SYSTEM FOR RECOVERING COMPRESSION ENERGY OF A GAS, CONDENSATOR WITH SUCH A SYSTEM AND METHOD FOR RECOVERING COMPRESSION ENERGY OF A GAS

Description

technical field

[0001] This presentation concerns the compression of a gas and in particular the recovery of energy from gas compression. Previous technique

[0002] The liquefaction of a gas generally requires a high-pressure gas compression stage. This compression stage is called isothermal and is usually achieved through a series of adiabatic compression stages during which the gas is heated. Thus, between each compression stage, the gas is cooled before entering the next compression stage.

[0003] The gas is cooled in a heat exchanger.

[0004] In liquefiers, also called "liquefiers" in English, the heat recovered in this heat exchanger is either lost to the atmosphere, or, for example as described in JP2005241232, used as a hot source for the vaporization of liquid natural gas.

[0005] The coupling of a liquefied natural gas (LNG) plant and a liquefied natural gas (LNG) plant requires that the liquefied natural gas plant and the plant be located in the same place. This heat recovery solution also severely limits the potential for heat recovery, due in particular to the number of LNG plant sites, the fluctuating demand for LNG which impacts the cooling of the compressed gas between compression stages, and the safety constraints related to the presence of LNG and liquid hydrogen, for example.

[0006] US2013 / 139509 shows a system for recovering energy from the compression of a gas by an organic Rankine cycle according to the prior art. Description of the invention

[0007] The present presentation aims to remedy at least some of these drawbacks.

[0008] To this end, the present exposition concerns 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 of 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 exiting 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 exiting the first heat exchanger to a cold source passing through the second heat exchanger.

[0009] Subsequently, the terms "upstream" and "downstream" are defined in relation to the normal direction of gas flow in the system. Thus, a second element located downstream of a first element receives the gas exiting the first element.

[0010] Thanks to the organic Rankine cycle module, it is possible to avoid losing the heat of the compressed gas in an adiabatic compression stage to the atmosphere, and this is achieved by eliminating the constraint of direct coupling with a liquefied natural gas unit.

[0011] As is known, an organic Rankine cycle module includes at least one heat exchanger configured to heat the heat transfer fluid circulating within the module from an external heat source, a device for expanding the heated heat transfer fluid, a condenser for cooling the heat transfer fluid, and a pump for circulating the heat transfer fluid within the module. The expansion device expands the heated, pressurized heat transfer fluid and converts the recovered energy from heat into mechanical energy. The expansion device is typically coupled with an energy recovery device that converts the recovered mechanical energy at the outlet of the expansion device into usable energy. In this discussion, the heat source is the gas exiting a compression stage of the adiabatic compressor.

[0012] The system includes, after each compression stage, a first exchanger configured to exchange heat between the gas exiting a compression stage and the heat transfer fluid of the organic Rankine cycle module, part of the heat generated during the adiabatic compression of the gas is recovered in the heat transfer fluid of the organic Rankine cycle module, the heated heat transfer fluid is then expanded to produce energy.

[0013] As a non-limiting example, the expansion device can be a turbine or a volumetric expansion device, for example, a spiral type, also known in English as a scroll expansion device. Generally, for high expansion ratios, for example, greater than or equal to 7, a turbine is preferred, and for lower expansion ratios, a volumetric expansion device is preferred. Criteria other than the expansion ratio may also be considered when choosing the expansion device.

[0014] As a non-limiting example, the expansion device can be coupled to an electric generator to recover energy in electrical form.

[0015] It is also possible to consider coupling another device to the expansion device to transform the energy into mechanical energy.

[0016] Coupling the organic Rankine cycle module with the first heat exchangers increases the flow rate of the vaporized heat transfer fluid, thus allowing for a larger turbine. As the turbine size increases, the relative clearances within the turbine decrease, improving turbine performance and thereby increasing energy recovery efficiency.

[0017] The electrical energy produced can be used to power components of the system itself or components external to the system, or even be injected into the electrical grid.

[0018] As a non-limiting example, the compressor in the isothermal compression stage can be a positive displacement compressor or a centrifugal compressor.

