WO2024170366A1

WO2024170366A1 - Method and device for providing electric current

Info

Publication number: WO2024170366A1
Application number: PCT/EP2024/052982
Authority: WO
Inventors: Victor Hugo Rangel-Hernandez; Michael Kohles; Manuel Kleinhenz; Vincent Dirk Wichard Michiel Oldenbroek; Holger BÜCH; Rico WESTERATH; Caspar PAETZ
Original assignee: Hydrogenious Lohc Technologies Gmbh
Priority date: 2023-02-13
Filing date: 2024-02-07
Publication date: 2024-08-22
Also published as: DE102023201170A1

Abstract

A method for providing electric current comprises the method steps of feeding a carrier material loaded with hydrogen into a dehydrogenation reactor (3), releasing hydrogen gas by dehydrogenating the carrier material in the dehydrogenation reactor (3), feeding released hydrogen gas into a fuel cell (2), reacting the fed hydrogen gas in the fuel cell (2) such that electric current and heat are produced, transferring heat produced in the fuel cell (2) to the dehydrogenation reactor (3) by thermal contact between the fuel cell (2) and the dehydrogenation reactor (3) and/or by using heat contained in the exhaust gases of the fuel cell (2) and/or by using a heat transfer medium.

Description

Method and device for providing electrical current

The present patent application claims the priority of the German patent application DE 10 2023 201 170.0, the contents of which are incorporated herein by reference.

The invention relates to a method and a device for providing electrical current.

It is known to provide electrical power by converting hydrogen gas released from a carrier material into electricity in a fuel cell. In particular for so-called on-board applications, in which both the hydrogen release and the hydrogen flow take place on a moving platform such as a ship or a train, there is a need to maximize the overall efficiency of the carrier material to electrical power, whereby the application must be able to be started and stopped reliably and, in particular, different operating points must be able to be adopted as dynamically as possible.

The invention is based on the object of increasing the overall efficiency of carrier material to electrical current and, in particular for on-board applications, to enable reliable influencing of the application, in particular reliable start conditions and stop conditions.

This object is achieved according to the invention by a method having the features of claim 1 and by a device having the features of claim 14.

The core of the invention is that hydrogen gas released in a dehydrogenation reactor can be advantageously converted in a fuel cell to generate electrical current and heat if heat generated in the fuel cell is supplied to the dehydrogenation reactor. The heat is supplied from the fuel cell to the dehydrogenation reactor in particular by means of a heat distribution unit. The heat transfer can take place directly by arranging the dehydrogenation reactor in direct thermal contact with or in a system of the fuel cell. In particular, the dehydrogenation reactor is directly, i.e. immediately, connected to or arranged in the fuel cell. In particular, a shared partition wall can be present which is part of both a housing of the dehydrogenation reactor and a housing of the fuel cell. In particular, the heat transfer takes place by thermal conduction.

Heat in the fuel cell can also be used by the exhaust gases discharged from the fuel cell. Fuel cell exhaust gases are in particular oxygen-reduced air, water or water vapor as well as hydrogen gas that has not been converted in the fuel cell, which is also referred to as unused hydrogen. These exhaust gases have an increased temperature, which can be recovered as exhaust heat in particular in an exhaust unit. For this purpose, the exhaust unit has in particular at least one heat exchanger in order to transfer the exhaust heat of the exhaust gases to a heat transfer medium and pass it on to the dehydrogenation reactor, in particular by means of another heat exchanger.

A heat transfer medium can also be used to transfer heat directly from the fuel cell to the dehydrogenation reactor in a closed circuit. In addition, the heat transfer medium can also be used to supply heat to other heat sinks, especially external heat sinks.

According to the invention, it was recognized that the overall efficiency of carrier material to electrical current can be increased by targeted interconnection of components of the device and/or targeted control and/or regulation of material flows and/or reaction conditions, whereby the reliability of the method, in particular the operation of the fuel cell, is ensured in various operating modes. The method and the device according to the invention are particularly suitable for on-board applications, in particular on mobile platforms such as trains or ships.

Liquid organic hydrocarbon compounds, also known as LOHC (liquid organic hydrogen carrier), are used as carrier material. In a form that is at least partially loaded with hydrogen (LOHC+), the carrier material can serve as perhydro-dibenzyltoluene (HixDBT), as perhydro-benzyltoluene (H12BT), as dicyclohexane (C12H22) and/or as methylcyclohexane (C7H14). The carrier material can be converted into a form that is at least partially discharged of hydrogen (LOHC-) by catalytic dehydrogenation and thereby Hydrogen gas is released. In the at least partially discharged form, the carrier material is present as dibenzyltoluene (C21H20), as benzyltoluene (C14H14), as biphenyl (C12H10) and/or as toluene (C6H5CH3).

If the carrier material is at least partially loaded, this means that it is in particular predominantly loaded and in particular fully loaded. The degree of loading is described by the so-called degree of hydrogenation. The carrier material to be dehydrogenated has in particular an initial degree of hydrogenation of at least 85%, in particular at least 90%, in particular at least 95%, in particular at least 98%, in particular at least 99% and in particular at least 99.9%.

