METHOD FOR WATER DESALATION

Description

[0001] The present invention relates to a method for desalinating water, comprising at least the following two process steps. In the first process step, hydrogen is initially stored by bringing hydrogen into contact with a carrier (T1), thereby obtaining a hydrogen-loaded carrier (T2) and additionally releasing heat. In the second process step, this released heat is fed into a device (V1) to desalinate water. The salt content of the water can be reduced so that the water is suitable as drinking water or process water, or the water can be completely desalinated. The completely desalinated water is then used in an electrolysis cell to generate hydrogen, the electrolysis preferably being spatially separated and / or temporally offset from the desalination.The hydrogen released from the loaded carrier (T2) or generated in an electrolysis cell can in turn be used for electricity or heat generation or as a chemical reaction partner, or it can be used to load a carrier (T1) with hydrogen.

[0002] EP-A 3 415 609 relates to a method for storing and preserving hydrogen, comprising two process steps. In the first process step, the hydrogen is stored by bringing it into contact with a carrier (T1), thereby obtaining a hydrogen-laden carrier (T2). The hydrogen is preferably chemically bound to the carrier (T1), in particular by means of hydrogenation. In the second process step, the hydrogen-laden carrier (T2) is stored in a device (V1) that is or was part of a biogas plant. The hydrogen stored in the carrier (T2) can then be released from the carrier (T2) and subsequently used to generate electricity and, optionally, heat. The method described in EP-A 3 415 609 can be integrated into an existing biogas plant or a biogas plant can be retrofitted accordingly.Furthermore, a method for generating electricity and, if applicable, heat is disclosed therein, wherein the method for storing and preserving hydrogen is carried out first.

[0003] DE 10 2011 111 565 A1 discloses a process in which N-ethylcarbazole is brought into contact with hydrogen as a carrier, a hydrogen-loaded carrier is obtained by hydrogenation and heat is released, which can be used, among other things, for home heating.

[0004] DE-A 10 2012 005 023 discloses an arrangement and a method for the autonomous provision of electricity via hydrogen. First, electrical current from a renewable source is provided and used to produce hydrogen from water in at least one electrolyzer. The hydrogen thus produced is transferred to a first chemical reactor containing at least one substrate with an extended pi-conjugated system, where at least partial hydrogenation of the substrate is carried out. This at least partially hydrogenated substrate is then transferred to a storage tank. From this storage tank, the at least partially hydrogenated substrate is transferred to a second chemical reactor, where dehydrogenation of this substrate takes place, releasing hydrogen.The hydrogen produced in the second chemical reactor is transferred to a system or machine for converting the hydrogen into electrical energy, preferably a fuel cell. From there, electricity is supplied to the point of need.

[0005] The process and corresponding system described in DE-A 10 2012 005 023 are suitable, for example, as emergency power generators or for use in locations without a public power grid, as well as in crisis situations such as wars. Potential applications include hospitals, chemical plants, computer centers, and even nuclear power plants. Ultimately, this process involves the intermediate storage of hydrogen, which can be carried out over extended periods for use in power generation when needed. The initial electricity supplied, derived from renewable sources, which is used to produce the hydrogen, can originate from sources such as hydropower, wind energy, solar radiation, or biogas. However, the implementation of this process in conjunction with water desalination is not disclosed in DE-A 10 2012 005 023.

[0006] A corresponding method or arrangement is disclosed in DE-A 10 2011 121 704. The arrangement (device) is used in particular for buffering excess electricity in buildings. The corresponding method serves for energy storage in buildings. The method and the corresponding arrangement necessarily require the use of a fuel cell for oxidizing the hydrogen released in the second chemical reactor, thereby releasing energy.

[0007] Desalination plants and water desalination processes are well-known to experts. A major problem in operating desalination plants is that desalination is very energy-intensive.

[0008] Background information on water desalination processes can be found, among other sources, in "A. Panagopoulos, K.-J. Haralambous, M. Loizidou, Desalination brine disposal methods and treatment technologies - A review, Science of the Total Environment 2019, Vol. 693, 133545", "M. Rommel, Fraunhofer ISE, Solar energy for Africa / Seawater desalination with solar energy, http: / / solarenergie-fuer-afrika.de / deutsch / konferenz-2003 / referate / rommel-meerwasserentsalzung.html", accessed on 06.07.2021; on the website of the German Geothermal Association ("https: / / www.geothermie.de", https: / / www.geothermie.de / bibliothek / lexikon-der-geothermie / m / meerwasserentsalung.html, accessed on July 6, 2021) or on the website of the German Seawater Desalination Association (DME eV). For example, in Saudi Arabia and the United Arab Emirates, large quantities of drinking and process water are desalinated using an MSF desalination plant, coupled to the Shoaibe power plant, respectively.The desalinated water is produced at the Jabad Ali power plant and seawater desalination plant. Due to global population growth and the increasing need for irrigation in agriculture, the demand for desalinated water is expected to continue rising sharply in the coming years. Significant amounts of PEM electrolysis capacity will be built worldwide in the coming years. Approximately 10 tons of fully desalinated water are required for PEM electrolysis to produce 1 ton of hydrogen.

[0009] In principle, the methods known to those skilled in the art for desalinating water can be divided into two main groups: thermal and electrical methods. Background information can be found, for example, in the literature references mentioned in the previous paragraph.

[0010] Thermal processes are based on the fundamental principle of distillation, with two main methods being used: multi-stage flash distillation (MSF) and multi-effect distillation (MED), which is the precursor to MSF. In the former, the water to be desalinated is typically heated to over 100 °C (for example, to 110 °C), usually with the aid of a heat exchanger, where the water itself is simultaneously used for cooling. Such a device for heating the water to be desalinated is often referred to as a brine heater in the relevant literature. The heated water is then passed into a chamber at atmospheric pressure or a pressure lower than atmospheric pressure.Since the boiling point of water at atmospheric pressure is 100 °C, the water instantly evaporates upon entering such a chamber and condenses on a corresponding heat exchanger. Depending on the system, a varying number of such chambers with variable pressure and temperature are conceivable, with the pressure and temperature decreasing in each step. A possible temperature range covered by the different chambers is between 130 and 20 °C. Although some of the energy required to heat the water can be recovered via the heat exchangers in the form of condensation heat, the process is still very energy-intensive.

