Liquid hydrogen degassing equipment

Abstract

The invention relates to a device for degassing liquid hydrogen circulating in a circuit, comprising a liquid inlet pipe (1), a pump feed pipe (2) for receiving a part of the liquid arriving through the inlet pipe and a return pipe (3) for receiving another part of the liquid arriving through the inlet pipe, the liquid inlet pipe, the pump suction pipe and the return pipe communicating with a vertical degassing chamber (4), the cross section of the vertical chamber at the level (N1) of the mouth (6) of the inlet pipe (1) for the liquid to reach the vertical chamber is greater than the cross section of the inlet pipe (1) for the liquid to reach its mouth, the ratio of these two cross sections being equal to or greater than 2, the degassing device comprising a deflector (7) arranged in the vertical chamber (4) opposite the mouth (6) of the inlet pipe (1).

Description

[Technical field]

[0001] Designation of related technical field The present invention relates to a cryogenic installation for the production, storage or use of liquid hydrogen, and more particularly to a fluid circuit arranged upstream of a pump for circulating liquid hydrogen.

[0002] The technical problem that the invention addresses Liquid hydrogen is stored and circulated through the fluid circuit at a temperature close to its boiling point at installed pressure. By its nature, the energy required for its liquid / gas phase change is low. Thus, a small amount of calories is all that is needed to trigger the formation of hydrogen bubbles.

[0003] Although the tanks and piping are insulated by a double circuit maintained under vacuum, the insulation is not perfect and the hydrogen heats up slightly as a result of heat input from the external environment. In addition, the flow of hydrogen in the circuit creates a small additional heating effect. This creates hydrogen bubbles in the circuit.

[0004] In liquid hydrogen circulation pumps, the presence of gas bubbles leads to additional heating of the hydrogen in the pump. Therefore, in order to limit the amount of heat introduced into the pump by these gas bubbles and to reduce the additional heating of the liquid hydrogen in the pump resulting from the presence of bubbles during aspiration, it is necessary to degas the liquid before it enters the pump.

[0005] Due to its very low density, no mechanical bubble traps exist for hydrogen, and although cyclonic liquid / gas separation solutions exist, they are complex and expensive.

[0006] A simple return line to the hydrogen storage tank is usually installed upstream of the cryogenic pump. This return line traditionally has a cross-sectional area equal to or less than that of the pump feed piping. However, its efficiency in degassing the liquid hydrogen at pump suction is limited and many gas bubbles are entrained at pump suction.

[0007] The present invention provides a novel solution to this problem. Summary of the Invention

[0008] According to the invention, a device is proposed for degassing liquid hydrogen circulating in a circuit. The liquid hydrogen can be stored in a storage tank, the circuit being a vertical degassing chamber in fluid communication with three pipes, - an inlet pipe through which the liquid flows from the storage tank into the vertical chamber; a pump feed pipe through which flows a portion of the liquid entering the vertical chamber through the inlet pipe; and a vertical degassing chamber in fluid communication with a return pipe receiving another portion of the liquid entering the vertical chamber through the inlet pipe, 1. An apparatus, characterized in that the cross section of the vertical chamber at the level of the mouth of the inlet pipe through which the liquid reaches the vertical chamber is greater than the cross section of the inlet pipe through which the liquid reaches its mouth, the ratio of these two cross sections being 2 or more, and a deflector is arranged in the vertical chamber opposite the mouth of the inlet pipe.

[0009] The device according to the invention ensures efficient degassing upstream of the pump. The flow velocity of the liquid hydrogen is significantly reduced, allowing the gas bubbles to rise in the vertical chamber towards the return circuit to the storage tank without being drawn in by an excessively strong current towards the pump feed pipe. This prevents the gas bubbles from being drawn into the pump.

[0010] The deflector encourages the air bubbles to rise in the vertical chamber, thus enhancing the degassing efficiency.

[0011] Advantageously, the deflector is located in the vertical chamber in line with the axis of the liquid inlet pipe to enhance its effectiveness. The deflector is advantageously located centrally in the vertical chamber, so that equal proportions of liquid hydrogen flow on either side of it.

