Compression device and method

Abstract

The invention relates to a fluid compression device comprising a compression chamber housing a piston (5) movable in translation between the first (3) and second (6) ends of the compression chamber, the device (1) comprising a regeneration circuit (7) connecting the first (3) and second (6) ends of the compression chamber and comprising a regenerator (17), the supply line (8) comprising a set of valve(s) (9), the device (1) comprising at least one compressed fluid discharge line (10) comprising an upstream end connected to the compression chamber and a downstream end intended to be connected to a compressed fluid receiver, characterized in that the regeneration circuit (7) comprises, between the regenerator (17) and the first (3) end of the compression chamber,a heat exchanger (15) configured to ensure heat exchange between the fluid flow that has passed through the regenerator (17) and a cold source. Abbreviated figure: Fig. 1,

Description

Title of the invention: Compression device and method

[0001] The invention relates to a compression device and method.

[0002] The invention relates more particularly to a fluid compression device comprising a compression chamber housing a movable piston, the device comprising a first end housing a first end of the compression chamber, the device comprising a second end housing a second end of the compression chamber, the piston being movable in translation between the first and second ends of the compression chamber, the device comprising a regeneration circuit connecting the first and second ends of the compression chamber and comprising a regenerator, the device comprising a supply line comprising an upstream end intended to be connected to a source of fluid to be compressed and a downstream end opening into the first end of the compression chamber, the supply line comprising a set of valve(s),The device includes at least one compressed fluid discharge pipe comprising an upstream end connected to the compression chamber and a downstream end intended to be connected to a compressed fluid receiver.

[0003] Documents FR2904401A1 and FR3007077A1 describe such a compression device sometimes called a "thermal compressor".

[0004] Devices of this type can exhibit satisfactory efficiency. Solutions are being sought to improve this efficiency, for example, energy optimization for pressure management in the device's power storage.

[0005] In operation, such a device generally comprises the following steps.

[0006] Compression: The piston is in its extreme position at the second end of the compression chamber (the relatively hot side of the device 1). The supply line valve has been opened, and fluid (gas or liquid) has been previously introduced and fills the volume of the first end of the compression chamber (from the pressure vessel or via a pump). Then, the piston is actuated towards the first end of the compression chamber. This results in a transfer of fluid from the first (cold) end to the second (hot) end. In practice, the force required is limited only by the impedance of the gas transfer through the regenerator.

[0007] When the gas heats up in the second hot end, the pressure begins to increase in the system. The supply line valve is closed, and the discharge line valve 10 remains closed as long as the pressure is below an opening threshold (for example, the pressure of an outlet tank connected to the discharge line). The excess fluid mass is then expelled through the valve of the The discharge line maintains a preferably constant pressure. When the piston reaches its extreme position at the bottom of the first end of the compression chamber, it preferably occupies the entire volume of that end of the compression chamber. During the transfer from the hot chamber to the cold chamber, the cold of the fluid coming from the cold chamber stores the cold in the walls of the regenerator, which will be released back to the fluid during the regeneration phase.

[0008] Regeneration: The piston is moved again to the second end of the compression chamber (regeneration phase). This moves the fluid from the second (hot) end to the first (cold) end of the compression chamber. During this process, the mass flow moves from the second (hot) end to the first (cold) end. The fluid recovers the cold stored in the walls of the regenerator. As the fluid cools, the pressure in the compression device begins to decrease. When the pressure in the first end of the compression chamber falls below a certain threshold, the drain line valve closes and the supply line valve can reopen to restart the process.

[0009] This last step can generate a large loss of efficiency of the thermal compressor. The fluid returning from the hot chamber carries in fact the inefficiencies of the regenerative exchanger (temperature pinch) and of compression (temperature differential due to the compression of the previous cycle).

[0010] For example, in the case of compressing liquid hydrogen from 1 bar to 20 bar, the temperature naturally increases from 20.2 K to 21.1 K due to the compression. This means that the cold side of the regenerator will be at least at a temperature of 21.1 K. Therefore, the fluid returning from the hot chamber will be at best greater than or equal to 21.1 K, plus the regenerator's compression. The amount of heat injected into the cold chamber then corresponds to the return flow rate from the hot chamber multiplied by the enthalpy difference between 20.2 K and 21.1 K.

[0011] The invention proposes an improvement in the efficiency of the thermal compressor and / or an energy optimization to reduce the pressurization consumption of the thermal compressor's supply storage.

