EP3390938B1 - Hybrid method for liquefying a fuel gas and facility for implementing same - Google Patents

Hybrid method for liquefying a fuel gas and facility for implementing same Download PDF

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Publication number
EP3390938B1
EP3390938B1 EP16834023.0A EP16834023A EP3390938B1 EP 3390938 B1 EP3390938 B1 EP 3390938B1 EP 16834023 A EP16834023 A EP 16834023A EP 3390938 B1 EP3390938 B1 EP 3390938B1
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Prior art keywords
heat exchange
flow
fuel gas
exchange region
cooling
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German (de)
French (fr)
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EP3390938C0 (en
EP3390938A1 (en
Inventor
Laurent Benoit
Denis FAURE-BRAC
Anna TORRES-MANSILLA
Emeline DROUET
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Engie SA
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Engie SA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0221—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using the cold stored in an external cryogenic component in an open refrigeration loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0262—Details of the cold heat exchange system
    • F25J1/0264—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/42—Nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/42—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/02—Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
    • F25J2240/12—Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream the fluid being nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/14—External refrigeration with work-producing gas expansion loop

Definitions

  • the present invention relates generally to a process and an installation for liquefying a combustible gas with a high methane content.
  • the overall problem that the present invention seeks to solve is to liquefy gas with a high methane content (at least 80 molar%), typically natural gas from the gas transport or distribution network, biomethane or even gas evaporations.
  • liquefied natural gas usually referred to by the acronym LNG.
  • Such an open cycle solution is known from the document FR1335277A which discloses a process for liquefying a combustible gas in which said combustible gas circulates in a circuit primary while a refrigerant consisting of nitrogen in the liquid or at least partially vaporized state circulates in an open secondary circuit from a liquid nitrogen tank to be released to the atmosphere.
  • the aim of the present invention therefore aims to overcome all or part of the disadvantages of the prior art, by setting up a hybrid process between on the one hand a process according to the Brayton cycle (or so-called expansion) and on the other hand a classic open cycle process. More precisely, instead of using a classic open cycle which uses the sole refrigerating power of the vaporization of the cold medium (typically liquid nitrogen) such as the process described in the French patent FR 1 335 277 , the method according to the invention proposes to first compress the cold medium then, initially, to use its vaporization as a cooling power, and finally in a second step, to relax it to generate additional cold.
  • a classic open cycle which uses the sole refrigerating power of the vaporization of the cold medium (typically liquid nitrogen) such as the process described in the French patent FR 1 335 277
  • the method according to the invention proposes to first compress the cold medium then, initially, to use its vaporization as a cooling power, and finally in a second step, to relax it to generate
  • the subject of the present invention is a process for liquefaction of a combustible gas according to claim 1, and an installation for liquefaction of a combustible gas for implementing the process according to the invention, according to claim 6.
  • nitrogen is meant, within the meaning of the present invention, a fluid comprising at least 97 mole% of nitrogen.
  • heat exchanger is meant, for the purposes of the present invention, a subassembly or part of a heat exchange zone integrating the entire heat exchange line of the phase considered of the process of the invention.
  • heat exchange zone is meant, within the meaning of the present invention, a set of heat exchangers in which all the heat exchanges of a given phase of the process of the invention take place, namely, the pre -cooling, liquefaction or subcooling.
  • heat exchange line is meant, within the meaning of the present invention, the succession of fluids exchanging heat with each other in the phase considered.
  • the liquid nitrogen coming from the liquid nitrogen tank can be pumped at a pressure of at least 1.2 MPa, depending on the nature of the combustible gas to be liquefied.
  • the flow of nitrogen at least partially vaporized at the outlet of the heat exchanger of the cooling heat exchange zone can be expanded, in the turbine (preferably an expansion turbine), at an equal pressure or less than 0.2 MPa (i.e. approximately 2 bars).
  • the gas to be liquefied may contain methane in a molar proportion of at least 80%.
  • the process according to the invention makes it possible to keep the advantages of a conventional open cycle by limiting its main disadvantage, namely its consumption of liquid nitrogen, and consequently the cost associated with this consumption.
  • sudden evaporation is meant, within the meaning of the present invention, a partial vaporization in the liquid line (during expansion), which occurs when the LNG under pressure (to facilitate its liquefaction) is expanded either using a valve.
  • Joule-Thomson either a liquid or even two-phase turbine.
  • CAEX costs are moderate: in the absence of cold to be created by intermediate cycles (as in the case of closed cycles), the number of rotating machines at implemented to operate the process according to the invention (compressor, turbine) is drastically reduced compared to conventional closed cycle processes, as well as the size of the exchange line.
  • OPEX operating costs
  • the OPX costs are moderate because the implementation of the method according to the invention requires only a small number of rotating machines such as compressors or turbines.
  • the associated maintenance costs are therefore “mechanically” reduced: the consumption of liquid nitrogen by the process according to the invention is reduced by approximately 10% compared to a conventional open cycle, hence a similar reduction in the associated OPEX. .
  • the installation according to the invention has the advantage of being very compact thanks to the reduction in the inventory of cooling fluids (that is to say the quantity and mass flow of refrigerant) and the size and the number of rotating machines; this compactness therefore allows its mobility (on truck, barge, boat, train, etc.).
  • FIG. 3 is a device according to the prior art allowing the implementation of a process for liquefying a combustible gas known from the prior art operating with an open liquid nitrogen cycle. This process serves as a point of comparison for the numerical simulations presented below in the examples.
  • FIG. 1 further shows that a turbine 22 (preferably expansion) is arranged, in the secondary circuit 34, connecting the outlet of the heat exchanger 20 of the cooling heat exchange zone 200 and the inlet of the exchanger thermal annex 31 of the heat exchange zone 300 of liquefaction, this turbine 33 makes it possible to relax and cool the vaporized nitrogen leaving the heat exchanger 20 of the heat exchange zone 200 of cooling, before its injection into the heat exchanger annex 31 of the liquefaction heat exchange zone 300.
  • a turbine 22 preferably expansion
  • FIG 2 shows the implementation of the method according to the invention on the installation according to the invention represented on the figure 1 .
  • the different phases of the process of the invention have been indicated at the level of the heat exchangers where they are carried out.
  • FIG. 2 shows in particular that the process according to the invention consists of liquefying a combustible gas comprising mainly methane, by circulating it in a primary circuit I open from a source of combustible gas to a tank for liquefied gas 2, while a mixture refrigerant consisting of liquid or at least partially vaporized nitrogen circulates in a secondary circuit 34 open from a nitrogen tank 3 to be released to the atmosphere.
  • a combustible gas comprising mainly methane
  • the initially completely liquid nitrogen, coming from the tank 3, is injected into the heat exchanger 40 of the subcooling heat exchange zone 400, in which it circulates countercurrent to the flow of combustible gas. Then, in subcooling zone 400, the nitrogen flow partially vaporizes. At the exit of zone 400, the partially vaporized nitrogen is injected into the exchanger 30 of the liquefaction heat exchange zone 300 to liquefy part of the fuel gas flow, between T 3 and T 2 .
  • This step makes it possible to best adjust the flow rate of combustible gas to be liquefied to optimize the process according to the invention, and facilitate its technical implementation because then at T 2 , the nitrogen is completely vaporized so that the exchangers involved ( exchangers 20 and 21) have purely monophasic inputs-outputs.
  • the completely vaporized nitrogen is, at the temperature T 2 , injected into the heat exchanger 20 of the cooling heat exchange zone 200, in which it circulates against the current of a part of the combustible gas which there is cooled between the pre-cooling temperature T1 up to the dew temperature T 2 .
  • the nitrogen At the outlet of the heat exchanger 20, the nitrogen, at a temperature close to T 1 , is completely vaporized, but still at high pressure.
  • the vaporized nitrogen is then expanded in the expansion turbine 22 (typically from a pressure of 1.2 MPa to less than 0.2 MPa, the precise values depending on the fuel gas to be cooled).
  • This makes it possible to obtain a flow of nitrogen that is certainly vaporized, but at a cryogenic temperature typically of the order of -160°C (here again the precise values depend on the case studied).
  • the nitrogen obtained is at a temperature well below T 3 (which is the bubble temperature of the gas to be liquefied).
  • T 3 which is the bubble temperature of the gas to be liquefied
  • the combustible gas (of initial flow rate m) is cooled from the ambient temperature T 0 to a pre-cooling temperature T 1 greater than the dew point temperature T 2 of the combustible gas, this pre-cooling phase being carried out by heat exchange with a flow of vaporized and low-pressure nitrogen circulating countercurrent to the flow of combustible gas in the heat exchanger 10 of the pre-cooling heat exchange zone 100.
  • the liquefied combustible gas, leaving the liquefaction heat exchange zone 300, is sub-cooled from the temperature T 3 to a sub-cooling temperature T 4 , this sub-cooling phase cooling 4000 being carried out in the subcooling heat exchange zone 400 comprising at least one heat exchanger 40 by heat exchange with the flow of initially completely liquid nitrogen circulating counter-current to the flow of combustible gas.

