FI3359867T4

FI3359867T4 - Method for supplying cryogenic liquid, and facility for implementing said method

Info

Publication number: FI3359867T4
Application number: FIEP16793944.6T
Authority: FI
Inventors: Simon Oury
Priority date: 2015-10-05
Filing date: 2016-10-05
Publication date: 2023-01-13
Also published as: PL3359867T5; EP3359867B2; CN108431487B; EP3359867B1; US20180299072A1; EP3359867A1; HUE047878T2; PT3359867T; ES2760074T5; WO2017060627A1; FR3041951B1; CN108431487A; PL3359867T3; FR3041951A1; DK3359867T3; US10774992B2; ES2760074T3

Description

16793944.6

METHOD FOR SUPPLYING CRYOGENIC LIQUID, AND FACILITY FOR

IMPLEMENTING SAID METHOD

The present invention relates to a method for delivering cryogenic liquid, as well as to an installation for implementing said method.

The invention may relate to any type of cryogenic liquid, that is, any liquid obtained by cooling to very low temperatures (generally below -100 °C) gases (pure gases or mixtures of gas), for example, nitrogen, helium, or natural gas (methane).

For some uses of cryogenic liquids, the liquid is stored in a relatively large vessel and means are provided for delivering relatively small amounts of liquid into containers, such as, for example, a tank of a truck. Therefore, a refueling station is provided with a storage vessel and pressurized dispensing means adapted to the container to be filled, generally including a pump allowing the cryogenic liquid to be transferred from the storage vessel to a tank of a vehicle. The invention also relates to the transfer of cryogenic liquid to another type of container, for example, a cryogenic liquid canister or a dewar. Hereafter, the term “container” is understood to mean any type of tank or receptacle or the like adapted to contain liquid, and more particularly a cryogenic liquid in this case. Additionally, for the purposes of succinctness, liquid transfers (from the vessel to, for example, a canister or a dewar) will be considered to be the same as refueling (from the vessel to a fuel tank of a vehicle).

Document FR-2 997 165 relates to a method for filling a tank with a cryogenic liquid, from an upstream storage means, where a filling station is available through which a first channel passes connecting the storage means to the tank and allowing the cryogenic liquid to be transferred from the storage means to the tank, and a second channel connecting a gas outlet from the tank to the filling station and allowing the gases to be discharged from the tank to be returned to the filling station, with the second gas return line to the station being devoid of an overflow valve but being provided with a solenoid valve or several solenoid valves arranged in parallel, and normally closed, with the filling being controlled by acting on the solenoid valve in order to open it as much as necessary so as to obtain a desired

16793944.6 pressure difference Delta P (between the storage means and the tank), and a final pressure value in the tank set to a desired setpoint value, associated with the considered tank to be filled.

Document FR-3 006 742 for its part discloses a device for filling a tank with a liquefied gaseous fuel at a cryogenic temperature, comprising a source tank for storing gaseous fuel in the liquid state at a cryogenic temperature, a drawing-off pipe comprising a pump, the drawing-off pipe comprising an upstream end connected to the source tank and a downstream end comprising a connector intended to be connected to a tank to be filled, the drawing-off pipe comprising, downstream of the pump, a bypass portion passing through the inside of the source tank and comprising a submerged heat exchanger, the drawing-off pipe comprising a system of bypass valves designed to control the relative proportions of the pumped fluid passing through and not passing through the bypass portion, in order to regulate the temperature of the liquid drawn-off during filling and the filling device comprises a cryorefrigerator connected to the source tank in order to selectively liquefy gas present in the source tank.

In the case of filling a tank of a vehicle, when the vehicle arrives for refueling at a station for delivering cryogenic liquid, such as LNG (Liquefied Natural Gas), for example, its tank is sometimes pressurized due to the evaporation of the cryogenic liquid in the tank. Thus, before carrying out the refueling, degassing needs to be carried out, that is, gas needs to be removed from the tank in order to lower the pressure therein. Then, during refueling, cryogenic liquid is transferred under pressure to the tank. Generally, the dispensing of liquid stops when one of the following two conditions is met: the pressure in the tank exceeds a predetermined threshold or the liquid flow drops below a predetermined threshold.

