Process for producing a stream containing dihydrogen from an organic hydrogen transport liquid
The process addresses energy-intensive hydrogen production by using endothermic dehydrogenation and energy recovery methods to produce a high-purity dihydrogen stream with reduced carbon emissions.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- TECHNIP ENERGIES FRANCE SAS
- Filing Date
- 2024-12-05
- Publication Date
- 2026-06-12
AI Technical Summary
Existing hydrogen production processes using organic hydrogen carriers (LOHC) are energy-intensive, particularly consuming non-decarbonized energy, which is undesirable.
A process involving endothermic dehydrogenation of LOHC with thermal energy, followed by mechanical and electrical purification, pressure swing adsorption, and energy recovery through expansion turbines and heat exchange, minimizes the need for non-decarbonized energy sources.
The process produces a high-purity dihydrogen stream with reduced carbon footprint and energy consumption, enabling flexible and decarbonized hydrogen supply.
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Abstract
Description
Title of the invention: Method for producing a stream comprising dihydrogen from an organic hydrogen transport liquid
[0001] The present invention relates to a method for producing a stream comprising dihydrogen at a molar percentage greater than 95% from an incoming stream comprising an organic hydrogen transport liquid having at least two possible states: a discharged state and a charged state, the transition from the charged state to the discharged state being obtained by means of an endothermic dehydrogenation reaction.
[0002] The invention also relates to an installation for the production of such a flow comprising dihydrogen.
[0003] In the field of hydrogen production, particularly as an energy carrier, numerous processes exist, including those based on methane reforming or water electrolysis. The hydrogen thus produced may require storage of varying lengths before use and / or transport over varying distances between the production site and the point of use.
[0004] To enable the storage and / or transport of dihydrogen, particularly in a safe manner, processes have been developed in which a Liquid Organic Hydrogen Carrier (LOHC) is used. The LOHC has at least two states: a charged state in which it stores hydrogen and an uncharged state. The transition from the charged to the uncharged state is achieved by a dehydrogenation reaction, which allows the dihydrogen of interest to be released at the desired time and / or location. The LOHC is generally chosen primarily for its hydrogen storage density, but also according to the chemical risk associated with the liquid in its charged and / or uncharged states, the amount of energy required for the dehydrogenation reaction, its availability, cost, and the carbon footprint of its production.
[0005] However, the dehydrogenation reaction of the organic hydrogen transport liquid requires a thermal energy input. Therefore, using an organic hydrogen transport liquid in a process for producing a stream containing dihydrogen implies significant energy consumption, particularly of non-decarbonized energy. It is desirable to limit this energy overconsumption, and more specifically the overconsumption of non-decarbonized energy.
[0006] One aim of the invention is therefore to propose a process for producing a stream comprising dihydrogen which is more decarbonized.
[0007] To this end, the invention relates to a process for producing a dihydrogen stream with a molar percentage greater than 95% for a user from an incoming stream comprising an organic hydrogen transport liquid having at least two possible states: a discharged state and a charged state, the transition from the charged state to the discharged state being obtained by means of an endothermic dehydrogenation reaction, the process comprising the following steps: - a dehydrogenation of the incoming flow in the charged state using a first flow of thermal energy, to obtain a second flow comprising dihydrogen and organic hydrogen transport liquid in the uncharged state; - a first purification of the second stream using a third stream of mechanical and / or electrical energy to obtain a fourth stream comprising organic hydrogen transport liquid in the uncharged state and to obtain a fifth stream comprising dihydrogen at a molar percentage higher than that of the second stream; - a second purification of the fifth stream in a pressure reversal adsorption unit to obtain a sixth stream comprising dihydrogen at a higher molar percentage than the fifth stream and to obtain a purge stream comprising unloaded organic hydrogen transport liquid and dihydrogen; - an expansion of a first fraction of the sixth flux in an expansion turbine to obtain a seventh flux of mechanical energy and an eighth flux comprising dihydrogen colder than the sixth flux, a second fraction of the sixth flux being said flux produced for the user; - a heat transfer from the purge flow to the eighth flow to obtain a cooled purge flow and to obtain a heated eighth flow; - a separation of the cooled purge stream to obtain a ninth stream comprising dihydrogen and a tenth stream comprising organic hydrogen transport liquid in the discharged state in a molar percentage higher than that of the purge stream; and - a combustion of at least a fraction of the eighth heated flux and optionally of the ninth flux to produce an eleventh flux of thermal energy of which at least a fraction is used to form at least a fraction of the first flux.
[0008] This process uses an organic hydrogen transport liquid, which allows for the management of both the site of hydrogen supply to its user and the timing of this supply, relative to the time and place of availability of a flow of dihydrogen source molecules.
[0009] In this process, the dehydrogenation step is the most energy-intensive step of the process. At least part of the first thermal energy flux required for the dehydrogenation reaction is obtained by combustion of at least part of the eighth heated flux.
