WO2023227710A1

WO2023227710A1 - Hydrogenation process and dehydrogenation process for a carrier medium for hydrogen and system for carrying out processes of this kind

Info

Publication number: WO2023227710A1
Application number: PCT/EP2023/064025
Authority: WO
Inventors: Jonas OBERMEIER; Alexander Weiss; Caspar PAETZ; Michael Kohles
Original assignee: Hydrogenious Lohc Technologies Gmbh
Priority date: 2022-05-25
Filing date: 2023-05-25
Publication date: 2023-11-30
Also published as: DE102022205290A1

Abstract

A system (1) for hydrogenating a carrier medium for hydrogen comprises a reactor (2) for catalytically hydrogenating the carrier medium for hydrogen, having an input degree of hydrogenation, at least one delivery means (10) for delivering the carrier medium for hydrogen to the reactor (2), and a control unit (17) which is in signal communication (18) with the at least one delivery means (10) and which is designed to control the catalytic hydrogenation in the reactor (2) by adapting the input degree of hydrogenation of the carrier medium for hydrogen.

Description

Hydrogenation process and dehydrogenation process for a hydrogen carrier medium and system for carrying out such processes

The present patent application claims the priority of the German patent application DE 10 2022 205 290.0, the content of which is incorporated herein by reference.

The invention relates to a hydrogenation process and a dehydrogenation process for hydrogen carrier media as well as a system for carrying out such processes.

DE 10 2020 215 444 A1 discloses a method and a system for the material use of hydrogen.

CN 101 993 721 A discloses a system and a method for hydrogenating a carrier material.

DE 10 2021 203 883 A1 discloses a method and a system for providing hydrogen gas.

EP 1 081 780 A2 discloses a hydrogen supply system for a fuel cell.

Hydrogen carrier media, in particular liquid organic hydrogen carriers (LOHC), can be reversibly hydrogenated, i.e. loaded, and dehydrogenated, i.e. discharged, with hydrogen in catalytic processes. Special process conditions, in particular pressure and temperature, are required to carry out the hydrogenation or dehydrogenation processes. In order to carry out the process as efficiently and therefore economically as possible, the greatest possible use of water absorption capacity is sought, i.e. almost complete hydrogenation in the hydrogenation process or almost complete dehydrogenation in the dehydrogenation process. This allows the logistics effort and costs to be reduced.

In addition to the technical optimum, real boundary conditions must be taken into account, with the so-called load flexibility being particularly important for hydrogenation and/or dehydrogenation systems. For example, if fluctuating hydrogen sources are used for hydrogenation This results in a volatile hydrogen gas supply. For example, when producing green hydrogen from renewable energies using wind turbines and/or photovoltaic systems, their electricity generation profiles cause fluctuations. A downstream electrolyzer can follow these current fluctuations. However, this creates a fluctuating fluid flow of hydrogen gas, with the process dynamics of the hydrogenation process being sluggish and the process itself being inflexible, especially when it is operated at partial load. Partial load means that the system is operated at an output below a nominal load or below a design point, the so-called normal operating point. The dynamics of the process refers to the speed of a load change. The limited partial load capability essentially results from the components of the system that are designed for nominal load, such as pumps, lines and/or filters.

Accordingly, volatile hydrogen reductions such as industrial processes and/or mobility applications, in particular gas stations, can cause fluctuations in the hydrogen demand that is to be covered by a dehydrogenation process. Similar challenges arise for the dehydrogenation reaction and the system required for it.

Fikrt, A. et al.: “Dynamic power supply by hydrogen bound to a liquid organic hydrogen carrier”, 194 (2017) 1-8, discloses a power control for a dehydrogenation reaction of LOHC. The power control is based on the input parameters pressure, temperature and educt mass flow. Educt mass flow is understood to mean the mass flow supplied to a reactor, i.e. in particular the sum of all starting materials supplied to the reactor, i.e. educts. It has been shown that power control using temperature is fundamentally possible. Due to the inertia of the hydrogenation and dehydrogenation processes, the temperature has proven to be unsuitable as a control parameter for volatile hydrogen sources or for reducing volatile hydrogen, i.e. for highly dynamic operation. Power control using pressure is also possible in principle, but has disadvantages in the lower partial load range. Power control by means of the educt mass flow is fundamentally possible and is particularly conceivable in the case of small power fluctuations in systems, which today are usually designed at load points of 80%, 100% and 120%. However, it has been shown that with greater power Fluctuations, i.e. in the lower partial load range, i.e. at a load of less than 80% of the nominal load, and in the peak load range, i.e. at a load of more than 120% of the nominal load, strong changes in the educt mass flow would be required, which would result in a greatly changed fluid dynamics of the entire system . The result would be that not all operating states can be implemented and, in particular, the design of system components, especially pumps, in a high load range would become very complex and, in particular, costly.

The invention is based on the object of improving the hydrogenation and dehydrogenation of hydrogen carrier medium under volatile conditions, in particular when coupled to volatile hydrogen sources and/or volatile hydrogen sinks, and in particular of providing a flexible power control for a hydrogenation process and/or a dehydrogenation process.

This object is achieved by a hydrogenation process with the features of claim 1, by a dehydrogenation process with the features of claim 9 and by a system with the features of claim 16.

The core of the invention is that power control in a hydrogenation process or a dehydrogenation process takes place based on the initial degree of hydrogenation of the hydrogen carrier medium provided. In particular, it was recognized that the educt, i.e. the hydrogen carrier medium, can be used advantageously and directly for power control. The power control according to the invention is therefore based on an inherent component of the method. The additional effort for implementing the power control according to the invention is minimized and, in particular, unnecessary. In particular, it is possible to easily retrofit the power control according to the invention to existing systems.

