Installation and method for storing and dispensing cryogenic fluid

Abstract

The invention relates to an installation for storing and distributing cryogenic fluid, for example liquid hydrogen, comprising a cryogenic tank (11) buried underground, a liquid withdrawal circuit (20) connected to the tank (11) with a downstream end located above the ground and intended to be connected to a user, the withdrawal circuit (20) comprising, arranged above the ground, a cryogenic pump (2), the installation (1) comprising a pipe (3) for recovering vaporization gases generated within the pump (2) having a downstream end connected to the tank (11), the pipe (3) for recovering the vaporization gases comprising at least one device (8, 9) for regulating the pressure and / or flow rate of the vaporization gas returned to the tank (11), the pressure and / or flow rate regulating device (8, 9) being configured to regulate the pressure within the tank (11) to a pressure level higher than the pressure at the inlet of the pump (2).

Description

[0001] The invention relates to an installation and a method for storing and distributing cryogenic fluid.

[0002] US2291678A discloses a liquefied gas storage and distribution facility.

[0003] The invention relates more particularly to a cryogenic fluid storage and distribution installation, for example liquid hydrogen, comprising a cryogenic tank buried underground, a liquid withdrawal circuit comprising an upstream end connected to the tank and a downstream end located above ground and intended to be connected to a user, the withdrawal circuit comprising, located above ground, a cryogenic pump, the installation comprising a vaporization gas recovery line generated within the pump having an upstream end connected to the pump and a downstream end connected to the tank.

[0004] The space constraints associated with hydrogen storage are a major challenge. One solution is underground storage. However, combining underground cryogenic storage with surface-mounted filling pumps raises the issue of supplying these pumps with liquid during their various lifecycle phases. Traditionally, the pump is supplied with liquid by gravity, provided there is sufficient liquid level in the storage tank to ensure the liquid reaches the pump inlet. Furthermore, in cryogenic fueling stations, the pump requires a cooling phase during startup, which causes some of its supply to evaporate (boiling gas, or "BOG"). This vaporization gas is usually returned to the storage tank via lines that carry the gas to the top of the tank. When the storage tank is located above the pump, this return occurs naturally.This function becomes more difficult to ensure in a configuration where the highest point of the storage is lower than the pump inlet.

[0005] One aim of the present invention is to overcome all or part of the disadvantages of the prior art noted above.

[0006] To this end, the installation according to the invention, which also conforms to the generic definition given in the preamble above, is essentially characterized in that the vaporization gas recovery line includes at least one pressure and / or flow control device for the vaporization gas returned to the tank, the pressure and / or flow control device being configured to regulate the pressure within the tank to a pressure level higher than the pressure at the pump inlet.

[0007] This arrangement ensures a good supply to the pump to guarantee its operation by allowing the recovery of vaporization gases from the pump in the storage to reduce overall station losses.

[0008] Furthermore, embodiments of the invention may include one or more of the following characteristics: The pressure and / or flow control device is configured to regulate the pressure within the tank to a level between 5 mbar and 500 mbar above the pressure at the pump inlet. The pressure and / or flow control device includes at least one of the following: a heater, a heat exchanger, a compressor, for example a cryogenic compressor. The pressure and / or flow control device includes, arranged in series, a heating heat exchanger and a compressor. The vaporization gas recovery line includes two separate passages in the heating heat exchanger, respectively before and after compression in the compressor, to ensure heating of the vaporization gas before compression and cooling before injection into the tank, respectively.The vaporization gas recovery line includes a bypass line from the heat exchanger and a set of valve(s) configured to allow at least a portion of the vaporization gas flow to bypass the heat exchanger. The vaporization gas recovery line includes a branch line fitted with a valve leading to a discharge area. The installation includes a tank pressurization device that is self-contained and separate from the vaporization gas recovery line and the control device. The invention also relates to a fluid withdrawal method using an installation according to any one of the above or below characteristics, characterized in that it comprises the following steps: pumping cryogenic liquid from the tank via the pump, and recovering vaporization gases generated at the pump.Compression of the recovered vaporization gases and injection of the compressed gases into the tank at a predetermined pressure.

[0009] Depending on other possible characteristics: The compression of the recovered vaporization gases is carried out with a cryogenic compressor or with a non-cryogenic compressor, the vaporization gases being heated before compression in the case of the non-cryogenic compressor, the compression of the recovered vaporization gases is carried out with a non-cryogenic compressor and also includes a step of cooling the compressed vaporization gases via a heat exchange with the vaporization gas stream upstream of the compressor.

