Method and device for transferring cryogenic fluid

Abstract

The invention relates to a method and a device for transferring liquefied cryogenic fluid, for example liquid hydrogen, from a cryogenic tank (1) containing liquefied cryogenic fluid having a gas phase in equilibrium with the liquid phase, the transfer of fluid being carried out to a receiver at least partly by pressure difference between the tank (1) and the fluid receiver, the method comprising a step of pressurizing the fluid contained in the tank (1), a step of withdrawing liquid from the pressurized tank, a step of measuring the volume flow rate of withdrawn fluid, a step of determining the mass of withdrawn liquid from the measured volume flow rate of withdrawn fluid and the density of the withdrawn fluid, the density of the withdrawn fluid being determined from the pressure of the fluid in the tank (1) measured before the pressurization step. Abstract figure: Fig. 1

Description

Title of the invention: Method and device for transferring cryogenic fluid

[0001] The invention relates to a method and a device for transferring cryogenic fluid.

[0002] The invention relates more particularly to a method for transferring fluid liquefied cryogenic fluid, for example liquid hydrogen, from a cryogenic tank containing liquefied cryogenic fluid having a gas phase in equilibrium with the liquid phase, the transfer of fluid being carried out towards a receiver at least in part by pressure difference between the tank and the fluid receiver, the method comprising a step of pressurizing the fluid contained in the tank, a step of withdrawing liquid from the pressurized tank, a step of measuring the volume flow rate of withdrawn fluid, a step of determining the mass of withdrawn liquid from the measured volume flow rate of withdrawn fluid and the density of the withdrawn fluid.

[0003] Measuring a liquid hydrogen flow rate faces several difficulties. The turbine-type flow meters currently used provide a volumetric flow rate value, whereas the billing of the quantity of liquid is based on mass. Coriolis-type mass flow meters are more expensive and difficult to install in a vacuum enclosure. In addition, the mass flow reading they provide can be disturbed by the presence of bubbles in the liquid.

[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 method according to the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the density of the withdrawn fluid is determined from the pressure of the fluid in the reservoir measured before the pressurization step.

[0006] Furthermore, embodiments of the invention may include one or more of the following features: - the method comprises a step of measuring the pressure of the fluid in the reservoir, a step of detecting a pressure increase corresponding to a pressurization step, the pressure of the fluid in the reservoir measured before the pressurization step being a pressure value measured before the detected pressure increase, - the density of the withdrawn fluid is calculated from the following formula: D=-2.36P +72.8 (D being the density in kg / m3 and P the pressure in bar abs) and / or from a specific table giving the density / volume mass of the fluid depending on its pressure, - the step of determining the mass of liquid withdrawn comprises the calculation of said mass by multiplying the density by the value of the measured volume flow rate of the withdrawn fluid, - the step of determining the mass of liquid drawn off includes a step of correction, for example by a multiplicative coefficient, of the measured volume flow rate value, - the step of measuring the volume flow rate of the withdrawn fluid is carried out with a volume flow meter.

[0007] The invention also relates to a device for transferring liquefied cryogenic fluid, for example liquid hydrogen, comprising a cryogenic tank intended to contain liquefied cryogenic fluid having a gaseous phase in equilibrium with the liquid phase, a liquid transfer pipe having an upstream end connected to the tank and a downstream end intended to be connected to a receiver, the liquid transfer pipe comprising a volume flow meter, the device comprising a system for pressurizing the fluid contained in the tank, a pressure sensor for the fluid in the tank, a temperature sensor, an electronic data storage and processing unit comprising a microprocessor, the electronic unit being configured to determine the density of the fluid drawn off by the transfer pipe from the pressure value of the fluid measured by the pressure sensor.

[0008] 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.

[0009] Other features and advantages will appear on reading the description below, given with reference to the figures in which: Brief description of the figures

[0010] 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:

[0011] [Fig. 1] is a schematic and partial view illustrating an example of structure and operation of a tank implementing 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 of different embodiments may also be combined and / or interchanged to provide other embodiments.

