Method for producing a stream comprising dihydrogen from a liquid organic hydrogen carrier
The method addresses the high energy consumption of LOHC dehydrogenation by using endothermic reactions and purification steps to produce a high-purity hydrogen stream, achieving decarbonized hydrogen production with reduced energy costs and emissions.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- TECHNIP ENERGIES FRANCE SAS
- Filing Date
- 2025-11-28
- Publication Date
- 2026-06-11
AI Technical Summary
The existing methods for producing hydrogen using liquid organic hydrogen carriers (LOHC) consume significant amounts of non-decarbonized energy due to the energy-intensive dehydrogenation reaction, leading to high carbon footprints and inefficiencies.
A method involving an endothermic dehydrogenation reaction followed by purification steps, including pressure swing adsorption and expansion turbine use, to produce a hydrogen stream with a molar percentage greater than 95%, utilizing thermal energy from the dehydrogenation process and minimizing non-decarbonized energy consumption.
This method achieves a partially decarbonized hydrogen production process by self-consumption of hydrogen, reducing energy costs and carbon emissions while maintaining flexibility in hydrogen provision.
Smart Images
Figure EP2025084696_11062026_PF_FP_ABST
Abstract
Description
HYDRO030-WO-PCTDESCRIPTIONTITLE: METHOD FOR PRODUCING A STREAM COMPRISING DIHYDROGEN FROM A LIQUID ORGANIC HYDROGEN CARRIER
[0001] The present invention relates to a method for producing a stream comprising hydrogen at a molar percentage greater than 95% from an incoming stream comprising a liquid organic hydrogen carrier having at least two possible states: a hydrogen-lean state and a hydrogen-rich state, the transition from the hydrogen-rich state to the hydrogen-lean state being achieved by means of an endothermic dehydrogenation reaction.
[0002] The invention also relates to a plant for producing such a stream comprising hydrogen.
[0003] In the field of hydrogen production, especially as an energy carrier, there are numerous methods, including methods based on methane reforming and water electrolysis. The hydrogen thus produced may need to be stored for a longer or shorter time before use and / or to be transported over a longer or shorter distance from the production site to the site of use.
[0004] To enable the hydrogen to be stored and / or transported, in particular safely, methods have been developed in which a Liquid Organic Hydrogen Carrier (LOHC) is used. The liquid organic hydrogen carrier has at least two states: a hydrogen-rich state in which it stores hydrogen and a hydrogen-lean state. The transition from the hydrogen-rich state to the hydrogen-lean state is achieved by a dehydrogenation reaction that allows the hydrogen of interest to be recovered at the desired time and / or place. The liquid organic hydrogen carrier is generally especially selected for its hydrogen storage density, but also according to the chemical risk associated with this liquid in the hydrogen-rich and / or hydrogen-lean state, or the amount of energy required for the dehydrogenation reaction, or its availability, its cost, and the carbon footprint of its production.HYDRO030-WO-PCT
[0005] However, the liquid organic hydrogen carrier dehydrogenation reaction is a reaction that requires an input of thermal energy. Involving a liquid organic hydrogen carrier in a method for producing a stream comprising hydrogen therefore implies a significant consumption of energy, and in particular of nondecarbonized energy. It is desirable to limit this over-consumption of energy, and more particularly the over-consumption of non-decarbonized energy.
[0006] One aim of the invention is therefore to propose a method for producing a stream comprising hydrogen that is more decarbonized.
[0007] To this end, the invention relates to a method for producing a stream of hydrogen at a molar percentage greater than 95% for a user from an incoming stream comprising a liquid organic hydrogen carrier having at least two possible states: a hydrogen-lean state and a hydrogen-rich state, the transition from the hydrogen-rich state to the hydrogen-lean state being achieved by means of an endothermic dehydrogenation reaction, the method comprising the following steps:- dehydrogenating the incoming stream in the hydrogen-rich state using a first stream of thermal energy, to obtain a second stream comprising hydrogen and liquid organic hydrogen carrier in the hydrogen-lean state;- a first purification of the second stream using a third stream of mechanical and / or electrical energy to obtain a fourth stream comprising liquid organic hydrogen carrier in the hydrogen-lean state and to obtain a fifth stream comprising hydrogen at a molar percentage greater than that of the second stream;- a second purification of the fifth stream in a pressure swing adsorption unit to obtain a sixth stream comprising hydrogen at a molar percentage greater than that of the fifth stream and to obtain a purge stream comprising liquid organic hydrogen carrier in the hydrogen-lean state and hydrogen;- expanding a first fraction of the sixth stream in an expansion turbine to obtain a seventh stream of mechanical energy and an eighth stream comprisingHYDRO030-WO-PCT hydrogen colder than the sixth stream, a second fraction of the sixth stream being said stream produced for the user;- transferring heat from the purge stream to the eighth stream to obtain a cooled purge stream and to obtain a heated eighth stream;- separating the cooled purge stream to obtain a ninth stream comprising hydrogen and to obtain a tenth stream comprising liquid organic hydrogen carrier in the hydrogen-lean state at a molar percentage greater than that of the purge stream; and- combusting at least a fraction of the heated eighth stream and optionally of the ninth stream to produce an eleventh stream of thermal energy, at least a fraction of which is used to form at least a fraction of the first stream.
[0008] This method uses a liquid organic hydrogen carrier, which makes it possible to manage both the site at which the hydrogen is provided to its user and the time of this provision, with respect to the time and place of availability of a stream of hydrogen source molecules.
[0009] In this method, the dehydrogenation step is the most energy-intensive step of the method. At least part of the first stream of thermal energy required for the dehydrogenation reaction is obtained by combusting at least part of the heated eighth stream.
