SYSTEM FOR RECOVERING COMPRESSION ENERGY OF A GAS, LIQUEFIER COMPRISING SUCH A SYSTEM AND METHOD FOR RECOVERING COMPRESSION ENERGY OF A GAS

Abstract

A system for recovering compression energy from a gas, the system comprising an organic Rankine cycle module and an adiabatic compressor, the organic Rankine cycle module comprising a heat transfer fluid and the adiabatic compressor comprising N adiabatic compression stages for the gas, N being greater than or equal to 2, and, downstream of each adiabatic compression stage, two heat exchangers, a first heat exchanger configured to extract heat from the gas leaving the adiabatic compression stage and to heat the heat transfer fluid passing through the first heat exchanger and a second heat exchanger configured to extract heat from the gas leaving the first heat exchanger to a cold source passing through the second heat exchanger. A liquefier comprising such a system and method for recovering compression energy from a gas.

Claims

1. A gas compression energy recovery system, the system comprising an organic Rankine cycle module and an adiabatic compressor, the organic Rankine cycle module comprising a heat transfer fluid and the adiabatic compressor comprising N adiabatic compression stages for the gas, N being greater than or equal to 2, and, downstream of each adiabatic compression stage, two heat exchangers, a first heat exchanger configured to extract heat from the gas leaving the adiabatic compression stage and to heat the heat transfer fluid passing through the first heat exchanger and a second heat exchanger configured to extract heat from the gas leaving the first heat exchanger to a cold source passing through the second heat exchanger.

2. The system according to claim 1, wherein the second heat exchanger is a gas-air exchanger.

3. The system according to claim 1, wherein the second heat exchanger is a gas-water exchanger.

4. The system according to claim 1, wherein the heat transfer fluid has a boiling temperature between a cold source inlet temperature and a gas outlet temperature in the adiabatic compression stage.

5. The system according to claim 4, in which the heat transfer fluid is methanol, isobutane or ethanol.

6. A liquefier comprising a system according to claim 1.

7. The liquefier according to claim 6, wherein the gas is the gas to be liquefied.

8. The liquefier according to claim 6, wherein the liquefier is a refrigerated liquefier comprising at least one cooling circuit and the gas is the gas of the at least one cooling circuit of the refrigerated liquefier and/or the gas to be liquefied.

9. The liquefier according to claim 7, wherein the gas to be liquefied is hydrogen, nitrogen, helium or natural gas.

10. A method for recovering compression energy from a gas, the method comprising the following steps: a) adiabatic compression of the gas in an adiabatic compression stage; b) extraction of part of the heat from the compressed gas in a first heat exchanger comprising a heat transfer fluid of an organic Rankine cycle module; c) extracting part of the heat from the gas coming from the first heat exchanger in a second heat exchanger comprising a cold source; repetition of steps a) to c) N times, where N is greater than or equal to 2; use of the heat extracted in the first heat exchanger to produce energy in the Rankine organic cycle module.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Further features and advantages of the object of the present disclosure will become apparent from the following description of embodiments, given by way of non-limiting examples, with reference to the appended figures.

[0036] FIG. 1 is a schematic view of a liquefier.

[0037] FIG. 2 is a schematic view of a gas compression energy recovery system.

[0038] FIG. 3 is a schematic view of a compression stage of the system shown in FIG. 2.

[0039] FIG. 4 is a flow chart representing the steps of a gas compression energy recovery method.

[0040] Throughout the figures, common elements are identified by identical numerical by identical numerical references.

DETAILED DESCRIPTION

[0041] FIG. 1 is a schematic view of a liquefier 10, for example a hydrogen (H2) liquefier using the Collins cycle. A liquefier comprises a cold box 12, an adiabatic compressor 14 and a heat exchanger 16 supplying pressurized hydrogen to the cold box 12. Together, the adiabatic compressor 14 and the heat exchanger 16 form an isothermal compressor. The cold box 12 is known per se and comprises a plurality of regenerators 18 arranged in series to reach a liquid hydrogen storage tank 24 via a Jole-Thompson isenthalpic expansion valve 22. A portion of the gaseous hydrogen gaseous form, leaving a regeneration stage 18 is directed to a heat exchanger 20 and redirected to the adiabatic compressor 14.

