System and method for operating a seawater electrolysis system to split seawater into hydrogen and oxygen

Abstract

System for operating a seawater electrolysis system (1) with seawater (9) as electrolyte for decomposing seawater (9) into hydrogen and oxygen, but without the use of semipermeable or polymer electrolyte membranes, wherein the seawater electrolysis system (1) comprises a seawater electrolyzer (4) filled with seawater (9) as electrolyte, wherein a plurality of cathodes (2) and anodes (3) are arranged parallel to each other and immersed in the seawater (9), wherein in the direction of flow of the seawater (9) the cathodes (2) and anodes (3) are arranged in series or alternately, and are connected via a control device (19) to at least one DC voltage (8), wherein an electrode heater (30) is integrated inside each of the electrodes (2, 3).wherein a hydrogen collection chamber (15) and oxygen collection chamber (16) are arranged directly above each cathode (2) and anode (3), and the cathodes (2) and anodes (3) are each attached to the associated hydrogen collection chambers (15) and oxygen collection chambers (16) via fastenings (24), and wherein the seawater electrolyzer (4) has at least one salinometer (34) which is electrically connected to the control unit (19).

Description

State of the art

[0001] The invention concerns a seawater electrolysis system for storing seawater in hydrogen and oxygen.

[0002] Seawater can be used, in particular, to produce drinking water by reducing its salt content. Numerous well-known and established techniques exist for removing salts and minerals from the water, but these are associated with high maintenance and energy costs.

[0003] The most common method used for seawater desalination is multi-stage flash evaporation. This is a thermal process in which seawater is heated to a high temperature using waste heat from a power plant. In subsequent flash evaporation stages, the resulting steam condenses on pipes filled with cooling fluid, and this condensate is then extracted as salt-free water. Large-scale plants of this type desalinate millions of cubic meters of seawater daily, but the energy consumption required is considerable, necessitating their proximity to nuclear power plants.

[0004] Another method for desalinating seawater is reverse osmosis, in which seawater is forced under high pressure through a semipermeable polyamide membrane with pore diameters as small as 5 nm. The membrane acts as a filter, allowing only specific ions and molecules to pass through, thus separating them from other constituents in the seawater such as salts, bacteria, viruses, calcium, and toxins like heavy metals. To prevent the crystallization of salt or minerals within the membranes, reverse osmosis is only practical up to a certain maximum salt concentration in the reflux. Depending on the salt concentration, the energy consumption can be up to approximately 4 kWh per m³. 3Drinking water is required. Furthermore, the membranes of a reverse osmosis system require significant maintenance to remove the buildup of deposits caused by minerals, biological substances, or particles that impede the permeation of water molecules through the membranes. Flushing the membranes with chemical cleaners is therefore necessary, but this process is not environmentally friendly and must be separated.

[0005] During the freezing process, ice crystals form when seawater cools; these crystals are free of salts. However, they are suspended in the mother liquor and must therefore be separated, a technically complex process. The ice crystals must then be washed from the mother liquor, requiring a significant amount of fresh water.

[0006] Electrolysis is a process for producing hydrogen, chlorine, or metals such as aluminum. In this process, an electric current is used to force a redox reaction, with oxidation occurring at the anode and reduction at the cathode. Electrons are transferred during the chemical reactions that take place in electrolysis. This requires a direct current (DC) voltage source, which supplies the electrical energy and drives the chemical reactions. In water electrolysis, where the electrodes are immersed in water and the water's conductivity is improved by adding an acid, preferably sulfuric acid or an alkali, hydrogen (H₂) is produced by electric current. In this process, the electric current splits the water into its two components: oxygen (O₂) and hydrogen (H₂).At the positively charged electrode (anode), electrons are removed from the water, and since the water particles thus oxidized are unstable, they decompose, releasing oxygen O2 and forming positively charged oxonium ions H3O. + If positively charged oxonium ions (H3O) are present + In the area of ​​the negatively charged electrode (cathode), the electrons are attracted by the negative charge of the electrode and discharged there, releasing hydrogen. The resulting gases, oxygen (O2) and hydrogen (H2), collect in the area of ​​the two electrode tubes and can be extracted using a gas valve. Some manufacturers offer electrolysis units with an efficiency of over 70%. However, water electrolysis is not used in large-scale or commercial applications.

[0007] Prior art EP 1 120 481 B1 discloses a chlor-alkali electrolysis cell based on the ion-exchange membrane process for the electrolytic decomposition of an alkali chloride. This cell comprises an anode chamber with an anode, an ion-exchange membrane, and a cathode chamber with a diffusion cathode. The cell further includes two chambers: an anode chamber and a cathode chamber. The anode chamber is filled with salt water, and the cathode chamber with an oxygen-containing gas generated from air via a pressure swing adsorption device. An oxygen-containing gas and an aqueous caustic alkali solution are discharged from the cathode chamber and separated from each other by means of a gas / liquid separator.Separating the oxygen-containing gas discharged from the cathode chamber and the aqueous alkali solution using the gas / liquid separation device is an essential function for EP 1 120 481 B1, with the aim of producing chlorine and a corrosive alkali.

[0008] US Patent 2019 / 0 284 707 A1 describes a hydrogen-generating fuel cell with an anode and a cathode, wherein at least one of these electrodes is porous and they are separated by a channel. The channel is configured to hold liquid water or water vapor, with the anode and cathode each having contact with the water vapor on only one side, but not with the water. The water is located in the reservoir, where it is heated to the required water vapor by the heat source. Furthermore, this invention includes an ultraviolet radiation source or an ultraviolet laser positioned to emit ultraviolet radiation from the anode to the cathode, from the cathode to the anode, or in both directions, to ionize oxygen and hydrogen gas.Against this background, the anode and cathode contain a proton exchange membrane configured to allow ionized oxygen gas and / or hydrogen gas to pass through due to the emitted ultraviolet radiation, while preventing liquid water or water vapor from passing through.

