Refrigeration installation and process
The refrigeration system recycles cycle fluid using the cycle circuit's own pressurized gas to manage fluid inventory during shutdowns and startups, addressing inefficiencies and costs associated with nitrogen injection, ensuring efficient and flexible operation.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- LAIR LIQUIDE SA POUR LETUDE & LEXPLOITATION DES PROCEDES GEORGES CLAUDE
- Filing Date
- 2024-04-25
- Publication Date
- 2026-04-24
AI Technical Summary
Existing refrigeration systems face challenges in managing cycle fluid inventory during shutdowns and startups, particularly when using hydrocarbon mixtures as refrigerants, as they risk losing fluid and face issues with nitrogen availability or pollution, and existing solutions like nitrogen injection or pressure building units are costly or unsatisfactory.
The system uses the cycle fluid from the cycle circuit as a pressurized gas to inject into the buffer storage, leveraging the cycle circuit's own pressure to move the cycle fluid during shutdowns and startups, eliminating the need for external nitrogen or costly units.
This approach ensures efficient recovery and reuse of cycle fluid without nitrogen pollution, maintaining fluid inventory and operational flexibility, while reducing costs and environmental impact.
Smart Images
Figure 00000013_0000
Abstract
Description
Title of the invention: Refrigeration installation and method
[0001] The invention relates to a refrigeration installation and method, for example for the liquefaction of a fluid stream.
[0002] The invention relates more particularly to a refrigeration installation, for example for the liquefaction of a fluid stream, comprising at least one heat exchanger and a cycle fluid refrigerator in heat exchange with the heat exchanger, the refrigerator comprising a cycle circuit configured to contain a cycle fluid and subject the cycle fluid to a thermodynamic cycle in order to produce cooling power, the cycle circuit comprising a cycle fluid compression device, a cycle fluid expansion device, the installation comprising a cycle fluid buffer storage and transfer circuitry connecting the cycle circuit to the cycle fluid buffer storage, the transfer circuitry being configured to allow the purging of at least a portion of the cycle fluid from the cycle circuit into the cycle fluid buffer storage,for example during a shutdown of the installation and to allow the return of cycle fluid from the cycle fluid buffer storage (5) into the cycle circuit, for example during a start-up of the installation, the installation further comprising a pressurization line configured to allow the injection of a pressurized gas into the cycle fluid buffer storage in order to ensure the movement of the cycle fluid in the cycle circuit.
[0003] One way to cool and / or liquefy hydrogen or natural gas is to supply cooling power via a heat exchanger. The cooling power can be supplied by a closed or semi-closed refrigeration cycle of a cycle fluid (refrigerant) in a cryogenic refrigerator.
[0004] A buffer storage of cycle fluid can be provided so as not to evacuate and lose the cycle fluid at each stop and restart of the installation.
[0005] In particular, when the cycle fluid is a hydrocarbon or a mixture of hydrocarbons, for environmental and economic reasons, it is important not to lose the inventory of the cycle fluid loop during shutdowns.
[0006] The cycle fluid buffer storage can, for example, be located at the bottom of a refrigerator's cold storage compartment (or below certain equipment). This allows the cycle fluid to be recovered in liquid form by gravity.
[0007] To reinject this cycle fluid in liquid form into the cycle circuit during a restart, it is necessary to "push" this liquid with a pressurized gas injected into the buffer tank. It is known to use pressurized nitrogen gas.
[0008] This known solution, however, has disadvantages, particularly when a nitrogen source is not available and / or when the cycle fluid contains little or no nitrogen (in the latter case there is indeed a risk of polluting the composition of the cycle fluid).
[0009] This problem relates in particular to cycle fluids consisting of a mixture of refrigerants (hydrocarbons) for example mixtures which may contain nitrogen, methane, ethane, ethylene, propane, propylene, isobutane, n-butane, isopentane and / or n-pentane.
[0010] Other solutions involve using a pressure building unit or a pumping system. These solutions are either unsatisfactory or costly.
[0011] The invention thus applies to installations for cooling and / or liquefying natural gas or hydrogen but can also be applied to other refrigerants and other applications.
[0012] One object of the present invention is to overcome all or part of the disadvantages of the prior art noted above.
[0013] To this end, the installation according to the invention, which also conforms to the generic definition given in the preamble above, is essentially characterized in that the pressurization line is connected to the cycle circuit to use the cycle fluid from the cycle circuit as a pressurized gas to be injected into the cycle fluid buffer storage.