[0011] A typical electrically driven process is reverse osmosis. This process is also energy-intensive and requires sophisticated technology and maintenance. Other processes, which, however, account for comparatively small shares of the global production of desalinated water, include steam compression, membrane distillation, and electrodialysis.

[0012] As mentioned above, a major problem in operating desalination plants is the high energy consumption. This is described, for example, in "K. Hennecke, A. Lokurlu, M. Rommel, F. Späte, Solar Process Heat for Industry, Seawater Desalination and Solar Chemistry. Conference Paper, FVS - LZE, Topics 2005" and the references contained therein, or in "Seawater Desalination with Solar Energy, Fraunhofer for Solar Energy Systems, ISE Annual Report 2003, page 82". Approximately 700 kWh of energy are required to evaporate one cubic meter of water, as can be read, for example, in "M. Rommel, Fraunhofer ISE, Solar Energy for Africa / Seawater Desalination with Solar Energy, http: / / solarenergie-fuer-afrika.de / deutsch / konferenz-2003 / referate / rommel-meerwasserentsalzung.html", accessed on July 6, 2021.

[0013] Currently, oil, natural gas, and nuclear energy are the primary energy sources used. In thermal desalination processes, the equivalent of approximately 70 liters of gasoline is consumed to evaporate one cubic meter of water. Similarly, electrical desalination processes require large amounts of electricity to overcome the significant pressure differences that arise, for example, during reverse osmosis. This poses a major problem, not only due to the finite nature of fossil fuel reserves but also because of the CO₂ released during fossil fuel combustion and the associated global warming. Consequently, there is an urgent need for methods that utilize renewable energy sources to provide the energy required in desalination processes.

[0014] A combination of water desalination with contacting a carrier with hydrogen for storage of the hydrogen through exothermic hydrogenation has not been described in the aforementioned articles or anywhere else to date.

[0015] The object underlying the present invention is therefore to provide a new method for desalinating water.

[0016] This problem is solved by a method for desalinating water according to claim 1.

[0017] A first advantage of the method according to the invention is that energy can be safely stored for extended periods. This advantage can be clearly illustrated by the following scenario. For example, during favorable times, a surplus of energy is generated in the form of electricity. This could include seasonally distributed windy days associated with wind power generation, or sunny days, particularly during the summer months, for generating electricity, for example, via photovoltaic systems or solar thermal collectors. The respective surplus of energy, especially electricity, can then be converted into hydrogen, for example.According to the invention, hydrogen, which can preferably be obtained from electricity as described above, is safely stored by contacting it with a suitable carrier, so that the hydrogen, or indirectly the energy, can be stored for a longer period of time. When needed, i.e., in the case of a continuous or sudden demand for desalinated water, the stored hydrogen or energy can be converted back into heat for use in a thermal desalination process.

[0018] A significant advantage of the method according to the invention is that the energy released during the exothermic storage of hydrogen in the seasonal storage of electricity described above can be reused. This is particularly advantageous when the storage and withdrawal of hydrogen, especially in the preferred LOHC process described below, are spatially and / or temporally separated. The intermediate storage of the energy released during hydrogen storage as a result of step a) according to the invention is generally difficult or involves relatively high losses, especially if said energy is to be stored for an extended period.

[0019] A significant advantage of the process according to the invention lies in the fact that the energy required for the relatively energy-intensive water desalination process is supplied by renewable energy sources, specifically in the form of heat released during the hydrogen loading of a carrier. The energy-rich, hydrogen-loaded carrier is then available for further processes. Simultaneously, drinking water, process water, or fully desalinated water is produced using renewable energy. The drinking water is available, for example, in water-scarce regions, while desalinated water can also be used for irrigation in agriculture or for industrial production.

[0020] Furthermore, fully demineralized water can be obtained, which is also needed for the electrolysis of water and thus for the production of hydrogen from water using renewable energy, especially photovoltaics. Additionally, if required, the carbonate hardness of the previously demineralized water can be increased again by adding calcium bicarbonate to enable its use in industrial processes that require sufficient carbonate hardness. Such processes are well known to experts.

[0021] The coupling of a hydrogen storage system according to step a), particularly within the framework of an LOHC process, to a water desalination plant according to step b), or the coupling to an electrolysis cell, is therefore advantageous in several respects. On the one hand, as already described, the heat generated during the storage (hydrogenation) of hydrogen in a suitable carrier, in particular an LOHC liquid (or in an LOHC process), can be efficiently utilized in the water desalination process. Furthermore, in a subsequent process step, the optionally fully demineralized water from the desalination process can again be used to carry out electrolysis and generate hydrogen, since electrolysis is a process that generally requires the use of fully demineralized water. This is absolutely essential, especially in PEM (polymer electrolyte membrane) electrolysis.

[0022] The inventive method can be carried out in several ways, both temporally and / or spatially, in the individual embodiments described below. Ultimately, the carriers used, in particular LOHC liquids, can be repeatedly loaded with hydrogen and subsequently discharged. The energy required or released in each case can also be used in a cycle and / or spatially or temporally staggered.

[0023] A further advantage of the method according to the invention is that, in a preferred embodiment, the existing infrastructure of water desalination plants in Europe or worldwide can be used to carry out the method according to the invention. This significantly reduces the initial investment costs compared to constructing or purchasing a completely new plant. Essential components of any common heat-based water desalination plant can be used for the method according to the invention without incurring substantial costs associated with modifying individual components of such a desalination plant.

[0024] Within the scope of the present invention, the term "in close proximity" (unless otherwise defined below) has the following meaning: The respective steps are carried out on the same company premises (or on adjacent company premises, for example, within an industrial park), preferably at a (spatial) distance of no more than 2 to 3 km, more preferably at a distance of no more than 500 m, and particularly at a distance of no more than 100 m (or the corresponding devices for carrying out these steps are located at the corresponding distances). Where specific numerical values ​​for a distance are given within the scope of the present invention, the respective distances refer to the straight-line distance.

[0025] Within the scope of the present invention, the term "spatially separated from one another" (unless otherwise defined below) has the following meaning: The respective steps are not carried out on the same company premises (or on an adjacent company premises), preferably at a (spatial) distance of at least 5 km, more preferably at a distance of 50 to 1,000 km (or the corresponding devices for carrying out these steps are located at the corresponding distances). According to the invention, it is in principle possible for the corresponding steps, which are to be carried out at a spatial distance, to be carried out at significantly greater distances, for example at a distance of several thousand kilometers. The same applies analogously to terms such as "at a spatial distance," "at a spatial distance," or "spatially offset."