In particular, it was recognized that the performance control of the chemical reaction, i.e. the hydrogenation reaction and/or the dehydrogenation reaction, is possible dynamically and flexibly by adjusting the input degree of hydrogenation. The power control is simplified compared to the prior art, in which a performance map is defined, for example, based on the reaction temperature, the reaction pressure and / or the hydrogenation stroke or dehydrogenation stroke. A process engineering design of the system components used is uncomplicated, especially here the educt mass flows are essentially unchanged. In particular, it was recognized that the process according to the invention can be operated stably even with major changes in the reaction conditions. Both the catalyst material and the hydrogen carrier medium are not negatively affected. There are no stability problems and in particular the quality, i.e. the purity of the hydrogen gas released, is unimpaired. Because the method according to the invention enables an enlarged performance map, it is possible to save hydrogen gas buffer storage capacities. Such a process causes reduced investment costs and makes economic sense. In particular, such a method can also be operated at low partial load and in particular at a load of up to 0%.

It was also recognized that the condition of the hydrogen carrier medium, i.e. its initial degree of hydrogenation, can advantageously be used as a basis for the power control.

This makes it possible in particular for the educt mass flow to be kept essentially constant and in particular completely constant. The design of system components for the liquid phase, especially pumps and lines, is therefore unproblematic. The driving force for the required chemical reactions can be defined and, in particular, influenced in a targeted manner via the initial degree of hydrogenation of the hydrogen carrier medium. If the initial degree of hydrogenation is reduced, the performance in the hydrogenation process is increased and the performance in the dehydrogenation process is reduced.

The initial degree of hydrogenation is understood to be the degree of hydrogenation that the hydrogen carrier medium has when it is fed into a reactor required for the hydrogenation process or the dehydrogenation process, i.e. a hydrogenation reactor or a dehydrogenation reactor.

The initial degree of hydrogenation is understood to be the degree of hydrogenation that the hydrogen carrier medium has when it is removed from the reactor required for this after the hydrogenation process or after the dehydrogenation process, i.e. after the reaction carried out in each case. During hydrogenation, the initial degree of hydrogenation is greater than the initial degree of hydrogenation. During dehydrogenation, the initial degree of hydrogenation is greater than the initial degree of hydrogenation. The difference between the input hydrogenation level and the output hydrogenation level indicates the hydrogenation or dehydrogenation stroke.

The degree of hydrogenation is understood to be the molar balance, i.e. the percentage of a carrier molecule or a mixture of carrier molecules that has already bound hydrogen. It has proven to be useful to define limit values for different degrees of hydrogenation.

For example, the degree of hydrogenation according to the hydrogenation process for the hydrogen carrier medium is more than 95%. Hydrogen carrier medium loaded in this way is referred to as LOHC-H. The degree of hydrogenation after the dehydrogenation process is in particular less than 15%. Such hydrogen carrier medium is referred to as LOHC-D. Partially hydrogenated hydrogen carrier medium or mixtures of different hydrogen carrier media can have a degree of hydrogenation between 15% and 95%. Such a hydrogen carrier medium is referred to as LOHC-X. Hydrogen carrier media that have a comparatively higher degree of hydrogenation than LOHC-D can be used to increase the initial degree of hydrogenation. An increased degree of initial hydrogenation results in a reduction in the performance of the hydrogenation process. An increased degree of initial hydrogenation results in an increase in performance in the dehydrogenation process.

The power control based on the input degree of hydrogenation is based on the knowledge that the input degree of hydrogenation serves as a thermodynamic driving force for the respective reaction, especially at the entry into the respective reactor. If an educt, i.e. a hydrogen carrier medium, is supplied to the hydrogenation process with a comparatively low initial degree of hydrogenation, in particular in relation to a normal operating point, the thermodynamic driving force and thus the performance in the hydrogenation process increases. Conversely, the thermodynamic driving force and thus the performance in the hydrogenation process decreases if the initial degree of hydrogenation is greater than that of the hydrogen carrier medium at the normal operating point. Conversely, the performance in the dehydrogenation process decreases if the initial degree of hydrogenation of the hydrogen carrier medium is lower than at the normal operating point. The performance in the dehydrogenation process increases accordingly if the initial degree of hydrogenation of the hydrogen carrier medium is greater than at the normal operating point. The background is that the changed driving force with the same residence time of the hydrogen carrier medium in the respective reactor results in a different performance, i.e. a different hydrogen absorption in the hydrogenation process or a different water gas release in the dehydrogenation process. The initial degree of hydrogenation is a result of the initial degree of hydrogenation and the performance achieved in the respective process.

A particularly suitable hydrogen carrier medium is a carrier material which is in the at least partially loaded form (LOHC-H) as perhydro-dibenzyltoluene (HisDBT), as perhydro-benzyltoluene (HnBT), as methylcyclohexane (C7H14), which is at least partially discharged to toluene (CTHS). can be, and/or is present as dicyclohexane. It is also possible to use a mixture of carrier material (LOHC-H) of perhydro-diphenylmethane and perhydro-biphenyl. These compounds can be dehydrogenated to diphenylmethane and biphenyl. A mixture of biphenyl and diphenylmethane in a ratio of 30:70, in particular 35:65 and in particular 40:60 is particularly advantageous.

Both the hydrogenation process and the dehydrogenation process each take place using a catalyst material. The catalyst material has a metal, in particular platinum, palladium, nickel, rhodium and/or ruthenium. The catalyst material is arranged in particular on a catalyst support and is in particular attached to it. A ceramic material, in particular aluminum oxide, silicon oxide, titanium oxide and/or zirconium oxide, and/or activated carbon serves as the catalyst support. In particular, the catalyst support is a porous oxide support. The material of the catalyst support in particular has pores with a diameter of at least 2 nm, in particular at least 10 nm, in particular at least 20 nm, in particular at least 50 nm and in particular at least 100 nm. The proportion by weight of the catalyst material, based on the catalyst support, is between 0.1% and 10%.