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  • Physics & Mathematics (AREA)
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Description

La présente invention se rapporte de manière générale à un procédé et une installation de liquéfaction d'un gaz combustible à forte teneur en méthane.The present invention relates generally to a process and an installation for liquefying a combustible gas with a high methane content.

Le problème global que cherche à résoudre la présente invention est de liquéfier du gaz à forte teneur en méthane (au moins 80% molaire), typiquement du gaz naturel issu du réseau gazier de transport ou de distribution, du biométhane ou encore des évaporations de gaz naturel liquéfié (usuellement désigné par l'acronyme GNL) .The overall problem that the present invention seeks to solve is to liquefy gas with a high methane content (at least 80 molar%), typically natural gas from the gas transport or distribution network, biomethane or even gas evaporations. liquefied natural gas (usually referred to by the acronym LNG).

Pour cela, on cherche à réduire les coûts de mise en œuvre du processus de liquéfaction du gaz combustible en particulier pour des installations de petite taille (notamment inférieures à 10 tonnes de GNL produites par heure), tout en conservant des coûts opérationnels modérés (notamment en termes de consommables).To do this, we seek to reduce the costs of implementing the fuel gas liquefaction process, particularly for small installations (notably less than 10 tonnes of LNG produced per hour), while maintaining moderate operational costs (notably in terms of consumables).