[0009] US Patent 2015 / 0233003A1 pertains to the electrolytic production of hypochlorite in dilute and impure salt solutions such as seawater for the purpose of decomposing hypochlorite. Furthermore, the objective is to reduce the frequency and / or duration of periodic downtimes of an electrochlorination plant due to the removal of deposits on the electrode surface, thereby reducing acid consumption and energy costs associated with routine plant maintenance. This is because, during the electrolysis of seawater to produce hypochlorite, numerous undesirable chemical reactions occur at both the anode and the cathode in conjunction with ions present in seawater, such as calcium and magnesium. These reactions lead to significant deposits / scaling on the electrode surface, which in turn increases the operating cell voltage and consequently the electrical power loss.This invention comprises the step of intermittently ejecting pressurized water, seawater or equivalent salt water with a plurality of nozzles arranged at regular intervals along the entire length, wherein water jets up to a high pressure of 10 N / m. 2 directed orthogonally and / or with an inclination to the direction of flow of the seawater towards the spaces between the anode and cathode.

[0010] GB 2 077 294 A relates to a bipolar electrolyzer with an anodic and a cathodic plate at each end of the housing, each equipped with a plurality of knife-shaped electrodes. These knife-shaped electrodes do not overlap but must overlap the bipolar electrode element with its sheet-shaped anodes and cathodes. The bipolar electrode elements are arranged so that they overlap with the electrodes of the next unit. This arrangement of bipolar electrodes is repeated along the entire length of the housing, with the aim of producing chlorine as a disinfectant and providing an improved method for the electrolysis of aqueous electrolytes, in particular alkali metal halide solutions. The use of aqueous sodium chloride as an electrolyte is an essential feature of this invention.

[0011] WO 2018 / 109 748 A relates to an electrolysis line for the production of chemical solutions such as disinfectants and cleaning fluids, which has a conical anode arranged coaxially to the cathode. The electrolysis cell consists of an anode, a cathode, and a membrane located between the electrodes. The electrolysis cell is operated with a process fluid consisting of an aqueous sodium chloride solution, which is split by electrolysis, resulting in the release of chlorine and sodium as electrolysis products. During the electrolysis of the aqueous sodium chloride solution, sodium passes through the ceramic membrane located between the anode and cathode, producing the cleaning fluid in the hydraulic line between the cathode and the membrane. Chlorine does not pass through the membrane and remains in solution, producing the disinfectant in the corresponding output line.In this process, the electrodes are operated with direct current and generate thermal energy, which must be adequately dissipated by water or air cooling systems to prevent excessive overheating of the components.

[0012] DE 43 34 319 A1 relates to a device designed for generating electricity from liquids containing dissociated substances. This device comprises galvanic cells for the flow of liquids containing dissociated substances, in particular seawater, with electrodes made of different materials arranged in a housing. This invention features several liquid-permeable electrodes electrically connected in series, the cylindrical electrodes having a central electrically conductive rod arranged along the longitudinal axis of the electrodes and flanged to the electrode end faces.

[0013] The state of the art, as described in ESPOSITO, DV: Membraneless Electrolyzers for Low-Cost Hydrogen Production in a Renewable Energy Future. In: Joule, Vol. 1, 2017, pp. 651-658. DOI: https: / / doi.org / 10.1016 / j.joule.2017.07.003, also includes low-temperature electrolyzer technologies, namely PEM electrolyzers (polymer electrolyte membranes) and alkaline electrolyzers. Commercial PEM electrolyzers are based on a "zero-gap" membrane electrode arrangement, in which ion-selective membranes or proton-conducting, solid polymer electrolytes made of Nafion are arranged between the porous electrode layers. The hydrogen atoms split in this process are first passed through the porous anode, then through the solid, but hydrogen-conducting, polymer electrolyte membrane, and finally through the cathode.In this "zero-gap" membrane electrode arrangement of the electrodes and polymer electrolyte membrane, only the anode has contact with the electrolyte, and only on one side, whereas the cathode has no contact with the electrolyte and is located directly on the polymer electrolyte membrane.

[0014] Alkaline electrolyzers split water in a liquid containing 25-35 wt% KOH electrolyte and use a microporous membrane to separate the two electrodes. Polymer electrolyte and microporous membranes are used to separate the anodes from the cathodes, with each anode and cathode of this invention having only one side in contact with the mostly alkaline electrolyte.

[0015] Membraneless water electrolysis of type I is carried out in strongly acidic or alkaline environments or in concentrated H₂SO₄ and KOH electrolytes. It features two electrodes, each with an anode and a cathode, which are in contact with the electrolyte only on one side of their electrode surface. Membraneless water electrolysis incorporates flow-by electrodes, in which the aqueous electrolyte flows parallel to the electrode surfaces. Hydrogen and oxygen products are transported into separate downstream drain channels by forced fluid flow and / or buoyancy forces before they can pass to the opposite electrode. This process utilizes the Segré-Silberberg effect, in which the fluid velocity gradient helps to trap the bubbles near the electrode surface.

[0016] Furthermore, membraneless water electrolysis of type II with flow-through electrodes is known, in which the flowing electrolyte passes through porous anodes and cathodes. The porous flow-through electrodes consist of two circular metal grid electrodes positioned in an opposing configuration. As fresh electrolyte is forced from a pressurized outer chamber into the electrode gap, the flow diverges and carries the products hydrogen and oxygen into separate drainage channels. The circular metal grid and electrolyte-permeable electrodes, including their number and arrangement, are key features of this water electrolysis process.