[0014] Furthermore, embodiments of the invention may include one or more of the following features: - The pressurization line includes an upstream end connected to the cycle circuit downstream of the cycle fluid compression system, - the cycle fluid is a hydrocarbon or contains a hydrocarbon, - The cycle fluid is composed of a mixture of refrigerants including: methane, ethane, ethylene, propane, propylene, isobutane, n-butane, n-pentane, isopentane and nitrogen, - The cycle circuit includes a phase separator pot, the transfer circuitry including a pipe connecting a liquid outlet from the phase separator pot to the cycle fluid buffer storage, - The transfer circuitry includes a pipe connecting an outlet of the cycle fluid buffer storage to an inlet of the phase separator pot, - the installation includes a supply circuit for a gas to be cooled or liquefied, for example hydrogen, the supply circuit being in heat exchange with at least one heat exchanger, the refrigerator being a pre-cooling device for the supply circuit at a a specific temperature, for example between 200K and 80K, or for example between 80K and 150K, - The cycle fluid buffer storage includes a self-pressurization device, for example, a heating element such as a heater.
[0015] The invention also relates to a refrigeration process using a refrigeration installation conforming to any one of the above or below characteristics, comprising a step of transferring cycle fluid from the cycle fluid buffer storage to the cycle circuit using a pressurized cycle gas stream taken from the cycle circuit.
[0016] According to other possible features: - the pressurized cycle gas flow has a temperature above -50°C and a pressure above 2 bar abs, for example between 5 and 35 bar abs, - The pressurized cycle gas flow is taken from the outlet of the compression device, - The pressurized cycle gas flow is taken from the outlet of the compression device when - the compressor is stopped in a portion of the pressurized cycle circuit, - The cycle fluid transfer step from the cycle fluid buffer storage to the cycle circuit is carried out during a system shutdown and / or during a system restart. - The fluid transfer step from the cycle fluid buffer storage to the cycle circuit is carried out after the compression device has been started. - during the cycle fluid transfer step from the cycle fluid buffer storage to the cycle circuit, the pressurized cycle gas taken from the cycle circuit is taken from a portion of the cycle circuit having a pressure higher than the pressure prevailing in the portion of the cycle circuit into which the cycle fluid from the buffer storage is injected, - the cycle fluid transfer step from the cycle fluid buffer storage to the cycle circuit is triggered in response to at least one of the following: a liquid level measurement in a piece of equipment in the cycle circuit, for example a pot, a determined pressure level in a determined portion of the cycle circuit, a cycle fluid flow measurement in the cycle circuit, a change in the load of the installation or refrigerator, i.e. a change in its cooling or production capacity, a measurement of the cycle fluid composition in the cycle circuit, - the step of transferring cycle fluid from the cycle fluid buffer storage to the cycle circuit is preceded by a cycle circuit purging step during which at least a portion of the cycle fluid is transferred to the cycle fluid buffer storage, - the purging stage is triggered in response to one of the following: a stoppage of the device for circulating the cycle fluid in the cycle circuit, for example a stoppage of the compression device, a change in the load of the installation or the refrigerator, i.e. a change in its cooling or production power.
[0017] The invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims.
[0018] Other features and advantages will become apparent from the following description, made with reference to the figures in which: Brief description of the figures
[0019] 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:
[0020] [Fig. 1] is a schematic and partial view illustrating the structure and operation of an example embodiment of the invention. Detailed description
[0021] In all figures, the same references refer to the same elements.
[0022] In this detailed description, the following embodiments are examples. Although the description refers to one or more embodiments, this 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.
[0023] The illustrated refrigeration installation 1 is, for example, designed for liquefying a fluid stream in a supply circuit 2. The installation 1 includes a heat exchanger 4 in heat exchange with the gas stream to be cooled from the supply circuit 2.
[0024] Installation 1 includes a cryogenic refrigerator 3 with cycle fluid in heat exchange with the heat exchanger(s) 4.
[0025] The refrigerator 3 includes a cycle circuit 13 configured to contain a cycle fluid (i.e. a refrigerant) and to subject the cycle fluid to a thermodynamic cycle in order to produce a cooling power at at least one end of the cycle circuit 13 via at least one expansion of the cycle fluid.
[0026] The cycle circuit 13 includes a device 23 for compressing the cycle fluid (one or more compressors in series and / or parallel), and a device 33 for expanding the cycle fluid (one or more turbines or valve(s) in series and / or parallel). The compressed cycle fluid can be cooled in the heat exchanger(s) 4 before expansion and can be reheated there after expansion and before being compressed again.