The catalyst material includes in particular a large number of catalyst particles, in particular catalyst support particles, which are in particular present as pellets. The catalyst particles are arranged in particular in the form of a fixed bed through which the hydrogen carrier medium, which is in particular liquid, flows. In the hydrogenation process according to the invention, hydrogen gas is stored, in particular on the hydrogen carrier medium. For this purpose, the hydrogen carrier medium and hydrogen gas are fed into a hydrogenation reactor, in particular via separate lines. The supplied hydrogen carrier medium is at least partially discharged and has the initial degree of hydrogenation. Through catalytic hydrogenation, hydrogen is bound to the hydrogen carrier medium. The hydrogenated hydrogen carrier medium leaving the hydrogenation reactor has an initial degree of hydrogenation that is greater than its input degree of hydrogenation.

Accordingly, the dehydrogenation process causes the release of hydrogen gas from the water carrier medium. For this purpose, hydrogen carrier medium, which is at least partially loaded and has the initial degree of hydrogenation, is fed to a dehydrogenation reactor. The dehydrogenation releases hydrogen gas from the hydrogen carrier medium, so that the dehydrogenated hydrogen carrier medium discharged from the dehydrogenation reactor has an initial degree of hydrogenation that is smaller than its input degree of hydrogenation.

For example, hydrogen carrier medium that has technical quality (LOHC-V) can also be used. LOHC-V is understood to mean, in particular, fresh hydrogen carrier medium that comes from a production process and in particular has not yet been hydrogenated. LOHC-V is in particular completely aromatic, i.e. in particular only has aromatic hydrocarbon compounds. The degree of hydrogenation of the LOHC-V is less than 10%, in particular less than 5%, in particular less than 3%, in particular less than 2%, in particular less than 1%, in particular less than 0.5% and is in particular 0%. LOHC-V acts like an inert component to specifically reduce the initial hydrogenation level.

Additionally or alternatively, hydrogen carrier medium that is at least partially oxidized (LOHC-OX) can be used to adjust the input hydrogenation level. The initial degree of hydrogenation of LOHC-OX is in particular at least 20%, in particular at least 30%, in particular at least 40%, in particular at least 50% and in particular at most 95%. The at least partially oxidized hydrogen carrier medium LOHC-OX enables the performance of the hydrogenation reaction to be increased because the absorption of hydrogen gas is increased by LOHC-OX. LOHC-OX is first reduced with hydrogen gas and then additionally hydrated. As a result, increased performance can be created in the hydrogenation process in which LOHC-OX is added, particularly in a flexible and particularly temporary manner. It is particularly advantageous if, for example, more hydrogen gas is temporarily and particularly spontaneously made available from a source. By adding LOHC-OX, this additional hydrogen gas can be used.

Method according to claim 2 or 10 enable a particularly uncomplicated adjustment of the initial hydrogenation level. In particular, additional media is not required. The hydrogen carrier medium removed from the hydrogenation reactor or dehydrogenation reactor can be immediately recycled and fed back into the respective reactor. Depending on the mixing ratio of newly supplied, so-called fresh, hydrogen carrier medium and already used, recycled hydrogen carrier medium, the initial degree of hydrogenation for this mixture can be changed in a targeted manner.

It was recognized that the catalytic reaction in the hydrogenation reactor or the dehydrogenation reactor causes the hydrogen carrier medium not to have a single, uniform initial degree of hydrogenation, but in particular to have different initial degrees of hydrogenation. The number of possible initial degrees of hydrogenation depends on the respective hydrogen carrier medium. For example, benzyltoluene as a hydrogen carrier medium has twelve discrete states of hydrogenation. The hydrogenation state H12 has a maximum loading, in which twelve hydrogen atoms are bonded to benzyltoluene. Correspondingly, in the medium degree of hydrogenation state H6, half of the maximum possible hydrogen atoms are bound to benzyltoluene and in HO no additional hydrogen atom is bound. These three hydrogenation states H12, H6 and HO are particularly important in practice. There are also intermediate states such as H3 or H9, but these occur rather rarely. The hydrogen carrier medium leaving the hydrogenation reactor or the dehydrogenation reactor can be understood as a mixture of the hydrogen carrier medium with different initial degrees of hydrogenation. It is advantageous to separate the hydrogen carrier medium into several fractions in a separation unit depending on the initial degree of hydrogenation. The fractions have the hydrogen carrier medium with the specific degree of hydrogenation state or with a certain degree of hydrogenation state range. A degree of hydrogenation state range exists in particular when several degrees of hydrogenation states are combined in one fraction, for example H12 and H6. A mixture of hydrogen carrier medium with a defined initial degree of hydrogenation can be specifically adjusted from the various fractions. For example, hydrogen carrier medium with a degree of hydrogenation of 90% can be mixed from 80% H12 and 20% H6 or from 90% H12 and 0% H O. The various fractions can in particular be temporarily stored in separate storage containers.

By specifically recycling hydrogen carrier medium with a specific degree of hydrogenation or with a specific degree of hydrogenation range, it is possible to specifically adjust the input degree of hydrogenation by recycling the hydrogenated or dehydrogenated hydrogen carrier medium. The control is possible in a more targeted manner and in particular is not limited by the fact that the initial degree of hydrogenation has a large range of degrees of hydrogenation. Such a procedure is efficient.

Adjusting the input hydrogenation level according to claim 3 or 11 enables increased flexibility with regard to the adjustment of the input hydrogenation level. In particular, it was found that additional hydrogen carrier media can be used and in particular added in order to influence the initial degree of hydrogenation.

Method according to claim 4 or 12 enable a more stable implementation of the method. Because the different material streams are mixed in a mixing unit before being fed into the respective reactor, inhomogeneous material properties of the material stream are avoided.

Alternatively, it is possible to feed the different hydrogen carrier media streams into the respective reactor by means of a separate line and in particular unmixed.

A method according to claim 5 enables the oversizing of a system so that flexible power control is improved, in particular in a partial load range and in a peak load range of the hydrogenation reactor. In particular, the increased absolute educt mass flow is selected so that the system performance at a new operating point is identical to the normal operating point. Method according to claim 6 or 14 in particular enable stable implementation. This avoids failures, particularly of pumps, lines and/or filters. A mass flow is considered constant if deviations of at most +/- 20% of a nominal mass flow occur, in particular of at most +/- 15%, in particular of at most +/- 10%, in particular of at most +/- 5%, in particular of at most +/- 3%, in particular at most +/- 2%, in particular at most +/- 1% and in particular no deviations, i.e. 0%.