[0026] Within the scope of the present invention, the term "in close temporal proximity" (unless otherwise defined below) has the following meaning: the respective steps are preferably carried out in parallel, i.e., at the same time, particularly if they are carried out on the same premises. If necessary, the respective steps can also be carried out with a certain time delay from one another, preferably at a (temporal) interval of no more than one day, more preferably at an interval of no more than six hours, and particularly at an interval of no more than one hour (or the corresponding devices for carrying out these steps are used within the corresponding time frame). The same applies analogously to terms such as "in direct temporal succession".

[0027] Within the scope of the present invention, the term "temporally separated" (unless otherwise defined below) has the following meaning: the respective steps are not carried out in parallel, i.e., not at the same time, and in particular, they are not carried out on the same premises. Instead, the respective steps are carried out with a time delay of at least one day. Preferably, the interval between carrying out the respective steps is at least one month, and more preferably at least three months (or the corresponding devices for carrying out these steps are deployed within the corresponding timeframe).

[0028] According to the invention, it is in principle possible for the corresponding steps, which are to be carried out at a time interval, to be carried out at significantly longer time intervals, for example, at intervals of several months or even several years. The same applies analogously to terms such as "at a time interval," "at a temporal distance," or "temporally offset."

[0029] The inventive method for desalinating water and the optional additional generation of electricity will be explained in more detail below.

[0030] The first object of the present invention is a method for desalinating water, wherein the method comprises steps a) and b).

[0031] In process step a), a carrier (T1) is brought into contact with hydrogen to store the hydrogen, resulting in a hydrogen-laden carrier (T2) and the release of heat.

[0032] In principle, any carrier (T1) known to those skilled in the art that is suitable for storing hydrogen in any form can be used. Furthermore, according to the invention, the carrier (T1) is capable of storing the hydrogen reversibly. This means that the hydrogen can be released from the hydrogen-loaded carrier (T2), which is obtained by bringing the hydrogen into contact with the carrier (T1), at a later time (and independently of the execution of process step b), thereby recovering the originally used carrier (T1).

[0033] The storage of hydrogen can be carried out, for example, by chemically or physisorptively, preferably chemically, binding hydrogen to the carrier (T1). However, within the scope of the present invention, it is necessary that the storage of hydrogen be reversible. In particular, carbon dioxide, which can react chemically with hydrogen to produce methane, is not a carrier (T1) within the meaning of the present invention because hydrogen cannot be released directly and / or easily reversibly from methane, nor can carbon dioxide be recovered. Consequently, methane is also not a hydrogen-loaded carrier (T2) within the meaning of the present invention.

[0034] A chemical bond between hydrogen and the carrier (T1) can be achieved, for example, by the carrier (T1) being a metal hydride storage medium containing a metal alloy material that absorbs and chemically binds hydrogen. Alternatively, the carrier (T1) can also be an organic compound, preferably liquid. Such organic compounds are also referred to as hydrogen carriers or LOHCs (liquid organic hydrogen carriers) or organic hydrides. Such hydrogen carriers (LOHCs) are known to those skilled in the art and are described, for example, in DE-B 10 2013 223 589, EP-A 1 475 349 and DE-A 10 2012 005 023.

[0035] This form of hydrogen storage using LOHCs has the particular advantage that the LOHC carrier (T1) is typically in liquid form under the process conditions used. The physicochemical properties of such an LOHC carrier are very similar to those of conventional liquid fuels, so pumps for transport or containers for storage from the plastics and printed materials logistics sector can be used. Storing hydrogen in chemically bound form in an organic liquid such as LOHC allows for pressureless storage under normal conditions for extended periods without significant hydrogen loss. If the carrier (T1) is an LOHC carrier, it is in its fully or at least partially dehydrated form. Preferably, it is in the fully dehydrated form.A partially dehydrated form can exist if, for example, a fully dehydrated form of such a support has two or more sites where the corresponding molecule can be hydrogenated, and at least one of these sites suitable for hydrogenation is already in hydrogenated form, but at least one site remains in dehydrated (non-hydrogenated) form. Examples include aromatic compounds, particularly polycyclic aromatic compounds with a conjugated π-electron system.

[0036] In principle, contacting the support (T1) with hydrogen can be carried out using any method known to a person skilled in the art, for example by passing hydrogen over the support (T1), passing it through the support (T1) or pressing it onto the support (T1).

[0037] By contacting the support (T1) with hydrogen in step a) of the process according to the invention, a hydrogen-loaded support (T2) is obtained. Both the support (T1) and the hydrogen-loaded support (T2) obtained by contacting it with hydrogen can exist as a mixture of two or more supports (T1) and / or (T2). If the hydrogen is chemically bound to the support (T1), this involves a complete or at least partial hydrogenation of the corresponding support (T1), so that the hydrogen-loaded support (T2) differs chemically from the corresponding unloaded support (T1). Preferably, this involves a complete hydrogenation of the support (T1) with hydrogen, resulting in the hydrogen-loaded support (T2).

[0038] The ratio of the supports (T1) and (T2) in the process according to step a) of the invention is explained below using toluene, a LOHC support known from the prior art. Toluene contains a benzene ring and thus three π-electron pairs. Toluene therefore represents a support (T1) in its completely dehydrated form. According to the invention, contacting the toluene with hydrogen results in at least partial or preferably complete hydrogenation of toluene to methylcyclohexane as the support (T2). If complete hydrogenation of toluene is carried out, all three π-electron pairs of the toluene are hydrogenated, so that methylcyclohexane represents the completely hydrogenated form of toluene. If only one or two of the π-electron pairs of the toluene have been hydrogenated, this is only a partial hydrogenation.Such at least partially hydrogenated compounds can be used as carriers (T1) or as carriers (T2) according to the invention.

[0039] According to the invention, the support (T1) is an unsaturated compound, preferably a compound with at least one carbon-carbon double bond, more preferably an aromatic or hetero-aromatic compound, even more preferably an N-alkylcarbazole, toluene, dibenzyltoluene, benzyltoluene, naphthalene or an azaborine, particularly preferably dibenzyltoluene.