[0027] Installation 1 includes a cycle fluid buffer storage 5 and a transfer circuit 6, 7 connecting the cycle circuit 13 to the cycle fluid buffer storage 5. This transfer circuit 6, 7 is configured to allow the purging of at least a portion of the cycle fluid from the cycle circuit 13 into the cycle fluid buffer storage 5 (for example, at least the liquid portion by gravity) in the event of a shutdown or load reduction of installation 1 (for example, a shutdown or reduction in power output by the refrigerator 3).
[0028] The buffer storage 5 can, in particular, be used to temporarily store part of the cycle fluid inventory without having to release it to the air or lose it. This makes it possible to adjust the quantity of cycle fluid in the cycle circuit 13 in the event of changes in operating conditions, such as, for example, load reductions in the installation. This operational flexibility is particularly useful when the installation 1 allows for regular variations in operating conditions, such as if it produces differently during the day and night and / or according to the seasons and / or depending on the price and availability of energy.
[0029] During a shutdown of the installation and in particular of the refrigerator 3 (short or long duration), the inventory of cycle fluid is therefore not lost because it is recovered (in two-phase liquid and gas or only liquid form) in the buffer storage 5 which acts as a recovery unit.
[0030] The transfer circuitry 6, 7 is also configured to allow the return of cycle fluid from the cycle fluid buffer storage 5 into the cycle circuit 13, for example during a start-up of the installation 1.
[0031] As illustrated, the transfer circuitry 6, 7 preferably includes a set of valve(s) 9 configured to control these draining and return operations of the cycle fluid.
[0032] The installation 1 further includes a pressurization line 8 configured to allow the injection of a pressurized gas into the cycle fluid buffer storage 5 in order to ensure the movement of the cycle fluid in the cycle circuit 13 (typically the pressurized gas pushes the cycle fluid in liquid form out of the buffer storage 5).
[0033] As illustrated, the pressurization line 8 is connected to the cycle circuit 13 to use pressurized gaseous cycle fluid from the cycle circuit 13 as gas engine to inject into buffer storage 5. That is to say, cycle fluid in a gaseous state and under pressure is used to push the liquid from buffer storage 5 in order to reinject it into equipment of the cycle circuit 13 located for example above buffer storage 5.
[0034] As illustrated, the pressurization line 8 may include an upstream end connected to the cycle circuit 13 downstream of the cycle fluid compression system 23 (or to the outlet of a compression stage).
[0035] The cycle fluid in gaseous form can, for example, be taken from the outlet of a compressor 23 at a temperature above -50°C, for example at or near ambient temperature, and preferably at a pressure above 5 bar absolute. Indeed, the refrigerant compressor 23 serves to increase the pressure of the gaseous cycle fluid and circulate it in the refrigerator's refrigeration loop.
[0036] The cycle fluid may be a hydrocarbon or may comprise a hydrocarbon.
[0037] The cycle fluid may in particular be composed of a mixture of refrigerants including: methane, ethane, ethylene, propane, propylene, isobutane, n-butane, isopentane, n-pentane and may also contain nitrogen.
[0038] The invention is advantageously applicable in particular to installations whose cycle fluid is a mixture of hydrocarbons containing little or no nitrogen (for example less than 5%mol).
[0039] Thus, installation 1 may relate to the cooling or liquefaction of natural gas with a mixture of hydrocarbons and nitrogen. The invention may also relate to the pre-cooling of hydrogen with a mixture of hydrocarbons and nitrogen (the hydrogen may be further cooled to a liquefaction temperature with an additional refrigerator if necessary).
[0040] As illustrated, the cycle circuit 13 may include at least one pot 43 separating the liquid and gaseous phases of the cycle fluid.
[0041] Such separator pots 43 can be provided to inject the gaseous and liquid phases of the cycle fluid into the heat exchanger(s) 4 of the installation in the most evenly distributed manner possible. For example, the gas and liquid from the separator pot 43 are mixed in the heat exchanger 4 via a mixing system, such as a grooved bar with holes for connecting the liquid grooves to the gas grooves.
[0042] The transfer circuitry may include a conduit 6 connecting a liquid outlet from the phase separator pot 43 to the cycle fluid buffer storage 5 (for purging or at least partial draining of the cycle circuit 13).
[0043] The transfer circuitry may include a conduit 7 connecting an outlet of the cycle fluid buffer storage 5 to an inlet of the phase separator pot 43 (to re-inject the liquid from the buffer storage 5).