Method according to claim 7 or 15 increase the overall efficiency of the respective method, since in particular the energy expenditure for preheating the hydrogen carrier medium to be supplied is reduced. In particular, the preheating of the hydrogen carrier medium to be supplied takes place in a heat exchanger and in particular by means of the hydrogen carrier medium returned from the reactor. The heat exchanger is a so-called recuperator.

In particular in the dehydrogenation process, a partial stream of the hot product stream, i.e. a mixture of at least partially dehydrogenated hydrogen carrier medium LOHC-D and released hydrogen gas, can be contacted directly with a reactant stream, i.e. fresh, at least partially hydrogenated hydrogen carrier medium LOHC-H. In the hot product stream, the at least partially dehydrated hydrogen carrier medium LOHC-D is present, in particular at least partially, in vapor form. The heat transfer from the hot product stream to the fresh educt is improved because, in addition to the sensible heat, condensation heat is also transferred by at least partially condensing the vaporous LOHC-D. In addition, there is a phase separation of the condensed LOHC-D from the hydrogen gas.

A method according to claim 8 enables the advantageous use of hydrogen gas, which can in particular also be provided in fluctuating quantities. This makes the process suitable for using hydrogen gas that has been generated with renewable energies, in particular by wind power, by means of photovoltaic systems and by hydropower. The process enables advantageous dynamics. A system according to claim 16 essentially has the advantages of the methods mentioned above, to which reference is hereby made. A system can be used for the catalytic hydrogenation or catalytic dehydrogenation of hydrogen carrier medium. It is essential that a control unit is designed to regulate the catalytic hydrogenation and/or catalytic dehydrogenation in the reactor by adjusting the input degree of hydrogenation. For this purpose, the control unit is in signal connection with at least one funding means. The at least one conveying means, in particular a pump, serves to convey the hydrogen carrier medium into the reactor. In particular, the at least one conveying means is arranged directly in front of the reactor and in particular upstream of a mixing unit. It goes without saying that several conveying means can be provided, in particular if different hydrogen carrier media streams are fed to the reactor, in particular via separate lines. In particular, at least one funding means is assigned to each line.

A system according to claim 17 simplifies the immediate return of the hydrogen carrier medium. The system simplifies a process according to claim 2 or 10. A separation unit for separating or enriching, i.e. only partially, not completely separating, the hydrogen carrier medium removed from the hydrogenation reactor or the dehydrogenation reactor is particularly advantageous. The separation unit enables the hydrogen carrier medium to be separated. The separation takes place in particular according to the chemical and/or physical properties of the hydrogen carrier medium. In particular, the separation takes place by distillation due to differences in boiling points and/or in a centrifuge due to differences in density. The separation unit can be a separate unit. The separation unit can also include several components, in particular several devices. For example, a coarse separation can be carried out depending on the density using a centrifuge and then a fine separation according to the boiling point using a distillation column. The separation unit can also be integrated into a product buffer container.

A system according to claim 18 enables the flexible provision of additional hydrogen carrier medium at the system.

A system according to claim 19 enables different hydrogen carrier media to be mixed directly before being fed into the reactor. A system according to claim 20 enables the processes to be carried out with increased overall efficiency.

Both the features specified in the patent claims and the features specified in the exemplary embodiments of systems according to the invention are each suitable, alone or in combination with one another, for further developing the subject matter according to the invention. The respective combinations of features do not represent any restrictions with regard to the developments of the subject matter of the invention, but are essentially only of an exemplary nature.

Further features, advantages and details of the invention result from the following description of four exemplary embodiments based on the drawing. Show it:

1 shows a schematic representation of a system according to the invention for hydrogenating hydrogen carrier medium according to a first exemplary embodiment,

2 is a diagram showing the dependence of a system performance on the input degree of hydrogenation of the hydrogen carrier medium in the system according to FIG. 1,

3 shows a representation corresponding to FIG. 1 of a system according to the invention for dehydrogenating hydrogen carrier medium according to a second exemplary embodiment,

Fig. 4 is a diagram corresponding to Fig. 2 for the system in Fig. 3,

5 shows a diagram corresponding to FIG. 2 to illustrate the power control for partial load states and peak load states,

6 is a diagram showing the functional relationship of the electrolyzer performance depending on the time of day when coupled to a renewable power generation source, 7 shows a representation of the hydrogenation reactor performance corresponding to FIG. 6 based on a peak performance of the electrolyzer,

8 shows a representation corresponding to FIG. 6 of a buffer storage charge state based on a daily electrolysis production,

9 is a representation corresponding to FIG. 1 of a system for hydrogenating hydrogen carrier medium according to a third exemplary embodiment,

Fig. 10 is a representation corresponding to Fig. 3 of a system for dehydrogenating hydrogen carrier medium according to a fourth exemplary embodiment.

A system marked 1 as a whole in FIG. 1 is used to hydrogenate a hydrogen carrier medium. The system 1 includes a reactor 2, which is designed as a hydrogenation reactor. A hydrogen gas supply line 3, to which a hydrogen gas buffer storage 4 is connected, opens into the hydrogenation reactor 2. In the hydrogen gas buffer storage 4, hydrogen gas can be temporarily stored, i.e. buffered, in comparatively small quantities and in particular temporarily. For this purpose, the hydrogen gas buffer storage is under pressure.

The hydrogen gas buffer storage 4 is fed by an electrolyzer 5, in which water is separated into hydrogen gas and oxygen gas by electrolysis, i.e. using electric current. The electrolyzer 5 is operated with electrical power provided by a power generation unit 6. The power generation unit 6 in particular enables the generation of electrical power from renewable energy sources such as wind power or solar radiation. The power generation unit 6 is in particular a photovoltaic system and/or a wind turbine. However, other designs of the power generation unit are also possible.