The fuel cell is in particular a solid oxide fuel cell, which is also referred to as SOFC (solid oxide fuel cell). The SOFC is a high-temperature fuel cell that can be operated in a high temperature range of 650 °C to 1000 °C. In particular, the fuel cell is operated in a temperature range that is above the dehydrogenation temperature in the dehydrogenation reactor. In particular, the fuel cell is operated at a temperature of at least 310 °C and in particular of at least 350 °C.

A method according to claim 2 enables the efficient use of heat for the dehydrogenation reactor. Hydrogen gas released in the dehydrogenation reactor is at least partially fed to a combustion unit and burned and/or catalytically utilized there. This proportion is in particular at most 50%, in particular between 1% and 30% and in particular between 5% and 15% of the hydrogen gas released in the dehydrogenation reactor. Hydrogen gas is thermally utilized as fuel in the combustion unit. The heat generated in this process is advantageously transferred back to the dehydrogenation reactor, in particular using the heat distribution unit.

The volume flow of hydrogen gas supplied to the combustion unit can be directly influenced in particular by at least a partial flow of the hydrogen gas being passed past the fuel cell, in particular by means of a bypass line. A partial flow is thus defined which is deliberately not intended for conversion in the fuel cell. The partial flow passed past the fuel cell is at most 50%, in particular at most 30 % and in particular between 1 % and 10 % of the hydrogen gas released in the dehydrogenation reactor.

Additionally or alternatively, at least part of the released hydrogen gas can be fed back into the dehydrogenation reactor, in particular by mixing it into the reaction educts of the dehydrogenation reactor, i.e. in particular into LOHC+. The mixing takes place in particular by means of a pressure boosting unit, in particular in the form of a screw compressor. The screw compressor is arranged in particular upstream of the dehydrogenation reactor and enables the supply of LOHC+ and recycled hydrogen gas from the dehydrogenation reactor.

Additionally or alternatively, additional, in particular independently available, fuels can be used to generate heat, in particular independently of hydrogen gas. Additional fuels can be, for example, LOHC+, LOHC- and/or fossil fuels such as diesel. These additional fuels can be burned in particular in an emergency situation, for example to enable a cold start of the device, for example on a ship on the high seas. The initial provision of electrical power, in particular when starting the device, is thereby simplified. For this purpose, the combustion unit in particular has at least one combustion chamber in which hydrogen gas and/or the additional fuels can be burned. It is also conceivable for a combustion unit to have several combustion chambers, each of which is designed to burn different fuels. Since the combustion unit is connected to the heat distribution unit, the heat generated in the combustion unit can advantageously be distributed in the device and in particular fed to the dehydrogenation reactor.

In the at least one combustion chamber, the fuel is burned in particular with an open flame. Alternatively, the combustion chamber is designed as a catalytic burner. The method is controlled in particular in such a way that the additional fuel is supplied to the combustion unit when an external heat supply is required because the hydrogen gas released alone is not sufficient to cover the power requirement and/or the heat requirement of the device through the conversion of the hydrogen gas in the fuel cell. Additionally or alternatively, other external heat sources can be used, in particular a hydrogen combustion engine and/or a hydrogen turbine, whereby the hydrogen gas required for this comes in particular directly from the dehydrogenation reactor.

Additionally or alternatively, an external heat sink can also be connected to the heat distribution unit, in particular in the form of a heat storage unit. This makes it possible to store excess heat that is generated at a first point in time and to release it again at a later point in time when there is a need for heat.

The use of electrical energy according to claim 3 enables an uncomplicated and flexible provision of heat for the dehydrogenation reactor. In particular, the proportion of energy provided for the dehydrogenation reactor, in particular in the form of heat, from electrical current is greater than 2% of the total heat requirement of the dehydrogenation reactor, in particular at least 5%, in particular at least 10%, in particular at least 15%, in particular at least 20% and in particular at most 50%. In particular, the proportion of electrical current for the provision of heat is at least large enough that fluctuations in the provision of heat, in particular in the form of exhaust gases from the fuel cell and/or thermal contact of the fuel cell with the dehydrogenation reactor and/or the combustion of hydrogen gas and/or at least one other fuel, can be compensated. In particular, it was recognized that electrical current is dynamically available and enables dynamic control of the provision of heat for the dehydrogenation reactor. The provision of hydrogen gas by means of the dehydrogenation reactor is ensured. The provision of electrical energy by means of the fuel cell is ensured.

For example, electrical energy can be used for an electric heater through which the heat transfer medium passes.

Additionally or alternatively, it is conceivable to thermally couple at least one electrical heating element to the dehydrogenation reactor, in particular directly, for example on or in the housing of the dehydrogenation reactor. In particular, the dehydrogenation reactor can be directly heated electrically. A method according to claim 4 enables the regulation of the electric current depending on the dehydrogenation reaction. In particular, the volume flow of the hydrogen gas discharged from the dehydrogenation reactor can be influenced by influencing the process parameters such as reaction temperature and reaction pressure in the dehydrogenation reactor. Additionally or alternatively, the volume flow of the LOHC+ carrier material fed into the dehydrogenation reactor and/or the volume flow of the LOHC- carrier material discharged from the dehydrogenation reactor can also be used to regulate the volume flow of the hydrogen gas released. Additionally or alternatively, it is also conceivable to return at least partially dehydrogenated LOHC- carrier material to the dehydrogenation reactor in order to change, in particular to reduce, the effective degree of hydrogenation of the carrier material fed into the dehydrogenation reactor.