Pour résoudre un tel problème, il est connu de l'homme de l'art différentes solutions, que l'on peut regrouper en trois catégories :

  1. 1. les procédés à cycle fermé avec changement de phase du réfrigérant, ce dernier pouvant être un corps pur ou un mélange réfrigérant afin d'améliorer l'efficacité. On les utilise principalement pour une production de GNL à grande échelle (dite "baseload"), soit plusieurs dizaines à plusieurs centaines de tonnes/heure (t/h) de GNL produit, en station fixe. il s'agit notamment des procédés industriels suivants : le procédé TEALARC de Technip et Air Liquide, les procédés de l'APCI et notamment le C3-MR et l'APX, le procédé à cascade optimisée (en anglais « optimized cascade ») de Conoco Phillips, le procédé MFC de Statoil-Linde, les procédés de Linde, le procédé PRICO de Black and Veatch, et le procédé OSMR de LNG limited. Toutefois, ce type de procédés est désormais aussi proposé à plus petite échelle (c'est-à-dire des procédés produisant seulement quelques dizaines voire quelques tonnes/heure (t/h) de de GNL produit. C'est notamment le cas pour les procédés industriels suivants : le procédé BOC du groupe industriel Linde) pour la liquéfaction du biogaz, les procédés SCMR et PCMR de Kryopak, le procédé MRC de GTI, le procédé NewMR de Waertsila, le procédé SGTS pour la liquéfaction du biogaz, le procédé d'Erié pour la liquéfaction du biogaz, et enfin le procédé MiniLNG de SINTEF pour la liquéfaction des évaporations de GNL ;
  2. 2. les procédés à cycle fermé de Brayton ou à détente, c'est à dire sans changement de phase mais avec détente du réfrigérant pour créer le froid. En raison de leur simplicité technique, ces procédés sont utilisés :
    • soit pour des productions de GNL de petite capacité. C'est le cas notamment pour le procédé d'Air Liquide pour la liquéfaction du biogaz, le procédé EXP de Kryopak, le procédé de Cryostar proposé à la fois pour la liquéfaction du biogaz et des évaporations de GNL,
    • soit pour des situations techniquement difficiles où simplicité et robustesse l'emportent sur la performance énergétique (production « offshore » notamment, ou pour la reliquéfaction des évaporations de GNL). C'est le cas notamment pour le procédé de Mustang, le procédé APX d'APCI, le procédé à plusieurs étapes de détente de SAIPEM et le procédé ZR-LNG de Gasconsult ;
  3. 3. les procédés à cycle ouvert, dans lequel le froid n'est pas créé mais apporté par un médium extérieur, typiquement de l'azote liquide, et où la liquéfaction du gaz naturel résulte d'un simple échange de chaleur (direct) avec le médium de froid qui se vaporise. Ce type de procédé est généralement utilisé en laboratoire ou pour des applications très ponctuelles ne nécessitant que très peu de performance et beaucoup de simplicité. C'est le cas notamment pour le procédé de Chart utilisant de l'azote liquide comme réfrigérant, actuellement utilisé en Asie du Sud-Est (notamment en Indonésie), et pour le procédé direct d'Hamworthy-Wärtsilä actuellement mis en oeuvre dans la petite installation de liquéfaction de Sköldvik en Finlande produisant 55 tonnes par jour de GNL.
To resolve such a problem, different solutions are known to those skilled in the art, which can be grouped into three categories:
  1. 1. closed cycle processes with phase change of the refrigerant, the latter being able to be a pure substance or a refrigerant mixture in order to improve efficiency. They are mainly used for large-scale LNG production (known as "baseload "), i.e. several tens to several hundred tonnes/hour (t/h) of LNG produced, at a fixed station. This concerns in particular the processes industrial processes: the TEALARC process from Technip and Air Liquide, the APCI processes and in particular C3-MR and APX, the optimized cascade process from Conoco Phillips, the MFC process from Statoil-Linde, Linde processes, Black and Veatch's PRICO process, and LNG limited's OSMR process. However, this type of process is now also offered on a smaller scale (i.e. processes producing only a few dozen or even a few tonnes/hour (t/h) of LNG produced. This is particularly the case for the following industrial processes: the BOC process of the Linde industrial group) for the liquefaction of biogas, the SCMR and PCMR processes of Kryopak, the MRC process of GTI, the NewMR process of Waertsila, the SGTS process for the liquefaction of biogas, the process of Erie for the liquefaction of biogas, and finally the MiniLNG process of SINTEF for the liquefaction of LNG evaporations;
  2. 2. closed Brayton cycle or expansion processes, i.e. without phase change but with expansion of the refrigerant to create cold. Due to their technical simplicity, these processes are used:
    • or for small capacity LNG production. This is particularly the case for the Air Liquide process for the liquefaction of biogas, the EXP process from Kryopak, the Cryostar process proposed both for the liquefaction of biogas and LNG evaporations,
    • either for technically difficult situations where simplicity and robustness prevail over energy performance (“ offshore ” production in particular, or for the reliquefaction of LNG evaporations). This is particularly the case for the Mustang process, the APX process from APCI, the multi-stage expansion process from SAIPEM and the ZR-LNG process from Gasconsult;
  3. 3. open cycle processes, in which the cold is not created but provided by an external medium, typically liquid nitrogen, and where the liquefaction of natural gas results from a simple (direct) heat exchange with the cold medium that vaporizes. This type of process is generally used in the laboratory or for very specific applications requiring very little performance and a lot of simplicity. This is particularly the case for the Chart process using liquid nitrogen as a refrigerant, currently used in South-East Asia (notably in Indonesia), and for the direct Hamworthy-Wärtsilä process currently used in the small liquefaction plant in Sköldvik in Finland producing 55 tonnes per day of LNG.