The system 1 further comprises a first educt storage container 7, in which hydrogen carrier medium LOHC and in particular at least partially discharged hydrogen carrier medium LOHC-D, especially unpressurized and at room temperature, is stored. The first educt storage container 7 is connected via a liquid line 8 to a mixing unit 9, which is connected to the hydrogenation reactor 2 via a further liquid line 8.

A liquid pump 10 is arranged on the liquid line 8 before and/or after the mixing unit 9 in order to convey the liquid hydrogen carrier medium into the hydrogenation reactor 2. Purely for reasons of illustration, the pump 10 is arranged between the first educt storage container 7 and the mixing unit 9 in FIG. The pump 10 forms a conveying means for conveying the hydrogen carrier medium along the liquid lines 8, in particular into the hydrogenation reactor 2 and out of the hydrogenation reactor 2. In principle, a pump or a comparable conveying means can be arranged along each of the lines shown in FIG.

A discharge line 11 is connected to the hydrogenation reactor 2 and opens into a product buffer container 12. A product storage container 13 is connected to the product buffer container 12 via a further liquid line 8. A return line 14, which opens into the mixing unit 9, is also connected to the product buffer container 12. It is also conceivable that the return line 14 opens directly into the liquid line 8 connected to the hydrogenation reactor 2 or, alternatively, directly into the hydrogenation reactor 2, similar to the liquid line 8 connected to the hydrogenation reactor 2 and in particular adjacent to the liquid line 8 into the hydrogenation reactor 2 ends.

The product buffer container 12 is particularly optional.

A separation unit 25 is arranged downstream of the hydrogenation reactor 2. The hydrogen carrier medium removed from the hydrogenation reactor 2 can be separated in the separation unit 25 and stored in particular in the separation unit 25. It is also conceivable that the hydrogen carrier medium is partially stored in the separation unit 25 and partially in the product buffer container 12. It is also conceivable to arrange several product buffer containers 12 in order to temporarily store the hydrogen carrier medium depending on the initial degree of hydrogenation. It is also conceivable that the hydrogenation level-dependent intermediate storage takes place in a single product buffer container 12, which can be designed in particular according to DE 10 2016 206 106 A1. The separation unit 25 can also be arranged downstream of the product buffer container 12.

The separation unit 25 can also be arranged along the return line 14.

The hydrogenation reactor 2, the upstream mixing unit 9 and the downstream product buffer container 12 form a hydrogenation module 15. The hydrogenation module 15 can also include the separation unit 25.

The system 1 has a second educt storage container 16, which is essentially identical to the first educt storage container 7 and is connected to the mixing unit 9 via a liquid line 8. A pump, also not shown, can be arranged along this liquid line 8. Hydrogen carrier medium is stored in the second educt storage container, which differs in particular from the hydrogen carrier medium stored in the first educt storage container 7. In particular, these are LOHC-V, LOHC-X or LOHC-OX. It can also be LOHC-D, the input degree of hydrogenation of which differs from the LOHC-D in the first educt storage container 7.

The system 1 comprises a control unit 17, which is in particular in a signal connection, in particular bidirectionally, with the pump 10. The signal connection can be wired or wireless, in particular via a radio connection. The radio connection is indicated by symbol 18 in Fig. 1.

In addition, the control unit 17 can also be in, in particular bidirectional, signal connection with the hydrogenation reactor 2.

In particular, the system 1 has a sensor device 19, shown purely schematically in FIG. 1, which is suitable for detecting the initial degree of hydrogenation before the hydrogen carrier medium is fed into the hydrogenation reactor 2. In particular, the sensor device 19 is in signal connection with the control unit 17. In particular, the measured input degree of hydrogenation serves as a feedback variable for the control circuit of the control unit 17. In particular, the sensor device 19 is arranged downstream of the mixing unit 9 and in particular immediately upstream of the hydrogenation reactor 2. The functionality of the system 1 is explained in more detail below with reference to FIG. 2 and FIGS. 5 to 8. For hydrogenation, the hydrogen carrier medium, in particular in at least partially discharged form LOHC-D, is fed from the first educt storage container 7 to the hydrogenation reactor 2. In addition, hydrogen, in particular hydrogen gas, which has been generated by the electrolyzer 5 and temporarily stored in the hydrogen gas buffer storage 4, is provided. Since the electrical power required for this has been obtained from renewable energies, the supply of hydrogen gas can be volatile.

In order to counteract the time-varying and in particular unpredictable supply of hydrogen gas in the hydrogenation reactor 2, the performance of the hydrogenation reaction in the hydrogenation reactor 2 is regulated by specifically changing the initial degree of hydrogenation of the supplied hydrogen carrier medium. For this purpose, for example, hydrogen carrier medium that has already been hydrogenated in the hydrogenation reactor 2 with an initial degree of hydrogenation that is greater than the input degree of hydrogenation can be returned to the mixing unit 9 via the return line 14 and mixed with hydrogen carrier medium LOHC-D from the first educt storage container 7. This mixture then has a higher initial degree of hydrogenation than LOHC-D. This allows the driving force for the hydrogenation reaction in the hydrogenation reactor 2 to be reduced.

To adjust the input degree of hydrogenation, it is therefore possible to mix LOHC-D from the first educt storage container 7 with LOHC-H from the product buffer container 12. Depending on the mixing ratio, the resulting initial degree of hydrogenation can be specifically adjusted. Additionally or alternatively, it is possible to mix LOHC-D from the first educt storage container 7 with LOHC-V and/or LOHC-OX from the at least one second educt storage container 16.

As can be seen in particular from FIG. 2, the hydrogenation process carried out with the system 1 makes it possible to reduce the system output by specifically adjusting the input degree of hydrogenation, which has been measured in particular by means of the sensor device 19, by increasing the input degree of hydrogenation. For example, for the characteristic curve of a constant educt mass flow (mEduct, abs = 100%), a reduction of the system output from 100%, which corresponds to the normal operating point (BPNormai), to a partial load range and in particular to a Reduce stand-by area (BPstand-By) with a system output of 0%. In this case, the initial degree of hydrogenation is approximately 100%.