A method according to claim 5 allows additional possibilities for influencing the regulation of the electric current. In a first variant, the ratio of heat to electricity generation of the hydrogen gas converted in the fuel cell is used as the basis for the regulation. In particular, the hydrogen gas not converted in the fuel cell is not taken into account in the regulation. This method is particularly uncomplicated and differs in particular from a method according to EP 3 375 034 A1.

The ratio of heat to electricity can be influenced in particular by controlling and/or regulating temperature and/or pressure in the fuel cell. Additionally or alternatively, a load variation of the fuel cell can cause a change in the heat-to-electricity ratio.

The load variation occurs in particular in a fuel cell system with several, in particular identically designed, fuel cells. It was recognized that a required total load of the fuel cell system can be achieved, whereby the individual fuel cells of the fuel cell system can be operated differently. With uniform operation, i.e. identical operating modes of the individual fuel cells, their heat loss is comparatively reduced and a comparatively higher proportion of electricity generation results, so that the ratio of heat to electricity is reduced. In particular, the heat loss of the fuel cells serves to provide additional heat to the heat distribution unit, in particular to the dehydrogenation reactor. Alternatively, one or a few of the fuel cells are operated at different power levels, with fuel cells that are operated at higher power levels having a disproportionately high heat output. In this case, the fuel cells are operated unevenly, resulting in a higher proportion of heat generation due to increased heat loss. Accordingly, with uneven load distribution, the heat-to-power ratio is increased.

According to a second variant, the electric current can also be defined as a function of a ratio of the exhaust heat to the heat that can be dissipated directly from the fuel cell. Heat that can be dissipated directly from the fuel cell is also referred to as direct heat and relates to heat transfer through heat conduction and/or through use of the heat transfer medium. The ratio of exhaust heat to direct heat is regulated in particular by the stoichiometric ratios of oxygen in the fuel cell. The oxygen supply takes place in particular by supplying air, in particular ambient air. In particular, the degree of the superstoichiometric supply of oxygen and/or air into the fuel cell serves as a control parameter. This superstoichiometric ratio is also referred to as lambda and is preferably selected to be as small as possible with the maximum possible dissipation of direct heat, so that the temperature level required for the reliable operation of the fuel cell is reliably maintained.

In particular, lambda is less than 10, in particular less than 5, in particular less than 2 and in particular less than 1.5. In particular, lambda is greater than 0.

In particular, at least 40% of the waste heat from the fuel cell is released as direct heat, in particular at least 50% and in particular at least 60%.

A minimum temperature in the fuel cell is in particular between 600 °C and 1000 °C.

Additionally or alternatively, the volume flow of hydrogen gas and/or of the at least one further fuel supplied to the combustion unit can be regulated in order to regulate the heat generated by combustion. Additionally or alternatively, the electrical current used to heat the dehydrogenation reactor directly and/or indirectly with the heat transfer medium can also be regulated.

A method according to claim 6 enables a more efficient conversion of the hydrogen gas in the fuel cell. The hydrogen gas purified in a conditioning unit has reduced pollutant levels and/or impurities that could impair the efficiency of the electricity generation in the fuel cell. The conditioning unit enables a chemical and/or physical purification of the hydrogen gas, in particular by alternating adsorption, in particular pressure swing and/or temperature swing adsorption. In alternating adsorption, an adsorbent is loaded with impurities.

In particular, it is possible to supply hydrogen gas from the dehydrogenation reactor to the fuel cell in purified and/or unpurified form, in particular in mixed form.

A method according to claim 7 enables additional, particularly efficient heat recovery. As the adsorbent's service life progresses, it can reach a saturation state, which makes it necessary to separate the impurities from the adsorbent again. A purge gas is used for this purpose, which is, for example, purified hydrogen gas from the conditioning unit and/or purge gas containing hydrogen gas. By purging the adsorbent, the separated impurities are absorbed by the purge gas from the adsorbent. It has been found that particularly efficient heat recovery results from feeding the purge gas to the combustion unit and using it thermally there. The purge gas can advantageously be used for additional heat recovery. The overall efficiency of the method is thereby increased.

In particular, it is possible to take into account the amount of hydrogen gas contained in the purge gas for regulating the heat supply to the dehydrogenation reactor, i.e. to regulate the amount of hydrogen gas contained in the purge gas. In particular, the amount of hydrogen gas contained in the purge gas is selected to be no more than is necessary to cover the heat requirement of the dehydrogenation reactor. A method according to claim 8 enables efficient use of hydrogen gas that has not been converted in the fuel cell. This hydrogen gas is also referred to as unused hydrogen gas and can advantageously be fed to the combustion unit and/or the dehydrogenation reactor. Heat can be generated directly by burning the unused hydrogen gas. The unused hydrogen gas can also be fed to other heat sources, in particular a hydrogen gas combustion engine and/or a hydrogen gas turbine. This results in additional heat potential.