[0017] Furthermore, DE 30 30 324 C2 is known as an electrolysis device for salt solutions, which has a housing made of electrically non-conductive material and is internally divided into several electrolysis cells. Removable stacks of alternately layered anode and cathode plates arranged at a distance from one another are immersed in the electrolyte, the stacks of anode and cathode plates being separated from one another along the axis of the housing by at least one electrically non-conductive partition. The objective here is to achieve a longer service life for the electrodes and to prevent contamination of the salt solutions, caused by deposits, from having a detrimental effect on the electrode plate arrangement. invention

[0018] The object of this invention is to create a process based on electrolysis to decompose seawater into its two components hydrogen H2 and oxygen O2 and to obtain electricity and salt-free water as reaction products from the energetic use of the hydrogen obtained.

[0019] This problem is solved according to the invention by the characterizing features of the claims. Further embodiments of the invention are the subject of the dependent claims.

[0020] According to the autoprotolysis of water, the water (H2O) contains oxonium ions (H3O). + ) and hydroxide ions (OH - ) in equilibrium, whereby the reaction equilibrium strongly favors water (H2O) (temperature-dependent reaction equation: 2H2O → H3O + + OH -). This property of water, and thus the reaction equilibrium, can, however, be altered by temperature and / or electrical energy to form oxonium ions (H3O). + ) and hydroxide ions (OH -The present invention relates to the seawater electrolyzer system (1), which utilizes these properties of water to decompose seawater (9) into its two components, hydrogen (H2) and oxygen (O2), using electrical energy. From the energetic utilization of the hydrogen (H2) obtained from the seawater electrolyzer system (1), salt-free water is obtained as a reaction product. The most important element for the utilization of hydrogen is the fuel cell, which converts the energy contained in the hydrogen (H2) into electricity and produces salt-free water as a reaction product. Therefore, fuel cells are considered future technologies, such as those used in electric vehicles.Furthermore, the fuel cell is ideal for use in large-scale systems for cities and industry, for home energy supply, or in mobile systems such as aircraft, ships, and trains, since the fuel cell provides electrical energy completely silently and emission-free. The end product is always water, which can be treated for drinking water or used directly for gardening, plumbing, or any other purpose. In contrast to the prior art of electrolysis of freshwater, the present invention does not involve the addition of acids or alkalis to make the seawater more electrically conductive. Also, in contrast to prior art electrolysis, the invention involves a plurality of electrodes (2, 3) immersed in the seawater (9), arranged in parallel and in series and connected to at least one DC voltage (8).In this system, the negatively charged cathodes (2) are arranged in parallel to the positively charged anodes (3), with these electrodes (2, 3) also being arranged in series or alternately in the direction of flow. As soon as the seawater electrolyzer (4) is filled with seawater (9) via the inlet (5), distributor (22), control valves (11, 12), adjustable feed pump (13), and control unit (19), and the cathodes (2) and anodes (3) are immersed in the seawater (9), to which at least a DC voltage (8) is applied, the electrolysis of the seawater (9) begins, whereby at least the substance-specific decomposition voltage U is required for electrolysis. z must be applied. At the positively charged anodes (3), electrons are extracted from the seawater (9), and since the water particles thus oxidized are unstable, they decompose, releasing oxygen and forming positively charged oxonium ions (H3O). + The positively charged oxonium ions (H3O) +) migrate in the electric field, which is generated by the DC voltage (8) and thus by the negatively charged cathodes (2) and the positively charged anodes (3), to the negatively charged cathodes (2), whereby the oxonium ions (H3O + ) thereby accepting an electron and releasing a hydrogen atom. The released hydrogen atoms then each combine with another hydrogen atom in the vicinity to form a hydrogen molecule. The gaseous hydrogen thus separated from the seawater (9) rises at the cathodes (2), collects in the respective hydrogen collection chambers (15), which are each arranged directly above the individual cathodes (2), and is removed from the hydrogen collection chambers (15) by means of a valve (17).

[0021] The negatively charged hydroxide ions (OH) -) in turn migrate, analogous to the processes in the cathode compartment, in the electric field to the positively charged anode (3), where the hydroxide ions (OH) are located. - ) convert to oxygen O2 by releasing electrons or neutralize with a free hydrogen atom to form water. Here too, the gaseous oxygen O2 separated from the seawater (9) rises at the anodes (3) and collects in the oxygen collection combs (16), which are each arranged directly above the individual anodes (3). The oxygen O2 thus obtained is also removed by means of a valve (18).

[0022] According to Ohm's law, the current flow in an electrolysis cell is impeded by the electrical resistance of an aqueous solution, which is why it must be minimized to avoid losing the input energy as heat. In general, the cell resistance R depends on... ZThe conductivity of an electrolysis cell depends on the electrode spacing, the size of the electrode area, and the conductivity, and is calculated according to the state of the art using the following formula. −z=electrode distance electrode area=1 conductivity