In Fig. 2, HG _per d of 99% and 95% are marked for the different degrees of hydrogenation of the product stream. The product stream after the hydrogenation reactor 2 therefore includes in particular LOHC-H.

In particular, Appendix 1 makes it possible to define a new operating point BPoptioni, at which there is a higher educt mass flow mEduct,abs = 150% and an input degree of hydrogenation of 40%. This new design operating point BPoptioni is marked in Fig. 5. This design therefore presupposes that hydrogen carrier medium with an initial degree of hydrogenation of 40% is already provided at the normal operating point, i.e. represents a mixture of LOHC-D and LOHC-H, i.e. LOHC-X. However, the design of system 1 is chosen such that the relative system output P _rei is unchanged compared to the initial normal operating point BPNormai. Since the mass flow remains essentially constant during power control. The changed operating point moves on the now steeper characteristic curve for mEduct,abs = 150%. Because the changed operating point BPoptioni is shifted towards higher hydrogenation levels, peak loads can be covered more easily by lowering the input hydrogenation level. Accordingly, partial load conditions can also be achieved here by further increasing the degree of hydrogenation, i.e. adding additional LOHC-H.

Fig. 6 shows a standardized profile of hydrogen gas production using electrical power, which is provided by the power generation unit 6 in the form of a photovoltaic system. Based on the time of day, there is a peak performance in the early afternoon. Based on this volatile hydrogen gas source, various operating modes of a hydrogenation system are explained below with reference to FIGS. 7 and 8. According to a first operating mode, the system is operated with constant power. The corresponding constant operation curve is labeled KB in Figures 7 and 8.

A second operating mode takes into account power control in a power range of 40% to 120%, i.e. with partial load and peak load ranges. The power is controlled via an adjustment of the mass flow. The corresponding graphs are labeled MS in Figures 7 and 8.

A third mode of operation corresponds to the hydrogenation process according to the invention, i.e. a dynamic power control in a power range from 0% to 145%, with a changed normal operating point corresponding to FIG. 5 being defined at an input hydrogenation level of 40% and the power control taking place by adjusting the input hydrogenation level. The corresponding graphs are labeled HG in Figures 7 and 8.

One finding is that constant operation (KB) cannot begin to reflect the volatile hydrogen gas source in terms of hydrogenation performance and this results in a large buffer storage requirement (see Fig. 8). The process of power control via the educt mass flow (MS) has been improved compared to constant operation (KB), but still has deficits. In contrast, the method according to the invention shows that the volatile profile of hydrogen gas production by means of the photovoltaic system can be ideally mapped due to the highly dynamic control and the buffer storage requirement is minimized and in particular is 0.

A comparison of the characteristics is summarized in Table 1.

The various systems differ in their basic design, i.e. their nominal load based on the peak performance of the electrolyser 5. Since KB is operated constantly throughout the day, a significantly smaller design is possible compared to electrolyser 5 and is about 28%, but about 56% of the daily production of hydrogen gas must be temporarily stored in the hydrogen gas buffer storage 4. A large hydrogen gas buffer storage 4 is expensive and disadvantageous.

In the MS system, which is more flexible in terms of load and therefore reduces the need for buffer storage, it requires an overall larger system of 42% based on the electrolyser 5.

As already indicated, due to the high dynamics of the HG system, no hydrogen gas buffer storage is required, or at least a minimal size. In particular, the system enables peak loads of up to 145% to be represented. Based on the daily balance, the system utilization is minimal compared to the two systems mentioned above and is less than half compared to the system in constant operation.

The method according to the invention enables, in particular, a continuous reduction in power towards partial load conditions and in particular towards 0% power. In the hydrogenation reaction, in order to reduce the power, the input degree of hydrogenation is increased, in particular continuously, i.e. in particular LOHC-H and/or LOHC-OX and/or LOHC-X are added, in the limit case completely hydrogenated LOHC. 0% power corresponds to a so-called hot standby state. In this hot standby state, the hydrogen carrier medium continues to flow through the hydrogenation reactor 2, but it does not produce any power or absorb any load, i.e. a hydrogenation reaction takes place. By changing the inlet degree of hydrogenation, i.e. by lowering the inlet degree of hydrogenation, the hydrogenation reactor can go back into operation directly.

A further exemplary embodiment of the invention will be described below with reference to FIGS. 3 and 4. Structurally identical parts have the same reference numbers as in the first exemplary embodiment, the description of which is hereby referred to. Parts that are structurally different but functionally similar receive the same reference numerals with an a after them.

In plant la, the reactor 2a is a dehydrogenation reactor. Accordingly, at least partially loaded hydrogen carrier medium LOHC-X and/or LOHC-H is stored in the first educt storage container 7. In the dehydrogenation reactor 2a, hydrogen gas is released from the hydrogen carrier medium, which can be removed from the dehydrogenation reactor 2a by means of a hydrogen gas discharge line 20 and temporarily stored in an optional hydrogen gas buffer storage 4 before the hydrogen gas is provided to a hydrogen gas consumer 21. The hydrogen gas consumer 21 is in particular a power generation unit and in particular a fuel cell. The hydrogen gas consumer 21 can be a stationary system. However, it is also fundamentally conceivable that the hydrogen gas consumer 21 is a mobile unit, for example in a motor vehicle. In particular, the hydrogen gas consumer 21 is a hydrogen gas interface, such as at a hydrogen gas filling station. Hydrogen gas is made available to a consumer, in particular to a hydrogen gas tank in a vehicle, via the hydrogen gas interface. The removal of hydrogen gas via the hydrogen gas interface is particularly volatile, so that power control of the dehydrogenation reaction in the dehydrogenation reactor 2a is required. The control unit 17 is used for this purpose.