When the unused hydrogen gas is returned to the dehydrogenation reactor, it is mixed in particular into reaction educts for the dehydrogenation reactor, in particular LOHC+. The pressure boosting unit, in particular in the form of the screw compressor, is used for this purpose.

A method according to claim 9 enables an additional and independent storage function by supplying unused and/or excess hydrogen gas, in particular in the form of hydrogen gas not converted in the fuel cell and/or hydrogen gas released by the dehydrogenation reactor, to a hydrogenation reactor. This, in particular excess, hydrogen gas can be used to hydrogenate at least partially dehydrogenated carrier material LOHC-. The loaded hydrogen carrier medium LOHC+ can be used for subsequent dehydrogenation processes. It is particularly advantageous if waste heat from the exothermic hydrogenation reaction can be dissipated for the dehydrogenation reaction at the dehydrogenation reactor and used there.

A method according to claim 10 enables efficient and, in particular, direct control of the power generation in the fuel cell. Unused hydrogen gas can be returned directly to the fuel cell. This makes it possible to ensure continuous power generation without additional dehydrogenation having to take place. A return line is used in particular to return the hydrogen gas to the fuel cell, which can in particular have a hydrogen gas buffer storage device in order to temporarily store hydrogen gas at least. This can improve the dynamics of the method. Additionally or alternatively, a cleaning unit and/or a conditioning unit can be arranged along the return line. In particular, this can also be the conditioning unit that is already present.

In particular, it was found that the ratio of used to unused hydrogen gas in the fuel cell can be regulated by feeding cathode exhaust gas from the fuel cell back into the fuel cell. Cathode exhaust gas is understood to be oxygen-reduced residual air in the fuel cell. When the oxygen-reduced residual air is fed back into the fuel cell, the oxygen concentration in the fuel cell drops, so that less hydrogen gas is converted into electricity and heat in the fuel cell.

The higher the amount of recirculated cathode exhaust gas, the lower the amount of hydrogen gas converted in the fuel cell.

A method according to claim 11 or 12 enables gentle operation of the fuel cell. By supplying water vapor to the hydrogen gas that is to be supplied to the fuel cell, the steam-to-carbon ratio of the contaminated hydrogen gas can be regulated. The water vapor used for this is obtained in particular from a water-containing exhaust gas from the fuel cell. By increasing the steam-to-carbon ratio, the reformation of carbon compounds to synthesis gas is promoted in order to improve the durability of the fuel cell. In particular, it was found that the amount of carbon compounds in the hydrogen flow can be measured or at least estimated in order to regulate the supply of water vapor to the anode gas circulation. It was found that in favor of the overall efficiency of carrier material to electrical current, the supply of water vapor to the anode gas circulation is kept as low as possible, so that an acceptable degradation of the fuel cell is just about reliably guaranteed. In particular, the volume fraction of water vapor in relation to the total flow is at most 50%.

A method according to claim 13 increases the flexibility in controlling the dynamics of the method. Intermediately stored energy can be requested at any time to operate electrical consumers, in particular to improve the starting behavior of the device. Energy can be present in a battery and/or as hydrogen gas in the hydrogen gas buffer storage and/or as LOHC+ after re-hydrogenation with excess hydrogen gas in the hydrogenation reactor.

Additionally or alternatively, it is possible that the dynamics in the provision of the electrical current are regulated by the output of the dehydrogenation reactor, i.e. the amount of hydrogen gas released. The regulation of the electrical current provided is carried out in particular in such a way that a maximum efficiency of carrier material to electricity is achieved, in particular instantaneously or as an average over a defined period of time, and/or that the secondary energy consumption is minimal, and/or that the process has speed-optimized dynamics, and/or that the process has reduced, in particular minimal, CO2 emissions. Secondary energy consumption means that external fuels are burned in the combustion unit and/or electrical energy is taken from the energy storage device, i.e. from the battery. A process has fast dynamics if new operating points can be reached at short notice, in particular in less than 30 minutes, in particular in less than 15 minutes, in particular in less than 10 minutes, in particular in less than one minute and in particular in less than 10 seconds.

The power control of the dehydrogenation reactor is carried out in particular by adjusting the energy share of electrical heating for the dehydrogenation reactor. It was recognized that electrical heating can be controlled very dynamically. In particular, the proportion of electrically generated energy in the form of heat can be adjusted quickly, so that even when the load changes, the fuel cell can provide electrical power reliably, in particular without interruption. Although the heat supply from the fuel cell to the dehydrogenation reactor can be limited during a load change by thermal contact, by the use of exhaust gases from the fuel cell and/or by the combustion of released hydrogen gas because the fuel cell waste heat and the hydrogen release react sluggishly to the dynamics of a load change, electrical heating enables a sufficiently fast response. Additionally or alternatively, rapid dynamic control of the dehydrogenation reactor output can be carried out by means of the combustion unit if the fuel can be used independently of the hydrogen gas generated by the dehydrogenation reactor. In this respect, at least one additional fuel serves in particular for this purpose.

A device according to claim 14 essentially has the advantages of the method according to the invention, to which reference is hereby made.

A heat distribution unit is particularly advantageously designed to transfer heat generated in the fuel cell to the dehydrogenation reactor.