[0019] In some embodiments, the second heat exchanger can be a gas-air exchanger.

[0020] In some embodiments, the second heat exchanger can be a gas-water exchanger.

[0021] In some embodiments, the heat transfer fluid may have a boiling point between an inlet temperature of the cold source and an outlet temperature of the gas in the adiabatic compression stage.

[0022] In some embodiments, the heat transfer fluid can be methanol, isobutane or ethanol.

[0023] This presentation also concerns a liquefier comprising a system as defined previously.

[0024] The electrical energy produced can be used to power components of the liquefier itself, components external to the liquefier, or even fed into the electrical grid. Energy recovery can represent approximately 2% to 5% of the power required to operate the liquefier, which is significant considering the lifespan of a liquefier, which can be at least 20 years.

[0025] In some embodiments, the gas can be the gas to be liquefied.

[0026] In some embodiments, the liquefier may be a refrigerated liquefier comprising at least one cooling circuit and the gas is the gas from at least one cooling circuit of the refrigerated liquefier and / or the gas to be liquefied.

[0027] In the case of a refrigerated liquefaction cycle with multiple cooling circuits, the energy recovery system for the compression of a gas can be implemented at the compression stages of at least one cooling circuit.

[0028] It is understood that the gas in the cooling circuit of the refrigerated liquefier can be a pure gas or a mixture of gases. A pure gas is defined as a gas comprising at least 99% of a gaseous compound.

[0029] In some embodiments, the gas to be liquefied can be hydrogen, nitrogen, helium or natural gas.

[0030] This presentation also concerns a process for recovering energy from the compression of a gas, the process 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) extraction of part of the heat from the gas from the first heat exchanger in a second heat exchanger comprising a cold source; repetition of steps a) to c) N times, N being greater than or equal to 2; use of the heat extracted in the first heat exchanger to produce energy in the organic Rankine cycle module. Brief description of the drawings

[0031] Other features and advantages of the object of this presentation will emerge from the following description of embodiments, given by way of non-limiting examples, with reference to the attached figures. [ Fig. 1 ] There figure 1 is a schematic view of a liquefier. Fig. 2 ] There figure 2 is a schematic view of a gas compression energy recovery system. Fig. 3 ] There figure 3 is a schematic view of a compression stage of the system of the figure 2 . [ Fig. 4 ] There figure 4 is a flowchart representing the steps of a gas compression energy recovery process.

[0032] Across all figures, common elements are identified by identical numerical references. Detailed description

[0033] There figure 1 This 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 the cold box 12 with pressurized hydrogen. The adiabatic compressor 14 and the heat exchanger 16 together form an isothermal compressor. The cold box 12 is known in itself 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. Some of the hydrogen, in gaseous form, exiting a regeneration stage 18 is directed to a heat exchanger 20 and then back to the adiabatic compressor 14.

[0034] For simplicity, the adiabatic compressor 14 and the heat exchanger 16 have been shown on the figure 1 as unique elements. However, the adiabatic compressor 14 is an adiabatic compressor comprising several adiabatic compression stages 14A, 14B, 14C, as shown on the figure 2 . Similarly, the heat exchanger 16 comprises a plurality of heat exchangers 50, 52. In particular, the heat exchanger 16 comprises, downstream of each adiabatic compression stage 14A, 14B, 14C, two heat exchangers.

[0035] In the implementation of the figure 2 The adiabatic compressor 14 comprises three adiabatic compression stages 14A, 14B, 14C. Therefore, 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.

[0036] In the implementation of the figure 2 , downstream of each adiabatic compression stage 14A, 14B, 14C, the heat exchanger 16 comprises, a first heat exchanger 50A, 50B, 50C and a second heat exchanger 52A, 52B, 52C.

[0037] There figure 2 represents a system for recovering energy from the compression of the gas to be liquefied from the liquefier, for example hydrogen.

[0038] The energy recovery system includes the adiabatic compressor 14 and the heat exchanger 16. The energy recovery system also includes an organic Rankine cycle module 40.

