Equipment and method for hydrogen cooling

Abstract

The present invention relates to an installation for cooling hydrogen to cryogenic temperatures, in particular for liquefying hydrogen, comprising a circuit (2) for the hydrogen to be cooled, the circuit (2) comprising an upstream end connected to a hydrogen source and a downstream end connected to a cooled hydrogen collecting element, a set of one or more heat exchangers (3, 4) for exchanging heat with the circuit (2) for the hydrogen to be cooled, and a device for cooling by heat exchange with the set of one or more heat exchangers (3, 4), the cooling device comprising a cooler (5) having a refrigeration cycle for a circulating gas such as hydrogen, the hydrogen circuit (2), the one or more ... The installation (1) comprises a set of heat exchangers (3, 4) and at least part of a cooling device housed in a vacuum insulated cold box (6), and the installation (1) comprises, within the cold box (6), at least one ejector (8), the suction inlet of the at least one ejector (8) being connected to the gas phase of the fluid volume (13), and the motor fluid suction inlet of the at least one ejector (8) being connected to at least one of the pressurized circulation gas of the cooler (5) and the hydrogen of the hydrogen circuit (2) cooled in the set of one or more heat exchangers (3, 4).

Description

[Technical Field]

[0001] The present invention relates to an installation and method for cooling hydrogen.

[0002] The invention more particularly relates to an installation for cooling hydrogen to very low temperatures, in particular for liquefying hydrogen, comprising a circuit for cooled hydrogen, the circuit having an upstream end intended to be connected to a hydrogen source and a downstream end connected to a means for collecting cooled and / or liquefied hydrogen, a set of heat exchangers in heat exchange relationship with the circuit for cooled hydrogen, and a cooling device in heat exchange relationship with the set of heat exchangers, said cooling device comprising a cooler performing a refrigeration cycle on a circulating gas in a working circuit, the circulating gas being hydrogen, the working circuit of the cooler comprising a member for compressing the circulating gas, a member for cooling the circulating gas, a member for expanding the circulating gas including at least one turbine, and a member for warming the circulating gas. [Background technology]

[0003] The expansion of the hydrogen market as a fuel for mobility purposes leads to the creation of large-scale hydrogen liquefaction capacities for logistics, where the product is used in liquid form. At the stage of storage and truck loading, very cold liquid hydrogen produces boil-off gas that must be recycled to recover not only the hydrogen molecules but also the cryogenic energy contained in these low-temperature gases. For this purpose, one known means is to pump the subcooled liquid into a volume that receives the liquid produced by the liquefier (storage vessel or semi-trailer).

[0004] Another solution is to use an ejector to return the boil-off gas to a fixed reservoir.

[0005] An ejector can be used to increase the pressure of the boil-off gas coming from a fixed reservoir and make it possible to inject this gas into the liquefier.

[0006] The ejector allows the expansion of a high pressure stream (the drive fluid) to pressurize a low pressure stream (the drawn in suction fluid).

[0007] The cooled hydrogen stream can be used as a motive fluid, however, using the pressure of the cooled hydrogen in this way reduces the possibility of cooling the stream (by expansion) to produce a cooler fluid. Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE INVENTION One object of the present invention is to alleviate all or part of the above-mentioned drawbacks of the prior art. [Means for solving the problem]

[0009] For this purpose, the installation according to the invention, otherwise in accordance with its general definition given in the preamble above, is essentially characterized in that it comprises at least an ejector, the drive fluid inlet of which is connected via a set of pipes and valves to the working circuit of the cooler downstream of the expansion member, the suction inlet of which is connected to a set of pipes equipped with a valve having an end intended to be connected to the gas overhead of at least one mobile tank for transporting liquefied hydrogen, in particular a liquefied hydrogen transport tank intended to be filled with liquefied hydrogen by the downstream end of the hydrogen circuit, and the outlet of the ejector is connected via a set of pipes and valves to the working circuit of the cooler.