A device according to claim 15 simplifies the control and/or regulation of the device. The control/regulation unit is in signal connection with all relevant components of the device, in particular in bidirectional signal connection. The signal connection can be wireless and/or wired. In particular, the control/regulation unit is in bidirectional signal connection with the dehydrogenation reactor, the fuel cell, the combustion unit, the conditioning unit, the heat distribution unit and the exhaust gas unit. In addition, the control/regulation unit can be in signal connection with sensors that record process parameters in the components. In addition, the control/regulation unit can be in signal connection with components that influence fluid flow, in particular valves, pumps and/or shut-off elements, in order to enable an automated sequence of the method.

A device according to claim 16 enables improved heat generation. It is advantageous if the combustion unit comprises several combustion chambers. This allows different fuels to be used efficiently to generate heat.

A device according to claim 17 enables, on the one hand, the provision of hydrogen gas of increased purity and, on the other hand, the efficient use of purge gas containing impurities for heat generation. Both the features specified in the patent claims and the features specified in the embodiment of a device according to the invention are each suitable, either alone or in combination with one another, for further developing the subject matter of the invention. The respective combinations of features do not represent any restriction with regard to the further development of the subject matter of the invention, but essentially only have an exemplary character.

Further features, advantages and details of the invention emerge from the following description of embodiments based on the drawing. They show:

Fig. 1 is a schematic representation of a device according to the invention.

A device, marked in Fig. 1 as a whole with 1, serves to provide electrical current by converting hydrogen gas in a fuel cell 2. The fuel cell 2 is in particular an SOFC fuel cell, but could also be implemented by a different type of fuel cell. It is in particular possible to provide a fuel cell system with several fuel cells 2, whereby the individual fuel cells 2 of the fuel cell system can be implemented in a similar way, i.e. of the same type and/or in a different way, of a different type. The similar fuel cells 2 can in particular be implemented with identical dimensions, i.e. with the same performance values.

The device 1 comprises a dehydrogenation reactor 3 in which hydrogen-loaded carrier material LOHC+ can be catalytically dehydrogenated. Hydrogen gas is released as a result of the catalytic dehydrogenation reaction.

The fuel cell 2 is fluidically connected to the dehydrogenation reactor 3. A conditioning unit 5 is connected to the dehydrogenation reactor 3 via a hydrogen gas line 4. The conditioning unit 5 has, in particular, an adsorption unit 6. The conditioning unit 5 is connected to a further hydrogen gas line 4 for supplying purified hydrogen gas to the fuel cell 2. The dehydrogenation reactor 2 and the conditioning unit 5, in particular with the adsorption unit 6, form a carrier material dehydrogenation unit 29. The hydrogen gas released in the dehydrogenation reactor 3 can also be passed past the conditioning unit 5 and into the fuel cell 2 by means of a bypass line 7.

In addition, the dehydrogenation reactor 3 is fluidically connected to a combustion unit 8. In the combustion unit 8, fuel can be burned with an open flame or converted into heat by means of a catalytic burner. The combustion unit 8 has at least one and in particular several combustion chambers.

The adsorption unit 6 is connected to an exhaust gas unit 10 and additionally to the combustion unit 8 by an exhaust gas line 9. The fuel cell 2 is also connected to the exhaust gas unit 10 by an exhaust gas line 9. In addition, an exhaust gas recirculation line 11 is connected to the exhaust gas line 9 in order to return exhaust gas generated in the fuel cell 2, in particular oxygen-reduced air, to the fuel cell 2. For this purpose, the exhaust gas recirculation line 11 can open into an oxygen supply line 12, via which oxygen-containing medium, in particular air and in particular ambient air, is supplied from an air source 13 to the fuel cell 2. The air source 13 is in particular the environment of the fuel cell 2. The air source 13 is connected to the combustion unit 8 by a further oxygen supply line 12.

The fuel cell 2 is connected to the combustion unit 8 by means of another hydrogen gas line 4.

In addition, a return line 14 is connected to the fuel cell 2 in order to return unused hydrogen gas in the fuel cell 2 to the fuel cell 2 and/or to the conditioning unit 5 and/or to the dehydrogenation reactor 3. A water gas buffer storage unit 15 can be arranged along the return line 14. An additional conditioning unit, in particular with an adsorption unit, can be arranged along the return line 14 in order to purify returned hydrogen gas. It is also conceivable to return hydrogen gas purified in the conditioning unit 12 to the dehydrogenation reactor 3 by means of a separate line. Hydrogen gas released in the dehydrogenation reactor 3 can be fed by means of a dehydrogenation reactor return line 16 to a pressure booster unit 17, which in particular has a screw compressor. Via the dehydrogenation reactor return line 16, hydrogen gas can be added to loaded carrier material LOHC+, which is fed to the dehydrogenation reactor 3 via a carrier material feed line 18 from a carrier material source 19. The carrier material source 19 is a storage container, in particular for liquids. In particular, LOHC+ is stored in the storage container. In addition, LOHC-, i.e. at least partially discharged carrier material, can also be stored in the storage container. For this purpose, the storage container can have separate storage chambers, which are separated from one another in particular by a movable partition. It is also conceivable to use several, in particular separately designed, storage containers.