[0012] Advantageously, the surface area of ​​the deflector is greater than the cross section of the mouth of the liquid inlet pipe in the vertical chamber. [Brief description of the drawings]

[0013] Further features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. [Figure 1] 1 is a schematic partial front view of a liquid hydrogen storage and delivery facility according to an example embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic partial top view of the vertical chamber according to FIG.

[0014] 1 shows a partial and schematic representation of a liquid hydrogen storage and supply installation. It comprises a storage tank 20, in particular a vertical cylindrical tank, which contains liquid hydrogen up to level N4 and gaseous hydrogen above that level. This gaseous hydrogen results mainly from the evaporation of liquid hydrogen due to heat input from the walls of the storage tank 20 and the fluid circuits.

[0015] At the lower end of the storage tank 20 is an inlet pipe 1 for supplying liquid hydrogen to downstream equipment (not shown). The inlet pipe 1 is highly insulated, typically with an insulating double jacket, and maintained under vacuum, but the supply of heat through its outer wall induces the formation of gas bubbles, in particular hydrogen bubbles.

[0016] The inlet pipe 1 opens into a vertical cylindrical chamber 4, which has a much larger diameter than the inlet pipe 1. The cross section of the vertical chamber 4 is therefore more than twice the cross section of the inlet pipe 1. The liquid hydrogen then flows through the vertical chamber 4 at a much slower speed than through the inlet pipe 1. The flow velocity of the liquid hydrogen in the inlet pipe 1 is typically 0.5 m / s to 2 m / s. The cross section of the vertical chamber 4 is selected so that the liquid hydrogen flows through the vertical chamber 4 at a reduced speed, for example 30% to 50% of the speed in the inlet pipe 1. This low liquid flow velocity in the vertical chamber 4 allows the gas bubbles to rise to the top of the vertical chamber 4, then up the return pipe 3 towards the storage tank 20, and finally up to the storage tank 20.

[0017] During operation, most of the liquid hydrogen flowing through the inlet pipe 1 flows into the feed pipe 2 which feeds the pump 10 and is entrained by the pump 10. For example, if 100 m 3 About 98m 3 advances to pump 10, 2m 3 proceeds to the storage tank 20.

[0018] The inlet pipe 1 may be horizontal or inclined. Advantageously, the inlet pipe 1 is inclined so that its downstream end is higher, so that the air bubbles are located at the top of the inlet pipe 1 and flow more easily towards the top of the vertical chamber 4.

[0019] The vertical chamber 4 is advantageously cylindrical, but may be of any other shape. It is insulated by an insulating outer double jacket that maintains a vacuum space to limit the transfer of heat from the external environment to the liquid hydrogen.

[0020] 1 and 2, a deflector 7 is placed in the vertical chamber 4 opposite the mouth of the inlet pipe 1 to encourage the bubbles to rise in the vertical chamber 4. This deflector 7 may be a metal sheet held by a support means connected to the inner wall of the vertical chamber 4.

[0021] At the bottom of the vertical chamber 4 there is a feed pipe 2 for feeding the pump 10. The mouth 8 of this pipe into the vertical chamber 4 is at a level N3 lower than the level N1 at which the mouth of the inlet pipe 1 into the vertical chamber 4 is located. The height difference between the levels N1 and N3 is chosen so as to prevent gas bubbles from the inlet pipe 1 from being drawn into the feed pipe 2 of the pump 10. However, in order to limit the heating of the liquid hydrogen, it must be limited so as to reduce the length of the path between the two ports 6 and 8 and also reduce the height of the vertical chamber 4.

[0022] The mouth 5 of the return pipe 3 to the storage tank 20 is at a level N2 higher than the level N1 at which the mouth of the inlet pipe 1 to the vertical chamber 4 is located. The mouth 5 is arranged in the upper part of the vertical chamber 4. Advantageously, it is horizontal and positioned substantially vertically from the mouth 6 of the inlet pipe 2 in order to restrict the path of the air bubbles in the vertical chamber 4 and to redirect them during this path.