[0010] The heated eighth stream is formed by heating the eighth stream, itself generated in the expansion turbine by expanding a fraction of the sixth stream.
[0011] The sixth stream comprises hydrogen at a molar percentage that is sufficient for the user and is available locally and at the desired time. Using the first fraction of the sixth stream in subsequent steps of the method avoids the need for a non-decarbonized energy source and, as a result, reduces the proportion of non-decarbonized energy in the thermal energy required for the hydrogenation step.HYDRO030-WO-PCT
[0012] The method makes it possible, while benefiting from the flexibility offered by the use of a liquid organic hydrogen carrier in terms of the site and date of hydrogen production, to obtain a stream of at least partially decarbonized hydrogen.
[0013] In other words, this method makes it possible, by self-consumption of hydrogen, to provide at least part of the energy required for the dehydrogenation step, which consumes mainly heat.
[0014] The method also minimizes LOHC losses throughout the method, and thus minimizes the costs of LOHC transport and continuous replacement, as well as the carbon footprint associated with this replacement. The method also limits the emissions that would result from excessive combustion of lost LOHC.
[0015] According to particular embodiments, the method comprises one or more of the following features, taken alone or in any technically possible combination:- at least a fraction of the third stream is obtained from the seventh stream and / or from the eleventh stream;- the method comprises producing a stream of electrical energy from a fraction of said heated eighth stream;- the entire first stream is obtained from the eleventh stream;- the entire third stream is obtained from the seventh stream and optionally from the eleventh stream;- the liquid organic hydrogen carrier is selected from toluene, benzyltoluene, dibenzyltoluene, n-ethylcarbazole, n-isopropylcarbazole, n-butylcarbazole, 1 ,2-dihydro-1 ,2-azaborine, formic acid, methanol, ethanol, propanol, butanol, potassium formate, naphthalene, 1 ,4-butanediol, 1 ,4- or 1 ,5-pentanediol, ethylene glycol or mixtures thereof;- the method further comprises the following steps: o producing an initial stream comprising hydrogen; andHYDRO030-WO-PCT o hydrogenating a stream of liquid organic hydrogen carrier in the hydrogen- lean state by the initial stream to produce the incoming stream;- the method further comprises at least one of the following steps: o transporting the liquid organic hydrogen carrier in the hydrogen-rich state between the hydrogenation and the dehydrogenation; o storing the hydrogen-rich liquid organic hydrogen carrier between the hydrogenation and the dehydrogenation; and- at least part of the stream of liquid organic hydrogen carrier in the hydrogen- lean state for hydrogenation comes from the first purification and / or from the separation.
[0016] The invention also relates to a plant for producing a stream comprising hydrogen at a molar percentage greater than 95% for a user from an incoming stream comprising a liquid organic hydrogen carrier having two states: a hydrogen-lean state and a hydrogen-rich state, the transition from the hydrogen-rich state to the hydrogen-lean state being achieved by means of an endothermic dehydrogenation reaction, the plant comprising:- a reactive section configured to receive the incoming stream in the hydrogen-rich state and a first stream of thermal energy, and to produce a second stream comprising hydrogen and liquid organic hydrogen carrier in the hydrogen-lean state;- a first purification unit configured to receive the second stream and a third stream of mechanical and / or electrical energy and to produce a fourth stream comprising liquid organic hydrogen carrier in the hydrogen-lean state and to produce a fifth stream comprising hydrogen at a molar percentage greater than that of the second stream;- a pressure swing adsorption unit configured to receive the fifth stream and to produce a sixth stream comprising hydrogen at a molar percentage greaterHYDRO030-WO-PCT than that of the fifth stream, and to produce a purge stream comprising liquid organic hydrogen carrier in the hydrogen-lean state and hydrogen;- an expansion turbine configured to produce a seventh stream of mechanical energy and an eighth stream comprising hydrogen colder than the sixth stream from a first fraction of the sixth stream, a second fraction of the sixth stream being the stream produced for the user;- a heat-exchange unit configured to receive the eighth stream and the purge stream and to provide a cooled purge stream and a heated eighth stream;- a separation unit configured to receive the cooled purge stream and to provide a ninth stream comprising hydrogen and to provide a tenth stream comprising liquid organic hydrogen carrier in the hydrogen-lean state at a molar percentage greater than that of the purge stream;- a thermal energy production unit, configured to produce, by combustion of at least a fraction of the heated eighth stream and optionally of the ninth stream, an eleventh stream of thermal energy; the production plant being further configured to form at least one fraction of the first stream from at least a fraction of the eleventh stream.
[0017] The invention will be better understood upon reading the following disclosure, given solely by way of non-limiting example, and made in reference to the drawings, wherein:[Fig. 1 ] Figure 1 is a schematic depiction of a plant according to the invention, and [Fig. 2] Figure 2 is a schematic depiction of part of the plant depicted in figure 1 .
[0018] Referring to figure 1 , a plant 1 is described for producing a stream 2 comprising hydrogen from a stream comprising a chemical species that is a source of hydrogen atoms, using a liquid organic hydrogen carrier, designated by the abbreviation LOHC in the subsequent description.
[0019] In the example, the plant 1 comprises a unit 3 for producing an initial stream 5 comprising hydrogen from a source stream 7 of material comprisingHYDRO030-WO-PCT a chemical species that is a source of hydrogen atoms and a stream 9 that is an energy source.
[0020] The plant 1 of the example comprises a hydrogenation unit 11 which is configured to receive the initial stream s and a hydrogen-lean stream 13 comprising LOHC in the hydrogen-lean state, and to produce an intermediate stream 15 comprising LOHC in the hydrogen-rich state.
[0021] The plant 1 of the example further comprises a transport unit 17 for transporting the intermediate stream 15.