In principle, it is conceivable that the hydrogen gas is removed from the dehydrogenation reactor 2a together with the at least partially dehydrogenated hydrogen carrier medium via a common discharge line and the two material streams are separated from one another in a separation unit.

The product buffer container 12 is connected to the product storage container 13 with the liquid line 8 in the manner described.

The system la also has a separation unit 25, which is arranged downstream of the dehydrogenation reactor 2a. The separation unit 25 can be arranged upstream and/or downstream of the product buffer container 12 and in particular along the return line 14.

The mixing unit 9, the dehydrogenation reactor 2a and the product buffer container 12 form a dehydrogenation module 22. The dehydrogenation module 22 can also include the separation unit 25. The dehydrogenation process works analogously to the hydrogenation process. In particular, the power control in the dehydrogenation reactor 2a takes place based on the adjustment of the input degree of hydrogenation. In particular, it can be seen that a reduction in system performance towards partial load ranges is possible by reducing the initial degree of hydrogenation of the hydrogen carrier medium, especially with a constant educt mass flow. The reduction in the initial degree of hydrogenation can be achieved in particular by adding at least partially dehydrogenated hydrogen carrier medium LOHC-X or LOHC-D. This can be done either via the return from the product buffer container 12 via the return line 14 and / or via the second educt storage container 16 by storing appropriate material.

With regard to the hot standby state already described, this is achieved in the dehydrogenation process by supplying increasingly more dehydrogenated hydrogen carrier material and in particular completely dehydrogenated hydrogen carrier material LOHC-D.

In order to put the dehydrogenation reactor 2a back into operation, it is necessary to increase the input degree of hydrogenation again. In addition, the dehydrogenation reactor 2a must be heated. Unlike hydrogenation processes, the dehydrogenation process requires heating, so that the dehydrogenation reactor 2a must be kept at the temperature in hot standby mode while absorbing heat. This means that the heating of the dehydrogenation reactor by means of a heating unit 23, which provides a heat flow Q from the heating unit 23 to the dehydrogenation reactor 2a, must be regulated separately by means of the control unit 17. The control unit 17 is in, in particular bidirectional, signal connection with the heating unit 23.

If no hydrogen gas requirement is reported by the hydrogen gas consumer 21 or the corresponding hydrogen gas interface, the dehydrogenation reactor 2a can be operated in the hot standby mode or in a so-called self-sustaining mode by releasing a minimum amount of hydrogen gas to the dehydrogenation reactor 2a to maintain a minimum operating temperature. In particular, the minimum amount of hydrogen gas released can be used exclusively to heat the dehydrogenation reactor 2a. In this case, the heating unit 23 is designed as a hydrogen gas burner and/or as a fuel cell, with in particular a branch of the hydrogen gas discharge line 20 being connected directly to the heating unit 23. A new change to a load state of the dehydrogenation reactor 2a, i.e. a hydrogen gas requirement in the hydrogen gas consumer 21, could be realized faster and faster and therefore more dynamically from the hot standby operation.

A further exemplary embodiment of the invention will be described below with reference to FIG. 9. Structurally identical parts receive the same reference numbers as in the previous exemplary embodiments, the description of which is hereby referred to. Structurally different and functionally similar parts receive the same reference numbers with a suffix b.

The system 1b includes a hydrogenation reactor 2 and essentially corresponds to the first exemplary embodiment. A difference compared to the first exemplary embodiment is that the hydrogenation module 15 additionally has a heat exchanger 24, which is used to preheat the educt. The heat exchanger 24 is arranged in particular upstream of the mixing unit 9. In particular, the heat exchanger is designed as a liquid-liquid heat exchanger. The comparatively warm hydrogen carrier medium LOHC-H, i.e. the product, which is at least partially hydrogenated in the hydrogenation reactor 2, serves to preheat the product, i.e. the at least partially dehydrogenated hydrogen carrier medium, in particular LOHC-D, LOHC-V or LOHC-X. Accordingly, the return line 14 is connected to both the mixing unit 9 and the heat exchanger 24. The product that is at least partially cooled in the heat exchanger 24 is fed from the heat exchanger 24 via a liquid line 8 to the product storage container 13.

This also results in advantages in terms of storing the cooled product.

A further exemplary embodiment of the invention will be described below with reference to FIG. 10. Structurally identical parts receive the same reference numbers as in the previous exemplary embodiments, the description of which is hereby referred to. Telephones that are structurally different but functionally similar receive the same reference numerals with a c after them. The system 1c includes the dehydrogenation reactor 2a and the heat exchanger 24, which, as in the previous exemplary embodiment, serves to preheat the educt stream from the first educt storage container 7.

It was surprisingly found that the heat exchanger 24 in this exemplary embodiment has the additional function of a separation unit. The material stream discharged from the dehydrogenation reactor 2a and returned via the return line 14 includes, on the one hand, the product, i.e. LOHC-D, and the released hydrogen gas, both of which are in particular present as vapor or in the gas phase. This hot mixture of LOHC-D and hydrogen gas can be fed to the mixing unit 9, whereby the mixer 9 could function as a washing unit and as a preheater. For example, the mixture of LOHC-D vapor and hydrogen gas could be introduced into fresh LOHC-H, i.e. starting material, using a distribution plate. Since LOHC-H has a comparatively lower temperature, the mixture of LOHC-D and hydrogen gas would cool and, in particular, LOHC-D would condense. Both the sensible heat generated by steam cooling and the enthalpy of condensation could be used to preheat the LOHC-H. The cooled hydrogen gas could be specifically discharged at the top of the mixing unit 9. The mixture of LOHC-D and LOHC-H, i.e. LOHC-X, could be fed to the dehydrogenation reactor 2a. Additionally or alternatively, the hot mixture of LOHC-D and hydrogen gas can be supplied to the heat exchanger 24, whereby condensation of the product, i.e. LOHC-D, can also take place in the heat exchanger.

