Method and device for delivering cryogenic fluids

Abstract

The invention relates to a method for transporting a liquefied cryogenic fluid, such as liquid hydrogen, from a cryogenic storage tank (1) containing the liquefied cryogenic fluid, the liquefied cryogenic fluid having a gas phase balanced with the liquid phase, the fluid is conveyed to the receiver at least partially through the pressure difference between the storage tank (1) and the receiver of the fluid. The method comprises a step of pressurizing a fluid contained in said tank (1), a step of extracting a liquid from said pressurized tank, a step of measuring the volumetric flow rate of the extracted fluid, a step of determining the mass of the extracted liquid as a function of the density of the extracted fluid and the measured volumetric flow rate of the extracted fluid, and a step of determining the mass of the extracted liquid as a function of the density of the extracted fluid and the measured volumetric flow rate of the extracted fluid. The density of the extracted fluid is determined as a function of the pressure of the fluid in the tank (1) measured prior to the pressurizing step. The invention also relates to a device for conveying a liquefied cryogenic fluid.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for conveying cryogenic fluids.

[0002] More particularly, the present invention relates to a method for delivering a liquefied cryogenic fluid (e.g., liquid hydrogen) from a cryogenic tank containing the liquefied cryogenic fluid, wherein the liquefied cryogenic fluid has a gas phase in equilibrium with a liquid phase, wherein delivery of the fluid to a receiver is achieved at least in part by a pressure difference between the tank and the fluid receiver, the method comprising the steps of pressurizing the fluid contained in the tank, extracting the liquid from the pressurized tank, measuring the volume flow rate of the extracted fluid, and determining the mass of the extracted liquid based on the density of the extracted fluid and the measured volume flow rate of the extracted fluid. Background Art

[0003] Measuring liquid hydrogen flow presents numerous challenges. Currently used turbine flowmeters provide volumetric flow rates, while liquid quantities are priced based on mass. Coriolis-type mass flowmeters are more expensive and difficult to place within a vacuum chamber. Furthermore, the mass flow readings they provide can be confounded by the presence of bubbles in the liquid. Summary of the Invention

[0004] The object of the present invention is to overcome all or part of the above-mentioned disadvantages of the prior art.

[0005] To this end, an essential feature of the method according to the invention, which otherwise corresponds to the general definition given above in the introduction, is that the density of the extracted fluid is determined from the pressure of the fluid in the tank measured before the pressurization step.

[0006] Additionally, embodiments of the present invention may have one or more of the following features:

[0007] - the method comprises the steps of measuring the pressure of the fluid in the tank, and detecting a pressure increase corresponding to the pressurizing step, wherein the pressure of the fluid in the tank measured before the pressurizing step is a pressure value measured before the pressure increase is detected;

[0008] -Calculate the density of the extracted fluid according to the following formula: D = -2.36P + 72.8 (D is in kg / m 3 where P is the density in bar (absolute) (bar abs) and / or the density of the extracted fluid is obtained from a determined table giving the density of the fluid as a function of the pressure of the fluid;

[0009] - the step of determining the mass of the extracted liquid comprises calculating said mass by multiplying the density by the value of the measured volume flow rate of the extracted fluid;

[0010] - the step of determining the mass of the extracted liquid comprises a step of correcting the value of the measured volume flow, for example by multiplication by a coefficient;

[0011] -The step of measuring the volume flow of the extracted fluid is performed using a volumetric flow meter.

[0012] The present invention also relates to a device for conveying a liquefied cryogenic fluid, such as liquid hydrogen, comprising a cryogenic tank intended for containing the liquefied cryogenic fluid having a gaseous phase in equilibrium with a liquid phase, a liquid conveying pipe having an upstream end connected to the tank and a downstream end intended to be connected to a receiver, the liquid conveying pipe comprising a volumetric flow meter, the device comprising a system for pressurizing the fluid contained in the tank, a temperature sensor, a pressure sensor for the fluid in the tank, an electronic data storage and processing unit comprising a microprocessor, the electronic unit being configured to determine the density of the fluid extracted by the conveying pipe based on the fluid pressure value measured by the pressure sensor.

[0013] The invention may also relate to any alternative device or method comprising any combination of the above or below features falling within the scope of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Further specific features and advantages will become apparent from the following description read with reference to the accompanying drawings.

