Apparatus and method for filling a housing with pressurized fluid and then evacuating the housing and recovering the fluid

Abstract

The present invention relates to a method for filling a housing (30) with fluid until a target pressure is reached and then emptying the housing at an appropriate time, characterized in that the filling is performed based on a first plurality of containers (R3, R4, R5, R6, R7, R8) with different pressures, successively starting from the container with the weakest pressure (R2) and ending at the container with the strongest pressure (R8), and the emptying is performed by transferring the contents of the housing (30) toward a second plurality of containers (R2, R3, R4, R5, R6, R7) successively, starting from the container with the strongest pressure (R7) and ending at the container with the weakest pressure (R2).

Description

Technical Field

[0001] This invention relates to a method for temporarily filling a housing with pressurized fluid, wherein, after the housing is emptied, all or part of the fluid needs to be recovered. For example, the fluid may be recovered because it is hazardous, polluting, or expensive.

[0002] The housing can have any properties; for example, the housing can be a hydrogen storage container for electric vehicles. The method can also have any properties; for example, a test method for testing the gas tightness of a hydrogen storage container.

[0003] This invention is applicable to any type of fluid, whether the fluid is liquid, gas, or a mixture of gas and liquid.

[0004] The following description focuses on a specific case of a test method for testing the gas tightness of a hydrogen container using a tracer gas, but does not limit the scope of application of the invention. Background Technology

[0005] The test for the airtightness of the hydrogen container using a tracer gas involves filling the container with a tracer gas (e.g., a nitrogen-helium mixture containing 2% helium at 600 bar). The airtightness of the container is then verified using a sensor that detects the presence of helium near the container in the event of a leak.

[0006] According to existing technology, the filling can be performed based on a first container, the pressure of which is greater than the pressure desired in the test container, and the volume of the first container is sufficient to maintain this pressure above the pressure of the test container (when the test container has reached the target pressure). During the evacuation, the gas is transferred from the test container to a second container. The compressor then returns the tracer gas from the second container to the first container, and the replenishment of the tracer gas is performed in the first container.

[0007] This solution is not very energy efficient because it requires a significant increase in the pressure of the tracer gas. It also results in substantial frost formation around valves and pipes due to the significant expansion of the tracer gas during the filling and evacuation of the test container.

[0008] This invention provides a new solution to these problems. Summary of the Invention

[0009] According to a first aspect of the invention, a method is provided for filling a housing with fluid until a target pressure is reached and then emptying the housing at an appropriate time, characterized in that the filling is performed based on a first plurality of containers with different pressures, successively from the container with the weakest pressure to the container with the strongest pressure, and the emptying is performed by transferring the contents of the housing toward a second plurality of containers, successively from the container with the strongest pressure to the container with the weakest pressure.

[0010] This invention limits fluid consumption by recovering most of the fluid and reusing that majority for new filling cycles. It also optimizes the filling method energy-wise because the fluid is recovered under pressure, thereby limiting the energy required to raise the pressure to the desired level at the end of the filling.

[0011] After the evacuation, fluid replenishment can be carried out in the second plurality of containers, which are then used as the first plurality of containers for new filling of the shell.

[0012] Advantageously, the evacuation is performed in a second plurality of containers, which are composed of containers from the first plurality of containers. Performing the evacuation in the same plurality of containers limits the number of containers while reducing the cost and footprint of the machine.

[0013] According to a second aspect of the invention, a machine is provided for filling a housing with fluid until a target pressure is reached and then emptying the housing at an appropriate time. The machine includes a first plurality of containers and a second plurality of containers with different pressures. Filling of the housing is performed based on the first plurality of containers. The fluid is transferred from the housing to the second plurality of containers during the emptying process. The machine is capable of implementing the method according to the first aspect of the invention.

[0014] Preferably, the second plurality of containers are composed of containers from the first plurality of containers. Attached Figure Description

[0015] Other features and advantages of the invention will become more apparent from the following detailed description and accompanying drawings, in which:

[0016] Figure 1 This is a schematic view of a machine according to an embodiment of the present invention. Detailed Implementation

[0017] The hydrogen container 30 to be tested first undergoes a hydrostatic test. The container is then dried and flushed with nitrogen to remove any trace amounts of oxygen. At the end of this operation, the hydrogen container is subjected to a residual nitrogen pressure of approximately 5 bar.