[0010] Furthermore, embodiments of the invention may have one or more of the following features. - the installation includes several ejectors, - the installation comprises at least one liquefied hydrogen tank transport tank intended to be filled with cooled hydrogen and including a fluid inlet configured to be removably connected to a downstream end of the hydrogen circuit, the at least one tank including a boil-off gas outlet configured to be removably connected to a suction inlet of an ejector (8) via a set of pipes equipped with a valve; - the cooling device includes a pre-cooling member in heat exchange relationship with a portion of the set of heat exchangers; the outlet flow leaving the ejector is at a pressure of between 1.25 and 2 bara, preferably between 1.3 and 1.45 bara; - the flow rate of the drive fluid is controlled as a function of the ejector outlet pressure, said flow rate being adjusted to maintain a constant pressure set point at the ejector outlet; - the working circuit of the cooler includes several heat exchangers in series between a high temperature end of the working circuit, where the working fluid is at a relatively high pressure, and a low temperature end of the working circuit, where the fluid is at a relatively low pressure, and the outlet flow from the ejector is injected into the working circuit at the low temperature end; The method includes simultaneously drawing boil-off gas from a plurality of mobile liquefied hydrogen transport tanks into a plurality of suction inlets using pressurized working gas from the working circuit as a driving fluid for the ejectors, the outlet streams from the ejectors being injected into the working circuit.

[0011] The present invention also relates to a method for cooling hydrogen to cryogenic temperatures, in particular for liquefying hydrogen, using an installation according to any one of the above or below characteristics, the method comprising the step of drawing boil-off gas from a mobile liquefied hydrogen transport tank into a suction inlet of the ejector using pressurized working gas from the working circuit as a driving fluid for the ejector, the outlet flow from the ejector being injected into the working circuit.

[0012] According to other possible distinguishing features: the boil-off gas pumped has a pressure and temperature of 1.01325 to 1.5 bara, preferably 1.15 to 1.3 bara, the saturation temperature of hydrogen and 60 K; the pressure of the driving fluid is between 5 and 10 bara, preferably between 6 and 7 bara, and the temperature of the driving fluid is between 28 and 35 K, preferably between 29.3 and 30 K; - The outlet flow leaving the ejector is at a pressure equal to or greater than the pressure of the circulating gas at the coldest point in the working circuit.

[0013] The invention may also relate to any cooling device or method including any combination of the above or below features within the scope of the claims.

[0014] Other distinctive features and advantages will become apparent on reading the following description given with reference to the following: [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic and partial view showing an example of the structure and operation of a hydrogen cooling / liquefaction facility according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The installation 1 for cooling hydrogen to very low temperatures, in particular for liquefying hydrogen, comprises a circuit 2 for the hydrogen to be cooled, the circuit 2 comprising an upstream end 21 intended to be connected to a hydrogen source and a downstream end 22 connected to a member for collecting the cooled hydrogen (a liquid buffer reservoir 17 and / or a pipe for filling the tank 13).

[0017] The refrigeration installation 1 comprises a set of heat exchangers 3, 4 in heat exchange relationship with a circuit 2 for hydrogen to be cooled. The installation 1 comprises a cooling device in heat exchange relationship with the set of heat exchangers 3, 4, said cooling device comprising a cooler 5 which performs a refrigeration cycle on a circulating gas consisting of or comprising hydrogen (and / or other suitable gases, e.g. helium).

[0018] The hydrogen circuit 2, the set of exchangers 3, 4 and at least part of the cooling device (its low temperature part) are preferably housed in a vacuum insulated cold box. In particular, given the temperature levels used (e.g., around 20 K), the hydrogen liquefaction and (super)cooling heat exchangers 3, 4 are installed under vacuum (i.e., at very low pressure) inside an enclosed space.

[0019] The working circuit of the cooler 5 comprises, arranged in series, a circulation gas compression member 6, a circulation gas cooling member 3, 4, a circulation gas expansion member 7 including at least one turbine, and a circulation gas heating member 4, 3.

[0020] The compression member 6 may, for example, comprise two compressors in series, the inlets of which are, for example, at different pressure levels.