[0040] Compounds with at least one carbon-carbon double bond (C-C double bond) can be, for example, an olefin, an aromatic compound, or a heteroaromatic compound. Such compounds are generally known to those skilled in the art. These compounds may optionally be substituted, for example, by one or more alkyl groups of any chain length, such as methyl, ethyl, propyl, or by other functional groups, such as halogen, amino, or carboxyl. Heteroaromatic compounds have at least one heteroatom as a heteroatom, which is preferably oxygen, nitrogen, and / or sulfur. Aromatic or heteroaromatic compounds can be monocyclic, bicyclic, or optionally polycyclic. Optionally, the corresponding cycles (rings) may also exist, at least partially, in hydrogenated form. It is also conceivable that, for example, in a bicyclic compound, one of the two cycles is completely hydrogenated.

[0041] If an N-alkylcarbazole is used as the support (T1), the alkyl group bonded to the nitrogen atom can assume any chain length; for example, it can be methyl, ethyl, propyl, isopropyl, or butyl, and optionally mixtures thereof. Preferably, it is N-ethylcarbazole.

[0042] Accordingly, in the inventive process, in step a) the corresponding partially or in particular completely hydrogenated form of the above-defined specific carriers (T1) is preferably obtained as a hydrogen-loaded carrier (T2).

[0043] In principle, it is possible for step a) to be carried out in the same device (V4) as the storage of the hydrogen-loaded carrier (T2), which is defined in more detail below. This can be achieved, for example, by integrating a special unit / device component into such a device (V4), which enables the execution of process step a) separately from the storage of the hydrogen-loaded carrier (T2). Such units or installation measures are known to those skilled in the art. Preferably, however, in the method according to the invention, step a) is carried out in a separate device (V8), which is preferably a chemical reactor.

[0044] Preferably, step a) is carried out in a pressure-stable device, in particular in a pressure-stable chemical reactor. It is further preferred that step a) is carried out at a temperature between 50 °C and 400 °C, in particular between 120 °C and 300 °C, and especially between 150 °C and 280 °C. The hydrogenation, i.e., the loading of the support (T1) with hydrogen, preferably takes place at a process pressure of 2 bar to 200 bar, in particular between 10 bar and 100 bar. It is further preferred that step a) is carried out in the presence of a metal-containing catalyst. Catalysts containing ruthenium and / or nickel are particularly suitable for loading the LOHC support (T1). Catalysts containing other elements or additional elements besides ruthenium and / or nickel are also possible. Essential are those elements that can bind hydrogen and transfer it to the LOHC support (T1).Besides ruthenium and / or nickel, metals such as chromium, iron, cobalt, copper, iridium, palladium or platinum are particularly suitable as catalysts.

[0045] Due to the exothermic storage of the hydrogen by contacting it with the carrier (T1), additional heat is released in step a) according to the invention.

[0046] In process step b), the heat released in step a) is again fed into a device (V1) in order to desalinate water in the device (V1).

[0047] In principle, all types of water known to those skilled in the art can be used. In the process according to the invention, seawater is desalinated in the apparatus (V1). It goes without saying that the salinity of the desalinated water is lower than the salinity of the water used. A classification of waters based on their chloride ion content, which is often used as a proxy for salinity, can be found in "S. EI-Manharawy, S. Hafez, A new chemical classification system of natural waters for desalination and other industrial use, Desalination 2003, 156, pages 163-180". According to this classification, fresh water contains 0.5 to 1.5 mmol / kg chloride, brackish water 1.5 to 50 mmol / kg, salt water 50 to 500 mmol / kg, seawater 500 to 700 mmol / kg, sub-brine 700 to 800 mmol / kg, and brine (saltwater concentrate) over 800 mmol / kg. Instead of mmol / kg, other concentration and weight units, such as g / kg, are also common and known to those skilled in the art.

[0048] A currently frequently used method is the measurement of electrical conductivity as a sum parameter for ion concentration, for example, for determining the salinity of seawater, for quality control of ultrapure water, or for density determination. A guideline for converting conductivity to salinity can be found, for example, in the Practical Salinity Scale (PSS78) from 1978. Background information on determining the salinity of waters can be found, for example, on the websites of the Federal Waterways and Shipping Administration (www.wsv.de, accessed on May 26, 2021), the Weser-Jade-North Sea Waterways and Shipping Authority (https: / / www.wsa-weser-jade-nordsee.wsv.de / , Waterways Construction and Maintenance - Hydrology - Salinity Measurement Methods, accessed on May 26, 2021), or the website http: / / salinometry.com / . Devices for determining conductivity are known to those skilled in the art.

[0049] Unless otherwise specified, the salt content of the water within the scope of the present invention is given in mmol / kg. The determination is carried out using methods known to those skilled in the art, such as measuring the conductivity and the corresponding conversion.

[0050] Methods for desalinating water are, as previously mentioned, known to a person skilled in the art. The same applies, mutatis mutandis, to the (chemical) properties of saline and desalinated water, suitable devices for carrying out water desalination, and / or further use of partially or fully desalinated water, for example, as drinking water, process water, irrigation water, or for carrying out water electrolysis on fully desalinated water. Background information in this context can be found, for example, in the articles mentioned at the beginning regarding desalination.

[0051] In principle, any device known to a person skilled in the art in which water can be desalinated by the application of heat is suitable as a device (V1). This device (V1) comprises at least one section for heating water. Furthermore, the device (V1) can also be connected to one or more heat exchangers, or such heat exchangers can be integrated into the device (V1).

[0052] Preferably the device (V1) is at least one desalination plant selected from the process of multi-stage flash evaporation or multiple-effect distillation.

[0053] The heat released in step a) can, for example, be transferred to the device (V1) via a pipe or piping system. To make the heat transfer from step a) to step b) as efficient as possible, it is advantageous to use heat exchangers.

[0054] Within the scope of the present invention, it is therefore preferred that in step b) i) the device (V1) comprises a seawater desalination plant, preferably comprising at least one heat exchanger, at least one pump, at least one water heating area, at least one storage vessel, at least one inlet and / or at least one outlet, and / or ii) the heat released in step a) is transferred to the device (V1) via a pipeline or piping system, and / or iii) the heat released in step a) is passed through a heat exchanger to heat the water, in particular seawater, contained in the device (V1), preferably at least one heat exchanger is used to further heat the water located at the highest temperature level in the device (V1), and / or iv) the device (V1) has at least two areas with different temperature zones.