During refueling, two main phenomena influence the prevailing pressure in the tank. The first tends to increase the pressure in the tank and the second tends to lower it. Indeed, when liquid fills the tank, the volume available for the gas decreases and therefore the gas is compressed, making the pressure increase. By contrast, since the liquid introduced into the tank is cold, a heat exchange occurs

16793944.6 with the gas and the gas then partly condensates. The amount (mass or number of moles) of gas therefore decreases, tending to lower the pressure in the tank.

Most often, refueling is carried out guickly. As a result, the drop in pressure (condensation of the gas) is limited and most often an increase in the pressure in the tank is observed. Sometimes the dispensing of liquid is stopped because the pressure in the tank exceeds a given threshold. Conseguently, the dispensing may stop before the tank is correctly filled. In extreme cases, if the tank is “hot” before refueling, the cryogenic liguid initially introduced into the tank will guickly vaporize, then causing the pressure in the tank to rise suddenly. The refueling then may be stopped because the pressure has exceeded the predetermined threshold, while the tank is not full, or even still almost empty.

Thus, as can be seen from the above, measuring the pressure prevailing in a tank that is being refueled is necessary. The flow of liquid entering the tank is also generally measured, even if this is only in order to be able to invoice the client, the owner of the refueled vehicle for the cryogenic liquid they receive. As indicated above, gas sometimes (or often) needs to be removed from the tank in order to lower the pressure therein. In order to take into account the amount of gas removed from the tank when invoicing, the amount of gas discharged from the tank is normally also measured.

The aim of the present invention is thus to allow proper filling of a tank, that is, to automatically fill the tank to its nominal filling level, which may correspond, for example, to the maximum permitted filling level.

Another aim of the present invention is to allow both the amount of liquid introduced into the tank and the amount of gas that is removed therefrom to be determined fairly precisely.

Advantageously, implementing the present invention will involve a preferably zero additional cost with respect to a cryogenic liquid delivery station (especially LNG).

Finally, the refueling time of a tank must not be substantially extended due to the implementation of the invention.

16793944.6

To this end, the present invention proposes a method for delivering cryogenic liguid including the following steps: - sealably connecting a tank to be filled to a storage vessel, - delivering cryogenic liguid to the tank and determining, on the one hand, the flow of liquid being delivered, and the amount of liquid delivered, and, on the other hand, the prevailing pressure in the tank, - stopping delivery of the liquid when the pressure exceeds a first predetermined threshold or else when the liguid flow drops below a second predetermined threshold.

According to the present invention, the method further includes the following steps: - degassing the tank after stopping the delivery while determining the amount of gas removed from the tank during the degassing; and - determining whether or not liguid should be delivered again based on the amount of gas removed during the degassing, and possibly other parameters.

In an original manner, degassing the tank after it is filled is proposed herein. It has been noted that knowing the amount of gas removed from the tank during the last degassing provided an indication of the filling state of the tank. It is therefore possible to use this information to determine whether or not the tank still needs to be filled. Other information also may be used, such as, for example, the amount of cryogenic liquid supplied to the tank during the last filling step: this amount is generally known. The amount of liguid delivered and/or the amount of gas removed from the tank may be determined by measuring, with a flow meter, for example, or else by estimating, for example, based on the delivery or degassing time, with the pressure of the fluid also being known.

Inamethod as proposed hereinbefore, provision is advantageously made so that as long as the amount of gas removed from the tank is greater than a third predetermined threshold, a new delivery of liguid involving determining the amount delivered during this new delivery, followed by degassing involving determining the

16793944.6 amount of gas removed from the tank, is carried out. Then, if the amount of liguid delivered when delivering liguid is greater than a predetermined amount of liguid, then a new degassing operation may be carried out, optionally followed by a final step of delivering liguid. 5 In order to avoid the risk of having an excessive time for filling a tank and/or filling beyond the maximum permitted filling level, provision is advantageously made so that the number of cryogenic liguid delivery steps is limited.

In a method according to the present invention, a degassing operation may be stopped, for example, when the pressure in the tank drops below a predetermined threshold and/or if an amount of gas, which is predetermined especially based on an amount of liquid delivered and/or an amount of gas removed during the preceding steps, is removed from the tank.