[0015] The invention will be better understood from reading the following description, which is given by way of example only and with reference to the accompanying drawings, in which:

[0016] Figure 1 is a schematic partial view showing an example of the structure and operation of a storage tank embodying the present invention. DETAILED DESCRIPTION

[0017] Throughout the drawings, the same reference numerals refer to the same elements.

[0018] In this detailed description, the following embodiments are examples. Although the description relates to one or more embodiments, it does not mean that these features only apply to a single embodiment. The individual features of different embodiments may also be combined and / or interchanged to provide other embodiments.

[0019] Figure 1 An example of an apparatus for transporting liquefied cryogenic fluid in which the present invention may be implemented is shown.

[0020] The device comprises a cryogenic tank 1 intended for containing a liquefied cryogenic fluid (such as hydrogen) having a gaseous phase in equilibrium with a liquid phase. The tank 1 is preferably a double-shelled tank comprising an insulating space (preferably under vacuum) between the two shells.

[0021] The device comprises a liquid conveying pipe 2 having an upstream end connected to the tank 1 and a downstream end intended to be connected to a receiver of the extracted fluid.

[0022] The liquid delivery pipe 2 comprises a volume flow meter 4 .

[0023] The device comprises a pressurizing system 3 for pressurizing the fluid contained in the tank 1 .

[0024] For example, the pressurizing device / pressurizing system 3 includes or is composed of a pressure generating unit (PBU). The pressurizing device / pressurizing system 3 includes, for example, a pressurizing pipe 13 connected to the storage tank in a closed loop (its first end is connected to, for example, the lower part of the storage tank 1, and its second end is connected to, for example, the upper part of the storage tank). Between these two ends, the pressurizing pipe 13 includes a heat exchanger 33 (for example, for exchanging heat with air) and a set of one or more valves, such as two valves 23 and 43 located on both sides of the heat exchanger 33.

[0025] The transfer of liquid from the storage tank 1 (mobile or fixed) to the receiver is achieved at least in part by a pressure differential. To this end, the storage tank 1 can be pressurized to achieve this transfer. Pressurization of the storage tank 1 in thermodynamic equilibrium can be conventionally achieved by removing liquid from the tank by opening valve 23 upstream of the heat exchanger 33, allowing the liquid to vaporize in the heat exchanger 33, and then returning the hot gas obtained by natural convection to the gas head space of the tank by opening valve 43 downstream of the heat exchanger 33.

[0026] This pressurization method increases the gauge pressure of the fluid by a certain value (typically about 0.2 bar to 3 bar). This pressure increase does not significantly increase the temperature of the liquid in the tank. This means that the fluid in the tank 1 changes from a saturated state to a subcooled liquid state.

[0027] Once the liquid is pressurized, it is poured out to a receiver by means of a pressure differential (opening one or more suitable valves in the delivery pipe 2).

[0028] For invoicing purposes, the measured value of the (volume) flow rate extracted is useful. Since invoicing requires mass measurements, the volume reading must be corrected for density.

[0029] Since the density of a liquid depends on its saturation pressure, measurements of volume flow (e.g. obtained with a turbine flow meter) are not possible without correcting the density value.

[0030] The device comprises a pressure sensor 5 for the fluid in the tank 1 , which is located, for example, on the delivery pipe 2 upstream of the flow meter 4 .

[0031] Since the liquid is not in thermodynamic equilibrium during extraction, the indication of the fluid pressure during extraction does not allow for a reliable correction.

[0032] According to one advantageous particular feature, the pressure in the tank is measured or determined when equilibrium is reached between the gaseous and liquid phases. The gauge pressure increase caused by pressurization is detected during startup of the pressurization system 3 and / or by detecting a sudden pressure increase that is significantly faster than the pressure increase in the tank associated with heat input (several bars per hour versus 15 mbar / hour for pressurization via a PBU). Thus, the pressure sensor 5 can detect the pressure increase associated with pressurization by detecting, for example, an interruption (e.g., discontinuity) in the measured pressure gradient. The gauge pressure value immediately before the start of the pressure increase can be retrieved / queried (e.g., recorded), for example, using a gauge pressure value at a time offset relative to the pressure increase.