[0039] In the implementation of the figure 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 by a supply line 26 and with gas recovered from the cold box 12 by a line 28.

[0040] The organic Rankine cycle module 40 includes a heat transfer fluid 54 circulating in the module 40.

[0041] In the implementation of the figure 2 The organic Rankine cycle module 40 comprises three initial heat exchangers 50A, 50B, 50C configured to heat the heat transfer fluid 54 circulating in the module 40 from a hot source external to the module 40, an expansion device 42, a condenser 46 to cool the heat transfer fluid 54 and a pump 48 to circulate the heat transfer fluid 54 in the module 40. The expansion device 42 allows the heat transfer fluid 54 heated in the heat exchangers 50A, 50B, 50C to expand under pressure and to transform the recovered energy in the form of heat into mechanical energy.

[0042] By way of non-limiting example, the expansion device 42 may be a turbine or a volumetric expansion device.

[0043] In the implementation of the figure 2 , the expansion device 42 is coupled to an energy recovery device 44.

[0044] By way of non-limiting example, the expansion device 42 can be a turbine and the energy recovery device 44 can be an electric generator to convert 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, allowing, for example, the conversion of the recovered energy into mechanical form.

[0045] In the implementation of the figure 2 , the hot source is the gas 56 exiting 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 which exits the expansion device 42.

[0046] The heat transfer fluid 54 passes successively through the first heat exchangers 50A, 50B, 50C, where, by exchanging heat with the gas 56 exiting the compression stages 14A, 14B, 14C, the heat transfer fluid 54 is brought to a boil. The heat transfer fluid 54, in vapor form, is then expanded in the expansion device 42, which is coupled to the energy recovery device 44. The vapor is then condensed in the condenser 46 by exchange with the ambient air 60. The heat transfer fluid 54 is once again in liquid form and can pass through the first heat exchangers 14A, 14B, 14C again.

[0047] The gas 56 exiting each adiabatic compression stage 14A, 14B, 14C passes into the first heat exchanger 50, 50B, 50C and exchanges some 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 exiting the first heat exchanger 50A, 50B, 50C then passes into the second heat exchanger 52A, 52B, 52C and exchanges the remaining stored heat with a cold source 58.

[0048] As a non-limiting example, the cold source 58 can be ambient air or water.

[0049] At the outlet of the second heat exchanger 52A, 52B, the 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 located downstream of the last adiabatic compression stage 14C, the gas 56 is sent into the cold box via a pipe 30.

[0050] As a non-limiting example, the heat transfer fluid 54 could be methanol. Methanol has a boiling point at approximately 1 bar of 338 K (Kelvin), and the cold source 58 could be ambient air, estimated at 300 K.

[0051] For the sake of simplicity of representation, the figure 3 represents a single adiabatic compression stage, for example the first adiabatic compression stage 14A. The elements common to the different figures are identified by the same numerical references.

[0052] As a non-limiting example, the temperature of the gas at the outlet of the adiabatic compression stage will be limited to 400 K. Also, the boiling point of the heat transfer fluid 54 is between the temperature of the inlet temperature of the cold source 58 in the second heat exchanger 52A, 52B, 52C and the temperature of the gas at the outlet of the adiabatic compression stage 14A, 14B, 14C.

[0053] Thus, in an ideal example, the hydrogen entering the first stage of adiabatic compression 14A has an ambient temperature of approximately 300 K (reference 1 of the figure 3 After adiabatic compression, the hydrogen exits at a temperature of 400 K (reference point 2 of the diagram). figure 3 ). After passing through the first heat exchanger 50A, the gas 56 is at a temperature of 338 K (reference 3 of the figure 3 ), which is the boiling point of the heat transfer fluid 56). After passing through the second heat exchanger 52A, the gas 56 is at a temperature of approximately 300 K (reference 4 of the figure 3 ). It is understood that in practice, in a non-ideal system, the temperature of gas 56 will be slightly above 338 K. Similarly, after passing through the second heat exchanger 52A, the temperature of gas 56 will be slightly above the ambient air temperature.

