Processes for producing hydrogen

Abstract

Method for producing hydrogen, comprising the following step a): a) Release of hydrogen from a hydrogen-laden carrier (T2), wherein at least a subset of the energy required for hydrogen release is obtained by the combustion of sewage sludge.

Description

[0001] The present invention relates to a method for producing hydrogen, wherein hydrogen is released from a hydrogen-loaded carrier (T2) and at least a portion of the energy required for hydrogen release is obtained by the combustion of sewage sludge. This released hydrogen can in turn be used for electricity generation, so that the present invention also relates to a method for generating electricity and optionally heat.

[0002] EP 3 415 609 A1 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 3 415 609 A1 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] EP 3 415 610 A1 relates to a process for converting a biogas plant into a hydrogen storage plant, comprising at least two process steps. In the first process step, the interior of at least one digester (F1) of the biogas plant is cleaned. In the optional second process step, at least one protective lining is installed inside the cleaned digester (F1). In the third process step, a hydrogen-laden carrier (T2) is introduced into the cleaned digester (F1) and stored there.

[0004] Biogas plants as such have been known for a long time (see, for example, the free encyclopedia Wikipedia under the term "Biogas plant"; https: / / de.wikipedia.org / wiki / biogasanlage; version of April 19, 2017). A biogas plant serves to produce biogas through the fermentation of biomass. Biogas plants are generally used on farms, where, for example, animal excrement (liquid / solid manure) or energy crops are used as substrate. A fertilizer known as digestate is often produced as a byproduct. The biogas, the main product of the biogas plant, is frequently used for decentralized combined heat and power (CHP) generation in cogeneration plants. In this process, the biogas, which may be dried and / or desulfurized, is fed into a gas engine that converts the biogas into electricity and, if necessary, heat. The electricity produced in this way is fed into the grid.Most often, electricity is generated directly on-site from biogas as part of a biogas plant. Alternatively, the biogas produced in a biogas plant can be purified to natural gas quality and fed into the natural gas grid as biomethane (biomethane).

[0005] A central component of such a biogas plant is typically a biogas reactor, also known as a fermenter (see also Wikipedia; https: / / de.wikipedia.org / wiki / bioreaktor; version of April 21, 2017). In this fermenter, biogas is produced through specific biological processes (bioconversion, biocatalysis), depending on the biomass input. In practice, there are numerous manufacturers of such reactors / fermenters, which differ in size and features, as well as the type and dimensions of the feed lines for internal components such as agitators or any heating systems present within the fermenter. A biogas plant can also contain two or more fermenters. Additional fermenters are also referred to as post-fermenters. Furthermore, biogas plants often have numerous storage tanks or reservoirs to store, for example, the biomass to be fermented or the digestate.The individual components of a biological plant are usually connected to each other by a corresponding piping system and by pumps.

[0006] A major problem with biogas plants is their economic viability. At least in Germany, and similarly in other European countries, the operation of biogas plants is subsidized as part of renewable energy initiatives. However, these government subsidies for renewable energy production are not unlimited and will be reduced or even phased out in the foreseeable future, particularly for biogas plants. Without government assistance, it is difficult for many farms, especially smaller ones, to continue operating biogas plants profitably. Another problem with operating biogas plants is the risk of gas leaks and heat loss. Handling and storing biogas, which is generally flammable, requires enhanced safety precautions.

[0007] DE 10 2012 005 023 A1 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.

[0008] The process and corresponding system described in DE 10 2012 005 023 A1 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 sewage sludge drying is not disclosed in DE 10 2012 005 023 A1.

[0009] A corresponding method or arrangement is disclosed in DE 10 2011 121 704 A1. 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.

[0010] Methods for drying and / or disposing of sewage sludge, for example by incineration, have also been known for a long time. Background information on the properties of sewage sludge and its disposal in Germany can be found, for example, in the article "Sewage Sludge Disposal in Germany" (as of October 2018, published by the Federal Environment Agency, available online at: www.umweltbundesamt.de / publikationen). Further information in this context can also be found in the article "Sewage Sludge Drying in Germany - Status and Perspectives" by Jürgen Geyer (pages 927-948; in Energy from Waste - Volume 10; TK Verlag Karl Thome-Kozmiensky; Neuruppin 2013).

[0011] The document "Sewage Sludge Incineration" (https: / / www.bayernwerk-natur.de / de / Technologie / klaerschlammverbrennung.html) concerns sewage sludge disposal in Straubing. The document reveals that a dedicated incineration plant for the utilization of municipal sewage sludge is planned in Straubing. Furthermore, the document addresses a subsequent flue gas cleaning process to remove heavy metals and other pollutants. According to the document, the heat released during incineration is used to generate steam in a downstream boiler, which then drives a turbine and a coupled generator to produce electricity. The document also indicates that the heat can be used to pre-dry sewage sludge or supplied to the district heating network. Finally, the document addresses phosphorus recovery.The document makes no mention of hydrogen storage, let alone the endothermic release of hydrogen from a hydrogen-laden carrier. However, the combination of sewage sludge incineration with the release of hydrogen from a hydrogen-laden carrier, where the energy required for this is obtained through the combustion of sewage sludge, has not been described in the aforementioned articles or anywhere else to date. The same applies, mutatis mutandis, to the generation of electricity using the released hydrogen.

[0012] The object underlying the present invention is to provide a new method for producing hydrogen or for generating electric current.

[0013] The problem is solved by a process for producing hydrogen, comprising the following step a): a) Release of hydrogen from a hydrogen-laden carrier (T2), wherein at least a subset of the energy required for hydrogen release is obtained by the combustion of sewage sludge.

[0014] Furthermore, the problem is solved by a method for generating electric current and, if necessary, heat, comprising the following steps a) and b): a) Release of hydrogen from a hydrogen-laden carrier (T2), wherein at least a subset of the energy required for hydrogen release is obtained by the combustion of sewage sludge, b) Transfer of the hydrogen obtained in step a) into a device (V2), wherein hydrogen is converted into electric current and optionally into heat in the device (V2).

[0015] A first advantage of the process according to the invention is that the heat generated during sewage sludge incineration can be usefully reused. In a dehydrogenation process, hydrogen can be released from a hydrogen-laden carrier, particularly in LOHC dehydrogenation, simply by supplying heat from the sewage sludge incineration. Such dehydrogenation, i.e., the release of hydrogen from a suitable carrier, is an endothermic process that requires the input of large amounts of energy, for example, in the form of heat. The energy required for this endothermic process therefore does not need to be generated separately or at considerable expense; instead, the energy generally released during sewage sludge incineration can be used effectively.