[0044] Such separator pots 43 can be emptied when the installation is shut down and refilled when it is restarted. Indeed, the liquid level in the separator pot 43 can be adjusted according to the pressure losses of the system in the cycle circuit 13 and can be designed to prevent a liquid level that would flood the lower part of the heat exchanger 4.
[0045] Thus, purging and / or (re)filling the cycle circuit 13 can be carried out at the level of one or more separator pots 43.
[0046] The purging (draining) and filling steps of the cycle circuit 13 can be carried out in different ways.
[0047] The compressor 23 of the cycle circuit 13 may be of the type that maintains pressure at its outlet when it is stopped (pressure higher than that of the buffer storage 5). In this case, the liquid from the buffer storage 5 can be reinjected into the cycle circuit 13 before or during the restart of the refrigerator thanks to this higher pressure available at the compressor 23 (pressure also higher than the pressure at the point of reinjection into the cycle circuit 13).
[0048] The gas used to push the liquid from the buffer storage 5 back into the cycle circuit 13 can be drawn from any point downstream of one (or more) compression stage 23 of the cycle circuit 13. This pressure should preferably be greater than the pressure at the point of reinjection into the cycle circuit 13 and increased by the hydrostatic head that must be overcome to inject the liquid at the injection point.
[0049] When the refrigerator 3 is restarted, the liquid and / or cycle gas from the buffer storage 5 can therefore be reinjected into the cycle circuit 13 by means of the injection into the buffer storage 5 of the refrigerant in gaseous form at a pressure higher than the point of reinjection.
[0050] This overpressure of the cycle circuit 13 is therefore used to push the liquid cycle fluid from the buffer storage 5 towards the cycle circuit 13 (and makes it possible to do without pumps or heating pins for example).
[0051] Alternatively or in combination, the cycle circuit 13 may include one or more two-phase reinjection vessels via a mixing system. In this case, it may be preferable to restart the compressor 23 and the refrigerant circulation in the cycle circuit 13 before beginning to reinject the liquid cycle fluid from the buffer storage 5. The reinjection is preferably carried out gradually during startup as the cycle load increases.
[0052] The shutdown sequence (with purging of cryogenic fluid to storage) and / or restart sequence (with reinjection of cycle fluid from storage into cycle circuit 13) can be manual or automatic.
[0053] In the event of automated triggering, the purging of the cycle fluid can be triggered, for example, in response to a shutdown of the compression device 23 of the cycle circuit 13 or of any other fluid circulation element in the cycle circuit 13. Alternatively or in combination, the purging can be triggered during a specific change in the operating conditions of the installation 1 (for example, a decrease in load and / or a change in the setpoint for the cycle fluid composition).
[0054] Reinjection into the cycle circuit 13 can be triggered by a specific level value in a separator pot 43 of the cycle circuit 13 (a measured value, for example) and / or a pressure value in the cycle circuit 13 (pressure, for example, measured before or after the compressor 23, preferably after the compressor). Alternatively, or in combination, reinjection into the cycle circuit 13 can be triggered based on a measured flow rate of the cycle fluid in the cycle circuit 13 and / or a measured value of the system's load increase and / or a measured value of the cycle fluid composition in the cycle circuit 13.
[0055] Although the invention makes it possible to do without it, the installation may nevertheless include in addition a heating pin in order for example to accelerate the reinjection of the liquid cycle fluid into the cycle circuit 13.
Claims
Demands
1. A refrigeration installation, for example for the liquefaction of a fluid stream, comprising at least one heat exchanger (4) and a refrigerator (3) with cycle fluid in heat exchange with the heat exchanger (4), the refrigerator (3) comprising a cycle circuit (13) configured to contain a cycle fluid and subject the cycle fluid to a thermodynamic cycle for the purpose of producing cooling power, the cycle circuit (13) comprising a cycle fluid compression device (23), a cycle fluid expansion device (33), the installation (1) comprising a cycle fluid buffer storage (5) and transfer circuitry (6, 7) connecting the cycle circuit (13) to the cycle fluid buffer storage (5), the transfer circuitry (6, 7) being configured to permit purging at least a portion of the cycle fluid from the cycle circuit (13) into the cycle fluid buffer storage (5),for example during a shutdown of the installation (1) and to allow the return of cycle fluid from the cycle fluid buffer storage (5) into the cycle circuit (13), for example during a start-up of the installation, the installation (1) further comprising a pressurization line (8) configured to allow the injection of a pressurized gas into the cycle fluid buffer storage (5) in order to ensure the movement of the cycle fluid in the cycle circuit (13), characterized in that the pressurization line (8) is connected to the cycle circuit (13) to use the cycle fluid from the cycle circuit (13) as a pressurized gas to be injected into the cycle fluid buffer storage, the installation being configured to move the liquid and / or gas of the cycle buffer storage (5) to the cycle circuit (13) by injection, into the buffer storage (5) and via the pressurization line (8),of the pressurized cycle fluid of the cycle circuit (13).