[0014] [Fig.l] illustrates an example of a device for transferring liquefied cryogenic fluid which can implement the invention.

[0015] The device comprises a cryogenic tank 1 intended to contain liquefied cryogenic fluid having a gaseous phase in equilibrium with the liquid phase (hydrogen for example). The tank 1 is preferably a double-jacketed tank comprising a thermally insulated space (preferably under vacuum) between the jackets.

[0016] The device comprises a liquid transfer pipe 2 having an upstream end connected to the reservoir 1 and a downstream end intended to be connected to a receiver of the withdrawn fluid.

[0017] The liquid transfer line 2 comprises a volume flow meter 4.

[0018] The device comprises a system 3 for pressurizing the fluid contained in the reservoir 1.

[0019] This pressurization device 3 comprises or is constituted for example by a pressure generation unit “PBU” (“Pressure Building Unit”). This pressurization device 3 comprises for example a pressurization pipe 13 connected in a loop to the tank (a first end connected for example to the lower part of the tank 1 and a second end connected for example to the upper part of the tank. Between these two ends the pressurization pipe 13 comprises a heating exchanger 33 (in heat exchange for example with the air) and a set of valve(s), for example two valves 13, 43 located on either side of the heating exchanger 33.

[0020] The transfer of liquid from the tank 1 (mobile or fixed) to a receiver is carried out at least in part by pressure difference. For this purpose, the tank 1 can be pressurized in order to carry out this transfer. The pressurization from the tank 1 to thermodynamic equilibrium can be carried out conventionally by withdrawing liquid from the tank via the opening of the valve 13 upstream of the heating exchanger 33, vaporization of this liquid in the heating exchanger 33, then return of the hot gas obtained by natural convection into the gaseous air of the tank via the opening of the valve 43 downstream of the heating exchanger 33.

[0021] This pressurization method increases the gauge pressure of the fluid by a determined value (typically of the order of 0.2 to 3 bar). This increase in pressure does not significantly increase the temperature of the liquid in the tank. That is to say, the fluid in the tank 1 passes from the saturated state to a subcooled liquid state.

[0022] Once the liquid is pressurized, the liquid is transferred by pressure difference to the receiver (opening of appropriate valve(s) in transfer line 2.

[0023] For billing purposes, a measurement of the flow rate 4 (volume) drawn off is carried out. Since billing must be carried out with a mass measurement, a density correction of the volume value read is necessary.

[0024] Since the density of the liquid depends on its saturation pressure, the measurement of volumetric flow rate (turbine flow meter for example) is not possible without correction of the density value.

[0025] The device comprises a sensor 5 for the pressure of the fluid in the tank 1, located for example on the transfer pipe 2, upstream of the flow meter 4.

[0026] The indication of the fluid pressure at the time of withdrawal does not allow a reliable correction because the liquid is not in thermodynamic equilibrium.

[0027] According to an advantageous feature, the pressure in the tank is measured or determined during the equilibrium between the gas phase and the liquid phase. The increase in manometric pressure caused by pressurization is detected, upon activation of the pressurization system 3, and / or by detection of a sudden rise in pressure significantly faster than the rise in pressure of the tank linked to the thermal inputs (of several bars per hour for pressurization by PBU vs. 15 mbar / h). The pressure sensor 5 can thus detect an increase in pressure linked to by detecting for example a break (discontinuity for example) in the measured pressure ramp. This manometric pressure value just before the start of the pressure rise can be recovered (recorded for example) for example by using the value at a time shifted temporally relative to the pressure rise.

[0028] This pressure value makes it possible to calculate or determine using an abacus the density of the liquid which is drawn off.

[0029] The density is obtained for example via a calculation and a formula D=-2.36xP +72.8 (D being the density in kg / m3 and P the pressure in bar abs) and / or via a tabulation or a predetermined correspondence table such as below:

[0030] [Tables 1] Pressure (MPa) Liquid density (kg / m3) 0.10000 70.899 0.20000 67.712 0.30000 65.189 0.40000 62.949 0.50000 60.847 0.60000 58.800 0.70000 56.748 0.80000 54.632 0.90000 52.381 1.0000 49.888 1.1000 46.942 1.2000 42.960

[0031] This density value makes it possible to correct the volume flow rate value read by the flow meter 4.