[0021] The set of exchangers 3, 4 comprises, for example, two heat exchangers in series, for example counter-current heat exchangers, which simultaneously cool and warm the working fluid according to the passage direction of the working circuit.

[0022] As shown, the cooling device of the installation 1 may include a pre-cooling element 15 in heat exchange relationship with part of the set of heat exchangers 3, 4, in particular the first heat exchanger 3 downstream of the compression element 6. This pre-cooling element 15 may, for example, be a separate cooler, for example, a separate working fluid, such as nitrogen. For example, this pre-cooling element 15 may allow the fluid to be pre-cooled to a temperature of 70-100K.

[0023] After this pre-cooling, the hydrogen cooler 5 performs additional cooling to the target temperature of the circuit 2 (the temperature at which hydrogen liquefies).

[0024] The working circuit of the cooler 5 imposes a thermodynamic cycle on the working fluid having a relatively low pressure portion (rising from bottom to top in the schematic diagram) and a relatively higher pressure portion (decreasing from top to bottom in the schematic diagram). In particular, the working fluid (hydrogen) undergoes expansion in at least one turbine of an expansion member to produce cold air.

[0025] The installation 1 comprises at least one ejector 8, the driving fluid inlet of which is connected via a pipe 9 and a valve 10 (in particular an isolation valve) to the working circuit of the cooler 5 downstream of the expansion member 7, in particular downstream of the expansion turbine.

[0026] The suction inlet of the ejector 8 is connected to a set of pipes 11 equipped with valves 12 (in particular isolation valves) and has an end that can be connected to the gas overhead of at least one mobile liquefied hydrogen transport tank 13 .

[0027] In particular, the suction inlet may be fluidly connected to the gas overhead of a liquefied hydrogen transport tank 13 intended to be filled with liquid hydrogen by the downstream end 22 of the cooled hydrogen circuit 2 of the installation 1 .

[0028] The outlet of the ejector 8 is connected for its part via a set of pipes 14 and valves 17 to the working circuit of the cooler so as to be reinjected therein.

[0029] The flow of gas (boil-off gas) drawn from the tank 13 directly connected to the circuit 2 supplying cooled (in particular liquefied) hydrogen may, for example, be at a pressure of 1.01325 to 1.5 bara, preferably 1.15 to 1.3 bara (for example, the pressure at the outlet of the tank 13). The temperature of this gas may be between the saturation temperature and 60 K.

[0030] The drive gas flow of the ejector 8 used for pressurization is part of the working gas of the hydrogen-based refrigeration cycle. This drive gas is preferably a gas that has passed through several exchangers and is expanded by at least one turbine 7 of the expansion element.

[0031] Ideally, this gas used as the driving flow to drive the ejector 8 is taken from the outlet of the last turbine (if there are several turbines in series in the working circuit) and / or from the coldest outlet of the circuit (if there are several turbines 7 in parallel in the circuit).

[0032] The pressure of the driving gas may be, for example, 5 to 10 bara, preferably 6 to 7 bara, and the temperature of the driving gas may be, for example, 28 to 35K, preferably 29.3 to 30K.

[0033] The gas flow exiting the ejector 8 depends on the performance of the ejector and the characteristics of the suction inlet flow and the driving gas flow.

[0034] Conventionally, in chillers using a refrigeration cycle, a circulating gas (working gas) is subjected to a thermodynamic cycle in which temperature and pressure conditions are determined according to the position in the cycle. In particular, at an end in the cycle known as the coldest end, the circulating fluid reaches a temperature that is relatively the coldest temperature in the cycle at the determined corresponding pressure conditions.

[0035] Preferably, the pressure of the gas stream leaving the ejector is at least equal to the pressure of the low-pressure stream of working fluid of the refrigeration cycle at its coldest point (in the working circuit) as it is recycled (injected). This pressure may be, for example, between 1.25 and 2 bara, preferably between 1.3 and 1.45 bara.

[0036] This means that upon leaving the ejector the stream will have a higher pressure than this pressure of the circulating gas at the coldest end of the cycle.