[0023] Silver has the highest conductivity of all metals, while pure water is not a good electrical conductor. However, if salts or acids are added to the water, which release freely moving ions in aqueous solution, the conductivity increases. And since the electric current is transported by dissolved ions, the conductivity of the water increases with increasing ion concentration. Seawater (9) has an average salt content of about 3.5% by mass and, due to the numerous salts dissolved in it, a typical conductivity of about 5 S / m. The salts dissolved in seawater (9) are freely moving ions and act as charge carriers that conduct the electric current; therefore, in the seawater electrolyzer system (1) according to the invention, the addition of acids or alkalis for desalination of seawater (9) is not necessary.The salinity of the seawater (9) increases with increasing electrolysis and thus with the increasing decomposition of the seawater (9) into oxygen O2 and hydrogen H2, resulting in a higher salinity in the seawater (9), which is subsequently referred to as seawater concentrate (10). These properties of the seawater (9), in conjunction with the other features of the seawater electrolyzer system (1), such as the adjustable electrolysis return (7) and adjustable feed pump (14), are used to return the seawater concentrate (10) from the outlet (6) to the inlet (5), thereby increasing the salinity in the seawater electrolyzer (4) and thus the conductivity of the seawater (9). This increases the average salinity of the seawater (9) and consequently the conductivity of the seawater (9), and as a result, the cell resistance R. Zthe electrolysis cell is reduced. As a result of the increased salt content, the ion concentration is also increased, which reduces the cell voltage required for the seawater electrolyzer system (1). Against this background, the DC voltage (8) for generating an electric field can be reduced to a lower value, which consequently leads to savings in electrical energy and thus lower energy costs. These modifications according to the invention increase the efficiency of the seawater electrolyzer system (1) according to the invention by reducing the cell resistance R Z is reduced.

[0024] In addition to the conductivity of the seawater (9), the cell resistance R depends Z The electrolysis process, according to the formula mentioned above, also depends on the electrode area; the larger the electrode area, the smaller the cell resistance R. ZThe seawater electrolyzer system (1) according to the invention, in contrast to the prior art, has not just one cathode and one anode, but a plurality of negatively charged cathodes (2) and positively charged anodes (3), resulting in a very large electrode area. The number, shape, and arrangement of the cathodes (2) and anodes (3) are freely selectable and are arranged alternately in parallel and in series or at any angle to each other inside the seawater electrolyzer (4). These features of the seawater electrolyzer system (1) according to the invention result in a large electrode area, which reduces the cell resistance R. ZThe electrical resistance is reduced, resulting in a higher efficiency of the seawater electrolyzer system (1) according to the invention for the electrolysis of seawater. In addition to increasing the conductivity and electrode area, the electrode spacing (26) is also minimized by the geometry, shape, and arrangement of the cathodes (2) and anodes (3) according to the invention, as the cathodes (2) and anodes (3) can be arranged with a small electrode spacing (26) relative to each other due to the features of the invention. A small electrode spacing (26) leads to a small cell resistance RZ, which in turn results in a higher efficiency of the seawater electrolyzer system (1) according to the invention.

[0025] The cations produced during electrolysis (oxonium ions H3O) + ) and anions (hydroxide ions OH) -According to the state of the art, charge changes occur close to the respective electrodes, which must be balanced by migration processes. The balancing of ions is achieved through ion migration, the migration speed of which depends, among other things, on the applied cell voltage and thus on the electric field. The loss of cations (oxonium ions H3O) + ) in front of the cathode must therefore be affected by the migration of excess cations (oxonium ions H3O) + The losses from the anode compartment are compensated for by the applied cell voltage and the associated electric field. This also applies to the loss of anions (hydroxide ions OH). - ) in front of the anode, which is affected by excess anions (hydroxide ions OH). -) from the cathode compartment must be compensated. This migration process, previously induced by the applied cell voltage and thus by the electric field, is supported by the flow of seawater (9) and seawater concentrate (10) within the seawater electrolyzer system (1), which can be controlled according to the invention, in conjunction with the alternating arrangement of the cathodes (2) and anodes (3). In this process, the positively charged oxonium ions (H3O) must be displaced. + ) no longer diffuse exclusively through the seawater (9) as an electrolyte solution to the negatively charged cathodes (2) with the help of the electric field. The excess anions (hydroxide ions OH) are carried away by the flow of the seawater (9). - ) from the cathode compartment directly to the subsequently arranged anode compartment as well as the excess cations (oxonium ions H3O +The seawater (9) and thus the seawater concentrate (10) are transported directly from the anode compartment to the cathode compartment located downstream. The flow of the seawater (9) and thus the seawater concentrate (10) is regulated via the inlet (5), feed pump (13), and control valves (11, 12) according to the requirements of the seawater electrolyzer system (1) by the control unit (19). The resulting flow of seawater (9) and seawater concentrate (10) through the seawater electrolyzer (4) is supplemented by the electrolysis return (7) and feed pump (14), which allows for numerous adjustments regarding flow rate and salinity.Depending on how the feed pump (13, 14) and control valves (11, 12) are controlled via the control unit (19), whether they are open, partially open, or closed, the seawater (9) and thus the seawater concentrate (10) flows at a corresponding flow rate from the inlet (5) through the seawater electrolyzer (4) and out of the seawater electrolyzer system (1) via the outlet (6). According to the invention, the seawater (9) and thus the seawater concentrate (10) can also be pumped in a circuit within the seawater electrolyzer (4) via the electrolysis return (7) and feed pump (14) at a controllable flow rate, thereby increasing the salinity of the seawater concentrate (10) as required by the seawater electrolyzer system (1) and retaining the excess cations (oxonium ions, H3O). + ) and anions (hydroxide ions OH) -) still in the seawater electrolyzer (4), where they are discharged at the cathodes (2) and anodes (3), respectively, and hydrogen H2 and oxygen O2 are obtained. With the aid of the flow of seawater (9) that can be controlled according to the invention, in conjunction with the number and alternating arrangement of the cathodes (2) and anodes (3) in the seawater electrolyzer (4), the migration process of the cations (oxonium ions H3O) is controlled. + ) and anions (hydroxide ions OH) - ) supports this, resulting in a higher material conversion and thus a higher efficiency of the electrolysis of the seawater.

[0026] The invention is described in more detail below with reference to the drawings of the exemplary embodiments.