[0016] This released hydrogen can then be used to generate electricity in a simple way. The heat typically released during the generation of electricity using hydrogen can, if necessary, be reused in the preceding process steps for releasing hydrogen from a hydrogen-laden carrier, which represents a further advantage of the process according to the invention. This is particularly advantageous if the corresponding devices for releasing hydrogen from the carrier and for generating electricity are located in close proximity to each other.

[0017] A further advantage of the process according to the invention is that it can be easily combined with further process steps for storing energy and / or electricity or heat. For example, the process according to the invention can be part of a cycle for storing energy or electricity, particularly in conjunction with a LOHC process, so that energy can be safely stored temporarily over a longer period of time.

[0018] This advantage can be clearly illustrated by the following scenario. For example, during favorable periods, 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 be converted into hydrogen. According to the invention, hydrogen, which can preferably be obtained from electricity, is safely stored by contacting it with a suitable carrier, so that the hydrogen, or indirectly the energy, can be stored for an extended period. In case of need, i.e., in the event of a sudden increase in demand, the hydrogen can be stored in the hydrogen carrier.In the event of a continuous demand for electrical energy, the hydrogen or energy stored in this way can be converted back into electricity or, if necessary, into heat.

[0019] A further 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 is generally difficult or involves relatively high losses, especially if said energy is to be stored for an extended period.

[0020] The coupling of a hydrogen storage system according to step d) defined below, particularly within the framework of an LOHC process, to a sewage sludge drying system according to step e) defined below, or to a sewage sludge incineration plant, is therefore advantageous in several respects. Firstly, 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 sewage sludge drying process. The dried sewage sludge can then be disposed of by incineration, thereby recovering the heat required in step a) of the inventive process for the release of hydrogen from a suitable carrier, thus effectively closing the energy cycle at this point.

[0021] 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.

[0022] A further advantage of the method according to the invention lies in the fact that, in a preferred embodiment, the existing infrastructure of the numerous biogas plants in Germany and Europe can be used to carry out the method according to the invention. This significantly reduces the initial investment costs compared to constructing a completely new plant or purchasing a completely new one. Essential components of any standard biogas plant can be used for the method according to the invention without incurring substantial costs associated with modifying individual components of the biogas plant.Furthermore, device elements that either belong directly to the biogas plant or are directly connected to it, such as a grid connection, a transformer, a combined heat and power plant or a gas engine contained therein, can also be used directly in the inventive method for operation in a biogas plant with subsequent electricity generation without further conversion.

[0023] It is also advantageous that the process according to the invention can be carried out in parallel and / or at a time delay with the conventional operation of a biogas plant. For example, it is conceivable that, in addition to the existing "conventional operation" of a biogas plant, appropriate device elements could be added to allow the process according to the invention to be carried out in parallel or at a time delay with the actual production of biogas or the subsequent generation of electricity or heat. In this variant of the process, it is further advantageous if the hydrogen produced from electricity is used, at least in part, for the production of biogas, particularly within the framework of methanization.

[0024] Alternatively, it is of course also possible to fully convert a conventionally used biogas plant to carry out the process according to the invention. This is particularly interesting in the case of smaller biogas plants operated in the agricultural sector, because their economic operation is very difficult or even impossible due to the end of subsidies for such biogas plants, at least in Germany.

[0025] 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 an adjacent company premises), preferably at a (spatial) distance of no more than 1 km, more preferably at a distance of no more than 500 m, and in particular 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.

[0026] 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 10-50 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 hundred km or even more than 1000 km. The same applies analogously to terms such as "at a spatial distance," "at a spatial distance," or "spatially offset."

[0027] 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 1 day, more preferably at an interval of no more than 6 hours, and particularly at an interval of no more than 1 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".

[0028] Within the scope of the present invention, the term “separately in time” (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 company premises.

[0029] 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, more preferably at least three months (or the corresponding devices for carrying out these steps are used within the corresponding timeframe). 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 time distance," or "temporally offset."

[0030] The inventive method for producing hydrogen and the optional additional production of electricity and / or heat will be explained in more detail below.

[0031] The first object of the present invention is a method for producing hydrogen, comprising the following step a): a) Release of hydrogen from a hydrogen-laden carrier (T2), wherein at least a subset of the energy required for hydrogen release is obtained by the combustion of sewage sludge.

[0032] According to the invention, in step a), hydrogen is released from a (hydrogen-loaded) carrier (T2). The release of the hydrogen also yields the carrier (T1). The two carriers (T1) and (T2) are characterized, according to the invention, by their ability to reversibly bind hydrogen (carrier (T1)) and reversibly release hydrogen (carrier (T2)), respectively. In other words, this means that when hydrogen is released from carrier (T2), carrier (T1) is formed, while carrier (T2) is formed from carrier (T1) through binding with hydrogen. The latter is also referred to as hydrogen storage.

[0033] According to the invention, it is therefore preferred that the hydrogen-loaded carrier (T2) used in step a) is obtained from a carrier (T1), wherein the carrier (T1) is brought into contact with hydrogen, preferably the hydrogen-loaded carrier (T2) serves as a hydrogen storage medium.

[0034] 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 again at a later time from the hydrogen-loaded carrier (T2), which is obtained by bringing the hydrogen into contact with the carrier (T1), thereby recovering the originally used carrier (T1).

[0035] 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.

[0036] 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 10 2013 223 589 B1, EP 1 475 349 A1 and DE 10 2012 005 023 A1.

[0037] 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, especially polycyclic aromatic compounds with a conjugated π-electron system.

[0038] In principle, contact between the carrier (T1) and hydrogen can be carried out using any method known to a person skilled in the art, for example by passing hydrogen over the carrier (T1), passing it through the carrier (T1) or pressing it onto the carrier (T1).

[0039] By contacting the carrier (T1) with hydrogen, as is carried out, for example, in the optional step d) of the process according to the invention defined below, a hydrogen-loaded carrier (T2) is obtained. Both the carrier (T1) and the hydrogen-loaded carrier (T2) obtained by contacting it with hydrogen can exist as a mixture of two or more carriers (T1) and / or (T2). If the hydrogen is chemically bound to the carrier (T1), this involves a complete or at least partial hydrogenation of the corresponding carrier (T1), such that the hydrogen-loaded carrier (T2) differs chemically from the corresponding unloaded carrier (T1). Preferably, this involves a complete hydrogenation of the carrier (T1) with hydrogen, resulting in the hydrogen-loaded carrier (T2).

[0040] The ratio of the supports (T1) and (T2) in the process according to the invention, as described in step a), 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, the hydrogenation is only partial.Such at least partially hydrogenated compounds can be used as carriers (T1) or as carriers (T2) according to the invention.

[0041] Normally 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.

[0042] 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.

[0043] 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.