2. Installation according to claim 1, characterized in that the pressurization line (8) comprises an upstream end connected to the cycle circuit (13) downstream of the cycle fluid compression system (23).
3. Installation according to claim 1 or 2, characterized in that the cycle fluid is a hydrocarbon or comprises a hydrocarbon.
4. Installation according to claim 1 or 2, characterized in that the cycle fluid is composed of a mixture of refrigerants from among: methane, ethane, ethylene, propane, propylene, isobutane, n-butane, n-pentane, isopentane and nitrogen.
5. Installation according to any one of the preceding claims, characterized in that the cycle circuit (13) comprises a phase separator pot (43), the transfer circuitry (6, 7) comprising a conduit (6) connecting a liquid outlet of the phase separator pot (43) to the cycle fluid buffer storage (5).
6. Installation according to claim 5, characterized in that the transfer circuitry (6, 7) comprises a conduit (7) connecting an outlet of the cycle fluid buffer storage (5) to an inlet of the phase separator pot (43).
7. Installation according to any one of the preceding claims comprising a supply circuit (2) for a gas to be cooled or liquefied, for example hydrogen, the supply circuit (2) being in heat exchange with at least one heat exchanger (4), characterized in that the refrigerator (3) is a pre-cooling device for the supply circuit (2) to a determined temperature, for example between 200K and 80K, for example between 80K and 150K.
8. A refrigeration method using a refrigeration installation (1) according to any one of the preceding claims, comprising a cycle fluid transfer step from the cycle fluid buffer storage (5) to the cycle circuit (13) using a pressurized cycle gas flow taken from the cycle circuit (13), the displacement of the liquid and / or cycle gas from the buffer storage (5) to the cycle circuit (13) being achieved by injecting, into the buffer storage (5) and via the pressurization line (8), the pressurized cycle fluid from the cycle circuit (13).
9. A method according to claim 8, characterized in that the pressurized cycle gas flow has a temperature greater than -50°C and a pressure greater than 2 bar abs, for example between 5 and 35 bar abs.
10. Method according to claim 8 or 9, characterized in that the pressurized cycle gas flow is taken from the outlet of the compression device (23).
11. A method according to any one of claims 8 to 10, characterized in that the pressurized cycle gas flow is taken from the outlet of the compression device (23) when the compressor is stopped in a portion of the pressurized cycle circuit (13).
12. A method according to any one of claims 8 to 11, characterized in that the cycle fluid transfer step from the cycle fluid buffer storage (5) to the cycle circuit (13) is carried out during a shutdown of the installation and / or during a restart of the installation.
13. Method according to claim 12, characterized in that the step of transferring cycle fluid from the cycle fluid buffer storage (5) to the cycle circuit (13) is carried out after starting the compression device (23).
14. A method according to claim 13, characterized in that during the step of transferring cycle fluid from the cycle fluid buffer storage (5) to the cycle circuit (13), the pressurized cycle gas taken from the cycle circuit (13) is taken from a portion of the cycle circuit (13) having a pressure greater than the pressure prevailing in the portion of the cycle circuit into which the cycle fluid from the buffer storage (5) is injected.
15. A method according to any one of claims 8 to 14, characterized in that the cycle fluid transfer step from the cycle fluid buffer storage (5) to the cycle circuit (13) is triggered in response to at least one of: a liquid level measurement in a piece of equipment in the cycle circuit, for example a pot, a determined pressure level in a determined portion of the cycle circuit (13), a cycle fluid flow measurement in the cycle circuit (13), a change in the load of the installation or refrigerator, i.e. a change in its cooling or production capacity, a measurement of the composition of the cycle fluid in the cycle circuit (13).
16. A method according to any one of claims 8 to 15, characterized in that the cycle fluid transfer step from the cycle fluid buffer storage (5) to the cycle circuit (13) is preceded by a cycle circuit (13) purge step during which at least a portion of the cycle fluid is transferred into the cycle fluid buffer storage.
17. Method according to claim 16, characterized in that the purging step is triggered in response to one at a time among: a stoppage of the device for circulating the cycle fluid in the cycle circuit (13), for example a stoppage of the compression device (23), a change in the load of the installation or of the refrigerator, i.e. a change in its cooling or production capacity.