[0018] The hydrogen container under test is then filled with tracer gas until the desired pressure is reached. This pressure is maintained during the airtightness test. Finally, the container is emptied after testing. The filling and emptying of the container are carried out by implementing the method according to the invention and by means of the machine according to the invention.

[0019] Figure 1 The machine 1 shown above includes a first container R2, which is supplied with a nitrogen-helium mixture containing 2% helium at a pressure of 40 bar via a supply circuit 3. The supply circuit includes a pump 4 and a mixer 5, which is supplied by a nitrogen circuit 6 and a helium circuit 7. The helium content at the output of the mixer is measured by an analyzer 8, and the nitrogen-helium ratio is adjusted by regulating valves 9 and 10.

[0020] Valve 11 closes during the filling phase of container R2, as does valve 13 located at the output end of the container.

[0021] Machine 1 includes a set of replenishment containers (six containers R3 to R8 in this embodiment) for receiving tracer gases with different and higher pressures.

[0022] Compressor 12 can supply tracer gas to containers R2 by increasing the pressure of the tracer gas from 40 bar to 718 bar, based on the tracer gas available in container R2. Containers R3 to R8 are supplied with gas by opening input valve 14, which is connected to the output of compressor 12. When the target pressure is reached in the container, input valve 14 closes again, and the pressure in the container is measured by pressure gauge 15.

[0023] For example, the last container R8 is at a nominal pressure of 718 bar, which is greater than the nominal pressure of 600 bar for the container under test 30, while the other containers are at multiple intermediate nominal pressures, which decrease down to 40 bar for container R2.

[0024] To fill the test container 30 with tracer gas at 600 bar, the test container is connected to each of containers R3 to R8 (starting with container R3, which has the lowest pressure) by means of transfer circuit 16 (which is connected to the output terminals of containers R3 to R8) by opening the output valve 17 of the involved containers. When the desired pressure is reached in the test container 30, the valve 17 of the involved container is closed, and the valve of the next container is opened to increase the pressure in the test container. When 718 bar is reached at the next container R8, the output valve 17 of the next container is opened until the pressure in the test container 30 is 600 bar. When this pressure is reached, container R8 is isolated by closing the output valve 17 of that container (R8).

[0025] The analyzer 28 controls the helium content in the container under test, and, when necessary, replenishes helium based on the buffer helium container 18 at 750 bar. The buffer container 18 is supplied with helium based on the helium supply container 19 via a booster 20.

[0026] When the sealing test is completed, the output valve 17 of container R7 is opened to connect it to the test container via transfer circuit 16. Due to the higher pressure in test container 30, a portion of the tracer gas in that container is transferred to container R7. It is possible to wait until the pressure between test container 30 and container R7 equalizes, but this could take too long, which is detrimental to the cycle time of the machine. Therefore, it is advantageous to stop the transfer between the two containers when the pressure difference between the two containers has reached the target value. Container R7 is then isolated by reclosing the output valve 17, and test container 30 is connected to container R6 by opening the output valve 17 of the container via transfer circuit 16. When the target pressure difference between the two containers is reached, container R6 is isolated by reclosing the output valve 17 of the container, and the same operation is subsequently performed on containers R5 through R2 to successively transfer the tracer gas contained in test container 30 into these containers.

[0027] To limit tracer gas loss and further slightly improve the energy efficiency of the machine, machine 1 may include a return loop 24 connected to the test container 30, and pumping by pump 4 can transfer the remaining tracer gas in container 30 to container R2. Valve 22 is arranged on the side where the machine under test 30 is located to isolate the return loop 24. During this step, mixer 5 is isolated by valve 25. At the end of this operation, after valve 22 is closed, valve 26 can bring container 30 to atmospheric pressure before the container is separated from the machine.

[0028] In a variant, the machine may not include return loop 24, and opening valve 22 may simply discharge any remaining test gas contained in the test container into the atmosphere and bring the pressure of the test container to atmospheric pressure.

[0029] Next, additional pressure is added to containers R3 through R8 using compressor 12 to bring them to their respective nominal pressures, and a new test container 30 is connected to the machine before starting the second test cycle. The tracer gas is also supplied to container R2 when its pressure gauge 15 detects that the container's pressure has reached a low threshold.