[0010] The eighth heated 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 dihydrogen at a molar percentage 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 process avoids the need for a non-decarbonized energy source and, consequently, reduces the proportion of non-decarbonized energy in the thermal energy required for the hydrogenation step.
[0012] The process therefore makes it possible, while benefiting from the flexibility offered by the use of an organic hydrogen transport liquid in terms of site and date of production of dihydrogen, to obtain a flow of hydrogen that is at least partially decarbonized.
[0013] In other words, this process allows, through self-consumption of hydrogen to provide at least part of the energy needed for the dehydrogenation step, which mainly consumes heat.
[0014] The process also minimizes LOHC losses throughout the process, thereby minimizing the costs of transporting and continuously replacing the LOHC, as well as the carbon footprint associated with this replacement. The process further limits emissions that would result from excessive combustion of the lost LOHC.
[0015] According to particular embodiments, the method comprises one or more of the following features, taken individually or in all technically possible combinations:
[0016] - at least a fraction of the third stream is obtained from the seventh stream and / or of the eleventh stream;
[0017] - the process comprises the production of an electrical energy flow from a fraction of said eighth heated stream;
[0018] - the entirety of the first stream is obtained from the eleventh stream;
[0019] - the entirety of the third stream is obtained from the seventh stream and optionally from the eleventh stream;
[0020] - the organic hydrogen transport liquid is chosen from toluene, the benzyltoluene, dibenzyltoluene, n-ethylcarbazole, n-isopropylcarbazole, n-butylcarbazole, l,2-dihydro-l,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;
[0021] - the process further comprises the following steps: • the production of an initial stream including dihydrogen; and • hydrogenation of an organic liquid hydrogen transport stream in the discharged state by the initial stream to produce the incoming stream;
[0022] - the method further comprises at least one of the following steps: • a transport of the organic hydrogen transport liquid in the charged state between hydrogenation and dehydrogenation; • a storage of the hydrogen-carrying organic liquid between hydrogenation and dehydrogenation; and
[0023] - at least a portion of the organic liquid flow transporting hydrogen to The uncharged state for hydrogenation is derived from the first purification and / or separation.
[0024] The invention also relates to an installation for producing a stream comprising dihydrogen at a molar percentage greater than 95% for a user from an incoming stream comprising an organic hydrogen transport liquid having two states: a discharged state and a charged state, the transition from the charged state to the discharged state being obtained by means of an endothermic dehydrogenation reaction, the installation comprising: - a reactive section configured to receive the incoming flow in the charged state and a first flow of thermal energy and to produce a second flow comprising dihydrogen and organic hydrogen transport liquid in the uncharged state; - a first purification unit configured to receive the second and a third stream of mechanical and / or electrical energy and to produce a fourth stream comprising unloaded organic hydrogen transport liquid and to produce a fifth stream comprising dihydrogen in a molar percentage higher than that of the second stream; - a pressure reversal adsorption unit configured to receive the fifth stream and produce a sixth stream comprising dihydrogen in a molar percentage higher than that of the fifth stream and to produce a purge stream comprising unloaded organic hydrogen transport liquid and dihydrogen; - an expansion turbine configured to produce a seventh stream of mechanical energy and an eighth stream comprising dihydrogen plus cold that 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 flow and the purge flow and to provide a cooled purge flow and a heated eighth flow; - a separation unit configured to receive the cooled purge stream and to provide a ninth stream comprising dihydrogen and to provide a tenth stream comprising organic hydrogen transport liquid in the discharged state in a molar percentage higher than that of the purge stream; - a thermal energy production unit, configured to produce, by combustion of at least a fraction of the eighth heated stream and optionally of the ninth stream, an eleventh thermal energy stream;
[0025] the production installation being further configured to form at least a fraction of the first stream from at least a fraction of the eleventh stream.
[0026] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings, in which:
[0027] [Fig-1] [Fig.1] is a schematic representation of an installation according to the invention, and
[0028] [Fig.2] [Fig.2] is a schematic representation of part of the installation shown in [Fig.1].
[0029] With reference to [Fig.1], an installation 1 for producing a stream 2 comprising dihydrogen from a stream comprising a chemical species source of hydrogen atoms and employing an organic hydrogen transport liquid, designated by the abbreviation LOHC in the following description, is described.
[0030] In the example, the installation 1 includes a production unit 3 of an initial stream 5 comprising dihydrogen from a source stream 7 of matter comprising a chemical source species of hydrogen atoms and a source stream 9 of energy.
[0031] The installation 1 of the example includes a loading unit 11 which is configured to receive the initial flow 5 and an unloaded flow 13 comprising LOHC in the unloaded state and to produce an intermediate flow 15 comprising LOHC in the loaded state.
[0032] Installation 1 of the example further includes a transport unit 17 for the intermediate flow 15.