Dehydrated carrier material LOHC in the dehydrogenation reactor 3 can be discharged into the carrier material source 19 via a carrier material discharge line 20.

The carrier material source 19 is connected to the combustion unit 8 by a further carrier material supply line 18. In particular, the at least one combustion chamber of the combustion unit 8 is designed in such a way that other fuels than hydrogen gas can also be used to generate heat. Other fuels are in particular fossil fuels such as diesel fuel. These fuels are stored in particular in a separate storage container 21, which is connected to the combustion unit 8 by means of a fluid line 22.

The carrier material source 19 is fluidically connected to a hydrogenation reactor 23 via a corresponding carrier material supply line 18 and a further carrier material discharge line 20. The fuel cell 2 is connected to the hydrogenation reactor 23 via a further hydrogen gas line 4 in order to supply unused hydrogen gas from the fuel cell 2 to the hydrogenation reactor 23.

The device 1 comprises a heat distribution unit 24, which is in a signal connection, in particular bidirectional, for regulated heat management of the device 1 with the control/regulation unit 25 shown purely schematically in Fig. 1. The heat flows within of the device 1, in particular towards the heat distribution unit 24 and away from the heat distribution unit 24, are shown with dash-dotted lines in Fig. 1. The signal connection can be wired or wireless, for example by radio.

Electric current generated in the fuel cell 2 is delivered to an electrical consumer 27 by means of an electrical line 26 and/or temporarily stored in particular in a battery 28.

The heat generated in the fuel cell 2 can be transferred to the dehydrogenation reactor 3 in various ways. For example, heat conduction is possible by arranging the dehydrogenation reactor 3 on or in the fuel cell 2. Furthermore, heat transfer by means of a heat transfer medium is possible, in particular in a closed heat transfer medium circuit that is part of the heat distribution unit 24. Accordingly, heat contained in the exhaust gases of the fuel cell 2, so-called exhaust heat, can be recovered in the exhaust unit 10 and transferred to the heat distribution unit 24 by means of a heat transfer medium.

Since the hydrogenation reaction carried out in the hydrogenation reactor 23 is exothermic, the heat generated there is made available to the heat distribution unit 24, in particular also by means of a heat transfer medium.

In addition, the device 1 can have additional, external heat sources 30 such as a hydrogen gas combustion engine or a hydrogen gas turbine. It is advantageous if hydrogen gas released in the dehydrogenation reactor 3, which has been cleaned in particular by means of the conditioning unit 5, is fed to the external heat source 30 by means of a hydrogen gas line 4.

In addition, the device 1 has at least one heat sink 31, which is designed in particular as a heat accumulator. The heat sink 31 is connected to the heat distribution unit 24 for the exchange of heat, in particular bidirectionally.

In particular, the heat distribution unit 24 is designed to deliver heat to the dehydrogenation reactor 3, in particular by means of a heat transfer medium. The control/regulation unit 25 is in signal connection with all components of the device 1, in particular with the fuel cell 2, the dehydrogenation reactor 3, the conditioning unit 5, the adsorption unit 6, the combustion unit 8, the exhaust gas unit 10, the hydrogen gas buffer storage 15, the pressure increase unit 17, the carrier material source 19, the storage container 21, the hydrogenation reactor 23, the heat distribution unit 24, the electrical consumer 27, the battery 28, the external heat source 30 and/or the heat sink 31. In addition, the control/regulation unit 25 is in signal connection with all units for influencing fluid flows in the device 1, in particular pumps, valves and/or pressure generating means.

A method for providing electrical current by means of the device 1 is explained in more detail below.

At least partially loaded carrier material LOHC+ is fed from the carrier material source 19 to the dehydrogenation reactor 3 and dehydrogenated there. The hydrogen gas released in this process is fed directly to the fuel cell 2 or is cleaned beforehand in the conditioning unit 5, in particular the adsorption unit 6. In the fuel cell 2, the hydrogen gas is converted into electrical current and heat, with the electrical current being temporarily stored in the battery 28 and/or requested by an electrical consumer 27. The electrical consumer is in particular a drive motor for the mobile platform.

The heat generated in the fuel cell 2 is made available to the dehydrogenation reactor 3 by direct heat transfer, via the exhaust gas unit 10 and in particular via the heat distribution unit 24. By means of a combustion unit 8, in which hydrogen gas or other fuels, in particular diesel and/or LOHC, are burned and/or catalytically converted, additional heat is generated, which is made available to the heat distribution unit 24. Exhaust gases from the combustion unit 8 are fed to the exhaust gas unit 10 for thermal utilization.

To increase the overall efficiency of carrier material to electrical current, various control methods are possible, each of which requires the components of the device 1 to be interconnected in a manner corresponding to the control method. The device 1 is in particular, it is designed in such a way that the various components can be connected to one another flexibly, i.e. variably. This means that in a first control variant, for example, two components are fluidically connected to one another and in another control variant these two components are fluidically separated from one another. The same applies to heat transfer between different components, which is enabled or prevented depending on the control state.