Une telle solution à cycle ouvert est connue du document FR1335277A qui divulgue un procédé de liquéfaction d'un gaz combustible dans lequel ledit gaz combustible circule dans un circuit primaire tandis qu'un réfrigérant constitué d'azote à l'état liquide ou au moins partiellement vaporisé circule dans un circuit secondaire ouvert depuis un réservoir d'azote liquide pour être relâché vers l'atmosphère.Such an open cycle solution is known from the document FR1335277A which discloses a process for liquefying a combustible gas in which said combustible gas circulates in a circuit primary while a refrigerant consisting of nitrogen in the liquid or at least partially vaporized state circulates in an open secondary circuit from a liquid nitrogen tank to be released to the atmosphere.

Toutefois, ces dispositifs connus de l'art antérieur présentent de nombreux inconvénients.However, these devices known from the prior art have numerous drawbacks.

Ainsi, les procédés à cycle fermé complet avec changement de phase du réfrigérant présentent les inconvénients suivants :

  • des coûts de développement ou de fourniture des pièces non-consommables (coûts généralement désignés par l'acronyme CAPEX) élevés, en raison du nombre élevé d'équipements et de la complexité que nécessitent de tels procédés,
  • il en est de même pour les coûts d'exploitation (généralement désignés par l'acronyme OPEX),
  • la complexité de tels procédés et les risques encourus (le réfrigérant est généralement inflammable),
  • la taille et l'encombrement importants des équipements pour la mise en œuvre de tels procédés, qui les rendent difficilement compacts : en effet, en plus du fluide à refroidir (typiquement du gaz naturel), le procédé doit intégrer une grande quantité de fluides de refroidissement dans des cycles intermédiaires pour obtenir le refroidissement souhaité (au final, le débit massique total des mélanges réfrigérants utilisé étant d'environ 8 fois celui du fluide à refroidir), et
  • les émissions de CO2 liés à la consommation de gaz lorsque celui-ci est utilisé pour l'appoint en énergie du procédé.
Thus, complete closed cycle processes with phase change of the refrigerant present the following disadvantages:
  • high development or supply costs for non-consumable parts (costs generally referred to by the acronym CAPEX), due to the high number of equipment and the complexity required by such processes,
  • the same goes for operating costs (generally referred to by the acronym OPEX),
  • the complexity of such processes and the risks involved (the refrigerant is generally flammable),
  • the significant size and bulk of the equipment for the implementation of such processes, which make them difficult to compact: in fact, in addition to the fluid to be cooled (typically natural gas), the process must integrate a large quantity of cooling fluids cooling in intermediate cycles to obtain the desired cooling (ultimately, the total mass flow of the refrigerant mixtures used being approximately 8 times that of the fluid to be cooled), and
  • CO 2 emissions linked to gas consumption when it is used to supplement the process with energy.

Par ailleurs, les procédés à cycle fermé complet de Brayton ou à détente présentent également des inconvénients, en partie identique avec ceux mentionnés ci-dessus pour les procédés avec changement de phase :

  • des coûts élevés de développement ou de fourniture des pièces non-consommables (coûts CAPEX) et des coûts élevés d'exploitation (coûts OPEX),
  • une performance énergétique faible, en d'autres termes une consommation d'énergie importante,
  • la taille et l'encombrement importants des équipements pour la mise en œuvre de tels procédés, qui les rendent difficilement compacts : ici également, en plus du fluide à refroidir (typiquement du gaz naturel), le procédé doit intégrer une grande quantité de fluides de refroidissement dans des cycles intermédiaires pour obtenir le refroidissement souhaité. Compte-tenu de l'absence d'évaporation, la quantité de réfrigérant est encore plus grande que dans le cas précédent (relatif aux procédés à cycle fermé complet avec changement de phase du réfrigérant), le débit massique de réfrigérant équivaut cette fois à plusieurs dizaines de fois le débit massique de fluide à refroidir.
  • les émissions de CO2 liées à la consommation de gaz lorsque celui-ci est utilisé pour l'appoint en énergie du procédé.
Furthermore, Brayton's complete closed cycle or expansion processes also have disadvantages, partly identical to those mentioned above for processes with phase change:
  • high costs of developing or supplying non-consumable parts (costs CAPEX) and high operating costs (OPEX costs),
  • poor energy performance, in other words significant energy consumption,
  • the significant size and bulk of the equipment for the implementation of such processes, which make them difficult to compact: here too, in addition to the fluid to be cooled (typically natural gas), the process must integrate a large quantity of cooling fluids cooling in intermediate cycles to achieve the desired cooling. Taking into account the absence of evaporation, the quantity of refrigerant is even greater than in the previous case (relating to complete closed cycle processes with phase change of the refrigerant), the mass flow rate of refrigerant this time is equivalent to several tens of times the mass flow of fluid to be cooled.
  • CO 2 emissions linked to gas consumption when it is used to supplement the process with energy.

Enfin, les procédés à cycle ouvert présentent des inconvénients liés principalement à leur rusticité et au cout d'approvisionnement du réfrigérant (qui est consommé du fait du cycle ouvert).Finally, open cycle processes have disadvantages linked mainly to their rusticity and the cost of supplying the refrigerant (which is consumed due to the open cycle).