[0055] Typically, when using the multi-stage flash evaporation process, the supplied seawater is heated to approximately 110 °C in the so-called brine heater and subsequently passed through flash evaporation stages in which the pressure and temperature decrease continuously. A possible temperature range covered by the various chambers is between 130 and 20 °C. Such heating chambers with downstream flash evaporation stages are known to those skilled in the art. A device for heating the water to be desalinated according to iii) is, as already mentioned above, frequently referred to in the relevant literature as a "brine heater".

[0056] Due to the heat transfer occurring in the inventive method between steps a) and b), it is advantageous if the two steps are carried out in close proximity to each other, i.e., the respective devices for carrying out these steps are preferably positioned not far apart. Distances of, for example, 500 m to 1 km between the respective devices for carrying out the two steps a) and b) are easily manageable in practice.

[0057] While it is conceivable and technically feasible to locate the respective devices for carrying out the two steps at a greater distance from each other, the energy loss increases with the distance between these devices. Appropriately designed pipelines, such as specially insulated pipelines, can bridge larger distances without significant heat loss. However, this has a disadvantage, as it increases installation costs. It is also conceivable that the respective devices could be located on different company premises in close proximity.

[0058] Furthermore, it is preferred that step a) is carried out in a separate device (V8), which is preferably a chemical reactor. A description of such a chemical reactor, which is preferably a pressure-resistant device, can already be found above in the description.

[0059] According to the invention, in step b) in the device (V1) i) seawater is desalinated and ii) desalinated water with a maximum salinity of not more than 1.5 mmol / kg, in particular drinking water, is obtained in the device (V1), and / or iii) the water is stored in a device (V2) before it is desalinated in the device (V1), and / or the water is delivered to the device (V1) by means of a truck, a railway wagon, a ship, a seagoing vessel, via a pipeline or by means of a pipe.

[0060] Figure 1The inventive process is illustrated in its broadest form, taking into account steps a) and b). First, according to step a), hydrogen is brought into contact with a suitable carrier (T1), preferably a hydrogen carrier (LOHC), in the device (V8), which is preferably a chemical reactor. This allows the hydrogen to be stored, preferably by chemical bonding to the carrier (T1), particularly by hydrogenation, thereby producing a hydrogen-loaded carrier (T2). The hydrogen-loaded carrier (T2) can remain in the device (V8), but preferably it is transferred to a separate device for storage. The individual steps and / or the entire process can be operated both batchwise and continuously. The heat released during hydrogen storage in step a) is transported to step b).

[0061] In step b), the heat released in step a) is fed into a device (V1) to desalinate water. The device (V1) generally comprises at least one water desalination unit, preferably employing multi-stage flash distillation (MSF). The desalination unit preferably includes at least one pump, at least one water heating section, at least one storage vessel, at least one inlet, and / or at least one outlet. Optionally, the desalination unit may include further device elements known to those skilled in the art, such as at least one heat exchanger.

[0062] The water to be desalinated is also fed into the device (V1), where it is desalinated by the application of heat, producing water with a lower salt content up to fully demineralized water. The water with a lower salt content up to fully demineralized water can optionally remain in the device (V1); however, preferably the desalinated water is reused and / or transported to another device. The devices (V8) and (V1) are preferably located in close proximity to each other, for example, on the same or an adjacent site.

[0063] In the present invention, the water obtained in process step b) with a lower salt content is further used, up to and including fully demineralized water. The further use of the demineralized water can be spatially and / or temporally independent of the storage and / or further processing of the hydrogen-loaded carrier (T2) obtained in process step a). In particular, the further use of the demineralized water can be spatially and / or temporally independent of the desalination of the saline water in the device (V1) according to process step b).

[0064] According to the invention, it is preferred that in the inventive method, after step b) or preferably following the storage of the hydrogen-loaded carrier (T2), a step c) is carried out: c) Release of hydrogen from the hydrogen-loaded carrier (T2) In principle, it is possible for the optional process step c) to also be carried out in the device (V8) and / or in the device (V4). Preferably, process step c) is carried out in a separate device (V7), which is in particular a chemical reactor. The process steps a) and c) according to the invention, as well as the optional intermediate storage of the hydrogen-loaded carrier (T2), are therefore preferably each carried out in separate devices. In principle, it is possible for the device (V7) for carrying out step c) to be of the same type as the device (V8) for carrying out process step a) according to the invention. Suitable devices for carrying out process step c) according to the invention are disclosed, for example, in DE-B 10 2013 223 589.

[0065] The release of hydrogen according to process step c) preferably takes place in a pressure-stable chemical reactor at a process temperature between 100 °C and 450 °C, preferably between 150 °C and 420 °C, and particularly between 180 °C and 390 °C. The process pressure is between 0.1 and 30 bar, particularly between 1 and 10 bar, and a metal-containing catalyst, especially one containing platinum and / or palladium, may be used. It is essential that the catalyst is suitable for releasing hydrogen emitted from the LOHC support (T2) as hydrogen gas. Besides platinum and / or palladium, metals such as chromium, iron, cobalt, nickel, copper, iridium, or ruthenium are particularly suitable for this purpose.

[0066] In a preferred embodiment, which includes step c), i) Step a) and step c) are carried out spatially separated from each other, preferably at a distance of at least 5 km, in particular 50 to 1000 km, and / or ii) Step a) and step c) are carried out temporally separated from each other, preferably step c) is carried out at least one day, in particular preferably at least one month, after step a), and / or iii) Step c) is carried out in a separate device (V7), which is preferably a chemical reactor.

[0067] Furthermore, it is preferred that the carrier (T1) is also recovered during the release of hydrogen according to step c).

[0068] Furthermore, it is preferred that, in the release of hydrogen according to step c), the carrier (T1) is additionally recovered and the carrier (T1) is used again to carry out step a).

[0069] Figure 2Figure 1 shows a preferred embodiment of the method according to the invention, taking into account steps a), b) and c). In connection with the execution of steps a) and b) in Figure 2 will initially focus on Figure 1 as well as the related explanations, where the method according to the invention is explained in its broadest sense. In addition to Figure 1 is in the preferred embodiment according to Figure 2 It is taken into account that the water, before being desalinated in the device (V1), is stored in a device (V2) and / or that the water is delivered to the device (V1) just in time by truck, railcar, ship, ocean-going vessel and / or via pipeline. For all figures containing devices marked with an asterisk (*), the components marked with an asterisk (*) are optional for this embodiment.