According to a first control variant, the electrical current provided is controlled as a function of the volume flow of hydrogen gas delivered by the dehydrogenation reactor 3 and by adjusting the ratio of heat to current of the hydrogen gas converted in the fuel cell 2. The volume flow is adjusted in particular by supplying at least part of the released hydrogen gas not to the fuel cell 2, but at least partially to the combustion unit 8. The ratio of heat to current of the converted hydrogen gas can be adjusted by adjusting the temperature and/or pressure of the fuel in the fuel cell 2. Additionally or alternatively, the load distribution in a fuel cell system consisting of several fuel cells 2 can be adjusted.

The ratio of heat to electricity can also be influenced by changing the ratio of exhaust heat and direct heat of the fuel cell 2 by a superstoichiometric supply of oxygen or air, in particular from the air source 13.

According to an alternative control method, which is used in particular when the electrical current to be provided or the heat requirement of the dehydrogenation reactor 3 or the fuel cell 2 deviates greatly from a target value and/or this deviation is to be reduced particularly quickly, is based on the adjustment of the volume flow of the released hydrogen gas and the adjustment of the hydrogen content that is fed from the dehydrogenation reactor 3 directly into the combustion unit 8 by means of the bypass line 7, i.e. without being fed to the fuel cell 2. By means of a purge gas, in particular hydrogen gas, in particular from the dehydrogenation reactor 3, impurities of the adsorbent in the adsorption unit 6 are flushed out and fed either to the exhaust gas unit 10 and/or the combustion unit 8, each for heat recovery.

A further control variant is based on the fact that the amount of hydrogen gas discharged in the purge gas is regulated according to the current heat requirement of the dehydrogenation reactor 3.

A further control method is based on the ratio of the hydrogen gas converted in the fuel cell 2 to the unreacted hydrogen gas being regulated by recirculating the amount of cathode exhaust gases from the fuel cell 2, i.e. residual air with a reduced oxygen content, in particular via the exhaust gas return line 11 and the oxygen supply line 12. The greater the amount of recirculated cathode exhaust gas, the more the oxygen concentration in the fuel cell 2 decreases and thus the conversion rate of hydrogen gas into electrical current and heat.

According to a further control variant, the external heat sources 30 and/or the additional fuels from the carrier material source 19 and the storage container 21 are used to maximize the overall efficiency of the carrier material to electrical power. In particular, the additional fuels other than hydrogen are only used when the electricity demand and the heat demand cannot be covered by the use of hydrogen gas alone.

A further control variant takes into account the comparatively sluggish dynamics of the dehydrogenation reactor 3 compared to the fuel cell 2 and/or the battery 28. The arrangement of the dehydrogenation reactor 3 with the fuel cell 2 and the hydrogenation reactor 23 enables an extension of the control variant, in which a reduced demand for electrical current is possible without molecularly stored hydrogen being accumulated or a particularly large battery capacity having to be kept available for intermediate storage. In particular, hydrogen gas that is not currently required can be used efficiently in the hydrogenation reactor 23 for the hydrogenation of at least partially discharged carrier material LOHC, in particular in particular the waste heat of the exothermic hydrogenation reaction can be used in the heat distribution unit 24. In particular, the mode of operation is such that the output of the dehydrogenation reactor 3 is operated for a variably definable period of time at a variably definable output level, in particular under full load. During this period, a dynamic use of the hydrogenation reactor 23 is used alone or in combination with other control variants already described to influence the amount of electricity provided.

According to an alternative variant, the release capacity of the dehydrogenation reactor 3 can be specifically limited by a pressure build-up. If the power requirement and the hydrogen gas requirement decrease, less hydrogen gas is removed from the dehydrogenation reactor 3. However, since hydrogen gas continues to be released in the dehydrogenation reactor 3 through dehydrogenation of the carrier material, the hydrogen gas pressure in the dehydrogenation reactor 3 increases. This has a detrimental effect on the reaction conditions for the release of hydrogen gas in the dehydrogenation reactor 3. The dehydrogenation reaction is slowed down and thus less hydrogen gas is released. This influence is possible in particular without the need for a hydrogenation reactor 23. This influence is based primarily on the reaction equilibrium in the dehydrogenation reactor 3 itself.

On the one hand, this allows the amount of temporarily stored hydrogen gas to be increased for the same volume, thereby building up a supply of hydrogen gas for later dynamics in the fuel cell 2. On the other hand, at least partially discharged LOHC carrier material can be temporarily stored for later use, in particular at operating points of the device with lower power requirements. This also allows the amount of molecularly stored hydrogen to be reduced.

In a further control variant, the hydrogen gas is returned, in particular in a hydrogen gas buffer storage 15 for intermediate storage. The amount of hydrogen gas stored temporarily can be changed in a targeted manner between a minimum and a maximum pressure. If the hydrogen demand falls or rises at a rate that the dehydrogenation unit 3 or the hydrogenation unit 23 cannot handle because they are too slow, the hydrogen gas buffer storage 15 serves to absorb and release water. material gas. In dynamic operating modes, the various buffers are used according to their dynamic regime, with the adaptation of the dehydrogenation reactor 3 having the highest priority. In another control variant, the supply of water vapor to an anode gas circulation is kept as low as possible in favor of the overall efficiency of the carrier material to electrical current, so that an acceptable degradation of the fuel cell 2 is just about reliably guaranteed. Depending on the current operating mode of the dehydrogenation reactor 3, the amount of carbon compounds in the hydrogen flow can be estimated and the supply of water vapor to the anode gas circulation can be adjusted. Alternatively, the amount of carbon compounds in the hydrogen flow is measured and this measurement is used for control.