[0033] Installation 1 finally includes a production installation 19 configured to produce stream 2 comprising dihydrogen from an incoming stream 21 comprising of the LOHC in the loaded state. This incoming flow 21 is in the example formed from the intermediate flow 15 transported by the transport unit 17.
[0034] The transport unit 17 includes suitable means for transporting the intermediate flow 15 from the loading unit 11 to the production installation 19, in particular in a secure manner.
[0035] In the example, the means of transport are fixed. For example, the means of transport comprise one or more conduits configured to receive the intermediate flow 15.
[0036] Alternatively, the means of transport are mobile. These are, for example, dedicated vessels. In this case, installation 1 can be seen as the grouping of two installations, 1a and 1b, located at a distance from each other. The first installation, 1a, comprises the production unit 3 and the loading unit 11, and the second installation, 1b, comprises the production unit 19.
[0037] The means of transport are then adapted to transport the intermediate flow 15 from the first installation la to the second installation 1b.
[0038] The means of transport are advantageously chosen according to the locations of the loading unit 11 and the production installation 19. In particular, the means of transport are chosen according to the locations of the hydrogen atom source for the source stream 7 and / or the energy source for the source stream 9 for the production unit 3, and / or an end user of the stream 2.
[0039] According to one embodiment, the transport unit 17 includes a storage capacity, not shown. The storage capacity is advantageously configured to allow the storage of the intermediate flow 15, so as to allow the unloading of the incoming flow 21 to be delayed relative to the production of the intermediate flow 15.
[0040] The production unit 3 is configured to receive the source stream 9 of energy and the source stream 7 of matter, preferably water or methane, and to produce an initial stream 5 comprising dihydrogen.
[0041] The production unit 3 in the example includes a reformer 4, or equivalently a natural gas steam-reforming unit.
[0042] 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 [Fig. 1], produced by the reformer 4.
[0043] Alternatively, the production unit 3 includes an electrolyzer.
[0044] The loading unit 11 is adapted to receive the initial flux 5 and the discharged flux 13 and to produce, by means of a hydrogenation reaction, the intermediate flux 15 which comprises LOHC in the charged state.
[0045] The LOHC has at least two possible states for this purpose: a discharged state and a charged state, the transition from the discharged (respectively charged) state to the charged (respectively discharged) state being obtained by an exothermic hydrogenation reaction (respectively endothermic dehydrogenation).
[0046] The LOHC allows in particular the storage and / or transport of dihydrogen.
[0047] The LOHC can be chosen according to one or more criteria chosen from among its hydrogen storage density, the low chemical risk associated with the molecule in the uncharged and / or charged state, the enthalpy of the dehydrogenation reaction, the availability of the molecule, in particular at low cost and / or with a limited carbon footprint.
[0048] Advantageously, the LOHC in the unloaded state is selected from toluene, benzyltoluene, dibenzyltoluene, n-ethylcarbazole, n-isopropylcarbazole, n-butylcarbazole, l,2-dihydro-l,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.
[0049] Preferably, the LOHC in the unloaded state is selected from toluene, benzyltoluene or a mixture of methanol and ethylene glycol.
[0050] Advantageously, the LOHC is chosen so that the enthalpy of the dehydrogenation reaction is less than 70 kJ / molH2, in particular less than 45 kJ / molH2.
[0051] Advantageously, the LOHC is chosen so that its hydrogen transport density is greater than 3%, or even greater than 6%, by mass of dihydrogen relative to the mass of LOHC discharged.
[0052] In the example, the production installation 19 is configured to receive the incoming flow 21 which is the intermediate flow 15 after its transport by the transport unit 17.
[0053] The production installation 19 of [Fig.2] is configured to receive the incoming stream 21 comprising LOHC in the charged state and to produce the stream 2 comprising dihydrogen at a molar percentage greater than 95%, advantageously greater than 98%, advantageously greater than 99.97%, in particular to be usable in fuel cells.
[0054] The production installation 19 includes for this purpose a reactive section 25, capable of receiving the incoming flow 21 and of producing a second flow 27 comprising dihydrogen and LOHC in the discharged state.
[0055] The production installation 19 includes a first purification unit 29 adapted to receive the second stream 27 and to produce a fifth stream 31 comprising dihydrogen.
[0056] The production facility 19 contains a pressure swing adsorption unit 33 (in English “Pressure Swing Adsorption” or PSA) capable of receiving the fifth stream 31 and producing a sixth stream 35 comprising dihydrogen.
[0057] The production installation 19 includes an expansion turbine 37 capable of receiving a first fraction 39 of the sixth stream 35 and of forming an eighth stream 41 comprising dihydrogen.
[0058] The production facility 19 includes a heat exchange unit 43, which is configured to receive the eighth stream 41, to produce a ninth heated stream 45 and to transmit the latter to a thermal energy production unit 47 of the production facility 19.
[0059] The production installation 19 includes a separation unit 49 adapted to receive a purge flow 50.