Le but de la présente invention vise donc à pallier tout ou partie des inconvénients de l'art antérieur, par la mise en place d'un procédé hybride entre d'une part un procédé selon le cycle de Brayton (ou dit à détente) et d'autre part un procédé à cycle ouvert classique. Plus précisément, au lieu d'utiliser un cycle ouvert classique qui utilise le seul pouvoir frigorifique de la vaporisation du médium de froid (typiquement l'azote liquide) tel que le procédé décrit dans le brevet français FR 1 335 277 , le procédé selon l'invention propose d'abord de comprimer le médium de froid puis, dans un premier temps, d'utiliser sa vaporisation comme pouvoir refroidissant, et enfin dans un deuxième temps, de le détendre pour générer du froid supplémentaire.The aim of the present invention therefore aims to overcome all or part of the disadvantages of the prior art, by setting up a hybrid process between on the one hand a process according to the Brayton cycle (or so-called expansion) and on the other hand a classic open cycle process. More precisely, instead of using a classic open cycle which uses the sole refrigerating power of the vaporization of the cold medium (typically liquid nitrogen) such as the process described in the French patent FR 1 335 277 , the method according to the invention proposes to first compress the cold medium then, initially, to use its vaporization as a cooling power, and finally in a second step, to relax it to generate additional cold.

Plus particulièrement, la présente invention a pour objet un procédé de liquéfaction d'un gaz combustible selon la revendication 1, et une installation de liquéfaction d'un gaz combustible pour la mise en oeuvre du procédé selon l'invention, selon la revendication 6.More particularly, the subject of the present invention is a process for liquefaction of a combustible gas according to claim 1, and an installation for liquefaction of a combustible gas for implementing the process according to the invention, according to claim 6.

Par azote, on entend, au sens de la présente invention, un fluide comportant au moins 97% molaire d'azote.By nitrogen is meant, within the meaning of the present invention, a fluid comprising at least 97 mole% of nitrogen.

Par échangeur thermique, on entend, au sens de la présente invention un sous-ensemble ou une partie d'une zone d'échange thermique intégrant la totalité de la ligne d'échange thermique de la phase considérée du procédé de l'invention.By heat exchanger is meant, for the purposes of the present invention, a subassembly or part of a heat exchange zone integrating the entire heat exchange line of the phase considered of the process of the invention.

Par zone d'échange thermique, on entend, au sens de la présente invention, un ensemble d'échangeurs thermiques dans laquelle se déroule l'ensemble des échanges thermiques d'une phase donnée du procédé de l'invention, à savoir, le pré-refroidissement, la liquéfaction ou le sous-refroidissement.By heat exchange zone is meant, within the meaning of the present invention, a set of heat exchangers in which all the heat exchanges of a given phase of the process of the invention take place, namely, the pre -cooling, liquefaction or subcooling.

Par ligne d'échange thermique, on entend, au sens de la présente invention, la succession de fluides échangeant de la chaleur entre eux dans la phase considérée.By heat exchange line is meant, within the meaning of the present invention, the succession of fluids exchanging heat with each other in the phase considered.

Le principe global du procédé selon l'invention est donc de tirer parti à la fois du refroidissement par évaporation de l'azote liquide et de sa détente. Par conséquent, cela signifie, d'un point de vue conceptuel, que le réfrigérant (c'est-à-dire l'azote liquide ou vaporisé va être utilisé deux fois sur une partie de la zone d'échange thermique (c'est-à-dire sur une même gamme de température). Mais l'azote ne sera pas dans le même état lors de ces deux passages :

  • une fois, il sera partiellement liquide et à haute pression,
  • l'autre fois, il sera vaporisé et à basse pression.
The overall principle of the process according to the invention is therefore to take advantage of both cooling by evaporation of liquid nitrogen and its expansion. Therefore, this means, conceptually, that the refrigerant (i.e. liquid or vaporized nitrogen) is going to be used twice on part of the heat exchange zone (i.e. i.e. over the same temperature range). But the nitrogen will not be in the same state during these two passages:
  • once it will be partially liquid and high pressure,
  • the other time it will be vaporized and at low pressure.

En outre, à chaque fois, seule une partie du gaz naturel à traiter sera refroidi.In addition, each time, only part of the natural gas to be treated will be cooled.

De manière avantageuse, les deux phases de redistribution du gaz combustible pourront être réalisées dans les conditions suivantes :

  • le débit m1 du sous-flux de gaz combustible injecté dans l'échangeur thermique de la zone d'échange thermique de refroidissement représentant au moins 80%, et de préférence au moins 85% du débit initial m de gaz ; et
  • le débit m3 du sous-flux de gaz combustible injecté dans l'échangeur thermique de la zone d'échange thermique de liquéfaction représentant au moins 60% du débit initial m de gaz combustible, et au plus la valeur de m1.
Advantageously, the two phases of redistribution of the fuel gas can be carried out under the following conditions:
  • the flow rate m 1 of the sub-flow of combustible gas injected into the heat exchanger of the cooling heat exchange zone representing at least 80%, and preferably at least 85% of the initial flow rate m of gas; And
  • the flow rate m 3 of the sub-flow of combustible gas injected into the heat exchanger of the liquefaction heat exchange zone representing at least 60% of the initial flow rate m of combustible gas, and at most the value of m 1 .

De manière avantageuse, l'azote liquide provenant du réservoir d'azote liquide pourra être pompé à une pression d'au moins 1,2 MPa, en fonction de la nature du gaz combustible à liquéfier.Advantageously, the liquid nitrogen coming from the liquid nitrogen tank can be pumped at a pressure of at least 1.2 MPa, depending on the nature of the combustible gas to be liquefied.

De manière avantageuse, le flux d'azote au moins partiellement vaporisé à la sortie de l'échangeur thermique de la zone d'échange thermique de refroidissement peut être détendu, dans la turbine (de préférence une turbine à détente), à une pression égale ou inférieure à 0,2 MPa (c'est à dire approximativement à 2 bars).Advantageously, the flow of nitrogen at least partially vaporized at the outlet of the heat exchanger of the cooling heat exchange zone can be expanded, in the turbine (preferably an expansion turbine), at an equal pressure or less than 0.2 MPa (i.e. approximately 2 bars).