[0037] To achieve that, the flow rate of the motive flow coming from the outlet of the turbine 7 and passing through the ejector 8 can be controlled as a function of the pressure conditions of the flow leaving the ejector 8. The flow rate can in particular be adjusted so that the pressure set point is constant and slightly higher than the pressure of the low pressure flow of working fluid in the cooling cycle.

[0038] Naturally, the flow rate of the ejector(s) 8 depends on the number of tanks 13 (trailers) used and filled at the downstream end 22 of the cooled hydrogen circuit of the installation.

[0039] The outlet stream from the ejector 8 enters the cold box of the facility's liquefier and must be mixed with the low-pressure stream of working fluid of the liquefier's refrigeration cycle. As shown, this outlet stream from the ejector 8 is preferably injected into the working circuit before the working fluid returns to the compression element 6 (before passing through the exchangers 4, 3 which warm up to the inlet of the low-pressure compressor 6).

[0040] Preferably, therefore, the mixing (injection) is carried out at the cold end of the last exchanger 4 of the working circuit (above the thermosiphon exchanger, if present, or in the last series exchanger 4 if no thermosiphon is present). This means that the boil-off gas recovered in the tank 13 is now mixed in the working circuit with the boil-off gas that may come from the fixed reservoir 16 (if applicable) and with the gas coming from the outlet of the thermosiphon (if applicable).

[0041] The boil-off gas supplied by the mobile tanks 13 filled with liquid is intermittent as it is linked to the presence of the filled trailer 13. Therefore, as shown, it is necessary to be able to isolate the ejector(s) 8 from the liquefier 8 and the pipes used to fill the trailer 13, preferably using a set of isolation valves 10, 12, 17. When no boil-off gas is to be recovered, these valves must be closed.

[0042] In a facility, several tanks 13 can be filled simultaneously, which means that the flow rate of the recovered boil-off gas can vary widely. However, the ejector 8 does not function optimally over a wide range of flow rates (the ejector's tolerance for inlet flow rate variation is approximately 75%-100%).

[0043] Thus, as shown, a plurality of (particularly two or more) ejectors 8 in the installation 1 can be arranged and connected in parallel with their respective valves. The recommended number of ejectors 8 is preferably the maximum number of tanks 13 that can simultaneously generate low-pressure boil-off gas (which occurs when this tank or these tanks 13 receive liquid from the reservoir 16 via line 22). In particular, trucks can be received in the installation 1 without generating these low-pressure gases, which can be in the process of being combined or in a depressurization stage (which generates high-pressure boil-off gas without the need for the use of ejectors). For example, two or four ejectors or any other number of ejectors depending on the installation can be provided.

[0044] For each ejector 8, a corresponding set of valves must be able to be placed in an open or closed position independently, depending on the number of tanks 13 producing boil-off gas at any given time. In the schematic diagram, a single tank 13 is connected and the installation includes two ejectors 8, one of which is isolated (valves shown in black are closed) and only one is in use (valves shown in white are open).

[0045] This solution makes it possible to recirculate a large amount of the boil-off gas stream, benefiting from its low temperature. Compared to current solutions that use the cooled hydrogen stream of circuit 2 as drive gas, this solution makes it possible to save the expansion of this hydrogen stream for more advantageous uses (e.g. expansion in a liquid turbine).