[0027] The Fig. Figure 01 shows the seawater electrolyzer system (1) according to the invention in cross-section AA. Fig. 02 with at least one inlet (5), distributor (22), control valves (11, 12), feed pump (13, 14), cathodes (2), anodes (3), control unit (19), seawater electrolyzer (4) and at least one outlet (6). The seawater (9) flows into the seawater electrolyzer (4) via at least one open inlet (5), distributor (22) and via any number and arbitrarily arranged control valves (11) and fills it in such a way that the multitude of flow channels (25) resulting from the cathodes (2) and anodes (3) arranged in series and parallel with any electrode spacing (26) are filled with seawater (9). In this process, the cathodes (2) and anodes (3) arranged in the seawater electrolyzer (4) are immersed in the seawater (9), the immersion depth of which can be controlled via the fill level (23) of the seawater electrolyzer (4) and thus via the inlet (5), outlet (6) and control unit (19).The cathodes (2) and anodes (3) are connected to at least one DC voltage (8), which electrically charges the cathodes (2) negatively and the anodes (3) positively. With the aid of the control unit (19), in which the DC voltage (8) is integrated, the series-arranged cathodes (2) and anodes (3) are alternately connected to a positive or negative voltage. There are various ways to arrange them in series and connect them to a positive or negative voltage. Depending on how the series-arranged cathodes (2) and anodes (3) are connected to the positive and negative voltages, the cathodes (2) and anodes (3) arranged in parallel to these must be arranged or connected such that an anode (3) is always opposite a cathode (2) and vice versa.This arrangement of cathodes (2) and anodes (3) creates a positive or negative voltage, and thus an electric field, between all parallel electrodes. The controllable flow of seawater (9) removes the excess anions (hydroxide ions OH). - ) from the cathode compartment directly to the subsequently arranged anode compartment as well as the excess cations (oxonium ions H3O +The seawater (9) is transported from the anode compartment directly to the cathode compartment located downstream via the seawater flow. The seawater flow (9) in the seawater electrolyzer system (1), and thus in the seawater electrolyzer (4), is regulated via the inlet (5), feed pump (13), and control valves (11, 12) according to the requirements of the seawater electrolyzer system (1) by the control unit (19). The inlet (5) and outlet (6) are additionally connected to each other via the electrolysis return (7) and adjustable pump (14), through which the seawater (9) or seawater concentrate (10) is pumped in an electrolyte circuit, firstly to increase the salinity in the seawater (9) and thus the seawater concentrate (10) and / or secondly to circulate the seawater (9) or seawater concentrate (10) in a flow with adjustable flow velocity.The salinity in the seawater (9) can preferably be determined via salinometers (34) or by taking and analyzing seawater samples and transmitted to the control unit (19) as a control parameter. The flow of the seawater (9) within the seawater electrolyzer (4) according to the invention, in conjunction with the arrangement of the cathodes (2) and anodes (3), is optimized with regard to the transport of the locally excess cations (oxonium ions H3O). + ) from the anode compartment as well as the locally excess anions (hydroxide ions OH) - ) from the cathode compartment to the cathodes (2) and anodes (3) arranged in series, so that they are discharged there with the release of oxygen O2 and hydrogen H2.

[0028] Fig. Figure 2 shows the seawater electrolyzer system (1) in longitudinal section, depicting the inlet (5), feed pump (13), distributor (22), control valves (11, 12), seawater electrolyzer (4), and outlet (6). This longitudinal section shows two cathodes (2) and two anodes (3) connected to the DC voltage (8) and control unit (19), with the negatively charged cathodes (2) and the positively charged anodes (3) arranged alternately in series. The control unit (19) allows the series-arranged cathodes (2) and anodes (3) to be connected so that they alternately supply one, two, or any number of electrodes with a positive or negative voltage.The cathodes (2) and anodes (3) arranged in series in the seawater electrolyzer (4) must be connected to a DC voltage (8) such that the parallel electrodes have a negative or positive DC voltage (8) and that an electric field is present between these electrodes (2, 3). Directly above each cathode (2) and anode (3) is a hydrogen collection chamber (15) and an oxygen collection chamber (16), each with a valve (17, 18). Cathodes (2) and anodes (3) are each attached to the associated hydrogen collection chambers (15) and oxygen collection chambers (16) via the respective fixings (24), so that the cathodes (2) and anodes (3) are immersed in the seawater (9) in such a way that the upper part of the cathodes (2) and anodes (3) protrudes from the seawater (9) above the level (23).The oxygen (O2) and hydrogen (H2) produced during the seawater electrolyzer system (1) rise along the respective cathodes (2) and anodes (3) and collect in the corresponding hydrogen collection chamber (15) and oxygen collection chamber (16), which are emptied by means of the respective valves (17, 18). Seawater (9) flows into the seawater electrolyzer (4) via the inlet (5) with the aid of the adjustable feed pump (13) and control valves (11), filling it so that the negatively and positively charged cathodes (2) and anodes (3) are immersed in seawater (9) up to the desired fill level (23). The outlet (6) is closed via the control valve (12), so that the seawater electrolyzer (4) is continuously filled with seawater (9).When the DC voltage (8) is applied, seawater electrolysis begins, during which the seawater (9) is continuously decomposed into hydrogen (H2) and oxygen (O2). Simultaneously, the salinity of the seawater (9) increases relative to the seawater (9) remaining in the seawater electrolyzer (4), resulting in a higher seawater concentrate (10). The features of this invention allow for any number of ways to operate this seawater electrolyzer system (1). Firstly, seawater (9) can flow in via the feed pump (13) and control valves (11) to refill the seawater electrolyzer (4) to the desired fill level (23). Secondly, the seawater concentrate (10) can be emptied from the seawater electrolyzer (4) via the outlet (6) and control valve (12), which can then be refilled with fresh seawater (9) to restart the seawater electrolyzer system (1).Furthermore, the seawater electrolyzer system (1) can also be operated such that the seawater electrolyzer (4) is continuously filled with seawater (9) at a controllable flow rate and velocity, and the seawater electrolyzer (4) is constantly filled with seawater (9) up to level (23). Since no environmentally harmful acids or alkalis are added to the seawater (9), the seawater concentrate (10) can be discharged directly back into the sea from the seawater electrolyzer (4) via the control valve (12) and outlet (6) after the electrolysis process is complete. In addition, the negatively and positively charged cathodes (2) and anodes (3) each have an electrode heater (30) inside the electrode, which heats the cathodes (2) and anodes (3) to increase the temperature of the electrolyte solution and the seawater (9), respectively.With the aid of the control unit (19), the respective electrode heaters (30) of the cathodes (2) and anodes (3) are connected with current and voltage so that they are brought to and regulated at the desired high temperature, with respect to heating the seawater (9) and cleaning the cathodes (2) and anodes (3) at the cleaning temperature. Oxygen or air (which contains approximately 21% oxygen) forms an explosive gas mixture with hydrogen when the hydrogen concentration is high. Therefore, the seawater electrolyzer (4) has at least one vent valve (32) with a corresponding venting system to continuously vent the interior volume (33) of the seawater electrolyzer (4) that is not filled with seawater (9), so that the ignitability of the gas mixture remains below any arbitrary limit or the 4% by volume limit.