[0044] Accordingly, in the inventive method, in step a) the corresponding partially or in particular fully hydrogenated form of the specific carriers (T1) defined above is preferably used as the hydrogen-loaded carrier (T2).

[0045] According to the invention, it is preferred that, prior to carrying out step a), the hydrogen-loaded carrier (T2) is stored in a device (V4) (defined in more detail below), preferably the device (V4) being 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. Furthermore, it is preferred that the hydrogen-loaded carrier (T2) is produced according to the optional step d) defined below.

[0046] Step a) can be carried out in any device (V1) known to a person skilled in the art, in particular a chemical reactor. As described below, it is possible that the optional process step d) is also carried out in the device (V1) and / or in the device (V4). Preferably, process step a) is carried out in a separate device (V1). The process steps a) and d) according to the invention, as well as the optional intermediate storage of the hydrogen-loaded carrier (T2) and / or the carrier (T1), are therefore preferably each carried out in separate devices. In principle, it is possible that the device (V1) for carrying out step a) according to the invention is of the same type as the device (V6) described below for carrying out the optional process step d).Suitable devices for carrying out the process step a) according to the invention are disclosed, for example, in DE 10 2013 223 589 B1.

[0047] The release of hydrogen according to process step a) 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, preferably from an 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.

[0048] Furthermore, it is preferred that the carrier (T1) is also recovered during the release of hydrogen according to step a).

[0049] Furthermore, it is preferred that, in the release of hydrogen according to step a), the carrier (T1) is additionally recovered and the carrier (T1) is used to carry out the optional step d) defined below.

[0050] Furthermore, it is preferred that, during the release of hydrogen according to step a), the carrier (T1) is additionally recovered and subsequently stored in a separate device (V5) or in the device (V4). Following storage, for example in the device (V5), the carrier (T1) is preferably used to carry out the optional step d) defined below. The devices (V4) and (V5) are defined in more detail below.

[0051] It has already been mentioned above that the hydrogen release according to step a) is an endothermic process, meaning that energy input is required to release the hydrogen from the (hydrogen-loaded) carrier (T2). According to the invention, the release of hydrogen from the hydrogen-loaded carrier (T2) according to step a) is carried out such that at least a portion of the energy required for the endothermic hydrogen release is provided in the form of heat obtained by the combustion of sewage sludge. Preferably, at least 50%, more preferably at least 75%, of the energy required for the hydrogen release in step a) is derived from the combustion of sewage sludge. In one embodiment of the present invention, the energy required for the hydrogen release in step a) is derived entirely, or at least almost entirely (i.e., at least 95%), from the combustion of sewage sludge.The process of sewage sludge incineration and the associated energy release are explained in more detail below using the example of the heat obtained in optional step c).

[0052] Fig. Figure 1 illustrates the inventive process in its broadest form, taking into account step a). First, according to step a), hydrogen is released in the device (V1), which is preferably a chemical reactor, from a suitable hydrogen-loaded carrier (T2), preferably the carrier (T2) being produced in a LOHC process, by supplying energy. At least a portion of the energy required for hydrogen release is obtained by the combustion of sewage sludge. Preferably, at least 50%, more preferably at least 75%, of the energy required for hydrogen release in step a) is obtained from the combustion of sewage sludge.

[0053] The hydrogen-loaded carrier (T2) may already be in the device (V1), preferably the hydrogen-loaded carrier (T2) is fed into the device (V1), which in Fig. 1 is represented by the symbol (T2*). The released hydrogen and / or the carrier (T1) formed during the hydrogen release can remain in the device (V1). Preferably, however, both the released hydrogen and the carrier (T1) formed during the hydrogen release are removed from the device (V1), optionally continuously. The latter is described in Fig. Figure 1 illustrates what is represented by the symbol (T1*) in the case of the carrier (T1) formed during hydrogen release. The individual steps and / or the entire process can be operated both batchwise and continuously.

[0054] According to the invention, it is preferred that after step a) an optional process step b) is carried out, wherein in step b) the hydrogen obtained in step a) is transferred into a device (V2), wherein in the device (V2) hydrogen is converted into electric current and optionally into heat.

[0055] Although the hydrogen released in step a) can be easily stored or transported, the optional step a) is preferably carried out in close spatial and / or temporal proximity to step b).

[0056] The device (V2) as such is known to those skilled in the art. Preferably, the device (V2) 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.

[0057] The aforementioned devices (V2) are often already included in a conventional biogas plant and can generally be used in the process according to the invention without major modifications. This applies in particular to a combined heat and power plant and / or a gas engine, which are frequently used in biogas plants.

[0058] In this embodiment, it is preferred that the devices (V1) and (V2) are located in close proximity to each other, for example on the same company premises or on an adjacent company premises. Likewise, steps a) and b) are preferably carried out in close temporal proximity to each other, in particular in parallel.

[0059] It is also preferred that at least a subset of the energy required for hydrogen release in step a) is provided in the form of heat, which is additionally generated during electricity production according to step b) and recycled after step a). The amounts of heat generated in both steps a) and b) can be used either completely independently of each other or jointly / simultaneously as an energy source for hydrogen release according to step a).

[0060] Fig. Figure 2 shows a preferred embodiment of the method according to the invention, taking into account steps a) and b). In connection with the performance of step a) according to the invention in Fig. 2 will initially be on Fig. Reference is made to reference 1 and the associated explanations, where the method according to the invention is explained in its broadest sense. In addition to Fig. 1 is in the preferred embodiment according to Fig. 2 takes into account that the hydrogen obtained in step a) is transferred to a device (V2), in which hydrogen is converted into electricity and optionally into heat. The optional return of the heat obtained in step b) to release hydrogen according to step a) is shown in Fig. 2 also shown.

[0061] Fig. Figure 2 thus illustrates the second subject matter of the present invention, the method for generating electric current and, optionally, heat. It is preferred that the devices (V1) and (V2) are located in close proximity to each other, for example, on the same premises or on adjacent premises. Likewise, steps a) and b) are preferably carried out in close temporal proximity to each other, in particular in parallel.

[0062] According to the invention, it is preferred that step c) is carried out before step b): c) Burning the dried sewage sludge in a device (V3).

[0063] In principle, any device known to those skilled in the art that can be used to incinerate dried sewage sludge is suitable as a device (V3). Suitable devices (V3) are also referred to as sewage sludge incineration plants. The device (V3) comprises at least one combustion unit and, optionally, further units, for example, for supplying and / or discharging heat, preferably heat exchangers or heating bundles. Optionally, the device (V3) may also contain two or more combustion units, which, for example, are operated in parallel or in series, and / or other containers, for example, one or more storage tanks for storing batches of sewage sludge at different drying levels. In particular, the device (V3) includes elements for controlling the exhaust gas (exhaust gas stream) that is produced during the combustion of the dried sewage sludge.The same applies, mutatis mutandis, to the heat released during sewage sludge incineration.