[0022] Finally, the plant 1 comprises a production plant 19 configured to produce the stream 2 comprising hydrogen from an incoming stream 21 comprising LOHC in the hydrogen-rich state. This incoming stream 21 is, in the example, formed from the intermediate stream 15 transported by the transport unit 17.
[0023] The transport unit 17 comprises means suitable for transporting the intermediate stream 15 from the hydrogenation unit 11 to the production facility 19, especially safely.
[0024] In the example, the transport means are stationary. For example, the transport means comprise one or more pipes configured to receive the intermediate stream 15.
[0025] Alternatively, the transport means are movable. These include, for example, dedicated ships. In this case, the plant 1 can be seen as the grouping of two plants 1a and 1 b that are at a distance from one another. The first plant 1 a comprises the production unit 3 and the hydrogenation unit 11 , and the second plant 1 b comprises the production plant 19.
[0026] The transport means are then suitable for transporting the intermediate stream 15 from the first plant 1a to the second plant 1 b.HYDRO030-WO-PCT
[0027] The transport means are advantageously selected according to the locations of the hydrogenation unit 11 and the production plant 19. Especially, the means of transport are selected as a function of the location of the source of hydrogen atoms for the source stream 7 and / or the source of energy for the source stream 9 for the production unit 3, and / or an end user of the stream 2.
[0028] In one embodiment, the transport unit 17 comprises a storage vessel, not shown. The storage vessel is advantageously configured to enable storage of the intermediate stream 15, so as to enable dehydrogenation of the incoming stream 21 at a later date with respect to the production of the intermediate stream 15.
[0029] The production unit 3 is configured to receive the source stream 9 of energy and the source stream 7 of material, preferably water or methane, and to produce an initial stream 5 comprising hydrogen.
[0030] The production unit 3 comprises, in this example, a reformer 4, or equivalently a steam methane reforming unit.
[0031] In this case, the production unit 3 is advantageously coupled with a device configured to capture and sequester a stream comprising carbon dioxide, not shown in figure 1 , produced by the reformer 4.
[0032] Alternatively, the production unit 3 comprises an electrolysis unit.
[0033] The hydrogenation unit 11 is suitable for receiving the initial stream 5 and the hydrogen-lean stream 13 and for producing, by means of a hydrogenation reaction, the intermediate stream 15 which comprises LOHC in the hydrogen-rich state.HYDRO030-WO-PCT
[0034] For this purpose, the LOHC has at least two possible states: a hydrogen-lean state and a hydrogen-rich state, the transition from the hydrogen-lean (or hydrogen-rich) state to the hydrogen-rich (or hydrogen-lean) state being achieved by an exothermic hydrogenation (or endothermic dehydrogenation) reaction.
[0035] In particular, the LOHC enables the hydrogen to be stored and / or transported.
[0036] The LOHC can be selected according to one or more criteria selected from among its hydrogen storage density, the low chemical risk associated with the molecule in the hydrogen-lean and / or hydrogen-rich state, the enthalpy of the dehydrogenation reaction, the availability of the molecule, especially at low cost and / or with a limited carbon footprint.
[0037] Advantageously, the LOHC in the hydrogen-lean state is selected from toluene, benzyltoluene, dibenzyltoluene, n-ethylcarbazole, n- isopropylcarbazole, n-butylcarbazole, 1 ,2-dihydro-1 ,2-azaborine, formic acid, methanol, ethanol, propanol, butanol, potassium formate, naphthalene, 1 ,4 butanediol, 1 ,4- or 1 ,5-pentanediol, ethylene glycol or mixtures thereof.
[0038] Preferably, the LOHC in the hydrogen-lean state is selected from toluene, benzyltoluene or a mixture of methanol and ethylene glycol.
[0039] Advantageously, the LOHC is selected so that the enthalpy of the dehydrogenation reaction is less than 70 kJ / molH2, especially less than 45 kJ / molH2.
[0040] Advantageously, the LOHC is selected so that its hydrogen transport density is greater than 3%, or even greater than 6%, by mass of hydrogen relative to the mass of hydrogen-lean LOHC.HYDRO030-WO-PCT
[0041] In the example, the production plant 19 is configured to receive the incoming stream 21 , which is the intermediate stream 15, after it has been transported by the transport unit 17.
[0042] The production plant 19 of figure 2 is configured to receive the incoming stream 21 comprising LOHC in the hydrogen-rich state and to produce the stream 2 comprising hydrogen at a molar percentage greater than 95%, advantageously greater than 98%, advantageously greater than 99.97%, in particular for use in fuel cells.
[0043] To this end, the production plant 19 includes a reactive section 25, capable of receiving the incoming stream 21 and of producing a second stream 27 comprising hydrogen and LOHC in the hydrogen-lean state.
[0044] The production plant 19 comprises a first purification unit 29 suitable for receiving the second stream 27 and for producing a fifth stream 31 comprising hydrogen.
[0045] The production plant 19 contains a pressure swing adsorption (PSA) unit 33 capable of receiving the fifth stream 31 and of producing a sixth stream 35 comprising hydrogen.
[0046] The production plant 19 comprises an expansion turbine 37 capable of receiving a first fraction 39 of the sixth stream 35 and of forming an eighth stream 41 comprising hydrogen.
[0047] The production plant 19 comprises a heat-exchange unit 43, which is configured to receive the eighth stream 41 , to produce a heated ninth stream 45, and to send the latter to a thermal energy production unit 47 of the production plant 19.HYDRO030-WO-PCT
[0048] The production plant 19 comprises a separation unit 49 suitable for receiving a purge stream 50.
[0049] The reactive section 25 is configured to receive the incoming stream 21 and a first stream 51 of thermal energy, and to produce the second stream 27 comprising hydrogen and LOHC in the hydrogen-lean state by means of an endothermic dehydrogenation reaction.