According to a preferred alternative embodiment, provision also may be made so that if the amount of gas removed during the last completed degassing operation andifthe amount of cryogenic liguid delivered during the last cryogenic liguid delivery operation are both below predetermined thresholds, then the delivery method is stopped.

The delivery method also may be stopped, for example, if the amount of gas removed during the last completed degassing operation is below a predetermined threshold and if the amount of cryogenic liquid delivered during the last cryogenic liguid delivery operation is above a predetermined threshold, after a final delivery of cryogenic liguid delivery has then been completed.

The present invention also relates to a cryogenic liguid delivery installation including a cryogenic liguid supply tube and optionally a degassing tube, characterized in that it further includes a management system for implementing each of the steps of a method as described hereinbefore.

To this end, such a delivery installation may include: - a cryogenic liguid supply tube,

16793944.6 - means for delivering cryogenic liguid including means for sealably connecting to a tank, - means for determining, on the one hand, a flow of liguid to the tank, and on the other hand, the prevailing pressure in said tank, - means for stopping the delivery of the cryogenic liguid, - means for degassing the tank, - means for determining the amount of gas removed from the tank during degassing, and - a management and control system acting, on the one hand, on the means for delivering and for stopping delivery based on the liquid pressure in the tank and/or even on the flow of liguid delivered to the tank and/or on the amount of gas removed during the preceding degassing, and, on the other hand, on the means for degassing in order to control a degassing of the tank after at least one cryogenic liquid delivery, and determining whether or not liquid should be delivered again based on the amount of gas removed during the degassing and possibly other parameters.

According to a first embodiment, an installation is proposed including: - a cryogenic liguid supply line, - a first valve arranged on the supply line, - a first flow meter arranged on the supply line downstream of the first valve, - a first flexible hose downstream of the first flow meter intended to connect the supply line to a tank to deliver cryogenic liguid thereto, - a degassing line connected to the supply line between the first flow meter and the first valve, and - a second valve arranged on the degassing line.

16793944.6

In a preferred embodiment, also allowing correct filling of a tank to be provided, and also ensuring precise measurement of the liguid introduced into a tank as well as of the gas removed therefrom, an installation according to the invention may include: - a cryogenic liguid supply line, - a first valve arranged on the supply line, - a first flow meter arranged on the supply line downstream of the first valve, - a second valve arranged on the supply line downstream of the first flow meter, - a first flexible hose downstream of the second valve intended to connect the supply line to a tank in order to deliver cryogenic liguid thereto, - a degassing line connected to the supply line between the first flow meter and the second valve, - a third valve arranged on the degassing line, and - a second flexible hose, called degassing pipe, intended to be connected to the tank to allow gas to be removed therefrom, said degassing pipe being connected to the supply line downstream of the second valve by means of a connector.

In order to determine the amount of gas removed from the tank during a degassing phase, providing the degassing line with a flow meter is proposed.

Details and advantages of the present invention will become more clearly apparent from the following description, which is provided with reference to the appended schematic drawings, in which:

Figure 1 is a flow chart illustrating a preferred alternative embodiment of a method according to the invention,

Figure 2 schematically illustrates an installation for delivering cryogenic liquid that advantageously may be used for implementing the method illustrated in Figure 1, and

16793944.6

Figure 3 schematically illustrates a delivery installation for implementing the method illustrated in Figure 1, simplified compared to that of Figure 2.

The method described hereafter is implemented when a tank 2 is connected to a cryogenic liquid delivery station. The tank 2 (see Figure 2) may be a tank of a vehicle or an independent container (cylinder, dewar, etc.). The cryogenic liquid is, for example, LNG (Liquefied Natural Gas), but it may be any other type of cryogenic liquid (liquid nitrogen, etc.). By way of illustrative and non-limiting example, it will be assumed throughout the remainder of the description that the liquid delivered herein is LNG for supplying a truck fuel tank.

Thus, the first step R herein consists in connecting the tank 2 to an LNG delivery station. The latter allows a limited amount of LNG to be transferred from a storage tank (not shown) to smaller tanks, or the like. The connection between the tank 2 and the delivery station is made by a flexible hose including two pipes: a first pipe, called the supply pipe 4, that is intended to bring the LNG from the storage vessel tothe tank 2 of the truck, and a second pipe, called a degassing pipe 6, that is intended to discharge the gaseous phase elements present in the tank 2.