[0064] According to the invention, it is preferred that in step c) heat is released during sewage sludge incineration and that this released heat is further used within the framework of the inventive process, preferably i) the heat is released from the exhaust gas of the combustion plant, and / or ii) at least a subset of the released heat, preferably using a heating bundle and / or a heat exchanger, is transferred after step a) to release hydrogen from the carrier (T2).

[0065] In a first preferred embodiment of the present invention, the method for producing hydrogen comprises steps a), b) and c) according to the preceding definitions.

[0066] According to the invention, it is further preferred that a step d) is carried out with the carrier (T1) obtained (in step a)) during the release of the hydrogen, wherein d) Contacting a carrier (T1) with hydrogen to store the hydrogen while obtaining a hydrogen-laden carrier (T2) and releasing heat.

[0067] In principle, it is possible for the optional step d) to be carried out in the same device (V4) as the previously mentioned storage of the hydrogen-loaded carrier (T2), which can optionally be carried out before step a). This can be achieved, for example, by integrating a special unit / device component into such a device (V4) that allows process step d) to be carried out 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 d) is carried out in a separate device (V6), which is preferably a chemical reactor.Furthermore, it is preferred that the hydrogen-loaded carrier (T2) formed in step d) of the inventive method does not remain in the device (V6), but is transferred to a separate device, for example the device (V4), for storage as described below.

[0068] Preferably, step d) is carried out in a pressure-stable device, in particular in a pressure-stable chemical reactor. It is further preferred that step d) 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 d) 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 LOHC supports (T1).Besides ruthenium and / or nickel, metals such as chromium, iron, cobalt, copper, iridium, palladium or platinum are particularly suitable as catalysts.

[0069] Preferably, step d) according to the invention is carried out spatially and / or temporally separately from steps a) and / or b) described above, preferably at a distance of at least 5 km, in particular 10 to 50 km, and / or step d) is carried out at least one month, particularly preferably at least three months, after steps a) and / or b) described above. However, step d) can optionally also be carried out in close proximity to and / or in direct temporal succession with step a).

[0070] As mentioned above, in step d) of the invention, additional heat is released due to the exothermic storage of the hydrogen by contacting it with the carrier (T1). According to the invention, it is preferred that the heat released in step d) is reused in the process according to the invention.

[0071] According to the invention, it is therefore also preferred that after step d) a step e) is carried out, wherein e) Feeding the heat released in step d) into a device (V7) to dry sewage sludge in the device (V7).

[0072] The process of sewage sludge drying is well-known to experts. The same applies to the (chemical) properties of sewage sludge itself, suitable equipment for carrying out sewage sludge drying, and / or the processing / further use of dried sewage sludge, for example, by incineration. Background information in this context can be found, for example, in the aforementioned articles "Sewage Sludge Disposal in the Federal Republic of Germany" (as of October 2018, published by the Federal Environment Agency, available online at: www.umweltbundesamt.de / publikationen) or "Sewage Sludge Drying in Germany - Status and Perspectives" by Jürgen Geyer (pages 927-948; in Energy from Waste - Volume 10; TK Verlag Karl Thomé-Kozmiensky; Neuruppin 2013).

[0073] In principle, any device known to those skilled in the art that can dry sewage sludge by applying heat is suitable as the device (V7). The device (V7) comprises at least one sewage sludge dryer. Optionally, the device (V7) may also contain two or more sewage sludge dryers, which may be operated, for example, in parallel or in series, and / or other containers, such as one or more storage tanks for storing batches of sewage sludge at different drying stages. Furthermore, the device (V7) may also be connected to one or more heat exchangers, or such heat exchangers may be integrated into the device (V7).

[0074] Preferably, the device (V7) is at least one sewage sludge dryer selected from a belt dryer, a drum dryer, or a disc dryer. Such sewage sludge dryers are commercially available, for example under the name "Huber Belt Dryer BT" from Huber SE (Berching, Germany).

[0075] The heat released in step d) can, for example, be transferred to the device (V7) via a pipeline or piping system. To make the heat transfer from step d) to step e) as efficient as possible, it is advantageous to use heat exchangers.

[0076] Within the scope of the present invention, it is therefore preferred that in step e) i) the device (V7) comprises at least one sewage sludge dryer selected from a belt dryer, a drum dryer or a disc dryer, and / or ii) the heat released in step d) is transferred to the device (V7) via a pipe or piping system, and / or iii) the heat released in step d) is passed through a heat exchanger to heat the drying air in the device (V7), in particular in a belt dryer, and / or iv) the device (V7) has at least two areas with different temperature zones.

[0077] Due to the heat transfer that preferably takes place in step d) and step e) in the method according to the invention, 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 not far apart. Distances of, for example, 500 m to 1 km between the respective devices for carrying out the two steps d) and e) are easily manageable in practice.

[0078] 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.

[0079] Within the scope of the present invention, it is further preferred that the two steps d) and e) are carried out in close temporal proximity, for example, in parallel to each other. Technically, it is also possible to store the released heat temporarily and to carry out the two steps at different times.

[0080] It is further advantageous in carrying out step e) according to the invention if the heat released in step d) is fed into the device (V7) in such a way that the device (V7) has at least two areas with different temperature zones. The device (V7) can have two or more temperature zones, which are controlled, for example, by feeding the heat into the device (V7) at different locations and / or in different quantities and / or by using heat exchangers.

[0081] For example, the device (V7) can comprise at least one low-temperature zone and / or at least one high-temperature zone. The corresponding temperature ranges that can be set in the respective zones or areas of the device (V7) for drying sewage sludge are known to those skilled in the art.

[0082] Preferably, the device (V7) comprises a) a low-temperature zone (Z1) which is operated at a temperature level of 50 to 90 °C, preferably at 60 to 80 °C, particularly at 70 °C, and b) a high-temperature zone (Z2) which is operated at a temperature level of 100 to 180 °C, preferably at 130 to 150 °C, particularly at 140 °C.

[0083] By appropriately regulating the heat input into the device (V7) and / or the residence time of the sewage sludge in the device (V7), the person skilled in the art can control the degree of dryness of the sewage sludge in step e). Likewise, the person skilled in the art knows that the water content of the sewage sludge to be dried and / or its chemical composition can influence the drying time and / or the degree of dryness of the sewage sludge in step e). Based on their expertise and / or, if necessary, with the aid of the literature references listed above at the beginning of the explanations for step e), the person skilled in the art knows how the desired or a high degree of dryness can be set for the different types of sewage sludge.