[0050] The reactive section 25 comprises, for example, one or more catalytic reactors.
[0051] The first purification unit 29 is configured to receive the second stream 27 as well as a third stream 53 of mechanical and / or electrical energy, to produce at least a fourth stream 55 comprising LOHC in the hydrogen-lean state, and to produce the fifth stream 31 comprising hydrogen at a molar percentage greater than that of the second stream 27.
[0052] The elements making up the first purification unit 29 are advantageously selected and sized according to the composition and pressure of the second stream 27 and the pressure required for the fifth stream 31 .
[0053] The first purification unit 29 advantageously makes it possible to recover the vast majority of the hydrogen-lean LOHC from the stream 27.
[0054] The second stream 27 has a pressure preferably greater than 5 bar absolute so as to minimize the compression power required in stages 63a to 63n.
[0055] To this end, the first purification unit 29 comprises in the example at least one first separation vessel 57.
[0056] The first vessel 57 is advantageously preceded by a first heat exchanger 59.HYDRO030-WO-PCT
[0057] Alternatively, the first purification unit 29 comprises one or more additional compression stages 63a, ..., 63n downstream of the first vessel 57.
[0058] In the example, only the two end additional compression stages 63a and 63n are depicted.
[0059] Each of the additional compression stages 63a, ..., 63n, not shown in detail, comprises a compressor, a compressor outlet exchanger and a separation vessel. The compression stages are configured to reach the setpoint pressure at the outlet of the unit 29, which is defined by the needs of the unit 33 in order to allow proper purification. This pressure is advantageously greater than 10 bar.
[0060] In addition, each compression stage makes it possible to produce a stream comprising hydrogen in a higher proportion than a stream entering that stage.
[0061] The PSA unit 33 is configured to receive the fifth stream 31 , to produce the sixth stream 35 comprising hydrogen at a molar percentage greater than that of the fifth stream 31 and to produce the purge stream 50 comprising LOHC in the hydrogen-lean state and hydrogen, as well as optionally traces of hydrogen-rich LOHC not converted in the reactive section 25.
[0062] The PSA unit 33, for example, comprises an adsorbent material which can be specifically defined according to the impurities specific to each LOHC and which is particularly suitable for adsorbing hydrogen-rich and hydrogen- lean LOHC molecules. Typically, in hydrogen PSAs, the materials used are activated alumina, silica gel, activated carbon and molecular sieves.
[0063] The expansion turbine 37 is configured to receive the first fraction 39 of the sixth stream 35, a second fraction 67 of the sixth stream 35 being theHYDRO030-WO-PCT stream 2 provided to the user, and to produce a seventh stream 69 of mechanical energy, by expanding the first fraction 39 of the sixth stream 35.
[0064] The heat-exchange unit 43 is configured to receive the eighth stream 41 and the purge stream 50 and to provide a cooled purge stream 71 and a heated eighth stream 45.
[0065] To this end, the heat-exchange unit 43 comprises in the example a second heat exchanger 73 in which the eighth stream 41 and the purge stream 50 are placed in thermal contact.
[0066] Note that the expansion turbine 37 in combination with the heat exchanger 43 avoids the need to resort to a complete refrigeration cycle comprising compressors, multiple exchangers, and a dedicated cryogenic fluid.
[0067] The separation unit 49 is configured to receive the cooled purge stream 71 and to provide a ninth stream 75 comprising hydrogen and to provide a tenth stream 77 comprising LOHC in the hydrogen-lean state as well as any traces of hydrogen-rich LOHC not converted in the reactive section 25 at a molar percentage greater than that of the purge stream 50.
[0068] The separation unit 49 comprises a second separation vessel 79, configured to form the ninth stream 75 at the top and the tenth stream 77 at the bottom.
[0069] The thermal energy production unit 47 is configured to produce, by combustion of at least a fraction of the heated eighth stream 45 and optionally of the ninth stream 75, an eleventh stream 81 of thermal energy.
[0070] To this end, the thermal energy production unit 47 comprises, for example, a boiler suitable for the combustion of hydrogen, as well as a deviceHYDRO030-WO-PCT for the direct or indirect transfer of at least part of the eleventh stream 81 to the reactive section 25, for example a steam network.
[0071] The operation of the production plant 19 will now be described with reference to figure 2, exemplifying a production method according to the invention.
[0072] The aim of the production method according to the invention is to obtain the stream 2 comprising hydrogen at a molar percentage greater than 95%, advantageously greater than 98%, advantageously greater than 99.97% or even than 99.99%, by means of the liquid organic hydrogen carrier.
[0073] To this end, the method comprises a step of dehydrogenating the incoming stream 21 comprising LOHC in the hydrogen-rich state in the reactive section 25, by means of the first stream 51 of thermal energy, to form the second stream 27, which comprises hydrogen and LOHC in the hydrogen-lean state.
[0074] The working pressure and / or temperature for dehydrogenation are advantageously selected according to the nature of the LOHC.
[0075] The working pressure in the reactive section 25 is advantageously between 1 and 30 bar, advantageously between 1 and 10 bar.
[0076] The working temperature in the reactive section 25 is advantageously between 100°C and 350°C, or even between 150°C and 300°C.
[0077] In the example, the second stream 27 is then provided to the first purification unit 29, wherein it is cooled in the first heat exchanger 59 by thermal contact with a cooling fluid 82, for example water or air.
[0078] This optional cooling enables the second stream 27, which is relatively hot after dehydrogenation, to reach a suitable temperature, for example 15°CHYDRO030-WO-PCT to 40°C depending on the region and the available cooling sources, for a first separation step.