The method according to the invention enables different operating points of the device 1, which can be achieved via different control methods. Depending on the requirement, a specific control path with the lowest overall energy consumption, with the lowest secondary energy consumption, with the lowest carbon dioxide emissions or a combination of different requirements can be selected.

Claims

Patent claims

1. A method for providing electrical current comprising the steps

Feeding a carrier material loaded with hydrogen into a dehydrogenation reactor (3),

Releasing hydrogen gas by dehydrogenating the carrier material in the dehydrogenation reactor (3),

Feeding released hydrogen gas into a fuel cell (2),

Converting the supplied hydrogen gas in the fuel cell (2) to generate electrical current and heat,

Transferring heat generated in the fuel cell (2) to the dehydrogenation reactor

(3) by

— thermal contact between the fuel cell (2) and the dehydrogenation reactor (3) and/or

— Use of heat contained in exhaust gases of the fuel cell (2) and/or

— Use of a heat transfer medium.

2. Process according to claim 1, characterized in that released hydrogen gas and/or at least one further fuel, in particular the carrier material and/or diesel, is fed into a combustion unit (8) and thermally utilized there, the heat generated thereby being transferred to the dehydrogenation reactor (3).

3. Process according to one of the preceding claims, characterized in that heat transferred to the dehydrogenation reactor (3) has been generated by means of electrical energy.

4. Method according to one of the preceding claims, characterized in that the generated electrical current is regulated by means of a control/regulation unit (25) depending on a volume flow of the hydrogen gas discharged from the dehydrogenation reactor (3).

5. Method according to claim 4, characterized in that the regulation of the generated electrical current takes place as a function of a ratio of heat to electricity generation of the hydrogen gas converted in the fuel cell (2) and/or a ratio of the exhaust heat of the fuel cell (2) to heat that can be dissipated directly from the fuel cell (2), and/or the volume flow of the hydrogen gas supplied to the combustion unit (8) and/or the at least one further fuel and/or a proportion of electrical heating of the dehydrogenation unit.

6. Process according to one of the preceding claims, characterized in that the hydrogen gas discharged from the dehydrogenation reactor (3) is purified in a conditioning unit (5), in particular by alternating adsorption in an adsorption unit (6).

7. The method according to claim 6, characterized by purging the adsorption unit (6), wherein contaminated purge gas from the adsorption unit (6) is burned in the combustion unit (8) and the heat generated thereby is transferred to the dehydrogenation reactor (3).

8. Method according to one of the preceding claims, characterized in that hydrogen gas not converted in the fuel cell (2) is fed to the combustion unit (8) and/or the dehydrogenation reactor (3).

9. Method according to one of the preceding claims, characterized in that hydrogen gas not converted in the fuel cell (2) and/or hydrogen gas released from the dehydrogenation reactor (3) is fed to a hydrogenation reactor (23), wherein in particular heat is transferred from the hydrogenation reactor (23) to the dehydrogenation reactor (3).

10. Method according to one of the preceding claims, characterized in that hydrogen gas not converted in the fuel cell (2) is returned to the fuel cell (2), in particular via a hydrogen gas buffer storage (17) and/or via a cleaning unit, which is in particular the conditioning unit (5).

11. Method according to one of the preceding claims, characterized in that water vapor is added to the hydrogen gas supplied to the fuel cell (2).

12. Method according to claim 10 and 11, characterized in that the water vapor is added to the hydrogen gas returned to the fuel cell (2), wherein in particular the amount of water vapor added is regulated as a function of the amount of carbon compounds in the hydrogen stream.

13. Method according to one of the preceding claims, characterized in that the dynamics of the electric current provided is controlled by

Energy is temporarily stored as electrical energy in a battery (28) and/or as hydrogen gas in the hydrogen gas buffer storage (17) and/or for hydrogenation in the hydrogenation reactor (23) and/or the output of the dehydrogenation reactor (3) is regulated.

14. Device for providing electrical current, comprising a. a dehydrogenation reactor (3) connected to a carrier material source (19) for releasing hydrogen gas by dehydrogenating the carrier material, b. a fuel cell (2) fluidly connected to the dehydrogenation reactor (3) for converting the supplied hydrogen gas in the fuel cell (2) to generate electrical current and heat, c. a heat distribution unit (24) for transferring heat generated in the fuel cell (2) to the dehydrogenation reactor (3).

15. Device according to claim 14, characterized by a control/regulation unit (25) for controlling and/or regulating material flows and/or reaction conditions in the device (1).

16. Device according to claim 14 or 15, characterized by a combustion unit (8) fluidically connected to the dehydrogenation reactor (3) which has at least one combustion chamber.

17. Device according to one of claims 14 to 16, characterized by a conditioning unit (5) fluidically connected to the dehydrogenation reactor (3), which has an adsorption unit (6) for alternating adsorption.