected metal plates (6,7).

16. Electrode system according to the preceding claim, characterized in that at least one of the plates (6,7) acts as a metallic control plate (3) together with the electrode (1), so that the control system (4) can monitor the potential difference between them.

17. Electrode system according to any of claims 15 or 16, characterized in that it comprises a heating system located between the two electrically connected metal plates (6,7).

18. Electrode system according to the preceding claim, characterized in that the heating system comprises at least one refractory ceramic plate (9) and an electrical resistance (10).

19. Electrode system according to any of the preceding claims, characterized in that it comprises elements of thermal insulating material (8) totally or partially covering the parts of the cooling device (5) that are not in direct contact with the dielectric material (2).

20. Electrode system according to any of the preceding claims, characterized in that all the preceding elements are located inside two outer casings (11).

21. Electrode system according to the preceding claim, characterized in that at least one of the outer casings (11) comprises at least one hole for the entry of the electrical connection of the electrode (12) and a hole (13) for the connection cable of the control board (3) with the control system (4).

22. Electrode system according to the preceding claim, characterized in that at least one of the outer casings (11) comprises inlet and / or outlet holes for the cooling fluid that circulates through the cooling device (5) and / or inlet holes for the connection cable of the heating system (24).

23. Electrode system according to any of the preceding claims, characterized in that it comprises light indication means and / or acoustic indication means and / or screen indication means.

24. Polarization device characterized in that it comprises at least one compartment in which at least one electrode system according to the preceding claims is housed and comprises the means necessary for the correct operation of the electrode system.

25. Polarization device according to the preceding claim, characterized in that it is divided into an upper part (20) and a lower part (21), where: • the lower part (21) includes the lower element (18), which is fixed; • the upper part (20) includes the upper element (17) comprising a vertical translation movement, configuring the distance between the electrode of the lower part (21) and the electrode of the upper part (20).

26. Polarization device according to the preceding claim, characterized in that the upper part (20) comprises means for completely separating the upper part (20) from the lower part (21).

27. Polarization device according to the preceding claim, characterized in that the means for completely separating the upper part (20) from the upper element (17) are a pivoting joint between the upper part (20) and the lower part (21), configured to allow relative rotation of the upper half with respect to the lower half.

28. Polarization device according to any of the preceding claims, characterized in that it comprises at least one hole for the entry of the electrical connection of the electrode (12), a hole (13) for the connection cable of the control board (3) with the control system (4) and / or the inlet and outlet of the cooling fluid and / or a hole for the connection cable of the heating system (24).

29. Polarization device according to any of the preceding claims, characterized in that it comprises thermal insulation means.

30. Electrolyzer comprising at least one electrochemical cell comprised of a cathode (14), an anode (15) and an electrolyte (16), characterized in that it comprises an electrode according to claims 1 to 11.

31. Electrolyzer comprising at least one electrochemical membrane comprised of a cathode (14), an anode (15) and an electrolyte (16), characterized in that it comprises an electrode system according to claims 12 to 23.

32. Device for gas separation comprising a ceramic membrane (22) characterized in that it comprises an electrode according to claims 1 to 11.

33. Device for gas separation comprising a ceramic membrane (22) characterized in that it comprises an electrode system according to claims 12 to 23.

34. Device for gas separation according to any of claims 32 or 33. 33 characterized in that it comprises a metal discharge plate (23) connected to the ceramic membrane (22) configured to conduct the electrons released by the gaseous ions to the ceramic membrane (22), and which also acts as a control plate.

35. Device for gas separation according to any of claims 32 to 34. 34 characterized in that the gas that separates the device is oxygen.

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