A user wishing to fill their tank then requests this filling by pressing a button (not shown), for example.

In order to be able to complete a filling operation, the pressure in the tank 2 needs to be determined first (step: P?). This pressure must be greater than the saturation pressure of the liquid (LNG) in order to avoid immediate evaporation of the liquid introduced into the tank 2. This condition is most often met since in general liquid is still present in the tank 2. However, it is worthwhile also checking that this pressure is not too high. Indeed, if the pressure is too close to the maximum permissible pressure of the tank or even if this pressure is too close to the maximum pressure that may be delivered by the filling system, then no liquid should be sent to the tank 2.

The method then provides a predetermined pressure (Po), from which provision is made for the tank 2 to be degassed.

16793944.6

Thus, if the pressure P in the tank 2 is greater than the predetermined pressure

Po (P>Po), then a degassing operation (step G1) is carried out. During this operation, gas is removed from the tank 2. The gas is sent back to the cryogenic liquid network. Preferably, the amount of gas that is removed is measured. This measurement may be carried out precisely with a flow meter adapted to the nature of the gas and to the measurement conditions. Since the gas pressure (measured) and the dimensions of the pipes and the downstream pressure are known, the amount of gas removed from the tank 2 may be estimated based on the duration of the degassing operation. Other methods may be used to determine the amount of gas removed from the tank 2.

When the pressure in the tank 2 has dropped below the predetermined pressure

Po, then filling the tank 2 with LNG can begin (step L1). As illustrated in the flow chart, this filling step is carried out without prior degassing if the pressure in the tank 2 is below Po.

Before allowing LNG to enter the tank 2, a step of cooling the system, not shown on the flow chart for the sake of simplification, may be necessary in order to cool elements of the delivery station and not risk introducing gas into the tank 2. This operation for cooling the system, also called a cold operation, will be described below with reference to Figure 2.

Generally, when filling the tank 2 with LNG, the degassing is stopped so that the gas contained in the tank 2 cannot exit toward the delivery system and remains in the tank 2. The amount of cryogenic liquid introduced into the tank 2 is measured in order to know the delivered amount so as to be able to establish the correct price for the transaction. In the case of an application in which the cryogenic liquid is not sold, the amount of liquid that is delivered may be determined by an estimate, for example, from the delivery time and the pressure of the liquid, with the dimensions of the pipes being known by construction.

The filling operation (step L1, but also subsequently the other steps/filling/delivery operations that will be provided) stops when one of the following two conditions is met:

16793944.6 - the pressure in the tank 2 reaches a first threshold value P1 and/or - the liquid flow (for example, expressed as liters per second, I/s) drops below a second threshold D2.

The first threshold value P1 may correspond to the previously defined predetermined value Po, but it may be another limit value.

The second threshold D2 is predetermined, especially based on the nominal flow Dn of the delivery station. For example, provision may be made for

D2 = Dn /10, that is, delivery of LNG stops when the liguid flow drops below 10 % of the nominal flow.

The amount Qu of LNG dispensed during this filling operation is preferably measured.

In an original manner, the method proposed herein provides for systematically carrying out a degassing step (step G2) after this first filling step (step L1). During this degassing step, the amount Qc of gas removed from the tank 2 is measured and/or estimated. A flow meter may measure the amount Oc, but provision also maybe made for a measurement of the time taken for the degassing step in order to fairly precisely estimate the amount Oc. Other measurement or estimation methods may be contemplated.

The remainder of the method depends on the amount of gas removed from the tank 2 during this degassing operation. If this amount is high, that is, greater than a predetermined amount Oo, it is estimated that there is still space in the tank 2 and a new filling step then may be launched.

By contrast, if this amount of gas is low, that is, less than the predetermined amount Oo, the filling method may be stopped. In this latter case, as can be seen on the right of the flow chart, two ways of proceeding are proposed based on the amount QL of LNG that was delivered during the last filling step.

If this amount Qu of LNG was low, for example, less than an amount Q1, then the cryogenic liguid delivery process is stopped (step F1). The present case

16793944.6 corresponds, for example, to a tank 2 that was already almost full when it was connected to the delivery station before the filling operation.