[0010] The invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims. Other features and advantages will become apparent from the following description, given with reference to the figures in which: Brief description of the figures

[0011] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which: [ Fig. 1 ] is a schematic vertical cross-sectional view describing an example of the structure and operation of an installation according to the invention. Detailed description

[0012] In all the figures, the same references refer to the same elements.

[0013] In this detailed description, the following embodiments are examples. Although the description refers to one or more embodiments, this does not mean that the features apply only to a single embodiment. Simple features from different embodiments can also be combined and / or interchanged to provide other embodiments.

[0014] The cryogenic fluid storage and distribution system illustrated (1) can be used, for example, for liquid hydrogen. The system includes a cryogenic tank (11) buried underground and a liquid withdrawal circuit (20) comprising an upstream end connected to the tank (11) and a downstream end located above ground and intended to be connected to a user.

[0015] The 20 withdrawal circuit includes, positioned above the ground, a cryogenic pump 2.

[0016] Installation 1 includes a vaporization gas recovery line 3 generated within pump 2, having an upstream end connected to pump 2 and a downstream end connected to tank 11. This vaporization gas recovery line 3 includes at least one pressure and / or flow control device for the vaporization gas returned to tank 11. This at least one pressure and / or flow control device 8, 9 being configured to regulate the pressure within tank 11 to a pressure level higher than the pressure at the inlet of pump 2.

[0017] This pressure and / or flow control device is preferably configured to regulate the pressure within the tank 11 above the pressure at the pump inlet so as to overcome the hydrostatic head between the tank and the pump inlet 2. For example, the pressure and / or flow control device is configured to regulate the pressure within the tank at a level between 5mbar and 500mbar above the pressure at the pump inlet, for example between 5mbar and 100mbar above the pressure at the pump inlet.

[0018] The pressure and / or flow control device includes at least one of the following: a heater 8, a heat exchanger 7, a compressor 9, for example a cryogenic compressor. For the sake of simplicity, the [ Fig. 1 ] represents the three aforementioned components in series. Of course, only one or two may be required.

[0019] The pressure and / or flow control device may include or consist, for example, of a reheating heat exchanger 7 in series with a compressor 9.

[0020] The vaporization gas produced by pump 2 is heated in heat exchanger 7 and can then be returned to tank 11.

[0021] Reservoir 11 can thus be kept under pressure to ensure an efficient supply to pump 2. Pump 2, which is located at a relatively higher elevation, is therefore at a lower pressure than reservoir 11. This pressure difference is, for example, between 10 and 100 mbar, as this is the pressure required to overcome the head difference between reservoir 11 and the inlet of pump 2, as well as the pressure losses in the inlet line. Recirculating the vaporization gas from pump 2 back into reservoir 11 compensates for this relative pressure difference.

[0022] This architecture allows for the recovery of vaporization gases generated by pump 2 during its various operating phases. During startup, pump 2 produces a relatively large quantity of vaporization gases. After cooling, during its operation, pump 2 generates a smaller quantity of vaporization gases, for example, due to leaks, thermal ingress, etc.

[0023] These vaporization gases can be collected and returned to tank 11 via recovery line 3.

[0024] This allows for the recovery of all or only part of these vaporization gases during these different operating phases.

[0025] The vaporization gases are collected in the recovery line 3, heated in the heating exchanger 7, and compressed before being returned to the tank. The compressor 9 circulates the vaporization gas flow by compressing it to the tank pressure, for example, to a level of a few tens of millibars.

[0026] The compressed vaporization gas can pass back through the reheating heat exchanger 7 to be cooled before being reinjected into the tank 11.

[0027] If this preheating exchanger 7 is not sufficient to heat the gas before compression (excessive vaporization gas flow rate, inlet temperature too cold, ...), an additional exchanger 8 (heater) may be provided to complete the heating up to a determined temperature (ambient temperature or compressor inlet temperature).

[0028] This optional heater 8 is shown in dotted lines between the heating exchanger 7 and the compressor 9.

[0029] As illustrated, a valve 5, for example an isolation valve, can be arranged in series between the pump 5 and the preheating heat exchanger 7. Similarly, a valve 5 is preferably provided upstream of the pump 2. A valve 5 can also be provided between the preheating heat exchanger 7 and the compressor 9. Likewise, a non-return valve 4 can be provided upstream of the pump 2.

[0030] As illustrated, the vaporization gas recovery line can make two separate passes (preferably counter-current) in the reheating heat exchanger 7 respectively before and after compression in the compressor 9 to respectively ensure reheating of the vaporization gas before compression and cooling before injection of the compressed gas into the tank 11.