[0032] For this purpose, the device 1 may comprise an electronic member 6 for storing and processing data with microprocessor(s). This electronic member 6 may be configured to determine the density of the fluid drawn off by the transfer pipe 2 from the pressure value of the fluid measured by the pressure sensor 5.

[0033] In the case where the tank 1 is mobile, during a tour with several deliveries, the energy injected during the delivery to pressurize the tank and the transport between two delivery points increase the temperature of the liquid (therefore the saturated pressure for a system in equilibrium).

[0034] The invention makes it possible to determine the density of the liquid at the time of delivery, which is not correlated with the manometric pressure during withdrawal.

[0035] The invention makes it possible to correct the density of the measurement of a volume flow meter during a delivery of cryogenic liquid.

[0036] Determining the mass of liquid drawn off may comprise calculating said mass by multiplying the density by the measured volume flow rate value of the drawn off fluid.

[0037] This makes it possible to determine a quantity in mass of liquid transferred. This is made possible even if the manometric pressure during this delivery is uncorrelated with the density of the delivered fluid (the liquid being sub-cooled).

Claims

Claims

1. A method of transferring liquefied cryogenic fluid, for example liquid hydrogen, from a cryogenic tank (1) containing liquefied cryogenic fluid having a gas phase in equilibrium with the liquid phase, the transfer of fluid being carried out to a receiver at least in part by pressure difference between the tank (1) and the fluid receiver, the method comprising a step of pressurizing the fluid contained in the tank (1), a step of withdrawing liquid from the pressurized tank, a step of measuring the volume flow rate of withdrawn fluid, a step of determining the mass of withdrawn liquid from the measured volume flow rate of withdrawn fluid and the density of the withdrawn fluid, characterized in that the density of the withdrawn fluid is determined from the pressure of the fluid in the tank (1) measured before the pressurization step.

2. Method according to claim 1, characterized in that it comprises a step of measuring the pressure of the fluid in the reservoir (1), a step of detecting a pressure increase corresponding to a pressurization step, the pressure of the fluid in the reservoir measured before the pressurization step being a pressure value measured before the detected pressure increase.

3. Method according to claim 1 or 2, characterized in that the density of the fluid drawn off is calculated from the following formula: D=-2.36P +72.8 (D being the density in kg / m3 and P the pressure in bar abs) and / or from a specific table giving the density / volume mass of the fluid as a function of its pressure.

4. Method according to any one of claims 1 to 3, characterized in that the step of determining the mass of liquid withdrawn comprises calculating said mass by multiplying the density by the measured volume flow rate value of the withdrawn fluid.

5. Method according to any one of claims 1 to 4, characterized in that the step of determining the mass of liquid withdrawn comprises a step of correction, for example by a multiplicative coefficient, of the measured volume flow rate value.

6. Method according to any one of claims 1 to 5, characterized in that the step of measuring the volume flow rate of fluid drawn off is carried out with a volume flow meter.

7. Device for transferring liquefied cryogenic fluid, for example liquid hydrogen, comprising a cryogenic tank (1) intended to contain liquefied cryogenic fluid having a gaseous phase in equilibrium with the liquid phase, a liquid transfer pipe (2) having an upstream end connected to the tank (1) and a downstream end intended to be connected to a receiver, the liquid transfer pipe (2) comprising a volume flow meter, the device comprising a system (3) for pressurizing the fluid contained in the tank (1), a pressure sensor (5) of the fluid in the tank (1), a temperature sensor (5), an electronic data storage and processing member (6) comprising a microprocessor, the electronic member (6) being configured to determine the density of the fluid withdrawn by the transfer pipe (2) from the pressure value of the fluid measured by the pressure sensor (5).

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