[0012] To this end, the device according to the invention, which also conforms to the generic definition given in the preamble above, is essentially characterized in that the regeneration circuit includes, between the regenerator and the first end of the compression chamber, a heat exchanger configured to ensure heat exchange between the fluid flow that has passed through the regenerator and a cold source.

[0013] Furthermore, embodiments of the invention may include one or more of the following features: - the cold source includes a cryogenic fluid stream, - the source of fluid to be compressed includes a liquefied fluid reservoir, for example of liquefied cryogenic fluid connected to the upstream end of the supply line, the cold source including a sampling line for a cryogenic fluid stream from the fluid source and ensuring passage through the heat exchanger, - the sampling line is a branch of the supply line, - the sampling line describes a loop connected to the fluid source and configured to form a thermosiphon, - the sampling line includes a set of valve(s), for example at least one pressure and / or flow control valve, - The entire valve assembly of the supply line includes a non-return device such as a non-return valve, - The second end of the device includes a heating system; - The first end of the device includes a cooling or heating system. - the regenerator includes a heat exchanger tube, in particular a cylindrical tube, filled with a material configured to store and release heat and allow the fluid to pass through in a liquid and / or gaseous state.

[0014] The invention also relates to a method of fluid compression by means of a device conforming to any one of the above or below characteristics, characterized in that it comprises the following successive steps: a) admission of a fluid in a liquid state at an initial pressure into the first end of the compression chamber via the supply line, b) compression by displacement of the piston towards the first end of the compression chamber and transfer of the fluid from the first end of the compression chamber to the second end of the compression chamber via the regeneration line, the second end of the device being maintained at a temperature higher than the temperature of the first end,c) regeneration by moving the piston towards the second end of the compression chamber and transferring the fluid from the second end of the compression chamber to the first end of the compression chamber via the regenerator, the process comprising, during regeneration step c), a cooling step of the fluid flow that has passed through the regenerator.

[0015] According to other possible features, the admission of the fluid in the liquid state at an initial pressure into the first end of the compression chamber is carried out from a liquefied fluid reservoir and in that the cooling stage uses fluid from the reservoir to cool the fluid flow.

[0016] The invention may also relate to any alternative device or method including any combination of the above or below features within the scope of the claims.

[0017] Other features and advantages will become apparent from the following description, given with reference to the figures in which: Brief description of the figures

[0018] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0019] [Fig. 1] represents a schematic and partial cross-sectional view illustrating an example of the structure and operation of an embodiment of a compression device according to the invention. Detailed description

[0020] In all figures, the same references refer to the same elements.

[0021] In this detailed description, the following achievements are examples. The fact that the description refers to one or more embodiments does not mean that the features apply only to a single embodiment. Simple features from different embodiments can also be combined and / or interchanged to provide other embodiments.

[0022] The fluid compression device 1 illustrated in [Fig. 1] (or "thermal compressor") comprises a frame or casing housing a compression chamber in which a movable piston 5 is housed. The device 1 includes a first end 2 housing a first end 3 of the compression chamber (relatively cold end), and a second end 4 housing a second end 6 of the compression chamber (relatively hot end). In this compressor, the two chambers or ends 3, 6 are generally at practically the same pressure, apart from the pressure losses of the regenerative heat exchanger. A heating system 16 may be provided at the second end.

[0023] The piston 5 is mobile in translation between the first 3 and second 6 ends of the compression chamber (via any suitable drive system not described for the sake of simplification).

[0024] The device 1 includes a regeneration line 7 connecting the first 3 and second 6 ends of the compression chamber and comprising a regenerator 17.

[0025] The device 1 further comprises a supply line 8 having an upstream end intended to be connected to a source 13 of fluid to be compressed and a downstream end opening into the first end 3 of the compression chamber. The source 13 is preferably a reservoir of cryogenic fluid, for example liquefied hydrogen.

[0026] The reservoir 13 preferably contains a cryogenic fluid in biphasic form and supplies the thermal compression device with liquid, preferably in a near-saturated state and possibly subcooled. The diagram does not show pressure control devices for tank 13 (pressurization and / or depressurization system), which can be implemented in a conventional manner.

[0027] The supply line 8 includes a set of check valve(s), in particular a non-return valve 9. The device 1 includes at least one compressed fluid discharge line 10 having an upstream end connected to the compression chamber and a downstream end intended to be connected to a compressed fluid receiver. This discharge line 10 also includes a set of check valve(s), for example a non-return valve 11.