[0084] Unless otherwise specified, the drying of the sewage sludge within the scope of the present invention is expressed as a percentage and refers to the dry residue (DR). This is defined as a measure of the solids content of the unfiltered sludge sample or the proportion of dry matter to the total sludge mass. The determination is carried out by evaporating the water (see also Table 1 on page 7 of the aforementioned article "Sewage Sludge Disposal in the Federal Republic of Germany").

[0085] Preferably, in step e) dried sewage sludge is obtained, which is dried in the device (V7) to a degree of dryness of at least 75%, preferably at least 85%, in particular at 95 to 100% (complete drying).

[0086] Within the scope of the present invention, it is therefore still preferred that i) Step d) and step e) are carried out in close proximity, preferably the respective devices for carrying out the two steps d) and e) are located on the same company premises, and / or ii) the device (V7) comprises a) a low-temperature zone (Z1) which is operated at a temperature level of 50 to 90 °C, preferably at 60 to 80 °C, particularly at 70 °C, and b) a high-temperature zone (Z2) which is operated at a temperature level of 100 to 180 °C, preferably at 130 to 150 °C, particularly at 140 °C, and / or iii) the sewage sludge is dried in the device (V7) to a degree of dryness of at least 75%, preferably at least 85%, in particular at 95 to 100% (complete drying).

[0087] As already mentioned, the sewage sludge to be dried in the device (V7) can have any chemical composition known to those skilled in the art and / or exhibit any degree of dryness. The sewage sludge to be dried is also referred to as wet sewage sludge or, optionally, as thin sludge. For example, within the scope of the invention, the wet sewage sludge may first be subjected to pre-drying in order to reduce the water content in a preliminary stage. This is also referred to as dewatering of sewage sludge, which results in (wet) sewage sludge with a degree of dryness of 20 to 30%. This preliminary dewatering of the sewage sludge can be carried out, for example, with a screw press, which is commercially available, for example, under the name "Huber Screw Press Q-Press" from Huber SE (Berching, Germany).

[0088] Furthermore, the wet sewage sludge can initially be temporarily stored in a separate device before being fed into the device (V7) for carrying out step e) according to the invention. It is also conceivable that wet sewage sludge is delivered, for example, by truck and fed directly into the device (V7). The temporary storage of the wet sewage sludge can also take place, for example, in a fermenter, a post-fermenter, or a digestate plant. The storage and / or transport and / or transfer of wet sewage sludge is known to those skilled in the art; for example, wet sewage sludge can be fed into the device (V7) from a suitable storage container using special pumps.

[0089] Within the scope of the present invention, it is therefore still preferred that i) the sewage sludge is first dewatered and has a dryness level of 20 to 30% before being fed into the device (V7) for drying, and / or ii) the sewage sludge is fed into the device (V7) for drying using a high-viscosity pump, and / or iii) the sewage sludge is stored in a device (V8) before drying in the device (V7), preferably the device (V8) 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 part of a biogas plant.

[0090] According to the invention, it is further preferred that the sewage sludge dried in step e) is transferred to the device (V3) in order to burn the dried sewage sludge in the device (V3) in accordance with step c) (defined above).

[0091] The required devices (V7) for drying the sewage sludge according to step e) and (V3) for incinerating the dried sewage sludge according to step c) can, in practice, be located in close proximity to each other, for example, on the same premises. Preferably, however, the respective devices are located at a greater distance from each other. It is also preferred that the two steps e) and c) are carried out sequentially or separately. Transport of the dried sewage sludge (tKS) over any number of kilometers is easily possible, for example, by trucks, trains, and / or ships. Intermediate storage of the dried sewage sludge (tKS) can also be easily carried out, for example, in close proximity to device (V7) and / or device (V3), or such intermediate storage facilities can be integrated directly into the respective devices.It is also possible that, within the scope of the present invention, the dried sewage sludge (tKS) is stored spatially at a great distance from the two devices (V7) and (V3) in a suitable intermediate storage facility, for example in a tank, before step c) is carried out.

[0092] Within the scope of the present invention, it is further preferred that i) before carrying out step c) the dried sewage sludge is temporarily stored, and / or ii) Step e) and step c) are carried out spatially separately from each other, preferably at a distance of at least 5 km, in particular 10 to 50 km, and / or iii) Step e) and step c) are carried out separately in terms of time, preferably step c) is carried out at least one month, particularly preferably at least three months, after step e).

[0093] In a preferred embodiment of the present invention, following the execution of optional step d) and independently of the execution of optional step e), the hydrogen-loaded carrier (T2) obtained in step d) is stored. The storage of the hydrogen-loaded carrier (T2) can, in principle, be carried out in the same device in which step d) is performed, for example, in device (V6). It has already been pointed out above that, within the scope of the present invention, it is preferred that the execution of step d) and the subsequent storage of the hydrogen-loaded carrier (T2) obtained thereby are carried out in different devices.

[0094] 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 two days and / or a maximum of six months.

[0095] It is also possible that the hydrogen-loaded carrier (T2) is not stored in a separate device after its production according to step d), but is processed directly by preferably transporting it to the suitable device (V1) for carrying out step a) according to the invention, where the hydrogen is released from the carrier (T2). Preferably, step a) and step d) 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 d).

[0096] Preferably, this embodiment is carried out such that the hydrogen-loaded carrier (T2) obtained in step d) is stored in the 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.

[0097] In principle, any device known to those skilled in the art is suitable as a device (V4), with preference given to devices that are or were part of a biogas plant. If a biogas plant is being retrofitted, the corresponding devices (V4) must be suitable for storing such a hydrogen-loaded carrier (T2) and / or they must be modified, preferably by simple steps, to enable such storage. It is conceivable, in principle, that a suitable device (V4) could be commercially acquired and installed in an existing biogas plant. In other words, this embodiment allows the use of a new device (V4) that has not previously been used in a biogas plant and / or is not suitable for use in biogas production.According to the invention, this can be carried out particularly if, according to a preferred embodiment described below, the corresponding biogas plant is to continue to be used for biogas production, for example, simultaneously (in parallel) or at a later time. However, if a corresponding biogas plant is no longer to be used for biogas production, a device (V4) that has already been used in the corresponding biogas plant is used as the device according to the invention. The latter option is, of course, also conceivable if the corresponding plant is to continue to be used for biogas production.

[0098] Biogas plants as such are, as already mentioned at the outset, known to those skilled in the art. Biogas plants typically include (among other things) one or more fermenters, storage tanks, power generation equipment, in particular gas engines, and other piping. As mentioned above, in principle, any device known to those skilled in the art that is or was part of a biogas plant is suitable as device (V4). Preferably, this is a fermenter or post-fermenter, or devices that have been produced by converting a fermenter or post-fermenter. According to the invention, it is more preferred that the device (V4) is a fermenter or has been produced by converting a fermenter. Furthermore, it is preferred according to the invention that the device (V4) is a separate device from the device (V1) in which the process step a) according to the invention is carried out.