De manière avantageuse, dans le cadre de la présente invention le gaz à liquéfier pourra contenir du méthane en une proportion molaire d'au moins 80%.Advantageously, in the context of the present invention the gas to be liquefied may contain methane in a molar proportion of at least 80%.

Le procédé selon l'invention permet de garder les avantages d'un cycle ouvert classique en limitant son principal inconvénient, à savoir sa consommation de d'azote liquide, et par conséquent le coût associé à cette consommation.The process according to the invention makes it possible to keep the advantages of a conventional open cycle by limiting its main disadvantage, namely its consumption of liquid nitrogen, and consequently the cost associated with this consumption.

Enfin, on observe, dans le procédé selon l'invention, une absence totale de phénomènes de type « évaporation brusque » (usuellement désignés en anglais par l'expression « flash gas ») lors de la détente finale du GNL car le GNL est sous-refroidi suffisamment pour qu'il ne génère pas de vapeur (« flash ») lors de cette détente finale. Cela permet de faire ainsi l'économie d'une recompression du gaz.Finally, we observe, in the process according to the invention, a total absence of phenomena of the “sudden evaporation” type (usually designated in English by the expression “ flash gas ”) during the final expansion of the LNG because the LNG is subcooled sufficiently so that it does not generate steam (“flash”) during this final expansion. This makes it possible to save on gas recompression.

Par évaporation brusque, on entend, au sens de la présente invention une vaporisation partielle dans la ligne liquide (durant la détente), qui survient lorsque le GNL sous pression (pour faciliter sa liquéfaction) est détendu soit à l'aide d'une vanne Joule-Thomson, soit une turbine liquide ou même diphasique.By sudden evaporation is meant, within the meaning of the present invention, a partial vaporization in the liquid line (during expansion), which occurs when the LNG under pressure (to facilitate its liquefaction) is expanded either using a valve. Joule-Thomson, either a liquid or even two-phase turbine.

Par ailleurs, les coûts de développement ou de fourniture des pièces non-consommables (coûts CAPEX) sont modérés : en l'absence de froid à créer par des cycles intermédiaires (comme dans le cas de cycles fermés), le nombre de machines tournantes à mettre en œuvre pour faire fonctionner le procédé selon l'invention (compresseur, turbine) est drastiquement réduit par rapport aux procédés à cycle fermé classiques, ainsi que la taille de la ligne d'échange.Furthermore, the costs of developing or supplying non-consumable parts (CAPEX costs) are moderate: in the absence of cold to be created by intermediate cycles (as in the case of closed cycles), the number of rotating machines at implemented to operate the process according to the invention (compressor, turbine) is drastically reduced compared to conventional closed cycle processes, as well as the size of the exchange line.

Il en est de même pour les coûts d'exploitation (généralement désignés par l'acronyme OPEX). Les coûts OPX sont modérés car la mise en oeuvre du procédé selon l'invention ne nécessite qu'un nombre peu élevé de machines tournantes de type compresseurs ou turbines. Les coûts de maintenance associés sont donc « mécaniquement » réduits : la consommation d'azote liquide par le procédé selon l'invention est réduite de 10% environ par rapport à un cycle ouvert classique, d'où une réduction similaire de l'OPEX associé.The same goes for operating costs (generally referred to by the acronym OPEX). The OPX costs are moderate because the implementation of the method according to the invention requires only a small number of rotating machines such as compressors or turbines. The associated maintenance costs are therefore “mechanically” reduced: the consumption of liquid nitrogen by the process according to the invention is reduced by approximately 10% compared to a conventional open cycle, hence a similar reduction in the associated OPEX. .

L'installation selon l'invention présente l'avantage d'être très compacte grâce à la réduction de l'inventaire des fluides de refroidissement (c'est-à-dire la quantité et le débit massique de fluide réfrigérant) et de la taille et du nombre de machines tournantes ; cette compacité permettant donc sa mobilité (sur camion, barge, bateau, train, etc.).The installation according to the invention has the advantage of being very compact thanks to the reduction in the inventory of cooling fluids (that is to say the quantity and mass flow of refrigerant) and the size and the number of rotating machines; this compactness therefore allows its mobility (on truck, barge, boat, train, etc.).

D'autres avantages et particularités de la présente invention résulteront de la description qui va suivre, donnée à titre d'exemple non limitatif et faite en référence aux figures annexées :

  • la figure 1 représente un schéma de principe général d'un mode de réalisation préférentiel de l'installation selon l'invention, sur lequel on a représenté l'agencement des différents échangeurs thermiques et des zones de distribution du gaz combustibles ;
  • la figure 2 représente le même schéma de principe général que celui représenté sur la figure 1, montrant en particulier les différentes phases du procédé de l'invention,
  • la figure 3 représente un schéma de principe général d'une installation selon l'art antérieur comportant un cycle ouvert à l'azote liquide.
Other advantages and particularities of the present invention will result from the description which follows, given by way of non-limiting example and made with reference to the appended figures:
  • there figure 1 represents a general principle diagram of a preferred embodiment of the installation according to the invention, on which the arrangement of the different heat exchangers and the fuel gas distribution zones is shown;
  • there figure 2 represents the same general principle diagram as that represented on the figure 1 , showing in particular the different phases of the process of the invention,
  • there Figure 3 represents a general principle diagram of an installation according to the prior art comprising an open cycle with liquid nitrogen.