[0054] The compression energy recovery system can also be implemented in a refrigerated liquefaction cycle.

[0055] Refrigerated liquefaction cycles are well-established and employ cooling / refrigeration circuits for the gas to be liquefied. These circuits utilize another gas or gas mixture maintained at a low temperature by a refrigeration cycle that includes compression stages specific to this gas or gas mixture and expansion stages. This other gas or gas mixture is used as a refrigerant for the main liquefaction circuit. The nature of the gases or gas mixtures used as refrigerants in such cycles may differ from the nature of the gas to be liquefied in the main liquefaction circuit.

[0056] It is then understood that within the framework of a refrigerated liquefaction cycle, the compression energy recovery system can be implemented at the level of the compression stages specific to the cooling circuit of the refrigerated liquefaction cycle.

[0057] 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.

[0058] The process 100 for recovering energy from the compression of gas 56 will be described with reference to figures 4.

[0059] Process 100 includes: a) an adiabatic compression stage 102 of the gas 56 in an adiabatic compression stage 14A, 14A, 14C; b) an extraction stage 104 of 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; c) an extraction stage 106 of part of the heat from the gas from the first heat exchanger 50A, 50B, 50C in a second heat exchanger 52A, 52B, 52C comprising a cold source 58;

[0060] Steps a) to c) are repeated 108N times, where N is greater than or equal to 2.

[0061] In the implementation of the figure 2 , steps a) to c) are repeated three times.

[0062] The process 100 includes a step 110 of utilizing the heat extracted in the first heat exchanger 50A, 50B, 50C to produce energy in the organic Rankine cycle module 40.

[0063] Although the present description has been made with reference to a specific embodiment, it is evident 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. Therefore, the description and drawings should be considered illustrative rather than restrictive.

Claims

1. A gas compression energy recovery system (56), the system comprising an organic Rankine cycle module (40) and an adiabatic compressor (14), the organic Rankine cycle module (40) comprising a heat transfer fluid (54) and the adiabatic compressor (14) comprising N adiabatic compression stages (14A, 14B, 14C) for the gas, N being greater than or equal to 2, and, downstream of each adiabatic compression stage (14A, 14B, 14C), a first heat exchanger (50A, 50B, 50C) configured to extract heat from the gas leaving the adiabatic compression stage (14A, 14B, 14C) and to heat the heat transfer fluid (54) passing through the first heat exchanger (50A, 50B, 50C), the system being characterized by a second heat exchanger (52A, 52B, 52C), likewise located downstream of each adiabatic compression stage and configured to extract heat from the gas leaving the first heat exchanger (50A, 50B, 50C) to a cold source (58) passing through the second heat exchanger (52A, 52B, 52C).

2. The system according to claim 1, wherein the second heat exchanger (52A, 52B, 52C) is a gas-air exchanger.

3. The system according to claim 1, wherein the second heat exchanger (52A, 52B, 52C) is a gas-water exchanger.

4. The system according to any one of claims 1 to 3, wherein the heat transfer fluid (54) has a boiling temperature between a cold source inlet temperature (58) and a gas outlet temperature in the adiabatic compression stage (14A, 14B, 14C).

5. The system according to claim 4, in which the heat transfer fluid (54) is methanol, isobutane or ethanol.

6. A liquefier (10) comprising a system according to any one of claims 1 to 5.

7. The liquefier (10) 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 (10) according to claim 7 or 8, wherein the gas (56) to be liquefied is hydrogen, nitrogen, helium or natural gas.

10. A method (100) for recovering compression energy from a gas, the method comprising the following steps: a) adiabatic compression (102) of the gas in an adiabatic compression stage (14A, 14B, 14C); b) extraction (104) of part of the heat from the compressed gas in a first heat exchanger comprising a heat transfer fluid (54) of an organic Rankine cycle module (40); c) extracting (106) 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); repetition (108) of steps a) to c) N times, where N is greater than or equal to 2; use (110) of the heat extracted in the first heat exchanger (50a, 50B, 50C) to produce energy in the Rankine organic cycle module (40).