[0033] This pressure value enables the density of the extracted liquid to be calculated or determined with the aid of a graph.

[0034] For example, by calculation and formula D = -2.36 × P + 72.8 (D is in kg / m 3 where P is the density in bar (absolute) (bar abs) and / or the density is obtained from a predetermined lookup table or list:

[0035] Table 1

[0036] Pressure (MPa) <![CDATA[Liquid density (in kg / m 3 units)]]> 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

[0037] This density value enables the volume flow value read by the flow meter 4 to be corrected.

[0038] To this end, the device 1 may comprise an electronic data storage and processing unit 6 having one or more microprocessors. The electronic data storage and processing unit 6 may be configured to determine the density of the fluid extracted by the delivery tube 2 based on the fluid pressure value measured by the pressure sensor 5.

[0039] In the case where the tank 1 is transportable, in multiple delivery / delivery cycles, energy is injected during delivery to pressurize the tank, and transportation between the two delivery points increases the temperature of the liquid (and therefore increases the saturation pressure of the equilibrium system).

[0040] The invention makes it possible to determine the density of the liquid at delivery, independently of the gauge pressure during extraction.

[0041] The invention makes it possible to correct the measured values of a volumetric flow meter during delivery of cryogenic liquids according to density.

[0042] Determination of the mass of the extracted liquid may comprise calculating said mass by multiplying the density by the value of the measured volumetric flow rate of the extracted fluid.

[0043] This enables the mass of the delivered liquid to be determined. This is possible even if the gauge pressure during the delivery is not related to the density of the delivered fluid (the liquid is subcooled).

Claims

1. A method for conveying a liquefied cryogenic fluid from a cryogenic tank (1) containing the liquefied cryogenic fluid, the liquefied cryogenic fluid being, for example, liquid hydrogen, the liquefied cryogenic fluid having a gas phase in equilibrium with a liquid phase, the conveying of the fluid to a receiver being achieved at least in part by a pressure difference between the tank (1) and the receiver for the fluid, the method comprising a step of pressurizing the fluid contained in the tank (1), a step of extracting liquid from the pressurized tank, a step of measuring the volume flow of the extracted fluid, a step of determining the mass of the extracted liquid based on the density of the extracted fluid and the measured volume flow of the extracted fluid, characterized in that The density of the extracted fluid is determined based on the pressure of the fluid in the tank (1) measured before the pressurizing step.

2. The method according to claim 1, characterized in that It includes: The step of measuring the pressure of the fluid in the storage tank (1); and detecting a pressure increase corresponding to the pressurizing step, wherein the pressure of the fluid in the storage tank measured before the pressurizing step is a pressure value measured before the pressure increase is detected.

3. The method according to claim 1 or 2, characterized in that The density of the extracted fluid is calculated according to the following formula: D = -2.36P + 72.8, where D is in kg / m 3 where P is the density in bar abs, and P is the pressure in bar abs, and / or the density of the extracted fluid is obtained from a determined table giving the density of the fluid as a function of the fluid pressure.

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

5. The method according to any one of claims 1 to 4, characterized in that The step of determining the mass of the extracted liquid comprises a step of correcting the value of the measured volume flow, for example by multiplying said value of the measured volume flow by a coefficient.

6. The method according to any one of claims 1 to 5, characterized in that The step of measuring the volume flow of the extracted fluid is accomplished using a volumetric flow meter.

7. An apparatus for conveying a liquefied cryogenic fluid, such as liquid hydrogen, comprising a cryogenic tank (1) intended to contain the liquefied cryogenic fluid having a gaseous phase in equilibrium with a liquid phase, a liquid conveying pipe (2) having an upstream end connected to the tank (1) and a downstream end intended to be connected to a receiver, the liquid conveying pipe (2) comprising a volumetric flow meter, the apparatus further comprising: a system (3) for pressurizing the fluid contained in the tank (1), the system being configured to pressurize the fluid contained in the tank (1) before extracting the fluid contained in the tank (1); A pressure sensor (5) for the fluid in the tank (1); a temperature sensor; and an electronic data storage and processing unit (6) including a microprocessor, the electronic data storage and processing unit (6) being configured to determine the density of the fluid extracted by the liquid delivery pipe (2) based on the fluid pressure value measured by the pressure sensor (5) before pressurization.

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