By contrast, if the amount OL of LNG delivered during the last filling step was greater than the amount Q1, then a final filling step (step L2) is carried out before stopping the filling method (step F2).

If the amount Qc of gas is greater than the amount Qo, then a new filling step (step Ln) is launched, during which the amount Qu of cryogenic liquid is measured.

As long as the amount QL remains below the predetermined amount Q1, provision is made for the degassing operation scheduled in step G2 to be repeated. A loop is thus created, in which filling and degassing operations follow one another as long as the amount of gas removed from the tank 2 remains greater than the predetermined value Qo and the amount of liquid transferred to the tank 2 remains below the predetermined value O.

In order to avoid extending the filling time of the tank 2 and/or filling the tank 2 beyond the recommended maximum level, ending this loop after a number N of loops is proposed. Therefore, provision is made, in a system for managing the filling method, to increment a number that counts the number of completed filling operations. If the number N is reached by the increment, the filling method is stopped after the Nth filling step.

For the sake of simplification, the flow chart of Figure 1 does not manage the initialization and the incrementation of the number of filling/degassing loops.

In most cases, the loop on the left-hand side of Figure 1 mentioned hereinbefore is only carried out once. Indeed, it is highly unlikely (but conceivable) that the amount of gas removed remains high during several successive degassing operations, even if filling operations are carried out between two degassing operations. This latter scenario would correspond, for example, to a relatively “hot” tank. Thus, most often, during a second, or optionally a third, filling step (steps Ln), the amount Qu of liquid introduced into the tank 2 drops below the threshold Oi and the filling method thus may be stopped. Since the last degassing operation

16793944.6 resulted in the removal of a relatively large amount of gas, a final degassing step (step G3) is carried out, followed by a final filling step (corresponding to step L2 described above). The filling process thus also ends in this case in the final step F2, which corresponds to the end of “normal” filling of the tank 2.

During each final step (steps F1, F2 and F3), the flexible hose with the filling pipe 4 and the degassing pipe 6 then may be uncoupled from the tank 2.

Figure 2 schematically illustrates a delivery station for implementing the method described above.

The right-hand side of Figure 2 shows the aforementioned tank 2, as well as the flexible hose connecting this tank to the delivery station. The delivery station firstly includes a cryogenic liquid supply line 8 that connects the storage vessel (not shown) containing the LNG reserve to the supply pipe 4.

A first valve 10 is arranged on the supply line 8 and allows the arrival of cryogenic liquid into the delivery system to be controlled.

A first flow meter 12 is arranged on the supply line 8 downstream of the first valve 10 to measure the amount of LNG supplying the delivery system. A non- return valve 14 is located downstream of this flow meter that prevents any cryogenic liguid and gas from returning to the storage vessel.

A second valve 16 is then arranged on the supply line 18, downstream of the first flow meter 12.

Finally, another non-return valve 18 on the supply line 8, before its junction with the flexible hose and more specifically the supply pipe 4 of this flexible hose, is provided to prevent any liguid but also gas from returning to this level of the supply line 8.

The delivery system shown in Figure 2 also includes a degassing line made of several sections.

A first section 20 of the degassing line connects the supply line 8 between the non-return valve 14 and the second valve 16 to a duct, not shown, allowing the

16793944.6 gas to be re-introduced into the storage vessel or into another recovery system, or optionally even into a combustion device. A third valve 22 controls the gas flow in this first section 20. A measuring device 24 allows the pressure and the temperature of the gas in this first section 20 to be known.

A second section 26 of the degassing line connects the supply line 8 to the flexible hose, and more particularly to the degassing pipe 6. This second section 26 is connected to the supply line 8 downstream of the second valve 16. A second flow meter 28 is located on this second section 26.

Inside the delivery system, a connection 30 connects the second section 26 to the supply line 8 near the supply pipe 4 and the degassing pipe 6. The connection 30 is connected to the second section 26 upstream of the second flow meter 28 and to the supply line 8 downstream of the non-return valve 18.

A third non-return valve 32 is provided in the second section 26 between the second flow meter 28 and the connection of the second section 26 to the supply line 8. It ensures that the gas flowing in this second section 26 is discharged from the tank 2.

The remainder of the present description indicates how the device described above and as illustrated in Figure 2 may be implemented to proceed with the steps of the method of Figure 1.