[0099] In principle, it is conceivable that the device (V4) could continue to be used as a fermenter. In this scenario, appropriate additional components or elements would be installed in the device (V4) to enable the storage of the hydrogen-laden carrier (T2) within the device (V4), particularly in a fermenter, without having to discontinue its existing use in connection with biogas production. It may be necessary to install additional inlets and / or outlets in the device (V4), particularly in a fermenter, to facilitate the introduction and subsequent removal of the carrier (T2) from the device, particularly the fermenter.

[0100] According to the invention, however, it is preferred that the device (V4), in particular a fermenter, is modified / reconfigured in such a way that its previous use within the biogas plant is no longer possible. In the case of a fermenter, for example, the stirring tools and the associated operating elements or lines typically present in a fermenter can be removed from the device (V4). Any heating elements present, on the other hand, can be left in the corresponding device (V4) without any problems, since they can also be used effectively in connection with the storage of the hydrogen-laden carrier (T2). If necessary, the corresponding feed and / or discharge elements previously present in the corresponding device (V4) can be converted for the purposes required for the process according to the invention or, if applicable, used without conversion.

[0101] Preferably the device (V4) has two spatially separated areas, wherein a first area is used for storing the hydrogen-loaded carrier (T2) and a second area is used for storing the carrier (T1).

[0102] Furthermore, it is preferred that the device (V4) be provided with a protective lining inside before the support (T1) is mounted. Such protective linings are described, for example, in EP 3 415 609 A1 in the context of optional method step g).

[0103] Furthermore, it is preferred that a floating partition is incorporated into the device (V4), whereby the support (T1) is stored separately from the hydrogen-loaded support (T2). For example, the support (T1) can be stored above and the support (T2) below the floating partition.

[0104] Furthermore, it is preferred that the device (V4) was part of a biogas plant and was cleaned of all substances that had accumulated inside it or, if applicable, in its supply lines as a result of biogas production, before the storage of the carrier (T2) is carried out. Furthermore, the device (V4) can also be subjected to an additional cleaning step, as described in EP 3 415 609 A1 as optional cleaning step f).

[0105] According to the invention, it is preferred that the device (V4) is located in close proximity to the device (V6) used in step d), provided that separate devices are used for carrying out step d) and for storing the resulting carrier (T2), and in particular that the corresponding devices are located on the same premises. The same applies analogously to any separate device (V5), which, as already explained above, can be used for storing the carrier (T1) recovered in step a).

[0106] In another embodiment, it is preferred that the device (V4) is located in close proximity to the device (V1) used in step a) described above; in particular, the corresponding devices are located on the same premises. The same applies analogously to any separate device (V5), which, as above, can be used for storing the carrier (T1) recovered in step a).

[0107] The device (V4) primarily serves to store the hydrogen-loaded carrier (T2). However, as mentioned above, it is easily possible for both the carrier (T1) and the hydrogen-loaded carrier (T2) to be stored separately in the same device, in particular a device (V4). If the carrier (T1) is stored in a separate device (V5), the device (V5) is essentially the same as the device (V4) described above. The method and / or duration of storage of the carrier (T1) can be carried out analogously to the storage of the hydrogen-loaded carrier (T2) in the device (V4) described above.

[0108] In the process according to the invention, it is further preferred that a step f) is carried out before step d). According to the optional step f) of the invention, hydrogen is produced in a device (V9), preferably in an electrolyzer, using water and electric current. The execution of process step f) as such is known to those skilled in the art. Suitable electrolyzers are described, for example, in DE 10 2013 223 589 B1 or DE 10 2012 005 023 A1. 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 in which the decomposition of water into hydrogen or oxygen can be carried out with the simultaneous input of electric current is suitable as a device (V9).The device (V9) typically contains two electrodes. The water used is usually demineralized water (see, for example, the Siemens Silyzer brochure).

[0109] The electrical current used in step f) 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 f) 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 f) of the process according to the invention is generated by hydropower, wind energy, or solar radiation. Since this electric current can, in principle, also originate from biomass obtained from renewable raw materials, in particular biogas, it is also conceivable that the biogas produced in parallel or at a time delay in an embodiment of the present invention is converted into electricity in a subsequent step, and that this electricity, for which there is currently no use, is converted into hydrogen within the framework of the process according to the invention, which is then stored and stored according to the invention.

[0110] As mentioned above, in step f) oxygen is (generally) produced in addition to hydrogen. Preferably, in step f) oxygen is also produced, and this oxygen is converted in the device (V2) according to step b) together with hydrogen into electricity and optionally heat, wherein the oxygen is optionally temporarily stored before its use in step b). Devices for temporarily storing oxygen are known to those skilled in the art.

[0111] In one embodiment, the method according to the invention comprises steps a), b), and c). In this embodiment, the optional step d) is not performed. In another preferred embodiment, the method according to the invention comprises steps a), b), and c), as well as additionally step d) and optionally step e). In these embodiments, steps a), b), and c) according to the invention are preferably performed in close proximity to one another, while they are preferably performed separately from steps d) and / or e). Close proximity between the performance of the two method steps d) and e) is particularly advantageous if heat transfer occurs between these two steps.

[0112] Fig. Figure 3 shows a particularly preferred embodiment of the method according to the invention, taking into account the steps described above a), b), c), d), e) and f). In connection with the performance of the two steps a) and b) in Fig. 3 will initially be applied to the two Fig. 1 and Fig. Reference is made to section 2 and the associated explanations. For the execution of steps c), d), e), and f), reference is made to the preceding description. Steps e) and / or f) may optionally be omitted in this embodiment, but preferably both steps e) and f) are carried out.

[0113] In addition to the two Fig. 1 and Fig. 2 is in the particularly preferred embodiment according to Fig. 3. It is taken into account that, according to step d), in the device (V6), which is preferably a chemical reactor, hydrogen is brought into contact with the carrier (T1) obtained in step a), preferably the carrier (T1) is a hydrogen carrier (LOHC), thereby storing the hydrogen, preferably by chemical bonding to the carrier (T1), in particular by hydrogenation, thereby producing a hydrogen-loaded carrier (T2). The hydrogen-loaded carrier (T2) can remain in the device (V6), but preferably the carrier (T2) 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 the storage of the hydrogen in step d) is transported to step e).