Les éléments identiques représentés sur les figures 1 et 2 sont identifiés par des références numériques identiques.The identical elements represented on the figures 1 And 2 are identified by identical numerical references.

La figure 3 est un dispositif selon l'art antérieur permettant la mise en oeuvre d'un procédé de liquéfaction d'un gaz combustible connu de l'art antérieur fonctionnant avec un cycle ouvert à l'azote liquide. Ce procédé sert de point de comparaison pour les simulations numériques présentées ci-après dans les exemples.There Figure 3 is a device according to the prior art allowing the implementation of a process for liquefying a combustible gas known from the prior art operating with an open liquid nitrogen cycle. This process serves as a point of comparison for the numerical simulations presented below in the examples.

Sur la figure 1, on a représente un schéma de principe général d'un mode de réalisation préférentiel de l'installation selon l'invention. Cette installation comprend : un circuit primaire 1 relié à une source 1 de gaz combustible et à un réservoir pour gaz liquéfié),

  • un circuit secondaire 34 ouvert relié à un réservoir d'azote liquide 3, et quatre zones d'échange thermiques 100, 200, 300, 400 disposées en cascade pour refroidir et liquéfier le gaz combustible circulant dans le circuit primaire 12, chacune des zones thermiques 100, 200, 300, 400 étant traversée par les circuits primaire 12 et secondaire 34 disposés de manière que le gaz combustible et l'azote y circulent à contre-courant.
On the figure 1 , we have shown a general principle diagram of a preferred embodiment of the installation according to the invention. This installation comprises: a primary circuit 1 connected to a source 1 of combustible gas and to a tank for liquefied gas),
  • an open secondary circuit 34 connected to a liquid nitrogen tank 3, and four heat exchange zones 100, 200, 300, 400 arranged in cascade to cool and liquefy the combustible gas circulating in the primary circuit 12, each of the thermal zones 100, 200, 300, 400 being crossed by the primary 12 and secondary 34 circuits arranged so that the combustible gas and the nitrogen circulate there in counter-current.

Les zones d'échange thermique 100, 200, 300, 400 sont réparties selon la configuration suivante :

  • une zone d'échange thermique 100 de pré-refroidissement comprenant au moins un échangeur thermique 10, une zone d'échange thermique 200 de refroidissement comprenant un échangeur thermique 20 et un échangeur annexe 21, la zone d'échange thermique 200 de refroidissement étant reliée, dans le circuit primaire 12, à la zone d'échange thermique 100 de pré-refroidissement par une première zone de distribution intermédiaire 150 apte à distribuer, à la sortie de la zone d'échange thermique 100 de pré-refroidissement, le gaz combustible en deux sous-flux de débits respectifs m1 et m2=m-m1, et à les injecter respectivement dans l'échangeur thermique 20 et l'échangeur annexe 21 de la zone d'échange thermique 200 de refroidissement, une zone d'échange thermique 300 de liquéfaction comprenant au moins un échangeur thermique 30 et un échangeur thermique annexe 31, et une deuxième zone de distribution intermédiaire 250 reliant, dans le circuit primaire 12, les zones d'échange thermique 200 de refroidissement et 300 de liquéfaction. Cette deuxième zone de distribution intermédiaire 250 est apte à réunir en un seul flux les deux sous-flux de gaz combustible sortant des échangeurs thermiques 20, 21 de la zone d'échange thermique 200 de refroidissement et à les redistribuer en deux autres sous-flux de gaz combustible de débits respectifs m3 et m4=m-m3 pour les injecter respectivement dans l'échangeur thermique 30 et l'échangeur thermique annexe 31 de la zone d'échange thermique 300 de liquéfaction, l'azote détendu et refroidi provenant de la turbine 22 circulant dans l'échangeur thermique annexe 31 à contre-courant du sous-flux de gaz de débit m4.
The heat exchange zones 100, 200, 300, 400 are distributed according to the following configuration:
  • a heat exchange zone 100 for pre-cooling comprising at least one heat exchanger 10, a heat exchange zone 200 for cooling comprising a heat exchanger 20 and an annex exchanger 21, the heat exchange zone 200 for cooling being connected , in the primary circuit 12, to the pre-cooling heat exchange zone 100 by a first intermediate distribution zone 150 capable of distributing, at the outlet of the pre-cooling heat exchange zone 100, the combustible gas into two respective flow sub-flows m 1 and m 2 =mm 1 , and to inject them respectively into the heat exchanger 20 and the annex exchanger 21 of the cooling heat exchange zone 200, a liquefaction heat exchange zone 300 comprising at least one heat exchanger 30 and an annex heat exchanger 31, and a second intermediate distribution zone 250 connecting, in the primary circuit 12, the heat exchange zones 200 for cooling and 300 for liquefaction. This second intermediate distribution zone 250 is able to combine into a single flow the two sub-flows of combustible gas leaving the heat exchangers 20, 21 of the cooling heat exchange zone 200 and to redistribute them into two other sub-flows of combustible gas of respective flow rates m 3 and m 4 =mm 3 to inject them respectively into the heat exchanger 30 and the annex heat exchanger 31 of the liquefaction heat exchange zone 300, the expanded and cooled nitrogen coming from the turbine 22 circulating in the annex heat exchanger 31 counter-current to the gas sub-flow of flow rate m 4 .