[0030] The table below shows the results based on Figure 1 Example of machine operating points, where column A indicates the nominal pressure of container 30 at the start of a test cycle, column B indicates the pressure of container 30 after it is filled, column C indicates the volume added to container 30 by each container, column D indicates the pressure of container 30 after gas is recovered from the tested container, column E indicates the volume recovered from container 30 by each container, and column F indicates the volume of gas to be added to the container to return it to its initial state and start a new test cycle.

[0031]

[0032] The test container 30 is based on containers R3 to R8 with a total volume of 142.8 Nm. 3 The tracer gas filling. When the test was performed, 127.7 Nm 3 The tracer gas has been recovered based on test container 30, i.e., 89% of the tracer gas. 75.6 Nm³ of tracer gas was replenished to containers R3 through R8 based on container R2. 3 A tracer gas is necessary, but only 47.4 Nm 3 The differential amount, already supplied by mixing station 5, was recovered into container R2 during the evacuation of the tested container. Only 16.4 Nm of [unspecified material] was consumed when the container needed to be connected to the atmosphere via opening valve 26. 3 The loss corresponds to the 68 bar remaining in the tested container after the evacuation. However, this gas is advantageously recovered by return loop 24.

[0033] Multiple models of container 30 can be tested on the machine, with varying volumes and / or test pressures. When switching to a new container model to be tested, the pressure levels in containers R3 through R8 can be adjusted according to the test pressure of the new container.

[0034] Advantageously, for testing the first container of the new model, the tracer gas filling of the first container can follow a strategy based on the pressure required for the test, which is defined by the pressures available in containers R3 through R8. Thus, when the test pressure is low (e.g., 400 bar), only the first containers R3 through R6 are used, and gas replenishment for these containers after the test can be performed based on container R7. The same operation is performed for subsequent tests when the pressure in container R7 allows it. When this pressure becomes insufficient, replenishment for containers R3 through R6 is performed based on container R8. When containers R7 and R8 have insufficient pressure for replenishment, the containers are integrated with a batch of containers used for filling the container under test. Each time a new container is added to the batch of containers used for filling, the pressure distribution in these containers is adjusted to optimize the energy efficiency of the testing method.

[0035] The number of containers R2 to R8 is optimized specifically based on the test pressure of the containers, the variability of the test pressure and volume of the containers under test, and the cycle time required for the container test. Load losses in the loop and the Kv value of the valve, which affects the flow of the tracer gas, are also taken into consideration. Kv represents the flow rate in the valve with a 1-bar load loss; when the valve involves a regulating valve, the value of Kv varies depending on the degree of valve opening. Hydrogen container 30 is typically equipped with an "overflow" type valve 27. For safety reasons, this valve closes when the flow rate exceeds a predetermined value. Thus, the maximum permissible flow rate during the purging of the test container is limited by this valve, and this maximum flow rate must be taken into account with respect to the size of the machine. Similarly, the volumes of containers R2 to R8 are selected based on these parameters; all containers do not need to have the same volume.

[0036] These choices are made after digital operation simulations of the machine in order to maintain an optimal trade-off between the operating costs and the purchase cost of the machine. Indeed, adding an extra container can improve the machine's energy efficiency, but this addition loses its benefit if the savings achieved in operating the machine cannot offset the additional costs incurred by the extra container.

Claims

1. A method for filling a housing (30) with fluid until a target pressure is reached and then emptying the housing at an appropriate time, characterized in that, The filling is performed based on a first plurality of containers (R3, R4, R5, R6, R7, R8) with different pressures, successively starting from the container with the weakest pressure (R3) and ending at the container with the strongest pressure (R8), and the emptying is performed by transferring the contents of the shell (30) toward a second plurality of containers (R2, R3, R4, R5, R6, R7) successively, starting from the container with the strongest pressure (R7) and ending at the container with the weakest pressure (R2).

2. The method according to claim 1, characterized in that, The emptying is performed in a second plurality of containers, which are composed of containers from the first plurality of containers.

3. The method according to claim 2, characterized in that, After the evacuation, fluid replenishment is carried out in the second plurality of containers, which are then used as the first plurality of containers for new filling of the shell.

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