[0042] For simplicity's sake, the adiabatic compressor 14 and the heat exchanger 16 have been shown on FIG. 1 as single elements. However, the adiabatic compressor 14 is an adiabatic compressor comprising several adiabatic compression stages 14A, 14B, 14C, as shown in FIG. 2. Similarly, heat exchanger 16 comprises a plurality of heat exchangers 50, 52. In particular, heat exchanger 16 comprises, downstream of each adiabatic compression stage 14A, 14B, 14C, two heat exchangers.

[0043] In the embodiment shown in FIG. 2, the adiabatic compressor 14 comprises three adiabatic compression stages 14A, 14B, 14C. Also, N the number of adiabatic compression stages is equal to 3. It is understood that N is not limited to 3 as long as N is greater than or equal to 2.

[0044] In the embodiment shown in FIG. 2, downstream of each adiabatic compression stage 14A, 14B, 14C, heat exchanger 16 comprises a first heat exchanger 50A, 50B, 50C and a second heat exchanger 52A, 52B, 52C.

[0045] FIG. 2 shows a system for recovering compression energy from the gas to be liquefied in the liquefier, e.g., hydrogen.

[0046] The energy recovery system comprises the adiabatic compressor adiabatic compressor 14 and heat exchanger 16. The energy recovery system also comprises an organic Rankine cycle module 40.

[0047] In the embodiment shown in FIG. 2, the gas 56 to be compressed enters the first adiabatic compression stage 14A. The first adiabatic compression stage 14A is supplied with gas 56 via a feed line 26 and with gas recovered from the cold box 12 via a line 28.

[0048] The organic Rankine cycle module 40 includes a heat transfer fluid 54 circulating in the module 40.

[0049] In the embodiment shown in FIG. 2, the organic Rankine cycle module 40 comprises three first heat exchangers 50A, 50B, 50C configured to heat the heat transfer fluid 54 circulating in the module 40 from a heat source external to the module 40, an expansion device 42, a condenser 46 for cooling the heat transfer fluid 54 and a pump 48 for circulating the heat transfer fluid 54 in the module 40. The expansion device 42 expands the heat transfer fluid 54 heated in heat exchangers 50A, 50B, 50C and under pressure, and converts the energy recovered in the form of heat into mechanical energy.

[0050] As a non-limiting example, the expansion device 42 may be a turbine or a volumetric expansion device.

[0051] In the embodiment shown in FIG. 2, the expansion device 42 is coupled to an energy recovery device 44.

[0052] As a non-limiting example, the expansion device 42 can be a turbine and the energy recovery device 44 can be an electrical generator for converting the mechanical energy recovered from the turbine into electrical energy. It is understood that the expansion device 42 of the organic Rankine cycle module 40 can be coupled to another energy recovery device 44, enabling the recovered energy to be converted into mechanical form, for example.

[0053] In the embodiment shown in FIG. 2, the hot source is the gas 56 leaving the compression stages 14A, 14B, 14C, and the condenser 46 is a heat exchanger using ambient air 60 as a cold source to cool the heat transfer fluid 54 leaving the expansion device 42.

[0054] The heat transfer fluid 54 passes successively through the first heat exchangers 50A, 50B, 50C, where, by heat exchange with the gas 56 leaving the compression stages 14A, 14B, 14C, the heat transfer fluid 54 is brought to boiling point. The heat transfer fluid 54, in the form of steam, is then expanded in the expansion device 42, which is coupled to the energy recovery device 44. The steam is then condensed in condenser 46 by exchange with ambient air 60. The heat transfer fluid 54 is once again in liquid form and can once again pass through the first heat exchangers 14A, 14B, 14C.

[0055] The gas 56 leaving each adiabatic compression stage 14A, 14B, 14C passes through the first heat exchanger 50, 50B, 50C and exchanges part of the heat stored in the gas 56 during compression with the heat transfer fluid 54 circulating in the first heat exchanger 50A, 50B, 50C. The gas 56 leaving the first heat exchanger 50A, 50B, 50C then passes through the second heat exchanger 52A, 52B, 52C and exchanges the remaining stored heat with a cold source 58.