[0029] The Fig. Figure 03 shows the seawater electrolyzer system (1) in cross-section BB according to Fig. Figure 01 shows the seawater electrolyzer (4), the parallel cathodes (2) and anodes (3), hydrogen collection chambers (15), oxygen collection chambers (16), level gauge (23), salinometer (34), and the valves (17, 18). The parallel cathodes (2) and anodes (3) are immersed in the seawater (9) at the level gauge (23) such that the upper portions of the cathodes (2) and anodes (3) protrude from the seawater (9). The parallel cathodes (2) and anodes (3) each have an arbitrarily selectable electrode spacing (26) and simultaneously form the flow channels (25), with each flow channel (25) being generated by two parallel cathodes (2) and anodes (3). The electrolysis return (7) is also shown.

[0030] The Fig. Figure 4 shows the seawater electrolyzer system (1) in cross-section CC according to the Fig. 02 with the cathodes (2) and anodes (3) arranged in parallel in the seawater electrolyzer (4). In the direction of flow, the cathodes (2) and anodes (3) are also arranged alternately in series, so that a cathode (2) is downstream of an anode (3) and an anode (3) is downstream of a cathode (2). The seawater (9) with the respective excess cations (oxonium ions H3O) + ) and anions (hydroxide ions OH) - The fluid flows in the flow channels (25), which result from the parallel cathodes (2) and anodes (3) with the corresponding electrode spacing (26), from the anode compartment directly to the downstream cathode compartment and from the cathode compartment directly to the downstream anode compartment. At the cathodes (2) and anodes (3), the cations (oxonium ions H3O) are deposited. + ) and anions (hydroxide ions OH) -The electrolyte is discharged, releasing oxygen (O2) and hydrogen (H2). The flow of seawater (9) and thus of the seawater concentrate (10) in the flow channels (25) can be controlled via the parameterization of the inlet (5), feed pump (13, 14), electrolysis return (7), and control valves (11, 12). The oxygen (O2) and hydrogen (H2) separated during seawater electrolysis rise along the respective cathodes (2) and anodes (3) and collect in the corresponding hydrogen collection chamber (15) and oxygen collection chamber (16).

[0031] The Fig. Figure 5 shows the seawater electrolyzer system (1) in longitudinal section, with the cathodes (2) and anodes (3) arranged parallel in the seawater electrolyzer (4). In the direction of flow, only either the cathodes (2) or the anodes (3) are arranged in series, which is why only the cathodes (2) are visible in this illustration. The seawater (9) also flows in the flow channels (25), which are formed by the parallel cathodes (2) and anodes (3) at the electrode spacing (26). In this embodiment, since either the cathodes (2) or the anodes (3) are arranged in series, the excess cations (oxonium ions H3O) must be removed. + ) and anions (hydroxide ions OH) - ) are no longer transported away from their current anode and cathode compartments by the current and thus by the flow velocity of the seawater (9). The discharge of the excess cations (oxonium ions H3O + ) and anions (hydroxide ions OH) -This occurs directly at their current location by switching the DC voltage (8) with the help of the control unit (19), whereby the current voltage of the cathodes (2) is switched from negative to positive and the voltage of the anodes (3) is switched from positive to negative. Due to this switching of the DC voltage (8), the cathodes become anodes and vice versa. This reversal of the DC voltage (8) at the cathodes (2) and anodes (3) causes the locally present excess cations (oxonium ions H3O) to be removed. + ) and anions (hydroxide ions OH) -) are discharged on site. Before this reversal of the DC voltage (8) is carried out, however, the oxygen O2 and hydrogen H2 contained in the hydrogen collection chambers (15) and oxygen collection chambers (16) must be emptied to avoid an explosive gas mixture of oxygen O2 and hydrogen H2. According to the invention, this is achieved by immersing the hydrogen collection chambers (15) and oxygen collection chambers (16), including the cathodes (2) and anodes (3) attached therein, hydraulically, electrically, or mechanically in the seawater electrolyzer (4) to such a depth that the inner volume of the hydrogen collection chambers (15) and oxygen collection chambers (16) is completely filled with seawater (9), so that the oxygen O2 and hydrogen H2 contained therein flow out of the seawater (9) via the respective valves (17, 18).Only then can the DC voltage (8) be switched and the seawater electrolyzer system (1) restarted. This inventive method of cyclically switching the DC voltage (8) takes place as needed by the seawater electrolyzer system (1) as soon as sufficient seawater (9) has been electrolyzed and excess cations (oxonium ions H3O) have been removed. + ) and anions (hydroxide ions OH) -) have accumulated in the anode and cathode compartments. An alternative embodiment to immersing the hydrogen collection chambers (15) and oxygen collection chambers (16) is to completely fill the volume (33) of the seawater electrolyzer (4) with seawater (9), thereby emptying the oxygen O2 and hydrogen H2 accumulated in the hydrogen collection chambers (15) and oxygen collection chambers (16) via the valves (17, 18) using the seawater (9). In conjunction with switching the DC voltage (8) and subsequently reactivating the seawater electrolyzer system (1), the valves (17, 18) in this embodiment are designed as switchable two-way valves so that oxygen O2 and hydrogen H2 are introduced into their respective oxygen or hydrogen storage compartments. In this embodiment, it should be noted that the electrode material can be used as both a cathode and an anode.The electrode heaters (30) arranged inside the cathodes (2) and anodes (3) shown here are also depicted. These heaters heat the cathodes (2) and anodes (3) in order to increase the temperature of the electrolyte solution and thus of the seawater (9). The control unit (19) supplies current and voltage to the respective electrode heaters (30) of the cathodes (2) and anodes (3) and heats them to the desired temperatures for heating the seawater (9) and cleaning the cathodes (2) and anodes (3).