[0060] 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 dihydrogen and LOHC in the discharged state by means of an endothermic dehydrogenation reaction.
[0061] The reactive section 25 includes, for example, one or more catalytic reactors.
[0062] 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 discharged state, and to produce the fifth stream 31 comprising dihydrogen in a molar percentage higher than that of the second stream 27.
[0063] The elements constituting the first purification unit 29 are advantageously chosen and dimensioned according to the composition and pressure of the second flow 27 and the pressure required for the fifth flow 31.
[0064] The first purification unit 29 advantageously allows the recovery of the vast majority of the LOHC discharged from the stream 27.
[0065] The second flow 27 preferably has a pressure greater than 5 bar absolute so as to minimize the compression power required in stages 63a to 63n.
[0066] To this end, the first purification unit 29 includes in the example at least one first separation flask 57.
[0067] The first balloon 57 is advantageously preceded by a first heat exchanger 59.
[0068] Alternatively, the first purification unit 29 includes one or more additional compression stages 63a, ..., 63n downstream of the first balloon 57.
[0069] In the example, only the two extreme additional compression stages 63a and 63n are shown.
[0070] Each of the additional compression stages 63a, ..., 63n, the details of which are not shown, comprises a compressor, a compressor outlet heat exchanger, and a separator. The compression stages are configured to reach the set pressure at the outlet of unit 29, a pressure defined by the requirements of unit 33 to ensure proper purification. This pressure is advantageously greater than 10 bar.
[0071] Moreover, each compression stage makes it possible to produce a flow comprising dihydrogen in a proportion greater than that of a flow entering that stage.
[0072] The PSA unit 33 is configured to receive the fifth stream 31, to produce the sixth stream 35 comprising dihydrogen in a higher molar percentage than the fifth stream 31 and to produce the purge stream 50 comprising LOHC in the discharged state and dihydrogen, as well as possibly traces of charged LOHC not converted in the reactive section 25.
[0073] The PSA 33 unit includes, for example, an adsorbent material that can be specifically defined according to the impurities inherent in each LOHC and that will be particularly suited to the adsorption of charged and uncharged LOHC molecules. Typically, on hydrogen PSAs, the materials used are activated alumina, silica gel, activated carbon, and molecular sieves.
[0074] 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 the stream 2 supplied to the user, and to produce a seventh stream 69 of mechanical energy, by expansion of the first fraction 39 of the sixth stream 35.
[0075] The heat exchange unit 43 is configured to receive the eighth flow 41 and the purge flow 50 and to provide a cooled purge flow 71 and a heated eighth flow 45.
[0076] To this end, the heat exchange unit 43 includes in the example a second heat exchanger 73 in which the eighth flow 41 and the purge flow 50 are brought into thermal contact.
[0077] It should be noted that the expansion turbine 37 in combination with the heat exchanger 43 makes it possible to avoid the need for a complete refrigeration cycle including compressors, multiple exchangers, and a dedicated cryogenic fluid.
[0078] The separation unit 49 is configured to receive the cooled purge stream 71 and to provide a ninth stream 75 comprising dihydrogen and to provide a tenth stream 77 comprising LOHC in the discharged state as well as possible traces of charged LOHC not converted in the reactive section 25 in a molar percentage greater than that of the purge stream 50.
[0079] The separation unit 49 includes in the example a second separation balloon 79, configured to form at the top the ninth flow 75 and at the bottom the tenth flow 77.
[0080] The thermal energy production unit 47 is configured to produce, by combustion of at least a fraction of the eighth reheated stream 45 and optionally of the ninth stream 75, an eleventh stream 81 of thermal energy.
[0081] To this end, the thermal energy production unit 47 includes, for example, a boiler adapted for the combustion of dihydrogen, as well as a device 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.
[0082] The operation of the production installation 19 will now be described with reference to [Fig.2] and illustrates a production process according to the invention.
[0083] The production process according to the invention aims to obtain the stream 2 comprising dihydrogen at a molar percentage greater than 95%, advantageously greater than 98%, advantageously greater than 99.97% or even 99.99%, by means of the organic hydrogen transport liquid.
[0084] To this end, the process includes a step of dehydrogenating the incoming stream 21 comprising LOHC in the charged state in the reactive section 25, by means of the first stream 51 of thermal energy, to form the second stream 27, which comprises dihydrogen and LOHC in the uncharged state.
[0085] The working pressure and / or temperature for dehydrogenation are advantageously chosen according to the nature of the LOHC.
[0086] The working pressure in the reactive section 25 is advantageously between 1 and 30 bar, advantageously between 1 and 10 bar.
[0087] The working temperature in the reactive section 25 is advantageously between 100°C and 350°C, or even between 150°C and 300°C.
[0088] In the example, the second stream 27 is then supplied to the first purification unit 29, in which it is cooled in the first heat exchanger 59 by thermal contact with a cooling fluid 82, for example water or air.