[0046] In addition, the present invention makes it possible to reduce the risk of impurities being sent to storage device 13, since the recovered boil-off gas will be purified again when combined with the feedstock of facility 1. The following is a summary of the claims as originally filed: [1] An installation for cooling hydrogen to cryogenic temperatures, in particular for liquefying hydrogen, comprising a circuit (2) for cooled hydrogen, the circuit (2) comprising an upstream end (21) intended to be connected to a hydrogen source and a downstream end (22) connected to a means for collecting the cooled and / or liquefied hydrogen, a set of heat exchangers (3, 4) in heat exchange relationship with the circuit (2) for cooled hydrogen, a cooling device in heat exchange relationship with the set of heat exchangers (3, 4), the cooling device comprising a cooler (5) for carrying out a refrigeration cycle on a circulating gas in a working circuit, the circulating gas being hydrogen, the working circuit of the cooler (5) comprising a means (6) for compressing the circulating gas, a means (3, 4) for cooling the circulating gas, and at least one turbine for expanding the circulating gas. and elements (4, 3) for warming the circulating gas, and the installation (1) comprises at least an ejector (8), the drive fluid inlet opening of which is connected via a set of pipes (9) and valves (10) to the working circuit of the cooler (5) downstream of the expansion element (7), the suction of which is connected to a set of pipes (11) equipped with valves (12) having an end intended to be connected to the gas overhead of at least one mobile tank (13) for transporting liquefied hydrogen, in particular a liquefied hydrogen transport tank (13) intended to be filled with liquefied hydrogen by the downstream end (22) of the hydrogen circuit (2), and the outlet of the ejector (8) is connected to the working circuit of the cooler via a set of pipes (14) and valves (16). [2] The installation according to [1], characterized in that it comprises several ejectors (8). [3] The installation according to [1] or [2], characterized in that it comprises at least one liquefied hydrogen tank transport tank (13) including a fluid inlet configured to be removably connected to the downstream end (22) of the hydrogen circuit (2) for the purpose of being filled with cooled hydrogen, and the at least one tank (13) includes a boil-off gas outlet configured to be removably connected to the suction inlet of the ejector (8) via the set of pipes (11) equipped with a valve. [4] The facility described in any one of [1] to [3], characterized in that the cooling device includes a pre-cooling member (15) that is in a heat exchange relationship with a part of the set of heat exchangers (3, 4). [5] A method for cooling hydrogen to cryogenic temperatures, in particular for liquefying hydrogen, using the installation according to any one of [1] to [4], comprising the step of drawing boil-off gas from a mobile liquefied hydrogen transport tank (13) into the suction inlet of the ejector (8) using pressurized working gas from the working circuit as a driving fluid for the ejector (8), and the outlet flow from the ejector (8) being injected into the working circuit. [6] The method according to [5], wherein the pumped boil-off gas has a pressure of 1.01325 to 1.5 bara, preferably 1.15 to 1.3 bara, and a temperature of the hydrogen saturation temperature to 60K. [7] The method according to [5] or [6], characterized in that the pressure of the driving fluid is 5 to 10 bara, preferably 6 to 7 bara, and the temperature of the driving fluid is 28 to 35 K, preferably 29.3 to 30 K. [8] The method according to any one of [5] to [7], wherein the outlet flow leaving the ejector (8) is at a pressure equal to or greater than the pressure of the circulating gas at the coldest point of the working circuit. [9] The method according to any one of [5] to [8], characterized in that the outlet flow leaving the ejector (8) is at a pressure of 1.25 to 2 bara, preferably 1.3 to 1.45 bara.

[10] The method according to any one of [5] to [9], characterized in that the flow rate of the driving fluid is controlled as a function of the outlet pressure of the ejector (8), and the flow rate is adjusted to maintain a constant pressure set point at the outlet of the ejector (8).

[11] The method according to any one of [5] to

[10] , characterized in that the working circuit of the cooler (5) comprises several heat exchangers (3, 4) in series between a high temperature end of the working circuit where the working fluid is at a relatively high pressure and a low temperature end of the working circuit where the fluid is at a relatively low pressure, and the outlet flow from the ejector (8) is injected into the working circuit at the low temperature end.

[12] The method according to any one of [5] to

[11] , characterized in that it comprises simultaneously drawing boil-off gas from a plurality of mobile liquefied hydrogen transport tanks (13) into the suction inlets of a plurality of (8) using pressurized working gas from the working circuit as a driving fluid for the ejectors (8), and the outlet flow from the ejectors (8) is injected into the working circuit.

