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] The invention relates more particularly to an installation for storing and distributing cryogenic fluid, 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 the ground and intended to be connected to a user, the withdrawal circuit comprising, arranged above the ground, a cryogenic pump, the installation comprising a pipe for recovering vaporization gases generated within the pump having an upstream end connected to the pump and a downstream end connected to the tank.

[0003] The size of hydrogen storage is a major issue. One solution is underground storage. However, combining buried cryogenic storage with ground-based filling pumps poses the problem of supplying these pumps during their various life phases. The liquid supply to the pump is traditionally carried out by gravity, with sufficient liquid level in the storage for the liquid to reach the pump inlet. In addition, in cryogenic fuel stations, the pump requires cooling during startup and causes part of its supply (boil-off gas "BOG") to evaporate. This boil-off gas is most often returned to the storage via lines that carry the gas to the top of the storage. When the storage is above the pump, this return occurs naturally.This function becomes more difficult to ensure in a configuration where the high point of the storage is lower than the pump inlet.

[0004] An aim of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

[0005] To this end, the installation according to the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the vaporization gas recovery pipe comprises at least one device for regulating the pressure and / or flow rate of the vaporization gas returned to the tank, the pressure and / or flow rate regulating device being configured to regulate the pressure within the tank to a pressure level higher than the pressure at the inlet of the pump.

[0006] This arrangement ensures a good supply to the pump to ensure its operation by allowing the recovery of vaporization gases from the pump in the storage to reduce the overall losses of the station.

[0007] Furthermore, embodiments of the invention may include one or more of the following features: the pressure and / or flow rate regulating device is configured to regulate the pressure within the tank to a level between 5 mbar and 500 mbar above the pressure at the inlet of the pump, the pressure and / or flow rate regulating device comprises at least one of: a heater, a heat exchanger, a compressor, for example a cryogenic compressor, the pressure and / or flow rate regulating device comprises, arranged in series, a reheating heat exchanger, a compressor, the vaporization gas recovery line comprises two separate passages in the reheating heat exchanger respectively before and after compression in the compressor to respectively ensure reheating of the vaporization gas before compression and cooling before injection into the tank, the vaporization gas recovery line comprises a heat exchanger bypass line and

[0008] a set of valve(s) configured to allow at least a portion of the vaporization gas stream to bypass passage into the heat exchanger, the vaporization gas recovery line comprises a tapping provided with a valve towards an evacuation zone, the installation comprises a device for pressurizing the tank which is autonomous and separate from the vaporization gas recovery line and from the regulation device, The invention also relates to a method for withdrawing fluid using an installation according to any one of the characteristics above or below, characterized in that it comprises the following steps: pumping cryogenic liquid from the tank via the pump, recovery of vaporization gases generated at the pump, compression of the recovered vaporization gases and injection of the compressed gases into the tank at a determined pressure.

[0009] According to other possible particularities: the compression of the recovered vaporization gases is carried out with a cryogenic compressor or with a non-cryogenic compressor, the vaporization gases being reheated 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 further comprises a step of cooling the compressed vaporization gases via a heat exchange with the vaporization gas flow 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.

[0011] Other features and advantages will appear on reading the description below, made with reference to the figures in which: Brief description of the figures

[0012] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which: [ Fig. 1 ] is a schematic vertical sectional view describing an example of structure and operation of an installation according to the invention. Detailed description

[0013] In all figures, the same references refer to the same elements.

[0014] 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. Single features of different embodiments may also be combined and / or interchanged to provide other embodiments.

[0015] The illustrated cryogenic fluid storage and distribution installation 1 can be used for example for liquid hydrogen. The installation comprises 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 the ground and intended to be connected to a user.

[0016] The withdrawal circuit 20 comprises, arranged above the ground, a cryogenic pump 2.

[0017] The installation 1 comprising a pipe 3 for recovering vaporization gases generated within the pump 2 having an upstream end connected to the pump 2 and a downstream end connected to the tank 11. This pipe 3 for recovering the vaporization gases comprises at least one device for regulating the pressure and / or flow rate of the vaporization gas returned to the tank 11. This at least one device 8, 9 for regulating pressure and / or flow rate 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.

[0018] This pressure and / or flow regulating device is preferably configured to regulate the pressure within the reservoir 11 above the pressure at the inlet of the pump so as to overcome the hydrostatic height between the reservoir and the inlet of the pump 2. For example, the pressure and / or flow regulating device is configured to regulate the pressure within the reservoir to a level between 5mbar and 500mbar above the pressure at the inlet of the pump, for example between 5mbar and 100mbar above the pressure at the inlet of the pump.

[0019] The pressure and / or flow rate regulating device comprises at least one of: a heater 8, a heat exchanger 7, a compressor 9, for example a cryogenic compressor. For the sake of simplification, the [ Fig. 1 ] represents the three above-mentioned components in series. Of course, only one or two can be provided.

[0020] The pressure and / or flow rate regulating device may comprise or consist, for example, of a reheating heat exchanger 7 in series with a compressor 9.

[0021] The vaporization gas produced by pump 2 is heated in heat exchanger 7 and can then be returned to tank 11.