[0070] Furthermore, in Figure 2It is taken into account that in device (V7) hydrogen is released from the hydrogen-laden carrier (T2). In principle, any device known to those skilled in the art in which hydrogen can be released from the hydrogen-laden carrier (T2) is suitable as device (V7). Preferably, (V7) is a chemical reactor.

[0071] In a preferred embodiment of the present invention, following the execution of step a) and independently of the execution of step b) according to the invention, the hydrogen-loaded carrier (T2) obtained in step a) is stored. The storage of the hydrogen-loaded carrier (T2) can, in principle, be carried out in the same device in which step a) is performed, for example, in device (V8). Within the scope of the present invention, it is preferred that the execution of step a) and the subsequent storage of the hydrogen-loaded carrier (T2) obtained thereby are carried out in different devices. Here, the hydrogen-loaded carrier (T2) obtained in step a) is stored in a device (V4).

[0072] The storage of the hydrogen-loaded carrier (T2) can, in principle, take place for any length of time. Typically, storage lasts for at least several days, but it can also last for several weeks, months, or even years. However, it is also conceivable that storage is carried out for only a few minutes or hours, or for a single day. Preferably, storage lasts for at least one day and / or a maximum of six months.

[0073] It is also possible that the hydrogen-loaded carrier (T2) is not stored in a separate device after its production according to step a), but is processed directly by preferably transporting it to a suitable device for carrying out step c) defined below, where the hydrogen is released from the carrier (T2). Preferably, steps a) and c) are carried out at a spatial distance from each other, and even more preferably with a temporal interval, so that the hydrogen-loaded carrier is preferably stored separately after step a).

[0074] A mobile device (V3) for transporting the hydrogen-laden carrier can be a truck, a railway wagon, a ship, a seagoing vessel and / or a pipeline.

[0075] Preferably, this embodiment is carried out such that the hydrogen-loaded carrier (T2) obtained in step a) is stored in a device (V4), preferably the device (V4) is selected from a tank, a fermenter or a container obtained by converting a biogas plant, in particular by converting a fermenter, or which is a component of a biogas plant.

[0076] In a preferred embodiment i) the hydrogen-loaded support (T2) obtained in step a) is stored in a device (V4), and / or ii) hydrogen is chemically or physisorptively, preferably chemically, bound to the support (T1) in step a), and / or iii) the support (T1) is an unsaturated compound, preferably a compound with at least one carbon-carbon double bond, more preferably an aromatic or heteroaromatic compound, even more preferably an N-alkylcarbazole, toluene, dibenzyltoluene, benzyltoluene, naphthalene or an azaborine, particularly preferably dibenzyltoluene, and / or iv) the hydrogen-loaded support (T2) is obtained in step a) by at least partial or complete hydrogenation, preferably by complete hydrogenation, with hydrogen from the support (T1).

[0077] It is also possible that the carrier (T1) is initially stored in a separate storage device (V5) and / or transported in a mobile device (V3) before being loaded with hydrogen in step a). Storage followed by transport and then re-storage before loading the carrier (T1) with hydrogen in step a) is also conceivable.

[0078] According to the invention, in a preferred embodiment, a step e) is carried out between steps a) and c): e) Transport of the hydrogen-loaded carrier (T2) in a mobile device (V3), wherein, optionally, before and / or after transport in the mobile device (V3), the hydrogen-loaded carrier (T2) can additionally be stored in a device (V4), preferably the mobile device (V3) is selected from a truck, a railway wagon or a ship, more preferably the mobile device (V3) is a ship, in particular the mobile device (V3) is a seagoing vessel.

[0079] Figure 3 Figure 1 shows a particularly preferred embodiment of the method according to the invention, taking into account steps a), b) and c) described above. In connection with carrying out steps a), b) and c) in Figure 3 First, attention will be paid to the two Figures 1 and 2Reference is made to the related explanations. For the execution of the additional steps, reference is made to the preceding description. In this embodiment, storage and transport of the carrier (T1) and the hydrogen-loaded carrier (T2) can optionally be omitted; however, preferably both steps are carried out.

[0080] In addition to Figure 2 is in the particularly preferred embodiment according to Figure 3It is taken into account that the carrier (T1) can preferably be stored in a separate device (V5), for example, in an intermediate storage facility in the form of a tank, after step c) has been completed and before step a) is carried out. However, the use of such a separate device (V5) is not mandatory in this particularly preferred embodiment, but rather optional. The use of such a separate device (V5) is particularly advantageous if there is a longer period of time between the execution of the two process steps c) and a) and / or if a very large quantity of carrier (T1) is to be loaded with hydrogen in step a). The same applies analogously to the storage of the hydrogen-loaded carrier (T2) in a separate device (V4).In addition to the storage devices (V4) and (V5), the use of a mobile device (V3) is conceivable, for example, to transport the loaded and / or unloaded carriers T1 and / or T2 between (V7) and (V8) in the event of a spatial separation between (V7) and (V8). The respective storage operations can be carried out at different times or (at least partially) overlapping; alternatively, it is also conceivable to store the carriers (T1) and (T2) in a single device (V4).

[0081] If necessary, the respective storage procedures, particularly in devices (V4) and / or (V5), can be omitted entirely or at least partially. If there is a spatial distance between devices (V8) on the one hand and (V7) on the other, the time required for the transport of, for example, the hydrogen-laden carrier (T2) must be taken into account, so that step c) can only be carried out with a time delay. Likewise, the transport of the hydrogen-laden carrier (T2) in a suitable transport device, such as a truck or a railway tank car, can be combined with temporary storage of the hydrogen-laden carrier (T2) by temporarily parking the transport device loaded with the carrier (T2). The same applies, of course, to the return transfer of the recovered carrier (T1) from step a) to step c).

[0082] In the method according to the invention, step d) is carried out before step a). According to step d) of the invention, hydrogen is produced in a device (V6), preferably in an electrolyzer, using water and electric current.

[0083] The execution of process step d) as such is known to those skilled in the art. Suitable electrolyzers are described, for example, in DE-B 10 2013 223 589, DE-A 10 2012 005 023, or EP-A 2780491. These can be, for example, a so-called PEM electrolyzer (polymer electrolyte membrane), a SOEC electrolyzer (solid oxide electrolysis cell), or a high-temperature electrolyzer. Ultimately, any type of device (V6) is suitable in which the decomposition of water into hydrogen or oxygen can be carried out while simultaneously supplying an electric current. The device (V6) typically contains two electrodes. The water used is usually demineralized water (see, for example, EP-A 2780491).