Claims

Patent claims

1. Hydrogenation process for a hydrogen carrier medium comprising the process steps

Feeding the hydrogen carrier medium into a hydrogenation reactor (2), the supplied hydrogen carrier medium being at least partially discharged and having an initial degree of hydrogenation,

Supplying hydrogen into the hydrogenation reactor (2), catalytically hydrogenating the hydrogen carrier medium in the hydrogenation reactor (2), so that the hydrogen carrier medium has an initial degree of hydrogenation that is greater than the initial degree of hydrogenation,

Controlling the hydrogenation reaction by adjusting the input hydrogenation level.

2. Hydrogenation process according to claim 1, characterized in that the adjustment of the input degree of hydrogenation is carried out by returning hydrogenated hydrogen carrier medium with the initial degree of hydrogenation into the hydrogenation reactor (2).

3. Hydrogenation process according to one of the preceding claims, characterized in that the adjustment of the input degree of hydrogenation is carried out by supplying further hydrogen carrier medium into the hydrogenation reactor (2), the further hydrogen carrier medium having a further degree of hydrogenation which is different from the input degree of hydrogenation.

4. Hydrogenation process according to claim 2 or 3, characterized in that the hydrogen carrier medium is mixed with the recycled hydrogen carrier medium and / or with the further hydrogen carrier medium in a mixing unit (9) before being fed into the hydrogenation reactor (2).

5. Hydrogenation process according to one of claims 2 to 4, characterized by operating the process in an operating point (BP option i) with a higher absolute educt mass flow mEduct, abs and / or with an increased input degree of hydrogenation, where mEduct, abs > 100%, in particular mEduct, abs > 150%, and in particular the initial degree of hydrogenation is at least 20% and in particular at least 40%.

6. Hydrogenation process according to one of the preceding claims, characterized in that the mass flow of the hydrogen carrier medium fed into the hydrogenation reactor (2) is constant.

7. Hydrogenation process according to one of the preceding claims, characterized by preheating the hydrogen carrier medium, in particular in a heat exchanger (24) connected upstream of the hydrogenation reactor (2) and in particular the mixing unit (9), the preheating taking place in particular by means of the recycled hydrogen carrier medium.

8. Hydrogenation process according to one of the preceding claims, characterized in that the, in particular dynamically changing, amount of hydrogen supplied into the hydrogenation reactor (2) is taken into account as an input variable for regulating the hydrogenation reaction.

9. Dehydrogenation process for a hydrogen carrier medium comprising the process steps

Feeding the hydrogen carrier medium into a dehydrogenation reactor (2a), the supplied hydrogen carrier medium being at least partially loaded and having an initial degree of hydrogenation, catalytic dehydrogenation of the hydrogen carrier medium in the dehydrogenation reactor (2a), so that hydrogen gas is released from the hydrogen carrier medium and the hydrogen carrier medium has an initial degree of hydrogenation, which is smaller than the input degree of hydrogenation, removing the released hydrogen gas from the dehydrogenation reactor (2a), regulating the dehydrogenation reaction by adjusting the input degree of hydrogenation.

10. Dehydrogenation process according to claim 9, characterized in that the adjustment of the input degree of hydrogenation is carried out by returning dehydrogenated hydrogen carrier medium with the initial degree of hydrogenation into the dehydrogenation reactor (2a).

11. Dehydrogenation process according to claim 9 or 10, characterized in that adjusting the initial degree of hydrogenation by supplying further hydrogen carrier medium the dehydrogenation reactor (2a), the further hydrogen carrier medium having a further degree of hydrogenation which is different from the initial degree of hydrogenation.

12. Dehydrogenation process according to claim 10 or 11, characterized in that the hydrogen carrier medium is mixed with the recycled hydrogen carrier medium and / or with the further hydrogen carrier medium in a mixing unit (9) before being fed into the dehydrogenation reactor (2a).

13. Dehydrogenation process according to one of claims 9 to 12, characterized by operating the process in an operating point (BP option i) with a higher absolute educt mass flow mEduct, abs and / or with an increased input degree of hydrogenation, where mEduct, abs > 100%, in particular mEduct, abs > 150%, and in particular the initial degree of hydrogenation is at most 80% and in particular at most 60%.

14. Dehydrogenation process according to one of claims 9 to 13, characterized in that the mass flow of the hydrogen carrier medium fed into the dehydrogenation reactor (2a) is constant.

15. Dehydrogenation process according to one of claims 9 to 14, characterized by preheating the hydrogen carrier medium, in particular in a heat exchanger (24) connected upstream of the dehydrogenation reactor (2a) and in particular the mixing unit (9), the preheating taking place in particular by means of the recycled hydrogen carrier medium.

16. System for carrying out a method according to one of the preceding claims, wherein the system comprises a. a reactor (2; 2a) for the catalytic hydrogenation and/or for the catalytic dehydrogenation of hydrogen carrier medium which has an initial degree of hydrogenation, b. at least one conveying means (10) for conveying the hydrogen carrier medium into the reactor (2; 2a), c. a control unit (17) which is in signal connection (18) with the at least one conveying means (10) and is designed to carry out catalytic hydrogenation and/or for to regulate catalytic dehydrogenation in the reactor (2; 2a) by adjusting the input degree of hydrogenation of the hydrogen carrier medium. Plant according to claim 16, characterized by a return line (14) for returning hydrogen carrier medium into the reactor (2; 2a). Plant according to claim 16 or 17, characterized by an additional storage container (16) in which further hydrogen carrier medium is stored, which has a different degree of hydrogenation from the initial degree of hydrogenation. Plant according to claim 17 or 18, characterized by a mixing unit (9) for mixing the hydrogen carrier medium with the recycled hydrogen carrier medium and/or with the further hydrogen carrier medium. Plant according to one of claims 17 to 19, characterized by a heat exchanger (24) for preheating the hydrogen carrier medium to be supplied to the reactor (2; 2a), the heat exchanger (24) being arranged in particular upstream of the mixing unit (9), and in particular the return line (14) connects the reactor (2; 2a) to the heat exchanger (24), in particular directly.