[0114] In step e), the heat released in step d) is fed into a device (V7) to dry sewage sludge. The device (V7) typically comprises at least one sewage sludge dryer, preferably selected from a belt dryer, a drum dryer, or a disc dryer. The wet sewage sludge (nKS) is also fed into the device (V7), where it is dried by the application of heat, resulting in dried sewage sludge. The dried sewage sludge (tKS) can optionally remain in the device (V7), but preferably the dried sewage sludge (tKS) is further processed and / or transported to another device. The devices (V6) and (V7) are preferably located in close proximity to each other, for example, on the same premises.

[0115] Additionally, in the preferred embodiment according to Fig. 3 takes into account that the wet sewage sludge (nKS) is preferably first located in a separate device (V8) before being fed into the device (V7).

[0116] Following step e), the dried sewage sludge (tKS) is transported to another device (V3) and further processed there according to step c). The dried sewage sludge is incinerated in the device (V3). During the combustion of the dried sewage sludge, exhaust gases (AG) are produced, which are discharged from the device (V3). The heat also generated during the combustion of the dried sewage sludge is used to release hydrogen from a hydrogen-laden carrier (T2) according to step a).

[0117] Devices (V3) and (V7) are preferably located at a spatial distance from each other, for example, 10-50 km apart. Ultimately, the spatial distance between the two devices (V7) and (V3) can be arbitrarily large. Furthermore, steps e) and c) are preferably also carried out separately in time, for example, at least one month apart, preferably at least three months apart. Ultimately, the time interval between carrying out these two steps can be arbitrarily large. Optionally, the dried sewage sludge (tKS) can be stored in a separate device, for example, in an intermediate storage facility in the form of a tank, after step e) has been completed and before step c) is carried out.

[0118] Furthermore, in Fig.Figure 3 shows that the dried sewage sludge (tKS) can preferably be stored in a separate device (ZL*), for example, in an intermediate storage facility in the form of a tank, after step e) has been completed and before step c) is carried out. However, the use of such a separate device (ZL*) is not mandatory, but optional, even in this particularly preferred embodiment. The use of such a separate device (ZL*) is particularly advantageous if there is a longer period of time between the execution of the two process steps e) and c) and / or a very large quantity of dried sewage sludge (tKS) is to be incinerated in step c), which, for capacity reasons, requires increased storage capacity in the device (V3).

[0119] In this embodiment, the recovered hydrogen-loaded carrier (T2) is additionally stored in a device (V4), and the carrier (T1) is stored in a separate device (V5). The respective storage operations can be performed 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).

[0120] If necessary, the respective storage steps, particularly in devices (V4) and / or (V5), can be omitted entirely or at least partially. In this scenario, for example, step d) would be carried out (relatively directly) after step a) and / or step a) would be carried out (relatively directly) after step d). If there is a spatial distance between devices (V1) and (V6), the time required for transporting, for example, the recovered hydrogen-laden carrier (T2), must be taken into account, meaning that step a) can only be carried out after a time delay.Similarly, 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 transfer of the carrier (T1) from step a) to step d).

[0121] Similarly, within the scope of the present invention, it is possible, for example, that when the cycle is executed at least once with respect to steps a) and d), and optionally steps b) and / or f), the steps, which are performed multiple times, are carried out in different devices. For example, hydrogen is released in a first device (V1) according to step a) because electricity is to be generated at a first location according to step b). The carrier (T1) released in step a) is transferred to device (V6) after optional intermediate storage in order to reload the carrier (T1) with hydrogen and obtain the carrier (T2) there according to step d). The hydrogen-loaded carrier (T2) is then transferred to a second device (V1) after optional intermediate storage in order to release hydrogen from the carrier (T2) again there according to step a).However, the second device (V1) is located at a different location than the first device (V1) because there is a power requirement at a different location. This location-independent execution of the individual process steps naturally applies analogously to all other steps / devices of the method according to the invention.

[0122] Devices (V1) and (V2), and optionally (V3), on the one hand, and devices (V6) and (V9), and optionally (V7), on the other hand, are preferably located at a spatial distance from each other, for example, at a distance of 10–50 km. Furthermore, steps e) and c) and / or steps a) and d) are preferably also carried out separately in time, for example, at an interval of at least one month, preferably at least three months. In contrast, in this embodiment, it is preferred that devices (V1) and (V2), and optionally (V3), and / or devices (V6) and (V9), and optionally (V7), are located in close proximity to each other, for example, on the same company premises or on an adjacent company premises. Likewise, steps d) and e), on the one hand, and / or steps c) and a), on the other hand, are carried out in close temporal proximity to each other, preferably in parallel.

[0123] In a further preferred embodiment of the present invention, the process is carried out in a plant that can also be used for the production of biogas. The production of biogas can be carried out in parallel or at a time delay with the inventive process for the production of hydrogen or with the optionally subsequent generation of electricity and, optionally, heat. This embodiment is preferably carried out when the biogas is produced in close spatial and / or temporal proximity to the execution of optional step d) or to the device (V6) and / or to the execution of optional step e) in connection with the drying of sewage sludge in the device (V7). It is also conceivable that the production of biogas is carried out in parallel with the process for the production of hydrogen only for a specific time interval.

[0124] Preferably, the production of biogas on the one hand and processes for the production of hydrogen or the production of electricity and, if applicable, heat on the other hand are carried out in parallel on the same plant.

[0125] Furthermore, it is preferred that 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).

[0126] Furthermore, it is preferred that the hydrogen produced in step f) is used partially and / or for a certain period of time for the production of biogas, in particular for methanization, wherein the hydrogen is preferably introduced into a separate fermenter and reacts there with CO2.

[0127] Furthermore, it is preferred that the hydrogen released in step a) is used partially and / or for a certain period of time to produce biogas, in particular for methanization, wherein the hydrogen is preferably introduced into a separate fermenter and reacts there with CO2.

[0128] Furthermore, it is preferred that the oxygen additionally generated in step f) be used partially and / or for a specific period of time for the production of biogas, with the oxygen preferably being introduced into a separate fermenter or post-fermenter. This embodiment is advantageous because the oxygen released during electrolysis can be added to a biogas process in normal operation to improve the quality of the biogas. The addition of oxygen instead of ambient air for aeration of the fermentation process avoids an increased nitrogen content in the biogas subsequently obtained.

[0129] Furthermore, it is preferred that the biogas produced, in particular methane, and the hydrogen produced or released in steps a) and / or f) are mixed together in order to transfer them together to the device (V2) in step b), where they are converted into electricity and, if necessary, into heat.

[0130] 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 biogas production, hydrogen storage, and / or electricity generation.

[0131] A further (second) object of the present invention relates to a method for generating electric current and optionally heat, comprising the following steps a) and b): a) Release of hydrogen from a hydrogen-laden carrier (T2), wherein at least a subset of the energy required for hydrogen release is obtained by the combustion of sewage sludge, b) Transfer of the hydrogen obtained in step a) into a device (V2), wherein hydrogen is converted into electric current and optionally into heat in the device (V2).