Claims

1. 1. An installation (1) for cooling hydrogen to cryogenic temperatures, comprising a hydrogen circuit (2) for the hydrogen to be cooled, the hydrogen circuit (2) comprising an upstream end (21) intended to be connected to a hydrogen source and a downstream end (22) connected to a means for collecting said cooled and / or liquefied hydrogen, the installation (1) comprising a set of heat exchangers (3, 4) in heat exchange relationship with the hydrogen circuit (2) for hydrogen to be cooled, The facility (1) comprises a cooling device in a heat exchange relationship with the set of heat exchangers (3, 4), the cooling device comprising a cooler (5) for performing a cooling cycle on a circulating gas in a working circuit, the circulating gas being hydrogen; The working circuit of the cooler (5) comprises a compression element (6) for compressing the circulating gas, a cooling element (3, 4) for cooling the circulating gas, an expansion element (7) for expanding the circulating gas, including at least one turbine, and a heating element (4, 3) for heating the circulating gas; The installation (1) comprises at least an ejector (8), the drive fluid inlet opening of which is connected to the working circuit of the cooler (5) downstream of the expansion member (7) via a set of pipes (9) and valves (10); The suction port of the ejector (8) is connected to a set of pipes (11) equipped with valves (12) having an end intended to be connected to the gas overhead of at least one mobile tank (13) for transporting liquefied hydrogen, The outlet of the ejector (8) is connected to the working circuit of the cooler through a set of pipes (14) and valves (17).

2. 2. Installation according to claim 1, characterized in that it comprises several ejectors (8).

3. 3. The installation according to claim 1 or 2, characterized in that it comprises at least one liquefied hydrogen transport tank (13) including a fluid inlet configured to be removably connected to the downstream end (22) of the hydrogen circuit (2) for the purpose of being filled with cooled hydrogen, and the at least one liquefied hydrogen transport tank (13) comprises a boil-off gas outlet configured to be removably connected to the suction port of the ejector (8) via the set of pipes (11) equipped with a valve.

4. Installation according to any one of claims 1 to 3, characterized in that the cooling device comprises a pre-cooling member (15) in heat exchange relationship with part of the set of heat exchangers (3, 4).

5. 5. A method for cooling hydrogen to cryogenic temperatures using an installation according to any one of claims 1 to 4, comprising the step of drawing boil-off gas from a mobile liquefied hydrogen transport tank (13) into the suction port of the ejector (8) using pressurized working gas from the working circuit as a driving fluid for the ejector (8), the outlet flow from the ejector (8) being injected into the working circuit.

6. 6. The method according to claim 5, wherein the pumped boil-off gas is at a pressure of 1.01325 to 1.5 bara and at a temperature of the saturation temperature of hydrogen to 60K.

7. 7. The method according to claim 5, wherein the pressure of the driving fluid is between 5 and 10 bara and the temperature of the driving fluid is between 28 and 35 K.

8. A method according to any one of claims 5 to 7, characterized in that the outlet flow leaving the ejector (8) is at a pressure equal to or greater than the pressure of the circulating gas at the coldest point of the working circuit.

9. A method according to any one of claims 5 to 8, characterized in that the outlet flow leaving the ejector (8) is at a pressure of 1.25 to 2 bara.

10. 10. The method according to any one of claims 5 to 9, characterized in that the flow rate of the driving fluid is controlled depending on the outlet pressure of the ejector (8), said flow rate being adjusted to maintain a constant pressure set point at the outlet of the ejector (8).

11. 11. The method according to any one of claims 5 to 10, characterized in that the working circuit of the cooler (5) comprises several heat exchangers (3, 4) in series between a high temperature end of the working circuit, where the driving fluid is at a relatively high pressure, and a low temperature end of the working circuit, where the driving fluid is at a relatively low pressure, and the outlet flow from the ejector (8) is injected into the working circuit at the low temperature end.

12. 12. The method according to claim 5, further comprising simultaneously drawing boil-off gas from a plurality of mobile liquefied hydrogen transport tanks (13) into the suction ports of a plurality of ejectors (8) using pressurized working gas from the working circuit as a driving fluid for the ejectors (8), and the outlet flows from the ejectors (8) are injected into the working circuit.

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