[0079] To carry out the first separation, the first purification unit 29 optionally receives, in addition to the second stream 27, a fraction of the third energy stream 53, which is at least partially decarbonized, advantageously totally decarbonized.
[0080] In the example, the first separation comprises a separation in the first separation vessel 57. At the bottom of the first separation vessel 57, a stream 84 that is richer in LOHC than the second stream 27 is collected. At the top of the first separation vessel 57, a stream 86 that is richer in hydrogen than the second stream 27 is collected, from which the fifth stream 31 is formed.
[0081] Optionally, as shown in figure 2, the stream 86 collected at the top of the first separation vessel 57 passes through the additional compression stages 63a, ..., 63n, in each of which it undergoes, for example consecutively and in this order, compression by means of the additional compressor, cooling in the additional heat exchanger, and an additional separation step by means of the additional separation vessel.
[0082] At the bottom of each additional separation vessel, a stream 83a, ..., 83n that is richer in LOHC than the stream entering the separation stage is collected. At the top of each additional separation vessel, a stream that is richer in hydrogen than the stream entering the separation stage is collected.
[0083] The molar percentages of LOHC of the streams 83a, ..., 83n collected at the bottom of the consecutive additional separation vessels are greater than that of the second stream.HYDRO030-WO-PCT
[0084] All or part of the streams 83a, 83n collected at the bottom of the separation vessels of the first purification unit 29 form the fourth stream 55, with a higher molar proportion of LOHC than that of the second stream 27.
[0085] At least some, advantageously all, of the streams 83a, ... , 83n collected at the bottom of the additional separation vessels form the fourth stream 55.
[0086] Advantageously, the fourth stream 55 has a molar percentage of liquid organic hydrogen carrier in the hydrogen-lean state greater than 95% and advantageously greater than 99%.
[0087] Advantageously, the fourth stream 55 has a molar percentage of hydrogen of less than 5% or even of less than 1 %.
[0088] The stream collected at the top of the last of the consecutive separation vessels of the first purification unit 29 forms the fifth stream 31 , with a higher molar proportion of hydrogen than that of the second stream 27.
[0089] The molar percentage of hydrogen in the fifth stream 31 is at least 95%, advantageously at least 99%.
[0090] The pressure of the fifth stream 31 is advantageously high enough for the operation of the PSA unit 33.
[0091] Advantageously, the absolute pressure of the fifth stream 31 is greater than 5 bar, or even greater than 10 bar.
[0092] The fifth stream 31 then undergoes a second purification in the PSA unit 33, so as to form a sixth stream 35 comprising hydrogen at a molar percentage greater than that of the fifth stream 31 , and a purge stream 50 comprising LOHC in the hydrogen-lean state, as well as optionally the hydrogen-rich LOHC not converted in the reactive section 25 and hydrogen.HYDRO030-WO-PCT
[0093] The working temperature in the PSA unit 33 is advantageously close to ambient temperature, typically 15 to 40°C depending on the location of the production plant 19.
[0094] The hydrogen content of the sixth stream 35 is equal to or greater than that required by the end user of the stream 2, so that the sixth stream 35 can be used beneficially.
[0095] The molar percentage of hydrogen in the sixth stream 35 is greater than or equal to 98%, advantageously greater than 99.97%.
[0096] The pressure of the sixth stream 35 is advantageously greater than 5 bar, or even 9 bar, or even 10 bar.
[0097] The purge stream 50 is a by-product for which the method contemplates optimized management, especially in terms of LOHC inventory loss and overall energy consumption, as will become clear from the following steps.
[0098] The purge stream 50 consists mainly of hydrogen and contains a molar percentage of LOHC of less than 20%
[0099] In the method according to the invention, the entire sixth stream 35 is not sent to the user. In contrast, the method comprises expanding the first fraction 39 of the sixth stream 35 in the expansion turbine 37 to obtain the seventh stream 69 of mechanical energy and the eighth stream 41 comprising hydrogen which is colder than the sixth stream 35 but of identical chemical composition.
[0100] The second fraction 67 of the sixth stream forms the stream 2 produced for the user and thus exits the production plant 19.HYDRO030-WO-PCT
[0101] In the PSA unit 33, the pressure drop between the fifth stream 31 and the sixth stream 35 is advantageously limited, so that the pressure of the first fraction 39 of the sixth stream 35 is high enough to enable operation of the expansion turbine 37.
[0102] The seventh stream 69 is used to form at least a part of the third stream 53. This arrangement makes it possible to limit the use of one or more non-decarbonized energy sources for the operation of the first purification unit 29, in particular for the operation of the compressors of the optional consecutive additional compression stages 63a, ..., 63n.
[0103] At the outlet of the expansion turbine 37, the eighth stream 41 comprises hydrogen in the same percentage as the first fraction 39 of the sixth stream, but cooled to a temperature advantageously lower than -30°C, preferentially lower than -50°C, even more preferably lower than -80°C. The temperature of the eighth stream 41 can be even lower than -100°C, or even -120°C.
[0104] The eighth stream 41 can thus be used beneficially in the following steps, thanks to its low temperature and its chemical composition, which makes it suitable for combustion with a high energy yield.
[0105] The eighth stream 41 is placed in thermal contact with the purge stream 50 in the second heat exchanger 73, which makes it possible to produce the cooled purge stream 71 as well as the heated eighth stream 45.
[0106] Alternatively, especially depending on the properties of the LOHC and the exact composition of the stream 50, an intermediate fluid can be used to transfer heat from the stream 50 to the stream 41 .
[0107] The temperature of the purge stream 50 before cooling is close to ambient temperature, typically 15 to 40°C depending on the region. The temperature ofHYDRO030-WO-PCT the cooled purge stream 71 is advantageously between -50°C and 10°C, especially between -30°C and -20°C, for example of the order of -25°C.