[0023] The height of the vertical chamber 4 is limited to that required for degassing so as to limit the heat ingress through its outer walls. The distance between the mouth 6 of the inlet pipe 2 and the mouth 5 of the return pipe 3 is for example 5 cm. The system dimensions are optimized to limit the heat ingress.

[0024] The length of the feed pipe 2 of the pump 10 is as short as possible in order to limit hydrogen heating in this feed pipe 2 upstream of the pump 10. The feed pipe 2 of the pump 10 may be horizontal or inclined. Advantageously, the feed pipe 2 is inclined such that, on the pump 10 side, the inlet of the feed pipe 2 is located at a higher height than its outlet. In this way, gas bubbles that would otherwise be present in the feed pipe 2 can rise up to the vertical chamber 4.

[0025] Figure 2 is a schematic partial top view of the vertical chamber 4 in the plane P of Figure 1. As shown in this figure, the width La of the deflector 7, its height and the distance at which the deflector 7 is positioned from the mouth 6 of the liquid inlet pipe 1 are selected so that the flow velocity of the liquid hydrogen bypassing the deflector 7 remains low, for example 0.2 m / s.

[0026] The axis of the inlet pipe 1 supplying the liquid in the vertical chamber 4 and the axis of the feed pipe 2 supplying the pump 10 are advantageously arranged in the same vertical plane, so that the flow of hydrogen between these two pipes in the vertical chamber 4 is as linear as possible and causes as little head loss as possible in order to limit as much as possible any heating of the hydrogen during that flow.

Claims

1. 1. An apparatus for degassing liquid hydrogen circulating in a circuit, said liquid hydrogen being capable of being stored in a storage tank (20), said circuit comprising a vertical degassing chamber (4) in fluid communication with three pipes (1, 2, 3), - an inlet pipe (1) through which liquid flows from said storage tank (20) into said vertical chamber (4); a feed pipe (2) for feeding a pump (10) through which flows a portion of the liquid entering the vertical chamber (4) through the inlet pipe (1); - a vertical degassing chamber (4) in fluid communication with a return pipe (3) which receives another portion of the liquid entering said vertical chamber (4) through said inlet pipe (1); 1. The device according to claim 1, wherein the cross section of the vertical chamber (4) at the level (N1) of the mouth (6) of the inlet pipe (1) through which the liquid reaches the vertical chamber (4) is greater than the cross section of the inlet pipe (1) through which the liquid reaches its mouth, the ratio of these two cross sections being equal to or greater than 2, and wherein a deflector (7) is arranged in the vertical chamber (4) opposite the mouth (6) of the inlet pipe (1).

2. 2. Device according to claim 1, characterized in that the deflector (7) is located in the vertical chamber in line with the axis (9) of the liquid inlet pipe (1).

3. 2. Device according to claim 1, characterized in that the surface area of ​​the deflector (7) is greater than the cross section of the mouth (6) of the liquid inlet pipe (1) in the vertical chamber.

4. 2. The device according to claim 1, characterized in that the mouth (5) of the return pipe into the vertical chamber is arranged at a level (N2) of the vertical chamber that is higher than the level (N1) at which the mouth (6) of the inlet pipe (1) that feeds the liquid into the vertical chamber is located, and the mouth (8) of the feed pipe (2) that feeds the pump (10) in the vertical chamber (4) is arranged at a level (N3) of the vertical chamber that is lower than the level (N1) of the mouth (6) of the liquid inlet pipe (1).

5. 5. A method for degassing circulating liquid hydrogen, carried out in an apparatus according to any one of claims 1 to 4, characterized in that the velocity of the liquid hydrogen is reduced at the mouth (6) of the inlet pipe (1) to the vertical chamber (4) in order to facilitate the evacuation of hydrogen bubbles towards the return pipe (3).

6. 6. The method of claim 5, wherein the velocity of the liquid hydrogen at the mouth (6) of the inlet pipe (1) to the vertical chamber (4) is between 30% and 50% of the velocity of the liquid hydrogen in the inlet pipe.

Images