[0089] This optional cooling allows the second stream 27, which is relatively hot after dehydrogenation, to reach a suitable temperature, for example 15°C to 40°C depending on the regions and available cooling sources, for a first separation step.
[0090] For the implementation of the first separation, optionally, the first purification unit 29 receives, in addition to the second stream 27, a fraction of the third energy stream 53, which is at least partly decarbonized, advantageously totally decarbonized.
[0091] In the example, the first separation includes a separation in the first separation tank 57. At the bottom of the first separation tank 57, a stream 84 richer in LOHC is collected than the second stream 27. At the top of the first tank of separation 57, we collect a stream 86 richer in dihydrogen than the second stream 27 from which the fifth stream 31 is formed.
[0092] Optionally, as shown in [Fig.2], the flow 86 collected at the head of the first separation tank 57 passes through the additional compression stages 63a,..63n in each of which it undergoes, for example successively and in this order, compression by means of the additional compressor, cooling in the additional heat exchanger, and an additional separation stage by means of the additional separation tank.
[0093] At the bottom of each additional separation flask, a flow 83a, ..., 83n richer in LOHC is collected than the flow entering the separation stage. At the top of each additional separation flask, a flow richer in dihydrogen is collected than the flow entering the separation stage.
[0094] The molar percentages in LOHC of the 83a, ..., 83n streams collected at the base of the successive additional separation balloons are greater than that of the second stream.
[0095] All or part of the flows 83a, ..., 83n collected at the base of the separation flasks of the first purification unit 29 constitutes the fourth flow 55, with a higher molar proportion in LOHC than that of the second flow 27.
[0096] At least part, advantageously all, of the flows 83a, ..., 83n collected at the base of the additional separation balloons forms the fourth flow 55.
[0097] Advantageously, the fourth stream 55 has a molar percentage in organic hydrogen transport liquid in the unloaded state greater than 95% and advantageously greater than 99%.
[0098] Advantageously, the fourth flux 55 has a molar percentage in dihydrogen of less than 5%, or even 1%.
[0099] The stream collected at the top of the last of the successive separation flasks of the first purification unit 29 constitutes the fifth stream 31, with a higher molar proportion of dihydrogen than that of the second stream 27.
[0100] The molar percentage of dihydrogen in the fifth flux 31 is at least 95%, advantageously at least 99%.
[0101] The pressure of the fifth flow 31 is advantageously sufficient for the operation of the PSA unit 33.
[0102] Advantageously, the absolute pressure of the fifth flow 31 is greater than 5 bars, or even greater than 10 bars.
[0103] The fifth stream 31 then undergoes a second purification in the PSA unit 33, so that a sixth stream 35 is formed comprising dihydrogen at a higher molar percentage than that of the fifth stream 31, and a purge stream 50 comprising LOHC in the discharged state, as well as possibly the unconverted charged LOHC in the reactive section 25 and dihydrogen and dihydrogen.
[0104] The working temperature in the PSA 33 unit is advantageously close to the ambient temperature, typically 15 to 40°C depending on the location of the production installation 19.
[0105] The dihydrogen content of the sixth stream 35 is equal to or greater than that required by the end user of stream 2, so that the sixth stream 35 can be utilized.
[0106] The molar percentage of dihydrogen in the sixth flux 35 is greater than or equal to 98%, advantageously greater than 99.97%.
[0107] The pressure of the sixth flow 35 is advantageously greater than 5 bars, or even 9 bars, or even 10 bars.
[0108] The purge flow 50 is a by-product for which the process envisages optimized management, particularly in terms of inventory loss in LOHC and overall energy consumption, as will be understood from reading the following steps.
[0109] The purge stream 50 is composed mainly of hydrogen and contains a molar percentage of LOHC of less than 20%
[0110] In the process according to the invention, the entire sixth stream 35 is not transmitted to the user. On the contrary, the process comprises the expansion of 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 dihydrogen which is colder than the sixth stream 35 but of identical chemical composition.
[0111] The second fraction 67 of the sixth flow forms the flow 2 produced for the user and therefore exits the production installation 19.
[0112] In the PSA unit 33, the pressure drop between the fifth flow 31 and the sixth flow 35 is advantageously limited, so that the pressure of the first fraction 39 of the sixth flow 35 is sufficient to allow the operation of the expansion turbine 37.
[0113] The seventh stream 69 is used to form at least 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 possible successive additional compression stages 63a,..., 63n.
[0114] At the outlet of the expansion turbine 37, the eighth stream 41 comprises dihydrogen in the same percentage as the first fraction 39 of the sixth stream, but cooled to a temperature advantageously below -30°C, preferably below -50°C, and even more preferably below -80°C. The temperature of the eighth stream 41 can even be below -100°C, or even -120°C.
[0115] The eighth stream 41 can thus be utilized in the following steps, both because of its low temperature and its chemical composition, which makes it suitable for high energy efficiency combustion.