[0031] As shown schematically, the vapor gas recovery line 3 may further include a bypass line 13 for the heat exchanger and a set of valve(s) 23 configured to allow at least part of the vapor gas flow to bypass the heat exchanger 7. For example, the bypass line 13 allows all or part of the compressed vapor gas flow to bypass the second pass through the reheating exchanger 7. This makes it possible to increase the temperature of the compressed vapor gas before returning it to the tank 11 to stabilize the pressure in the tank 11 if it rises too rapidly.

[0032] As also illustrated, the vaporization gas recovery line 3 may include a branch 33 equipped with a valve leading to a discharge area. This branch may be located between the preheating exchanger 7 and the compressor inlet 9.

[0033] The tank 11 may include a self-contained pressurization device 10 configured to increase its pressure as required (by drawing off, heating and reinjecting fluid).

[0034] This recovery and utilization of vaporization gases allows the reservoir 11 to be maintained under positive pressure relative to the pump 2. This ensures good continuous intake into the pump 2. If the recovered vaporization gases are insufficient to maintain a sufficiently high pressure during pump operation, the pressurization device 10 can be used to pressurize the reservoir 11.

[0035] Of course, the invention is not limited to this example of embodiment described above.

[0036] Thus, for example, the reheating heat exchanger 7 and the compressor 9 could be replaced by a cryogenic compressor (which can compress the gas at cryogenic temperature without the need for prior heating).

Claims

1. An installation for storing and distributing a cryogenic fluid, for example liquid hydrogen, comprising a cryogenic reservoir (11) buried underground, a liquid withdrawal circuit (20) comprising an upstream end connected to the reservoir (11) and a downstream end located above ground and intended to be connected to a user, the withdrawal circuit (20) comprising, arranged above ground, a cryogenic pump (2), the installation (1) comprising a line (3) for recovering vaporization gas generated within the pump (2) having an upstream end connected to the pump (2) and a downstream end connected to the reservoir (11), characterized in that the line (3) for recovering vaporization gas comprises at least one device (8, 9) for regulating the pressure and / or flow rate of the vaporization gas returned to the reservoir (11), the device (8, 9) for regulating pressure and / or flow rate being configured to regulate the pressure within the reservoir (11) to a pressure level higher than the pressure at the inlet of the pump (2).

2. The installation according to claim 1, characterized in that the device for regulating pressure and / or flow rate is configured to regulate the pressure within the reservoir to a level comprised between 5 mbar and 500 mbar above the pressure at the inlet of the pump (2).

3. The installation according to claim 1 or 2, characterized in that the device (8, 9) for regulating pressure and / or flow rate comprises at least one from among: a heater (8), a heat exchanger (7), a compressor (9), for example a cryogenic compressor.

4. The installation according to claim 3, characterized in that the device (8, 9) for regulating pressure and / or flow rate comprises, arranged in series, a reheating heat exchanger (7), a compressor (9).

5. The installation according to claim 4, characterized in that the line (3) for recovering vaporization gas comprises two distinct passages in the reheating heat exchanger (7) respectively before and after compression in the compressor (9) to ensure respectively a reheating of the vaporization gas before compression and a cooling before injection into the reservoir (11).

6. The installation according to claim 4 or 5, characterized in that the line (3) for recovering vaporization gas comprises a bypass line (13) for the heat exchanger and a set of valve(s) (23) configured to allow at least part of the vaporization gas flow to avoid passing through the heat exchanger (7).

7. The installation according to any one of claims 1 to 6, characterized in that the line (3) for recovering vaporization gas comprises a tapping point (33) equipped with a valve towards an evacuation zone.

8. The installation according to any one of claims 1 to 7, characterized in that it comprises a pressurization device (10) for the reservoir that is autonomous and distinct from the line (3) for recovering vaporization gas and from the regulation device (8, 9).

9. A method for withdrawing fluid using an installation according to any one of claims 1 to 8, characterized in that it comprises the following steps: pumping cryogenic liquid from the reservoir via the pump (2), recovering vaporization gas generated at the level of the pump (2), compressing the recovered vaporization gas and injecting the compressed gas into the reservoir (2) at a determined pressure.

10. The method according to claim 9, characterized in that the compression of the recovered vaporization gas is performed with a cryogenic compressor or with a non-cryogenic compressor, the vaporization gas being heated before compression in the case of the non-cryogenic compressor.

11. The method according to claim 10, characterized in that the compression of the recovered vaporization gas is performed with a non-cryogenic compressor and further comprises a step of cooling the compressed vaporization gas via a heat exchange with the flow of vaporization gas upstream of the compressor (9).

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