[0108] The temperature of the heated eighth stream 45 is advantageously between 14°C and 40°C.
[0109] The use of the eighth stream 41 exiting the expansion turbine 35 avoids the need for additional, especially non-decarbonized, energy sources to cool the purge stream 50 before it passes into the separation unit 49 for the separation described hereinafter. This unit also makes it possible to heats the eighth stream 41 prior to its combustion, which will be described hereinafter.
[0110] The LOHC is used for its ability to store and release hydrogen. The dehydrogenation reaction requires an initial stream 51 of thermal energy of varying magnitude depending on the nature of the LOHC. The larger the first stream 51 , the larger the second fraction 39 that makes it possible to form this first stream 51 . Consequently, the larger the first stream 51 , the greater the cooling capacity of the eighth stream 41 . In this way, the nature of the LOHC can be selected so that the eighth stream 41 makes it possible not only to achieve at least the desired fraction of the first stream 51 , but also to provide at least sufficient cooling of the purge stream 50 for the operation of the production plant 19.
[0111] Alternatively, for example in particularly hot regions and / or for LOHCs with low energy consumption for dehydrogenation, the heat-exchange unit 43 receives an additional coolant stream (not shown) capable of cooling the purge stream 50, in addition to the eighth stream 41 .
[0112] In the example, the entire heated eighth stream 45 enters the thermal energy production unit 47, wherein an eleventh stream 81 of thermal energy is produced by combustion of the heated eighth stream 45.HYDRO030-WO-PCT
[0113] In the example, the entire first stream 51 required for the dehydrogenation reaction in the reactive section 25 is formed from the entire eleventh stream 81 of thermal energy. The eleventh stream 81 , for example, is transported via a steam network to the reactive section 25, where the first stream 51 is then formed.
[0114] The reactive section 25 is the most energy-intensive component of the production plant 19. It is therefore understood that obtaining the eleventh stream 81 by taking the first fraction 39 of the sixth stream 35 to produce the first stream 51 makes it possible to ensure partial energy autonomy for the production plant 19 and at least partially avoids the need to use local energy sources, decarbonized or non-decarbonized.
[0115] Moreover, since the molar percentage of hydrogen in the sixth stream 35, and therefore in the eighth stream 41 , is at least 95%, advantageously greater than 98%, advantageously greater than 99.97%, undesirable or polluting by-products are formed in controlled amounts.
[0116] Alternatively, the first fraction 39 is selected so that the eleventh stream 81 makes it possible to form, at least temporarily, only a fraction of the first stream 51 , for example in cases where one or more decarbonized energy sources are locally available. The choice of the first fraction 39 may depend on the nature of the decarbonized energy sources that are locally available.
[0117] In this case, one or more additional streams of thermal energy, not shown, are provided to the reactive section 25 in addition to the eleventh stream 81 .
[0118] In the example, the combustion of the heated eighth stream 45 also makes it possible to produce a twelfth stream 87 of thermal energy, which is used to produce at least part of the third stream 53.
[0119] Alternatively, at least a fraction of the heated eighth stream 45 passes through at least one additional heat exchanger of one of the optional additionalHYDRO030-WO-PCT compression stages 63a, 63n before combustion of this fraction of the heated eighth stream 45 in the thermal energy production unit 47. This arrangement makes it possible to avoid the need for an auxiliary cold source for the operation of the additional heat exchangers, while further heating the heated eighth stream 45 prior to the combustion thereof.
[0120] Optionally, a surplus stream 91 of thermal energy is provided by the thermal energy production unit 47 to a device external to the production plant 19, not shown.
[0121] A fraction 90 of the heated eighth stream 45 and / or the twelfth stream 87 and / or the seventh stream 69 are optionally received by a mechanical and / or electrical energy production unit 89 configured to produce all or part of the third stream 53 from these different streams and optionally a stream of mechanical or electrical energy provided to the rest of the production plant 19 (not shown).
[0122] In the example, the fraction 90 of the heated eighth stream 45 is thus optionally sent to the mechanical and / or electrical energy production unit 89 to produce a stream of electrical energy by means of an energy conversion device not shown, such as a fuel cell.
[0123] In the example, the twelfth stream 87 of thermal energy is received by the mechanical and / or electrical energy production unit 89 so as to form at least part of the third stream 53. For this purpose, the mechanical and / or electrical energy production unit 89 comprises, for example, a turbine and, optionally, an alternator coupled to the turbine (not shown).
[0124] In the example, the mechanical and / or electrical energy production unit 89 also receives the entire seventh stream 69.
[0125] Alternatively, the seventh stream 69 alone directly forms the third stream 53.HYDRO030-WO-PCT
[0126] The cooled purge stream 71 obtained in the heat-exchange unit 43 undergoes a separation step in the separation unit 49. In the example, the ninth stream 75 comprising hydrogen is obtained at the top of the second vessel 79, and the tenth stream 77 comprising LOHC in the hydrogen-lean state at a molar percentage greater than that of the purge stream 50 is obtained at the bottom of the second vessel 79.
[0127] The molar percentage of hydrogen in the ninth stream 75 is advantageously greater than or equal to 90 molar %, advantageously greater than 95% or even greater than 99.9%.
[0128] The molar percentage of LOHC in the ninth stream 75 is relatively low, for example less than 10%, advantageously less than 5% or even less than 0.1 %, so that its combustion can be envisaged without excessive losses of LOHC inventory. The ninth stream 75 is, in the example, provided to the thermal energy production unit 47 to undergo combustion with the heated eighth stream 45.
[0129] The molar percentage of LOHC in the hydrogen-lean state of the tenth stream 77 is greater than or equal to 95% and advantageously greater than 99%.