[0116] The eighth stream 41 is brought into 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 eighth heated stream 45.
[0117] Alternatively, depending in particular on the properties of the LOHC and the exact composition of the flux 50, an intermediate fluid is used to carry out the heat transfer from the flux 50 to the flux 41.
[0118] The temperature of the purge flow 50 before cooling is close to the ambient temperature, typically 15 to 40°C depending on the region. The temperature of the cooled purge flow 71 is advantageously between -50°C and 10°C, in particular between -30°C and -20°C, for example on the order of -25°C.
[0119] The temperature of the eighth heated flux 45 is advantageously between 14°C and 40°C.
[0120] The use of the eighth stream 41 from the expansion turbine 35 avoids the need for additional energy sources, particularly non-decarbonized ones, to cool the purge stream 50 before it passes through the separation unit 49 for the separation described below. It also allows the eighth stream 41 to be heated before its combustion, which will be described later.
[0121] The LOHC is used for its ability to store and release hydrogen. The dehydrogenation reaction requires a first flux 51 of thermal energy, the size of which varies depending on the nature of the LOHC. The larger the first flux 51, the larger the second fraction 39 that forms this first flux 51. Consequently, the larger the first flux 51, the greater the cooling capacity of the eighth flux 41. Thus, the nature of the LOHC can be chosen so that the eighth flux 41 not only provides at least the desired fraction of the first flux 51 but also provides sufficient cooling of the purge flux 50 for the operation of the production plant 19.
[0122] 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 cooling fluid flow (not shown) suitable for cooling the blowdown flow 50, in addition to the eighth flow 4L
[0123] In the example, the entire eighth heated stream 45 enters the thermal energy production unit 47, in which an eleventh thermal energy stream 81 is produced by combustion of the eighth heated stream 45.
[0124] In the example, the entirety of the first flux 51 required for the dehydrogenation reaction in the reactive section 25 is constituted from the entirety of the eleventh thermal energy flux 81. The eleventh flux 81 is, for example, transported via a steam network to the reactive section 25 where the first flow 51 is then formed.
[0125] The reactive section 25 is the most energy-consuming element of the production installation 19. It is therefore understood that obtaining the eleventh stream 81 by means of taking the first fraction 39 of the sixth stream 35 to produce the first stream 51 makes it possible to ensure partial energy autonomy of the production installation 19 and to avoid at least partially the use of local energy sources, decarbonized or non-decarbonized.
[0126] Moreover, the molar percentage in dihydrogen of the sixth stream 35, and therefore that of the eighth stream 41, being equal to at least 95% advantageously greater than 98%, advantageously greater than 99.97%, the undesirable or polluting by-products are formed in controlled quantity.
[0127] Alternatively, the first fraction 39 is chosen so that the eleventh stream 81 makes it possible to constitute, at least temporarily, only a fraction of the first stream 51, for example in cases where one or more decarbonized energy sources are available locally. The choice of the first fraction 39 may depend on the nature of the locally available decarbonized energy sources.
[0128] In this case, one or more additional thermal energy fluxes, not shown, are supplied to the reactive section 25 in addition to the eleventh flux 81.
[0129] In the example, the combustion of the eighth heated flux 45 makes it possible to produce in addition a twelfth thermal energy flux 87 which is used to produce at least part of the third flux 53.
[0130] Alternatively, at least a fraction of the eighth heated stream 45 passes through at least one additional heat exchanger of one of the optional additional compression stages 63a, ..., 63n before combustion of this fraction of the eighth heated stream 45 in the thermal energy production unit 47. This arrangement avoids the need for an auxiliary cold source for the operation of the additional heat exchangers, while further heating the eighth heated stream 45 before its combustion.
[0131] Optionally, an excess flow 91 of thermal energy is supplied by the thermal energy production unit 47 to a device external to the production installation 19 not shown.
[0132] A fraction 90 of the eighth heated stream 45 and / or the twelfth stream 87 and / or the seventh stream 69 are optionally received by a mechanical and / or electrical power generation unit 89 configured to produce all or part of the third stream 53 from these different streams and optionally a mechanical or electrical power stream supplied to the rest of the production facility 19 (not shown).
[0133] In the example, fraction 90 of the eighth heated flux 45 is thus optionally transmitted to the mechanical and / or electrical power generation unit 89 to produce an electrical power flux by means of an energy conversion device not shown, such as a fuel cell.
[0134] In the example, the twelfth thermal energy flow 87 is received by the mechanical and / or electrical energy production unit 89 so as to form at least part of the third flow 53. For this purpose, the mechanical and / or electrical energy production unit 89 includes, for example, a turbine and, optionally, an alternator coupled to the turbine (not shown).
[0135] In the example, the mechanical and / or electrical energy production unit 89 also receives the entirety of the seventh flow 69.
[0136] Alternatively, the seventh stream 69 directly forms the third stream 53 by itself.