[0084] The electrical current used in step d) can, in principle, originate from any source. For example, it is conceivable that the electrical current is drawn from a separate grid (consumer grid). Preferably, however, the electrical current used according to step d) is renewably generated electrical current. This renewably generated electrical current is preferably produced directly or in the immediate vicinity of where the process according to the invention is carried out. The electrical current can be obtained, for example, from hydropower, wind energy, solar radiation, geothermal energy, biogas, bioethanol, wood, or by the tides. The machines and apparatus necessary for generating the electrical current are also known. These can be water turbines, wind turbines, photovoltaic systems, solar thermal systems, combustion engines, or turbines whose fuel is biomass.Preferably, the electric current used in step d) of the method according to the invention is generated by hydropower, wind energy or solar radiation.

[0085] Preferably, step d) is carried out by i) preferably the electricity is generated from renewable energy sources, and / or ii) the desalinated water used in the electrolysis is obtained at least partially in accordance with step b), and / or iii) the electricity is generated in a photovoltaic or wind power plant.

[0086] In the process according to the invention, steps a), b) and d) are carried out in combination, i.e. the hydrogen obtained from the electrolysis in step d) is again used in step a) to load a carrier (T1) with hydrogen and the heat released during loading is used in step b) for water desalination.

[0087] In the process according to the invention, it is further preferred that step f) is carried out after step c). f) Transfer of the hydrogen obtained in step c) into a device (V9), wherein in the device (V9) hydrogen is converted into electricity and / or hydrogen is converted into heat for residential or industrial processes and / or hydrogen is used as a chemical reaction partner.

[0088] Examples of possible reactions in which hydrogen can be used as a reactant, without limiting ourselves to these examples, are the Fischer-Tropsch synthesis, methanation and its use in refineries.

[0089] In a preferred embodiment, hydrogen is converted into electric current in the device (V9).

[0090] As mentioned above, in step d) oxygen is (generally) produced in addition to hydrogen. Preferably, in step d) oxygen is also produced, and this oxygen is converted together with hydrogen into electricity and, optionally, heat in the (subsequently defined) device (V9) according to step f), wherein the oxygen is optionally temporarily stored before its use in step f). Devices for temporarily storing oxygen are known to those skilled in the art.

[0091] The device (V9) as such is known to those skilled in the art. Preferably, the device (V9) is a component of a combined heat and power plant, a gas engine, a fuel cell, an internal combustion engine, an internal combustion engine with an attached generator, a turbine or a hydrogen turbine with an attached generator, preferably a gas engine.

[0092] Furthermore, it is preferred that any heat generated in step f) is returned after step c).

[0093] In a preferred embodiment, i) in the release of hydrogen according to step c), the carrier (T1) is additionally recovered, and / or ii) in the release of hydrogen according to step c), the carrier (T1) is additionally recovered and the carrier (T1) is reused to carry out step a), and / or iii) in the release of hydrogen according to step c), the carrier (T1) is additionally recovered and the carrier (T1) is transported in a mobile device (V3) to reuse the carrier (T1) to carry out step a), preferably the mobile device (V3) is selected from a truck, a railway wagon or a ship, more preferably the mobile device (V3) is a ship, in particular the mobile device (V3) is a seagoing vessel, and / or iv) in the release of hydrogen according to step c), the carrier (T1) is additionally recovered and the carrier (T1) is subsequently stored in a separate device (V5) or in the device (V4).

[0094] Figure 4 Figure 1 shows a particularly preferred embodiment of the method according to the invention, taking into account steps a), b), c), d), e) and f) described above. In connection with carrying out steps a), b), c) and e) in Figure 4 will first focus on the Figures 1, 2 and 3 Reference is made to the relevant sections and the accompanying explanations. For the execution of steps d) and f), reference is made to the preceding description. Steps d) and / or f) may optionally be omitted in this embodiment, but preferably both steps d) and f) are carried out.

[0095] In addition to Figure 3 is in the particularly preferred embodiment according to Figure 4 taking into account that the water desalinated in step b) is fed to an electrolysis in the device (V6).

[0096] The release of hydrogen according to process step c) preferably takes place in a pressure-stable chemical reactor at a process temperature between 100 °C and 450 °C, preferably between 150 °C and 420 °C, and particularly between 180 °C and 390 °C. The process pressure is between 0.1 and 30 bar, particularly between 1 and 10 bar, and a metal-containing catalyst, especially one containing platinum and / or palladium, may be used. It is essential that the catalyst is suitable for releasing hydrogen emitted from the LOHC support (T2) as hydrogen gas. Besides platinum and / or palladium, metals such as chromium, iron, cobalt, nickel, copper, iridium, or ruthenium are particularly suitable for this purpose.

[0097] Within the scope of the present invention, it is further preferred that i) the devices (V7) and (V4) and / or (V5) are located in close proximity to each other, preferably on the same operating premises, and / or ii) the device (V4) has two spatially separate areas, a first area being used for storing the hydrogen-loaded carrier (T2) and a second area being used for storing the carrier (T1), and / or iii) the device (V4) is provided with a protective lining inside before the storage of the carrier (T2) and optionally the carrier (T1) is carried out, and / or iv) a floating partition is installed in the device (V4) and the hydrogen-loaded carrier (T2) is stored below the floating partition, and / or v) the device (V4) was part of a biogas plant and had been cleaned of all substances that had been present inside it or optionally in its supply lines as a result of biogas production.before the storage of the support (T2) and, if applicable, the support (T1) is carried out.

[0098] According to the invention, it is further preferred that the process for storing hydrogen and releasing heat is carried out in a plant that can also be used for the production of biogas.

[0099] Within the scope of the present invention, it is further preferred that i) the production of biogas on the one hand and the storage and storage of hydrogen or the generation of electricity and, where applicable, heat on the other hand are carried out in parallel on the same plant, and / or ii) the production of biogas is carried out in a separate fermenter which is not part of the device (V4) for storing the hydrogen-laden carrier (T2).

[0100] The timeframes mentioned in the aforementioned options are essentially arbitrary. They can be one or more hours, one or more days, or even longer periods such as weeks and months. This depends entirely on the specific requirements for desalinated water production, hydrogen storage, and / or electricity generation.