[0130] In order to form the incoming stream 21 , the production method may comprise the following additional steps, described with reference to figure 1.
[0131] First of all, the production method may comprise a step of producing the initial stream 5 comprising hydrogen from the source stream 7 of material comprising a chemical species that is a source of hydrogen atoms and the energy source stream 9. In the example, the production step is carried out in the production unit 3.
[0132] Advantageously, the source stream 9 is at least partially, and preferably entirely, a decarbonized energy stream. The source stream 9 is generated, forHYDRO030-WO-PCT example, by means of a source of mechanical energy, especially wind and / or water, and / or by solar energy not shown in figure 1 .
[0133] The molar percentage of hydrogen in the initial stream s is advantageously greater than 99%.
[0134] The hydrogenation reaction takes place in the hydrogenation unit 11 at a temperature advantageously between 150°C and 500°C and under a total absolute pressure advantageously between 20 bar and 100 bar.
[0135] As the hydrogenation reaction is exothermic, an additional stream 85 of thermal energy is generated in the hydrogenation unit 11. The additional stream 85 is advantageously used in any of the elements of the plant 1 and / or in another device requiring thermal energy input.
[0136] In the example, the initial stream 5 is sent to the hydrogenation unit 11 , where a hydrogenation reaction of the hydrogen-lean stream 13 comprising LOHC in the hydrogen-lean state makes it possible to produce the intermediate stream 15, which comprises LOHC in the hydrogen-rich state.
[0137] Advantageously, at least a fraction of the tenth stream 77 is reused to form at least part of the hydrogen-lean stream 13 entering the hydrogenation unit 11.
[0138] Advantageously, the tenth stream 77 is entirely reused to form at least part of the hydrogen-lean stream 13 entering the hydrogenation unit 11.
[0139] Advantageously, the fourth stream 55 is at least partially reused to form at least part of the hydrogen-lean stream 13 comprising LOHC in the hydrogen-lean state entering the hydrogenation unit 11.HYDRO030-WO-PCT
[0140] In the latter two cases, the one or more reused streams are transported by dedicated transport means, optionally similar to those of the transport unit 17 and / or by the transport unit 17.
[0141] In this example, the intermediate stream 15 is transported by the transport unit 17 and, after transport, forms the entire incoming stream 21 for the reactive section 25.
[0142] Optionally, the fourth stream 55 undergoes an additional separation step, for example by means of a gravity separation vessel 95 to form a stream 100, recovered at the bottom of the separation vessel 95 and comprising LOHC in a greater proportion than the stream 55, and a stream 105, recovered at the top and comprising hydrogen, the stream 105 being provided to the thermal production unit 74 where it undergoes combustion.
[0143] In this case, the stream 100 is at least partially reused to form at least part of the hydrogen-lean stream 13 comprising LOHC in the hydrogen-lean state entering the hydrogenation unit 11.
[0144] The production method makes it possible to obtain the sixth stream 35 comprising hydrogen with a carbon dioxide footprint of preferably less than 3 kg of carbon dioxide per kilogram of hydrogen, preferably less than 1 .5 kg of carbon dioxide per kilogram of hydrogen.
[0145] Drawing off part of the sixth stream 35, which comprises hydrogen in a higher proportion than that of the second stream 27, for reuse in subsequent steps of the production method, especially to produce the thermal energy required for the dehydrogenation step, ensures at least partial decarbonization of the production method. This arrangement does away with the need to use an energy source external to the production plant 19 to form the eleventh stream 81 , as the external energy sources available locally at any given time are not necessarily decarbonized.HYDRO030-WO-PCT
[0146] This partial decarbonization makes it possible to maintain the choice of LOHC technology, which has the advantage of allowing highly flexible management of hydrogen production in terms of production site and availability date of the hydrogen stream.
[0147] The production of the seventh stream 69 in the expansion step from the sixth stream 37 enables even greater decarbonization, since it allows the first purification step and the heat-transfer step to be at least partially decarbonized.
[0148] The reuse of the fourth stream 55 and / or of the tenth stream 77 for the hydrogenation step also makes it possible to reduce liquid organic hydrogen carrier inventory losses, as well as to limit or even reduce the amounts of LOHC sent to the thermal energy production unit 47 and the resulting CO2 emissions.
[0149] The step of separating the purge stream 50 makes it possible to optimize the use of this by-product by generating a tenth stream 77 that can be reused in the hydrogenation step. This separation step necessitates the heat-transfer step of the method, but the additional consumption associated with this heat-transfer step is limited, since the energy required to cool the purge stream 50 comes from the second fraction 39 of the sixth stream.
[0150] The step of separating the purge stream 50 also generates the ninth stream 75, the combustion of which is more efficient and generates fewer undesirable by-products, especially carbon dioxide, than if the purge stream 50 had been burned directly in the thermal energy production unit 47. This makes it possible to reduce the carbon footprint of the hydrogen delivered, for example by between 0.2 and 1.0 kg of carbon dioxide per kg of hydrogen, which represents a very significant reduction and may be key to the development of sufficiently decarbonized hydrogen transport chains.