[0056] By way of non-limiting example, cold source 58 may be ambient air or water.

[0057] At the outlet of the second heat exchanger 52A, 52B, gas 56 enters the adiabatic compression stage located downstream of the second heat exchanger 52A, 52C. At the outlet of the second heat exchanger 52C downstream of the last adiabatic compression stage 14C, gas 56 is fed into the cold box via a pipe 30.

[0058] By way of a non-limiting example, heat transfer fluid 54 can be methanol. Methanol has a boiling temperature at approximately 1 bar equal to 338 K (Kelvin) and the cold source 58 can be ambient air estimated at 300 K.

[0059] For simplicity of representation, FIG. 3 shows a single adiabatic compression stage, for example the first adiabatic compression stage 14A. Elements common to the various figures are identified by the same numerical references.

[0060] As a non-limiting example, the gas temperature at the outlet of the adiabatic compression stage is limited to 400 K. Also, the boiling temperature of the heat transfer fluid 54 is between the temperature of the cold source 58 entering the second heat exchanger 52A, 52B, 52C and the temperature of the gas leaving the adiabatic compression stage 14A, 14B, 14C.

[0061] Thus, in an ideal example, the hydrogen entering the first adiabatic compression stage 14A has an ambient temperature of around 300 K (item 1 in FIG. 3). After adiabatic compression, the hydrogen exits at a temperature of 400 K (item 2 in FIG. 3). After passing through the first heat exchanger 50A, gas 56 is at a temperature of 338 K (item 3 in FIG. 3), which is the boiling temperature of heat transfer fluid 56). After passing through the second heat exchanger 52A, gas 56 is at a temperature of around 300 K (item 4 in FIG. 3). We understand that, in practice, in a non-ideal system, the temperature of gas 56 will be slightly higher than 338 K. Similarly, after passing through the second heat exchanger 52A, the temperature of gas 56 will be slightly higher than the ambient air temperature.

[0062] The compression energy recovery system can also be implemented in a refrigerated liquefaction cycle.

[0063] Refrigerated liquefaction cycles are well known to the state of the art and implement circuits for cooling/refrigerating the gas to be liquefied by using another gas or gas mixture maintained at low temperature by a refrigeration cycle which comprises compression stages specific to this gas or gas mixture and expansion stages, this other gas or gas mixture being used as refrigerant for the main liquefaction circuit. The nature of the gases or gas mixtures used as refrigerant gases in such cycles can be distinct from the nature of the gas to be liquefied in the main liquefaction circuit.

[0064] It is therefore understood that in the case of a refrigerated liquefaction cycle, the compression energy recovery system can be implemented at the compression stages specific to the refrigerated liquefaction cycle's cooling circuit.

[0065] In the case of a refrigerated liquefaction cycle with multiple cooling circuits, the gas compression energy recovery system can be implemented at the compression stages of one or more cooling circuits.

[0066] The method 100 for recovering gas compression energy 56 will be described with reference to Figures to 4.

[0067] Method 100 comprises: [0068] a) an adiabatic compression step 102 of gas 56 in an adiabatic compression stage 14A, 14A, 14C; [0069] b) a step 104 of extracting part of the heat from the compressed gas in a first heat exchanger 50A, 50B, 50C comprising the heat transfer fluid 54 of the organic Rankine cycle module 40; [0070] c) a step 106 of extracting part of the heat from the gas coming from the first heat exchanger 50A, 50B, 50C in a second heat exchanger 52A, 52B, 52C comprising a cold source 58; [0071] Steps a) to c) are repeated 108 N times, where N is greater than or equal to equal to 2.

[0072] In the embodiment shown in FIG. 2, steps a) to c) are repeated three times.

[0073] The method 100 includes a step 110 of using the heat extracted in the first heat exchanger 50A, 50B, 50C to produce energy in the organic Rankine cycle module 40.

[0074] Although the present disclosure has been described with reference to a specific example embodiment, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments mentioned can be combined in additional embodiments. Consequently, the description and drawings are to be considered in an illustrative rather than a restrictive sense.