[0022] The reservoir 11 can thus be maintained under pressure to ensure efficient supply of the pump 2. The pump 2, which is relatively high up, is therefore at a lower pressure than that of the reservoir 11. This depression represents, for example, between 10 and 100 mbar, because this is the pressure necessary to overcome the manometric height between the reservoir 11 and the inlet of the pump 2 and the pressure losses of the inlet line. The recycling of vaporization gas from the pump 2 into the reservoir 11 makes it possible to compensate for this relative pressure difference.

[0023] This architecture allows the recovery of vaporization gases generated by pump 2 during its various operating phases. When it starts up, pump 2 produces vaporization gases in relatively large quantities. After cooling down, during its operation, pump 2 generates vaporization gases in smaller quantities, for example due to leaks, thermal inputs, etc.

[0024] These vaporization gases can be collected and returned to tank 11 via recovery line 3.

[0025] This makes it possible to recover all or only part of these vaporization gases during these different operating phases.

[0026] The vaporization gases are collected in the recovery line 3, are reheated in the reheat exchange 7 and compressed before being returned to the tank. The compressor 9 allows the vaporization gas flow to be circulated by compressing it to the tank pressure, for example to a level of a few tens of millibars.

[0027] The compressed vaporization gas can pass back into the reheating heat exchanger 7 to be cooled before being reinjected into the tank 11.

[0028] If this reheating exchanger 7 is not sufficient to reheat the gas before compression (vaporization gas flow rate too high, inlet temperature too cold, etc.), an additional exchanger 8 (reheater) can be provided to complete the reheating to a determined temperature (the ambient temperature or compressor inlet temperature).

[0029] This optional heater 8 is shown in dotted lines between the reheat exchanger 7 and the compressor 9.

[0030] As illustrated, a valve 5, for example an isolation valve, may be arranged in series between the pump 5 and the reheating heat exchanger 7. Similarly, a valve 5 is preferably provided upstream of the pump 2. A valve 5 may also be provided between the reheating exchanger 7 and the compressor 9. Similarly, a non-return valve 4 may be provided upstream of the pump 2.

[0031] As illustrated, the vaporization gas recovery line can make two separate passages (preferably counter-current) in the reheating heat exchanger 7 respectively before and after compression in the compressor 9 to ensure respectively reheating of the vaporization gas before compression and cooling before injection of the compressed gas into the tank 11.

[0032] As shown schematically, the vaporization gas recovery line 3 may further comprise a heat exchanger bypass line 13 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. For example, the bypass line 13 allows all or part of the compressed vaporization gas flow to avoid the second passage through the reheating exchanger 7. This makes it possible to increase the temperature of the compressed vaporization gas before returning it to the tank 11 to stabilize the pressure in the tank 11 if it rises too quickly.

[0033] As also illustrated, the vaporization gas recovery line 3 may comprise a tapping 33 provided with a valve to an evacuation zone. This tapping may be located between the reheat exchanger 7 and the inlet of the compressor 9.

[0034] The reservoir 11 may comprise an autonomous pressurization device 10 configured to increase its pressure if necessary (by drawing off, heating and re-injecting fluid).

[0035] This recovery and recovery of the vaporization gases makes it possible to maintain the reservoir 11 at overpressure relative to the pump 2. This guarantees good continuous admission into the pump 2. If the recovered vaporization gases are insufficient to maintain the pressure high enough during operation of the pump, the pressurization device 10 can be used to pressurize the reservoir 11.

[0036] Of course, the invention is not limited to this exemplary embodiment described above.

[0037] Thus, for example, the reheat heat exchanger 7 and the compressor 9 could be replaced by a cryogenic compressor (which can compress the gas to cryogenic temperature without the need for prior reheating).

Claims

1. Installation for storing and distributing cryogenic fluid, for example liquid hydrogen, comprising a cryogenic tank (11) buried underground, a liquid withdrawal circuit (20) comprising an upstream end connected to the tank (11) and 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 an upstream end connected to the pump (2) and a downstream end connected to the tank (11), characterized in thatthe vaporization gas recovery pipe (3) comprises 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).

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

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

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

5. Installation according to claim 4, characterized in that the vaporization gas recovery pipe (3) comprises two separate passages in the reheating heat exchanger (7) respectively before and after compression in the compressor (9) to ensure respectively reheating of the vaporization gas before compression and cooling before injection into the tank (11).

6. Installation according to claim 4 or 5, characterized in that the vaporization gas recovery line (3) comprises a heat exchanger bypass line (13) 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. Installation according to any one of claims 1 to 6, characterized in that the vaporization gas recovery pipe (3) comprises a tapping (33) provided with a valve towards an evacuation zone.

8. Installation according to any one of claims 1 to 7, characterized in that it comprises a device (10) for pressurizing the tank, independent and separate from the pipe (3) for recovering the vaporization gases and from the regulation device (8, 9).

9. 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 tank via the pump (2), recovery of vaporization gases generated at the pump (2), compression of the recovered vaporization gases and injection of the compressed gases into the tank (2) at a determined pressure.

10. Method according to claim 9, characterized in thatthe compression of the recovered vaporization gases is carried out with a cryogenic compressor or with a non-cryogenic compressor, the vaporization gases being reheated before compression in the case of the non-cryogenic compressor.

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

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