[0137] The cooled purge flow 71 obtained in the heat exchange unit 43 undergoes a separation step in the separation unit 49. In the example, at the top of the second balloon 79 we obtain the ninth stream 75 comprising dihydrogen, and at the bottom of the second balloon 79 the tenth stream 77 comprising LOHC in the discharged state in a molar percentage higher than that of the purge stream 50.
[0138] The molar percentage of dihydrogen in the ninth flux 75 is advantageously greater than or equal to 90% molar, advantageously greater than 95% or even greater than 99.9%.
[0139] 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 resulting in excessive LOHC inventory losses. In the example, the ninth stream 75 is supplied to the thermal power generation unit 47 for combustion with the reheated eighth stream 45.
[0140] The molar percentage in LOHC in the unloaded state of the tenth flux 77 is greater than or equal to 95% and advantageously greater than 99%.
[0141] In order to constitute the incoming flow 21, the production process may include the following additional steps, described with reference to [Fig.1].
[0142] First, the production process may include a production step of the initial stream 5 comprising dihydrogen from the source stream 7 of matter comprising a chemical species source of hydrogen atoms and the energy source stream 9. In the example, the production step is implemented in the production unit 3.
[0143] Advantageously, the source stream 9 is at least partly, preferably entirely, a decarbonized energy stream. The source stream 9 is, for example, produced by means of from a source of mechanical energy, in particular wind and / or hydraulic, and / or solar energy not shown in [Fig.1].
[0144] The molar percentage of dihydrogen in the initial stream 5 is advantageously greater than 99%.
[0145] The hydrogenation reaction takes place in the loading 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.
[0146] Since the hydrogenation reaction is exothermic, an additional flux 85 of thermal energy is produced in the loading unit 11. The additional flux 85 is advantageously used in any of the elements of the installation 1 and / or in another device requiring a supply of thermal energy.
[0147] In the example, the initial flux 5 is transmitted to the loading unit 11 in which a hydrogenation reaction of the discharged flux 13 comprising LOHC in the discharged state produces the intermediate flux 15, which comprises LOHC in the loaded state.
[0148] Advantageously, at least a fraction of the tenth stream 77 is reused to form at least in part the discharged stream 13 entering the loading unit 11.
[0149] Advantageously, the tenth stream 77 is entirely reused to form at least in part the discharged stream 13 entering the loading unit 11.
[0150] Advantageously, the fourth stream 55 is at least partly reused to form at least partly the discharged stream 13 comprising LOHC in the discharged state entering the loading unit 11.
[0151] In these last two cases, the reused flow(s) are transported by dedicated means of transport, similar or not to those of transport unit 17 and / or by transport unit 17.
[0152] In the example, the intermediate flow 15 is transported by the transport unit 17 and after transport constitutes the entirety of the incoming flow 21 for the reactive section 25.
[0153] Optionally, the fourth stream 55 undergoes an additional separation step, for example by means of a gravity separator 95 to form a stream 100, recovered at the bottom of the separator 95 and comprising LOHC in a greater proportion than the stream 55, and a stream 105, recovered at the top and comprising dihydrogen, the stream 105 being supplied to the thermal production unit 74 where it undergoes combustion.
[0154] In this case, the stream 100 is at least partly reused to form at least partly the discharged stream 13 comprising LOHC in the discharged state entering the loading unit 11.
[0155] The production process makes it possible to obtain the sixth stream 35 comprising dihydrogen with a carbon dioxide footprint preferably less than 3 kg of carbon dioxide per kilogram of dihydrogen, preferably less than 1.5 kg of carbon dioxide per kilogram of dihydrogen.
[0156] Taking a portion of the sixth stream 35, which contains dihydrogen in a higher proportion than the second stream 27, for reuse in subsequent stages of the production process, particularly to produce the thermal energy required for the dehydrogenation stage, ensures at least partial decarbonization of the production process. This arrangement avoids the need to use an energy source external to the production facility 19 to constitute the eleventh stream 81, as external energy sources available locally at any given time are not necessarily decarbonized.
[0157] This partial decarbonization makes it possible to maintain the technological choice of LOHC, which has the advantage of allowing very flexible management of dihydrogen production in terms of production location and availability date of the dihydrogen flow.
[0158] The production of the seventh stream 69 at the expansion stage from the sixth stream 37 allows for even greater decarbonization, since it allows for at least partial decarbonization of the first purification stage and the heat transfer stage.
[0159] Reusing the fourth stream 55 and / or the tenth stream 77 for the loading step also reduces inventory losses in organic hydrogen transport liquid, as well as limiting or even reducing the quantities of LOHC sent to the thermal energy production unit 47 and the resulting CO2 emissions.
[0160] The purge stream separation step 50 optimizes the use of this by-product by generating a tenth stream 77 that can be reused in the loading step. This separation step necessitates the heat transfer step of the process, but the additional energy 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.