[0032] The Fig. Figure 6 shows the seawater electrolyzer system (1) in longitudinal section, in which the hydrogen collection chambers (15) and oxygen collection chambers (16), including the cathodes (2) and anodes (3) attached therein, are immersed in the seawater (9) of the seawater electrolyzer (4). The internal volume of the hydrogen collection chambers (15) and oxygen collection chambers (16) is completely filled with seawater (9) in order to empty the oxygen (O2) and hydrogen (H2) contained therein via the respective valves (17, 18), which are designed as two-way valves. Subsequently, the cathodes (2) and anodes (3) are withdrawn from the seawater (9) and returned to their original positions in order to restart the seawater electrolyzer system (1) with the DC voltage (8) changed at the cathodes (2) and anodes (3).

[0033] The Fig. Figure 7 shows the seawater electrolyzer system (1) in cross-section DD according to the Fig. 05 with the cathodes (2) and anodes (3) arranged in parallel in the seawater electrolyzer (4). In the direction of flow, the cathodes (2) and anodes (3) are arranged in series, i.e., in each series either cathodes (2) or anodes (3) are arranged one behind the other. The oxygen O2 and hydrogen H2 produced during seawater electrolysis rise along the respective cathodes (2) and anodes (3) and collect in the associated hydrogen collection chambers (15) and oxygen collection chambers (16).

[0034] According to the invention, the geometric shape of the cathodes (2) and anodes (3) is arbitrarily selectable. They are preferably flat and as thin as possible to allow for the parallel arrangement of as many electrodes as possible in the seawater electrolyzer (4) with a small electrode spacing (26) between them. Platinum, copper, silver, gold, or palladium, as known from the prior art, can be used as electrode materials for the cathodes (2) and anodes (3), since these materials are inert and do not dissolve in the electrolyte solution during electrolysis. Electrocatalysts for the cathodes (2) and anodes (3), respectively, are also available according to the prior art. To reduce costs, the cathodes (2) and anodes (3) do not need to be made of solid electrode material, but are instead formed, according to the invention, as a thin and porous layer, preferably of platinum, deposited on a preferably ceramic substrate.The porous structure of the cathodes (2) and anodes (3) increases their surface area, thereby reducing the cell resistance R. Z is reduced.

[0035] With regard to economic efficiency, the seawater electrolyzer system (1) should be operated at the highest possible current densities. This is achieved, firstly, by increasing the conductivity of the cell resistance R. ZThe salt concentration is increased by increasing the salinity, and thus the salt content, and secondly by increasing the temperature of the seawater (9) as the electrolyte solution. According to the invention, the salinity is increased by increasing the seawater concentrate (10) via the inlet (5), electrolysis return (7), and continuously with the seawater electrolyzer system (1) of the seawater (9). The temperature of the seawater (9) as the electrolyte solution is increased to approximately 60–90 °C or any other specific temperature range by means of the electrode heaters (30) integrated according to the invention inside the cathodes (2) and anodes (3), which are each connected to the control unit (19) with current and voltage such that the seawater (9) reaches the desired temperature.Furthermore, according to the invention, the cathodes (2) and anodes (3) can be cleaned of deposits from components of the seawater (9) by heating the cathodes (2) and anodes (3) to a sufficiently high cleaning temperature using the electrode heaters (30) integrated into the cathodes (2) and anodes (3). The cleaning interval and the cleaning temperature of the cathodes (2) and anodes (3) depend, among other things, on the quantity and nature of the deposits. This cleaning process of the seawater electrolyzer system (1) according to the invention ensures that the surfaces of the cathodes (2) and anodes (3) are cleaned of deposits, thereby creating optimal conditions for the decomposition of the seawater (9). Maintenance is minimized because only the cathodes (2) and anodes (3) need to be heated to the cleaning temperature to clean the seawater electrolyzer system (1).The seawater electrolyzer system (1) is briefly interrupted, and the seawater (9) contained in the seawater electrolyzer (4) is emptied via the outlet (6) so that energy is used only to heat the cathodes (2) and anodes (3), and not also to heat the seawater (9). After the deposits have been separated from the cathodes (2) and anodes (3), they are removed by rinsing the seawater electrolyzer (4) with fresh seawater (9) via the inlet (5) and outlet (6). After refilling the seawater electrolyzer (4) with seawater (9), the seawater electrolyzer system (1) is restarted. This simple cleaning process reduces maintenance costs and thus increases the economic efficiency of the seawater electrolyzer system (1) according to the invention.