Claims
HYDRO030-WO-PCTClaims1. A method for producing a stream (2) comprising hydrogen at a molar percentage greater than 95% for a user from an incoming stream (21 ) comprising a liquid organic hydrogen carrier having at least two possible states: a hydrogen- lean state and a hydrogen-rich state, the transition from the hydrogen-rich state to the hydrogen-lean state being achieved by means of an endothermic dehydrogenation reaction, the method comprising the following steps:- dehydrogenating the incoming stream in the hydrogen-rich state using a first stream (51 ) of thermal energy, to obtain a second stream (27) comprising hydrogen and liquid organic hydrogen carrier in the hydrogen-lean state;- a first purification of the second stream (27) using a third stream (53) of mechanical and / or electrical energy to obtain a fourth stream (55) comprising liquid organic hydrogen carrier in the hydrogen-lean state and to obtain a fifth stream (31 ) comprising hydrogen at a molar percentage greater than that of the second stream (27);- a second purification of the fifth stream (31 ) in a pressure swing adsorption unit (33) to obtain a sixth stream (35) comprising hydrogen at a molar percentage greater than that of the fifth stream (31 ) and to obtain a purge stream (50) comprising liquid organic hydrogen carrier in the hydrogen-lean state and hydrogen;- expanding a first fraction (39) of the sixth stream (35) in an expansion turbine (37) to obtain a seventh stream (69) of mechanical energy and an eighth stream (41 ) comprising hydrogen colder than the sixth stream (35), a second fraction of the sixth stream (35) being said stream (2) produced for the user;- transferring heat from the purge stream (50) to the eighth stream (41 ) to obtain a cooled purge stream (71 ) and to obtain a heated eighth stream (45);- separating the cooled purge stream (71 ) to obtain a ninth stream (75) comprising hydrogen and to obtain a tenth stream (77) comprising liquid organic hydrogen carrier in the hydrogen-lean state at a molar percentage greater than that of the purge stream (50); and26HYDRO030-WO-PCT- combusting at least a fraction of the heated eighth stream (45) and optionally of the ninth stream (75) to produce an eleventh stream (81 ) of thermal energy, at least a fraction of which is used to form at least a fraction of the first stream (51 ).
2. The method according to claim 1 , wherein at least one fraction of the third stream (53) is obtained from the seventh stream (69) and / or from the eleventh stream (81 ).
3. The method according to claim 1 or 2, characterized in that it comprises producing a stream of electrical energy from a fraction (90) of said heated eighth stream (45).
4. The method according to any one of claims 1 to 3, wherein the entire first stream (51 ) is obtained from the eleventh stream (81 ).
5. The method according to any one of claims 1 to 4, wherein the entire third stream (53) is obtained from the seventh stream (69) and optionally from the eleventh stream (81 ).
6. The method according to any one of claims 1 to 5, wherein the liquid organic hydrogen carrier is selected from toluene, benzyltoluene, dibenzyltoluene, n-ethylcarbazole, n-isopropylcarbazole, n-butylcarbazole, 1 ,2-dihydro-1 ,2-azaborine, formic acid, methanol, ethanol, propanol, butanol, potassium formate, naphthalene, 1 ,4-butanediol, 1 ,4- or 1 ,5-pentanediol, ethylene glycol or mixtures thereof.
7. The method according to one of the preceding claims, characterized in that it further comprises the following steps:- producing an initial stream (5) comprising hydrogen; andHYDRO030-WO-PCT- hydrogenating a stream (13) of liquid organic hydrogen carrier in the hydrogen-lean state by the initial stream (5) to produce the incoming stream (21 ).
8. The method according to claim 7, characterized in that it further comprises at least one of the following steps:- transporting the liquid organic hydrogen carrier in the hydrogen-rich state between the hydrogenation and the dehydrogenation;- storing the hydrogen-rich liquid organic hydrogen carrier between the hydrogenation and the dehydrogenation.
9. The method according to claim 7 or claim 8, wherein at least part of the stream (13) of liquid organic hydrogen carrier in the hydrogen-lean state for hydrogenation comes from the first purification and / or from the separation.
10. A plant (19) for producing a stream (2) of hydrogen at a molar percentage greater than 95% for a user from an incoming stream (21 ) comprising a liquid organic hydrogen carrier having two states: a hydrogen- lean state and a hydrogen-rich state, the transition from the hydrogen-rich state to the hydrogen-lean state being achieved by means of an endothermic dehydrogenation reaction, the plant comprising:- a reactive section (25) configured to receive the incoming stream (21 ) in the hydrogen-rich state and a first stream (51 ) of thermal energy and to produce a second stream (27) comprising hydrogen and liquid organic hydrogen carrier in the hydrogen-lean state;- a first purification unit (29) configured to receive the second stream (27) and a third stream (53) of mechanical and / or electrical energy and to produce a fourth stream (55) comprising liquid organic hydrogen carrier in the hydrogen-lean state and to produce a fifth stream (31 ) comprising hydrogen at a molar percentage greater than that of the second stream (27);- a pressure swing adsorption unit (33) configured to receive the fifth stream (31 ) and to produce a sixth stream (35) comprising hydrogen at aHYDRO030-WO-PCT molar percentage greater than that of the fifth stream (31 ), and to produce a purge stream (50) comprising liquid organic hydrogen carrier in the hydrogen-lean state and hydrogen;- an expansion turbine (37) configured to produce a seventh stream (69) of mechanical energy and an eighth stream (41 ) comprising hydrogen colder than the sixth stream (35) from a first fraction (39) of the sixth stream, a second fraction (67) of the sixth stream being the stream (2) produced for the user;- a heat-exchange unit configured to receive the eighth stream (41 ) and the purge stream (50) and to provide a cooled purge stream (71 ) and a heated eighth stream (45);- a separation unit (43) configured to receive the cooled purge stream (71 ) and to provide a ninth stream (75) comprising hydrogen and to provide a tenth stream (77) comprising liquid organic hydrogen carrier in the hydrogen-lean state at a molar percentage greater than that of the purge stream; - a thermal energy production unit (47), configured to produce, by combustion of at least a fraction of the heated eighth stream (45) and optionally of the ninth stream (75), an eleventh stream (81 ) of thermal energy; wherein the production plant (19) is further configured to form at least a fraction of the first stream (51 ) from at least a fraction of the eleventh stream (81 ).