[0161] The purge stream separation step 50 also generates the ninth stream 75, the combustion of which has a better efficiency and generates less undesirable by-products, particularly 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 on the delivered hydrogen, for example by 0.2 to 1.0 kg of carbon dioxide per kg of dihydrogen, which represents a very significant reduction and can be key in the development of sufficiently decarbonized hydrogen transport chains.
Claims
1. Demands A process for producing a stream (2) comprising dihydrogen at a molar percentage greater than 95% for a user from an incoming stream (21) comprising an organic hydrogen transport liquid having at least two possible states: a discharged state and a charged state, the transition from the charged state to the discharged state being obtained by means of an endothermic dehydrogenation reaction, the process comprising the following steps: • a dehydrogenation of the incoming flow in the charged state using a first flow (51) of thermal energy, to obtain a second flow (27) comprising dihydrogen and organic hydrogen transport liquid in the uncharged 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 uncharged organic hydrogen transport liquid and to obtain a fifth stream (31) comprising dihydrogen at a molar percentage higher than that of the second stream (27); • a second purification of the fifth stream (31) in a pressure reversal adsorption unit (33) to obtain a sixth stream (35) comprising dihydrogen at a higher molar percentage than the fifth stream (31) and to obtain a purge stream (50) comprising unloaded organic hydrogen transport liquid and dihydrogen; • an expansion of 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 dihydrogen colder than the sixth stream (35), a second fraction of the sixth stream (35) being said stream (2) produced for the user; • a heat transfer from the purge flow (50) to the eighth flow (41) to obtain a cooled purge flow (71) and to obtain a heated eighth flow (45); • a separation of the cooled purge stream (71) to obtain a ninth stream (75) comprising dihydrogen and to obtain a tenth stream (77) comprising organic hydrogen transport liquid in the discharged state in a molar percentage greater than that of the purge stream (50); and • a combustion of at least a fraction of the eighth heated 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. A method according to claim 1, wherein at least a fraction of the third stream (53) is obtained from the seventh stream (69) and / or the eleventh stream (81).
3. A method according to claim 1 or 2, comprising the production of an electrical energy stream from a fraction (90) of said eighth heated stream (45).
4. A method according to any one of claims 1 to 3, wherein the entirety of the first stream (51) is obtained from the eleventh stream (81).
5. A 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. A method according to any one of claims 1 to 5, wherein the organic hydrogen-carrying liquid is selected from toluene, benzyltoluene, dibenzyltoluene, n-ethylcarbazole, n-isopropylcarbazole, n-butylcarbazole, l,2-dihydro-l,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. A process according to any one of the preceding claims, further comprising the following steps: • production of an initial stream (5) comprising dihydrogen; and • hydrogenation of a stream (13) of organic hydrogen transport liquid in the discharged state by the initial stream (5) to produce the incoming stream (21).
8. A process according to claim 7, further comprising at least one of the following steps: • transport of the charged organic hydrogen transport liquid between hydrogenation and dehydrogenation; • storage of the charged organic hydrogen transport liquid between hydrogenation and dehydrogenation.
9. A process according to claim 7 or claim 8, wherein at least a portion of the stream (13) of organic hydrogen-carrying liquid in the discharged state for hydrogenation is derived from the first purification and / or separation.
10. Production installation (19) of a stream (2) of dihydrogen with a molar percentage greater than 95% for a user from an inlet stream (21) comprising an organic hydrogen transport liquid having two states: an uncharged state and a charged state, the transition from the charged state to the uncharged state being obtained by means of an endothermic dehydrogenation reaction, the installation comprising: • a reactive section (25) configured to receive the inlet stream (21) in the charged state and a first stream (51) of thermal energy and to produce a second stream (27) comprising dihydrogen and organic hydrogen transport liquid in the uncharged 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 uncharged organic hydrogen transport liquid and to produce a fifth stream (31) comprising dihydrogen in a molar percentage higher than that of the second stream (27); • a pressure reversal adsorption unit (33) configured to receive the fifth stream (31) and to produce a sixth stream (35) comprising dihydrogen in a molar percentage higher than that of the fifth stream (31) and to produce a purge stream (50) comprising; organic hydrogen transport liquid in the discharged state and dihydrogen; • an expansion turbine (37) configured to produce a seventh stream (69) of mechanical energy and an eighth stream (41) comprising dihydrogen 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 flow (41) and the purge flow (50) and to provide a cooled purge flow (71) and a heated eighth flow (45); • a separation unit (43) configured to receive the cooled purge stream (71) and to provide a ninth stream (75) comprising dihydrogen and to provide a tenth stream (77) comprising organic hydrogen transport liquid in the discharged state in 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 eighth reheated stream (45) and optionally of the ninth stream (75), an eleventh stream (81) of thermal energy; the production facility (19) being further configured to form at least a fraction of the first stream (51) from at least a fraction of the eleventh stream (81).