[0036] The present invention offers the following advantages in the desalination of seawater compared to the prior art with regard to environmental protection, economic efficiency and technology: Sustainable energy production in the form of hydrogen H2, from whose energetic use salt-free water is obtained. Utilizing naturally occurring and unlimited energy from wind or sun for seawater electrolysis.

[0037] No purification of the seawater concentrate (10) is required after no foreign substances harmful to health or the environment, such as acids or alkalis, are added to the seawater (9) as an electrolyte.

[0038] Disposal of the seawater concentrate (10) directly into the sea.

[0039] Minimal maintenance required thanks to an integrated cleaning process to remove possible deposits on cathodes (2) and anodes (3).

[0040] Use of the seawater electrolyzer system (1) as an energy storage system to store fluctuations in wind or solar energy as hydrogen H2.

[0041] No semipermeable membranes are used, as in reverse osmosis. This also eliminates the significant maintenance associated with reverse osmosis, which requires chemical cleaners to remove deposits of minerals, biological substances, or particles.

[0042] No use of polymer electrolyte membranes as in the electrolyzer.

[0043] Proximity to nuclear power plants is not required to evaporate seawater as in the multi-stage flash evaporation process.

[0044] No fresh water is consumed to wash the ice crystals out of the mother liquor, as is done in the freezing process.

[0045] Use of any number of cathodes (2) and anodes (3) directly in seawater (9) as electrolyte, which can be arranged in series, parallel or at any angles to each other.

[0046] The cathodes (2) and anodes (3) are connected as required with positive and negative DC voltage to remove the locally excess hydroxide ions (OH). - ) and oxonium ions (H3O + ) to unload on site and convert them into oxygen O2 and hydrogen H2.

[0047] Transport of seawater (9) with the excess hydroxide ions (OH) - ) and oxonium ions (H3O + ) via the controllable flow to the cathodes (2) and anodes (3) arranged in series.

[0048] Adjustable salinity in the seawater electrolyzer system (1).

[0049] Seawater (9) is available in unlimited quantities, and hydrogen (H2) and oxygen (O2) are obtained from it using the present invention, a seawater electrolyzer system (1). The energetic use of the hydrogen obtained, preferably in fuel cells for generating electrical energy for electric vehicle drives, produces salt-free water as a reaction product. This salt-free water can be used in a variety of ways, such as drinking water, in households for gardens and sanitation, in industry, or in agriculture. The electrical energy required for this process is obtained from renewable energy sources, for which wind and solar energy are particularly suitable. Solar energy is available in abundant quantities, especially in southern regions such as Southern Europe or Africa.Northern regions such as Germany also offer significant potential in this regard, with the North Sea providing excellent conditions for the inventive seawater electrolyzer system (1), given the abundant availability of both wind energy and seawater (9). Furthermore, the hydrogen (H2) produced can be directly fed into the existing natural gas network. The present invention, the seawater electrolyzer system (1), offers advantages for the sustainable production of hydrogen and freshwater from seawater (9), contributing to alleviating the global water shortage.

Claims

[1] System for operating a seawater electrolysis (1) with seawater (9) as electrolyte for decomposing seawater (9) into hydrogen and oxygen, but without the use of semipermeable or polymer electrolyte membranes, wherein the seawater electrolysis system (1) comprises a seawater electrolyzer (4) filled with seawater (9) as electrolyte, wherein a plurality of cathodes (2) and anodes (3) are arranged parallel to each other and immersed in the seawater (9), wherein in the direction of flow of the seawater (9) the cathodes (2) and anodes (3) are arranged in series or alternately, and are connected via a control device (19) to at least one DC voltage (8), wherein an electrode heater (30) is integrated inside each of the electrodes (2, 3),wherein a hydrogen collection chamber (15) and oxygen collection chamber (16) are arranged directly above each cathode (2) and anode (3), and the cathodes (2) and anodes (3) are each attached to the associated hydrogen collection chambers (15) and oxygen collection chambers (16) via fastenings (24), and wherein the seawater electrolyzer (4) has at least one salinometer (34) which is electrically connected to the control unit (19). [2] Method for operating the seawater electrolysis system (1) according to claim 1 for decomposing seawater (9) into hydrogen and oxygen using seawater (9) as the electrolyte, without the use of additional acids and alkalis, characterized by , that the temperature of the seawater (9) as electrolyte in the seawater electrolyzer (4) is set and regulated via the electrode heaters (30) and the control unit (19) integrated in the cathodes (2) and anodes (3). [3] Method according to claim 2 characterized by, that the cathodes (2) and anodes (3) are cleaned of deposits above a cleaning temperature by heating and regulating the cathodes (2) and anodes (3) to a cleaning temperature via the integrated electrode heaters (30) and the control unit (19). [4] Method according to claims 2 to 3 characterized by , that the salinity of the seawater (9) in the seawater electrolyzer (4) is regulated via an electrolysis return (7), the salinometer (34), an inlet (5), an outlet (6) and the control unit (19). [5] Method according to claims 2 to 4 characterized by , that an applied electrical voltage at the cathodes (2) and the anodes (3) is switched and regulated via the control unit (19). [6] Method according to claims 2 to 5 characterized by, that a flow of seawater (9) is regulated via an inlet (5), control valves (11, 12), an outlet (6), feed pumps (13, 14), an electrolysis circuit (7), the seawater electrolyzer (4) and the control unit (19).

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