[0132] The process steps a) and b) described above in connection with the process for generating electricity and, optionally, heat, are carried out analogously to the first subject matter of the invention, i.e., the process for generating hydrogen. The second subject matter of the invention is particularly preferably carried out as a process comprising the process steps a), b), and c) described above.

[0133] Furthermore, within the scope of this second subject matter of the invention (i.e., the method for generating electric current and, optionally, heat), all other process steps of the first subject matter of the invention, in particular process steps c) to f), can be carried out analogously. This also applies to the corresponding preferred, more preferred, even more preferred, or particularly preferred definitions of all process steps of the first subject matter of the invention.

Claims

[1] Process for the production of hydrogen, comprising the following step a): a) Release of hydrogen from a hydrogen-laden carrier (T2), wherein at least a subset of the energy required for hydrogen release is obtained by the combustion of sewage sludge. [2] Method according to claim 1, characterized by , that after step a) a step b) is carried out: b) Transfer of the hydrogen obtained in step a) into a device (V2), wherein hydrogen is converted into electric current and optionally into heat in the device (V2). [3] Method according to claim 2, characterized by , that i) the device (V2) is part 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, and / or ii) the heat generated in step b) is returned to step a). [4] Method according to any one of claims 1 to 3, characterized by , that step c) is performed before step a): c) Burning of dried sewage sludge in a device (V3). [5] Method according to claim 4, characterized by , that in step c) heat is released during sewage sludge incineration, whereby i) the heat is released from the exhaust gas of the combustion plant, whereby at least a subset of the released heat, preferably using a heating bundle and / or a heat exchanger, is transferred after step a) to release hydrogen from the carrier (T2). [6] Method according to any one of claims 1 to 5, characterized by, that the hydrogen-loaded carrier (T2) used in step a) is obtained from a carrier (T1), wherein the carrier (T1) is brought into contact with hydrogen, preferably the hydrogen-loaded carrier (T2) serves as a hydrogen storage medium. [7] Method according to any one of claims 1 to 6, characterized by , that i) before carrying out step a) the hydrogen-loaded carrier (T2) 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 part of a biogas plant, and / or ii) hydrogen is chemically or physisorptively, preferably chemically, bound to the support (T1), 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 carrier (T2) is obtained by at least partial or complete hydrogenation, preferably by complete hydrogenation, with hydrogen from the carrier (T1). [8] Method according to any one of claims 1 to 7, characterized by , that i) in the release of hydrogen according to step a) the carrier (T1) is additionally recovered, or ii) in the release of hydrogen according to step a) the carrier (T1) is additionally recovered and subsequently the carrier (T1) is stored in a separate device (V5) or in the device (V4), and / or iii) Step a) is carried out in a device (V1) which is preferably a chemical reactor. [9] Method according to claim 8, characterized by , that with the carrier (T1) obtained during the release of the hydrogen a step d) is carried out, wherein d) Contacting a carrier (T1) with hydrogen to store the hydrogen while obtaining a hydrogen-laden carrier (T2) and releasing heat, [10] Method according to claim 9, characterized by , that after step d) a step e) is carried out, wherein e) Feeding the heat released in step d) into a device (V7) to dry sewage sludge in the device (V7). [11] Method according to claim 10, characterized by , that in step e) i) the device (V7) comprises at least one sewage sludge dryer, preferably selected from a belt dryer, a drum dryer or a disc dryer, and / or ii) the heat released in step d) is transferred to the device (V7) via a pipe or piping system, and / or iii) the heat released in step d) is passed through a heat exchanger to heat the drying air in the device (V7), in particular in a belt dryer, and / or iv) the device (V7) has at least two areas with different temperature zones. [12] Method according to claim 10 or 11, characterized by , that i) Step d) and step e) are carried out in close proximity, preferably the respective devices for carrying out the two steps d) and e) are located on the same company premises, and / or ii) the device (V7) comprises a) a low-temperature zone (Z1) which is operated at a temperature level of 50 to 90 °C, preferably at 60 to 80 °C, particularly at 70 °C, and b) a high-temperature zone (Z2) which is operated at a temperature level of 100 to 180 °C, preferably at 130 to 150 °C, particularly at 140 °C, and / or iii) the sewage sludge in the device (V7) is dried to a degree of dryness of at least 75%, preferably at least 85%, particularly at 95 to 100% (complete drying), and / or iv) the sewage sludge is first dewatered and has a dryness level of 20 to 30% before being fed into the device (V7) for drying, and / or v) the sewage sludge is fed into the device (V7) for drying using a high-viscosity pump, and / or vi) the sewage sludge is stored in a device (V8) before drying in the device (V7), preferably the device (V8) 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 part of a biogas plant. [13] Method according to any one of claims 10 to 12, characterized by , that i) the sewage sludge dried in step e) is transferred to the device (V3) in order to incinerate the sewage sludge dried in the device (V3) in accordance with step c), and / or ii) before carrying out step c) the dried sewage sludge is temporarily stored, and / or iii) Step e) and step c) are carried out spatially separately from each other, preferably at a distance of at least 5 km, in particular 10 to 50 km, and / or iv) Step e) and step c) are carried out separately in terms of time, preferably step c) is carried out at least one month, particularly preferably at least three months, after step e). [14] Method according to any one of claims 9 to 13, characterized by , that step f) is performed before step d): f) Production of hydrogen in a device (V9), preferably in an electrolyzer, using water and electric current. [15] Method according to any one of claims 9 to 14, characterized by , that i) step d) is carried out in a separate device (V6), which is preferably a chemical reactor, and / or ii) the device (V4) has two spatially separated areas, wherein a first area is used for storing the hydrogen-loaded carrier (T2) 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 storage of the support (T2) and, if applicable, the support (T1) is carried out, and / or iv) a floating partition is installed in the device (V4), whereby the support (T1) is stored separately from the hydrogen-loaded support (T2), and / or v) the device (V4) was part of a biogas plant and was cleaned of all substances that had been inside it or, where applicable, in its supply lines as a result of the production of biogas, before the storage of the carrier (T2) and, where applicable, the carrier (T1) is carried out. [16] Method according to any one of claims 1 to 15, characterized by that the process is carried out in a facility that can continue to be used for the production of biogas. [17] Method according to claim 16, characterized by , 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). [18] Method for generating electric current and, optionally, heat comprising the following steps a) and b): a) Release of hydrogen from a hydrogen-laden carrier (T2), wherein at least a subset of the energy required for hydrogen release is obtained by the combustion of sewage sludge, b) Transfer of the hydrogen obtained in step a) into a device (V2), wherein hydrogen is converted into electric current and optionally into heat in the device (V2).

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