[0028] For example, the compressed fluid discharge line 10 has its upstream end connected to the first and / or second end of the compression chamber.

[0029] For example, and as illustrated, device 1 may have two exhaust outlets (from the hot room and the cold room). It is also possible to consider an exhaust at an intermediate temperature between these two ends.

[0030] For example, the upstream end of the compressed fluid discharge line 10 is connected to the first end 3 of the compression chamber. That is to say, the compressed fluid is discharged from the relatively cold end 3 of the device 1. This makes it possible to produce relatively cold compressed fluid.

[0031] The regeneration line 7 is preferably separate from the discharge line 10. That is to say, this regeneration line 7 connects the two ends 3, 6 of the compression chamber via the regenerator 17 and thus only allows direct passage between these ends during the moments of the piston 5.

[0032] The downstream end of the supply line 8 is preferably connected directly to the first end 3 of the compression chamber, i.e. without passing through a pre-compression chamber. That is to say, the fluid to be compressed is injected directly into the compression chamber 3.

[0033] Conventionally, the regenerator 17 may comprise a heat exchanger tube, in particular a cylindrical tube, filled with a material configured to store and release heat and allow the fluid to pass through in a liquid and / or gaseous state. Of course, any other suitable heat exchanger structure may be considered.

[0034] One operation may be as follows. In a first compression stage, the first end 3 (cold) is filled with cold fluid supplied from the reservoir 13. The second end 6 (hot) is at its minimum volume. The piston 3 is moved from the second end 6 to the first end 3, forcing the fluid into the regenerator 17. The fluid heats up in the regenerator and possibly in a additional heat exchanger.

[0035] The heated fluid pressurizes the ends 3, 6 of the compression chamber (iso-pressure). Once the discharge pressure is reached, the outlet valve 11 opens. In a subsequent regeneration and injection phase, the piston 5 is moved from the first end 3 to the second end 6, forcing the fluid to pass back into the regenerator 17. The fluid cools, reducing the pressure within the compressor. Once this pressure is lower than that of the reservoir 13, the feed valve 9 opens. Thus, the inlet fluid (from the reservoir 13) and the fluid returning from the regenerator 17 mix in the cold chamber (first end 3). The liquid level in the feed reservoir decreases, which in turn reduces the pressure within the reservoir 13. An internal or external pressurization system can maintain the pressure there.

[0036] According to an advantageous feature, the device 1 includes, preferably at the level of the regeneration circuit 7, between the regenerator 17 and the first 3 end of the compression chamber, a heat exchanger 15 configured to ensure heat exchange between the fluid flow having passed through the regenerator 17 and a cold source.

[0037] Integrating such a heat exchanger 15 on the cold side of the thermal compressor allows for heat exchange between the fluid returning from the second hot chamber (end 6) of the thermal compressor, whose flow carries the inefficiencies of the heat exchange, and the regenerative exchanger (regenerator 17) described previously. This allows the fluid returning from the second end 6 to be cooled to a temperature close to that of the liquid admitted at the inlet of the first end 3. This reduces the amount of heat returned to the cold chamber (first end 3) due to the inefficiency of the compression.

[0038] As illustrated, the cold source may include a sampling line 12 for drawing a cryogenic fluid flow from the fluid source 13 and ensuring passage through the heat exchanger 15. For example, the sampling line is a branch of the supply line 8.

[0039] The cold fluid can be drawn from the thermal compressor supply, corresponding to the coldest point in the system. As it passes through the cold heat exchanger 15, this branch of the thermal compressor supply heats up and can vaporize.

[0040] As illustrated, the sampling line 12 can form a loop of which two ends are connected to the fluid source 13 and the loop is configured to form a thermosiphon.

[0041] Thus, the fluid returning from chamber 6 or the second hot end of the thermal compressor returns to the cold chamber or end 3 at a temperature close to the temperature of the inlet fluid, the mixture is carried out with the feed fluid. The use of this heat exchanger 15 then improves the liquid content of the cold room (first end 3). This increases the efficiency of the thermal compressor. The sampling line 12 may include a set of valve(s) 14, for example, at least one pressure and / or flow control valve.

[0042] The cryogenic cold fluid supplied by the reservoir 13 may have a temperature close to its saturation point and may evaporate following heat exchange in the heat exchanger 15. This fluid can be returned to the reservoir 13 to mitigate the need for a pressurization system. The fluid can be returned to any level (height) in the reservoir (into the lower liquid or upper gaseous section). This pressurization is carried out with a fluid having a low return temperature, for example, close to saturation.