Initially, before connecting the flexible hose to the tank 2, the first valve 10 is closed to prevent LNG from flowing, while the second valve 16 and the third valve 22 are opened (continuously or alternately) to allow gas to return, that originates, for example, from the evaporation of liguid present in the pipes, to the storage vessel (or any other gas recovery system).

When the flexible hose is connected to the tank 2, the third valve 22 closes in order to control the flow of gas exiting the tank 2. If a degassing operation (step G1) is scheduled, then this third valve 22 is opened to allow gas to be removed from the tank 2. The second flow meter 28 then measures the amount of gas removed from the tank 2.

16793944.6

As mentioned above, prior to the first filling step (step L1), an operation for cooling the delivery system may be contemplated in order to bring the system to operating temperature. For this operation, LNG is admitted into the delivery system by opening the first valve 10. The LNG then flows through the first flow meter 12 and returns to the storage vessel through the third valve 22. The second valve 16 remains closed during this cooling operation and the control and management system associated with the delivery system does not take into account the amount of LNG measured by the first flow meter 12.

For a filling step, (steps L1, L2 or Ln), the first valve 10 and the second valve 16 are opened to allow the LNG to pass through the supply line 8 from the storage vessel to the tank 2. The third valve 22 remains closed so as to prevent gas from returning to the storage vessel during the filling steps.

At the end of a filling step, the first valve 10 is closed first, then the second valve 16. A delay is provided for the liguid remaining in the line to evaporate. This ensures that the flexible hose is only handled when it contains gas, which improves the safety of the delivery system. The delay is determined herein based on parameters related to the delivery station based on computations and/or experimental tests.

Then, during an operation for degassing the tank 2, the first valve 10 is closed so that the delivery system is no longer supplied with cryogenic liquid and the second valve 16, as well as the third valve 22, are opened to allow the gas to flow to the storage vessel (or other).

The present device thus may be used to guarantee correct filling of the tank 2 by implementing the method described above.

A simplified embodiment of the delivery station of Figure 2 is illustrated in Figure 3.

For the sake of simplification, the references used in Figure 2 are used in Figure 3 to designate similar elements.

The delivery station illustrated in this Figure 3 firstly includes a cryogenic liguid supply line 8. It is connected to a storage vessel (not shown).

16793944.6

In order to control the delivery of cryogenic liquid to a tank 2, a first valve 10 is arranged on the supply line 8. A first flow meter 12 arranged on the supply line 8 downstream of the first valve 10 is used to measure the amount of liguid (LNG) that is delivered. This delivery is carried out by a first flexible pipe 4 connected to the supply line 8 downstream of the first flow meter 12.

To allow vaporized liguid to return, a degassing line 20 is connected to the supply line 8. In this case, the connection is made between the first flow meter 12 and the first valve 10. The gas flow in the degassing line is controlled by a second valve 22 arranged on the degassing line 20.

The filling method allows nominal filling of the tank to be guaranteed. Degassing carried out after a first filling operation means that it is possible to estimate whether the tank is properly filled, knowing the amount of gas removed during the degassing and advantageously also the amount of liguid transferred into the tank.

If a large amount of liguid has been transferred and a small amount of gas has beenremoved, the tank is probably full, and then a top-up is simply carried out.

Conversely, if a small amount of liguid has been transferred to the tank, but a considerable amount of gas has been removed, it may be assumed that the tank was “hot”, and the liquid introduced into the tank evaporated rapidly.

The proposed method also allows intermediate situations between these two situations to be managed.

The proposed device allows the method according to the invention to be implemented. It also allows precise measurement of the amount of LNG supplied to the client, while also taking into account the gas removed from the tank. This device and this method thus may be used for commercial transactions.

Guaranteeing correct filling of a tank for a truck allows it to be guaranteed of maximum autonomy.

16793944.6

The proposed system is also a safe system, for which provision is especially made for the tank connection tube to be handled only when the tank is filled with gas (not wih liguid).

Of course, the present invention is not limited to the embodiment of the installation shown in the drawing, to the variants mentioned in the preceding description and to the method described above. It also relates to all the alternative embodiments within the abilities of a person skilled in the art in accordance with the definition of the following claims.