Claims

1. Method for desalinating water comprising the following steps a) and b): a) Bringing a carrier (T1) into contact with hydrogen to store the hydrogen, thereby obtaining a hydrogen-loaded carrier (T2) and releasing heat, b) feeding the heat released in step a) into a device (V1) in order to desalinate water in the device (V1), wherein seawater is desalinated in the device (V1) and water with a maximum salt content of no more than 1.5 mmol / kg is obtained in the device (V1), and wherein the carrier (T1) is an unsaturated compound, and wherein a step d) is carried out prior to step a): d) Generation of hydrogen in an electrolyzer using water and electric current, wherein the desalinated water used in the electrolysis is obtained at least in part according to step b).

2. Method according to claim 1, characterized in that in step b) i) the device (V1) comprises a seawater desalination plant, preferably the seawater desalination plant comprises at least one pump, at least one area for heating water, at least one storage vessel, at least one supply line and / or at least one outlet, and / or ii) the heat released in step a) is conducted into the device (V1) via a pipe or a pipe system, and / or iii) the heat released in step a) is conducted through a heat exchanger in order to heat the water contained in the device (V1), in particular seawater, preferably at least one heat exchanger is used to further heat the water at the highest temperature level in the device (V1), and / or iv) the device (V1) has at least two areas with different temperature zones.

3. Method according to claim 1 or 2, characterized in that i) step a) and step b) are carried out in close proximity to each other, preferably the respective devices for carrying out the two steps a) and b) are located on the same premises, and / or ii) step a) is carried out in a separate device (V8), which is preferably a chemical reactor.

4. Method according to any of claims 1 to 3, characterized in that i) drinking water is obtained in the device (V1), and / or ii) the water is stored in a device (V2) before being desalinated in the device (V1) and / or the water is delivered to the device (V1) by truck, rail car, ship, ocean-going vessel, or by means of piping or a pipeline.

5. Method according to any of claims 1 to 4, characterized in that after step a) a step c) is carried out: c) Release of hydrogen from the hydrogen-loaded carrier (T2).

6. Method according to claim 5, characterized in that i) step a) and step c) are carried out spatially separated from each other, preferably at a distance of at least 5 km, in particular 50 to 1000 km, and / or ii) step a) and step c) are carried out at different times, preferably step c) is carried out at least one day, particularly preferably at least one month, after step a), and / or iii) step c) is carried out in a separate device (V7), which is preferably a chemical reactor.

7. Method according to any of claims 1 to 6, characterized in that i) the hydrogen-loaded carrier (T2) obtained in step a) is stored in a device (V4), and / or ii) in step a), hydrogen is chemically or physisorptively, preferably chemically, bound to the carrier (T1), and / or iii) the carrier (T1) is a compound with at least one carbon-carbon double bond, more preferably an aromatic or heteroaromatic compound, even more preferably an N-alkylcarbazole, toluene, dibenzyltoluene, benzyltoluene, naphthalene or an azaborine, particularly preferably dibenzyltoluene, and / or iv) in step a), the hydrogen-loaded carrier (T2) is obtained from the carrier (T1) by at least partial or complete hydrogenation, preferably by complete hydrogenation.

8. Method according to any of claims 1 to 7, characterized in that the electrical current comes from renewable energy generation, with particular preference for current generated in a photovoltaic or wind power plant.

9. Method according to one of claims 5 or 6, characterized in that a step e) is carried out between step a) and step c): e) transporting the hydrogen-loaded carrier (T2) in a mobile device (V3), wherein, if necessary, before and / or after transport in the mobile device (V3), the hydrogen-loaded carrier (T2) can additionally be stored in a respective device (V4), preferably, the mobile device (V3) is selected from a truck, a railway wagon, or a ship, more preferably, the mobile device (V3) is a ship, in particular, the mobile device (V3) is an ocean-going vessel.

10. Method according to any of claims 5, 6, or 9, characterized in that after step c), a step f) is carried out: f) transferring the hydrogen obtained in step c) into a device (V9), wherein in the device (V9) hydrogen is converted into electrical current and / or hydrogen is converted into heat for residential or industrial processes and / or hydrogen is used as a chemical reaction partner.

11. Method according to claim 10, characterized in that i) the device (V9) is part of a block heat and power plant, a gas engine, a fuel cell, an internal combustion engine, an internal combustion engine with a connected generator, a turbine, or a hydrogen turbine with a connected generator, preferably a gas engine, and / or ii) the heat generated in step f), if applicable, is returned into step c).

12. Method according to any of claims 5, 6, 10, or 11, characterized in that i) during the release of hydrogen according to step c), the carrier (T1) is additionally recovered, and / or ii) during the release of hydrogen according to step c), the carrier (T1) is additionally recovered and the carrier (T1) is reused to perform step a), and / or iii) during the release of hydrogen according to step c), the carrier (T1) is additionally recovered and the carrier (T1) is transported in a mobile device (V3) in order to reuse the carrier (T1) for carrying out step a), preferably the mobile device (V3) is selected from a truck, a railway wagon or a ship, more preferably, the mobile device (V3) is a ship, in particular, the mobile device (V3) is an ocean-going vessel, and / or iv) during the release of hydrogen according to step c), the carrier (T1) is additionally recovered and subsequently the carrier (T1) is stored in a separate device (V5) or in the device (V4).

13. Method according to any of claims 1 to 12, characterized in that i) the devices (V7) and (V4) and / or (V5) are located in close proximity to each other, preferably on the same premises, and / or ii) the device (V4) has two spatially separated areas, wherein a first area is used for storing the carrier (T2) loaded with hydrogen and a second area is used for storing the carrier (T1), and / or iii) the device (V4) is provided with a protective lining inside before the carrier (T2) and, if applicable, the carrier (T1) are stored, and / or iv) a floating partition is installed in the device (V4) and the hydrogen-loaded carrier (T2) is stored below the floating partition, and / or v) the device (V4) was part of a biogas plant and was cleaned of all substances that were as a result of biogas production inside it or, if applicable, in its supply lines, before the carrier (T2) and, if applicable, the carrier (T1) are stored.

14. Method according to any of claims 1 to 13, characterized in that the method is carried out in a plant that can also be used to produce biogas.

15. Method according to claim 14, characterized in that i) the production of biogas on the one hand and the storage and warehousing of hydrogen or the generation of electrical power and, if applicable, heat on the other hand are carried out in parallel on the same plant, and / or ii) the production of biogas is carried out in a separate fermenter which is not part of the device (V4) for storing the hydrogen-loaded carrier (T2).