[0043] This cooling circuit 12 is independent of the thermal compressor. The coupling of the reservoir 13 with the cooling circuit 12 preferably constitutes a thermosiphon.

[0044] Thus, the circulation of the cooling fluid in the heat exchanger 15 is established naturally with a driving force corresponding to the hydrostatic head of the reservoir 13 and the heat exchanged in the heat exchanger 15. Therefore, no additional force is required to achieve this circulation.

[0045] A regulating valve can be integrated on the sampling line 12 to limit the flow of the thermosiphon and thus to regulate the quantity of fluid returned to the reservoir 13 for its pressurization.

[0046] The compression device 1 can be supplied with gas or liquid. In the latter case, greater compression performance is obtained.

[0047] The invention is advantageously applicable to the compression of liquid hydrogen but could relate to a fluid chosen from the list including He, H2, Ne, CO, Ar, N2, O2, CH4, CO2, NO, Kr, Xe or any mixture of two or more of these chemical species.

Claims

Demands

1. A fluid compression device comprising a compression chamber housing a movable piston (5), the device comprising a first end (2) housing a first end (3) of the compression chamber, the device (1) comprising a second end (4) housing a second end (6) of the compression chamber, the piston (5) being movable in translation between the first (3) and second (6) ends of the compression chamber, the device (1) comprising a regeneration circuit (7) connecting the first (3) and second (6) ends of the compression chamber and comprising a regenerator (17), the device (1) comprising a supply line (8) comprising an upstream end intended to be connected to a source (13) of fluid to be compressed and a downstream end opening into the first end (3) of the compression chamber, the supply line (8) comprising a set of valve(s) (9),the device (1) comprising at least one compressed fluid discharge line (10) having an upstream end connected to the compression chamber and a downstream end intended to be connected to a compressed fluid receiver, the regeneration circuit (7) comprising, between the regenerator (17) and the first (3) end of the compression chamber, a heat exchanger (15) configured to ensure heat exchange between the fluid flow having passed through the regenerator (17) and a cold source, characterized in that the source (13) of fluid to be compressed comprises a reservoir (13) of liquefied fluid, for example of liquefied cryogenic fluid connected to the upstream end of the supply line (8), and in that the cold source comprises a line (12) for taking a cryogenic fluid flow from the fluid source (13) and ensuring passage through the heat exchanger (15).

2. Device according to claim 1, characterized in that the sampling line (12) is a branch of the supply line (8).

3. Device according to any one of claims 1 or 2, characterized in that the sampling line (12) describes a loop connected to the fluid source (13) and configured to form a thermosiphon.

4. Device according to any one of claims 1 to 3, characterized in that the sampling line (12) comprises a set of valve(s) (14) for example at least one pressure and / or flow control valve.

5. Device according to any one of claims 1 to 4, characterized in that the valve assembly(ies) of the supply line (8) includes a non-return device (9) such as a non-return valve.

6. Device according to any one of claims 1 to 5, characterized in that the second end (4) of the device (1) comprises a heating system (16).

7. Device according to any one of claims 1 to 6, characterized in that the first end (2) of the device (1) comprises a cooling or heating system.

8. Device according to any one of claims 1 to 7, characterized in that the regenerator (17) comprises a heat exchanger tube, in particular a cylindrical tube, filled with a material configured to store and release heat and allow the fluid to pass through in the liquid and / or gaseous state.

9. A method for compressing fluid using a device according to any one of claims 1 to 80, characterized in that it comprises the following successive steps: a) admission of a fluid in the liquid state at an initial pressure into the first end (3) of the compression chamber via the supply line (8), b) compression by displacement of the piston (5) towards the first end (3) of the compression chamber and transfer of the fluid from the first end (3) of the compression chamber to the second end (6) of the compression chamber via the regeneration line (7), the second end (4) of the device (1) being maintained at a temperature higher than the temperature of the first end (2),c) regeneration by displacement of the piston (5) towards the second end (6) of the compression chamber and transfer of the fluid from the second end (6) of the compression chamber to the first end (3) of the compression chamber via the regenerator, the process comprising, during regeneration step c), a cooling step of the fluid flow having passed through the regenerator (17).

10. A method according to claim 9, characterized in that the admission of the fluid in the liquid state at an initial pressure into the first end (3) of the compression chamber is carried out from a reservoir (13) of liquefied fluid and in that the cooling step uses fluid from the reservoir to cool the fluid flow.

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