La figure 1 montre en outre qu'une turbine 22 (de préférence à détente) est disposée, dans le circuit secondaire 34, reliant la sortie de l'échangeur thermique 20 de la zone d'échange thermique 200 de refroidissement et l'entrée de l'échangeur thermique annexe 31 de la zone d'échange thermique 300 de liquéfaction, cette turbine 33 permet de détendre et refroidir l'azote vaporisé sortant de l'échangeur thermique 20 de la zone d'échange thermique 200 de refroidissement, avant son injection dans l'échangeur thermique annexe 31 de la zone d'échange thermique 300 de liquéfaction.There figure 1 further shows that a turbine 22 (preferably expansion) is arranged, in the secondary circuit 34, connecting the outlet of the heat exchanger 20 of the cooling heat exchange zone 200 and the inlet of the exchanger thermal annex 31 of the heat exchange zone 300 of liquefaction, this turbine 33 makes it possible to relax and cool the vaporized nitrogen leaving the heat exchanger 20 of the heat exchange zone 200 of cooling, before its injection into the heat exchanger annex 31 of the liquefaction heat exchange zone 300.

La figure 2 montre la mise en oeuvre du procédé selon l'invention sur l'installation selon l'invention représentée sur la figure 1. Pour cela, on a indiqué les différentes phases du procédé de l'invention au niveau des échangeurs thermiques où elles sont réalisées.There figure 2 shows the implementation of the method according to the invention on the installation according to the invention represented on the figure 1 . For this, the different phases of the process of the invention have been indicated at the level of the heat exchangers where they are carried out.

La figure 2 montre en particulier que le procédé selon l'invention consiste à liquéfier un gaz combustible comprenant majoritairement du méthane, en le faisant circuler dans un circuit primaire I ouvert depuis une source de gaz combustible vers un réservoir pour gaz liquéfié 2, tandis qu' un mélange réfrigérant constitué d'azote liquide ou au moins partiellement vaporisé circule dans un circuit secondaire 34 ouvert depuis un réservoir d'azote 3 pour être relâché vers l'atmosphère.There figure 2 shows in particular that the process according to the invention consists of liquefying a combustible gas comprising mainly methane, by circulating it in a primary circuit I open from a source of combustible gas to a tank for liquefied gas 2, while a mixture refrigerant consisting of liquid or at least partially vaporized nitrogen circulates in a secondary circuit 34 open from a nitrogen tank 3 to be released to the atmosphere.

Les différentes étapes du procédé selon l'invention sont détaillées ci-après, selon que l'on examine la circulation de l'azote dans le circuit secondaire 34 ou la circulation du gaz combustible à traiter dans le circuit primaire 12 :The different stages of the process according to the invention are detailed below, depending on whether we examine the circulation of nitrogen in the secondary circuit 34 or the circulation of the combustible gas to be treated in the primary circuit 12:

A. Circulation de l'azote dans le circuit secondaire 34. A. Circulation of nitrogen in the secondary circuit 34.

  • étape préliminaire (avant échange thermique) : on pompe l'azote liquide contenu dans le réservoir d'azote liquide 3 à une pression typiquement de 1,2 MPa (12 bars) (mais une pression plus élevée est possible, par exemple 20 voire 30 bars, en fonction de la nature du gaz naturel à liquéfier). preliminary step (before heat exchange): the liquid nitrogen contained in the liquid nitrogen tank 3 is pumped at a pressure typically of 1.2 MPa (12 bars) (but a higher pressure is possible, for example 20 or even 30 bars, depending on the nature of the natural gas to be liquefied).
• Vaporisation de l'azote liquide :• Vaporization of liquid nitrogen :

L'azote initialement complètement liquide, en provenance du réservoir 3, est injecté dans l'échangeur thermique 40 de la zone d'échange thermique 400 de sous-refroidissement, dans lequel il circule à contre-courant du flux de gaz combustible. Puis, dans la zone 400 de sous-refroidissement, le flux d'azote se vaporise partiellement. A la sortie de la zone 400, l'azote partiellement vaporisé est injecté dans l'échangeur 30 de la zone d'échange thermique 300 de liquéfaction pour liquéfier une partie du flux de gaz combustible, entre T3 et T2. Cette étape permet d'ajuster au mieux le débit de gaz combustible à liquéfier pour optimiser le procédé selon l'invention, et faciliter sa mise en oeuvre technique car alors à T2, l'azote est totalement vaporisé si bien que les échangeurs impliqués (échangeurs 20 et 21) ont des entrées-sorties purement monophasiques.The initially completely liquid nitrogen, coming from the tank 3, is injected into the heat exchanger 40 of the subcooling heat exchange zone 400, in which it circulates countercurrent to the flow of combustible gas. Then, in subcooling zone 400, the nitrogen flow partially vaporizes. At the exit of zone 400, the partially vaporized nitrogen is injected into the exchanger 30 of the liquefaction heat exchange zone 300 to liquefy part of the fuel gas flow, between T 3 and T 2 . This step makes it possible to best adjust the flow rate of combustible gas to be liquefied to optimize the process according to the invention, and facilitate its technical implementation because then at T 2 , the nitrogen is completely vaporized so that the exchangers involved ( exchangers 20 and 21) have purely monophasic inputs-outputs.

Puis, l'azote complètement vaporisé est, à la température T2, injecté dans l'échangeur thermique 20 de la zone d'échange thermique de refroidissement 200, dans lequel il circule à contre-courant d'une partie du gaz combustible qui y est refroidi entre la température T1 de pré-refroidissement jusqu'à la température T2 de rosée. A la sortie de l'échangeur thermique 20, l'azote, à une température proche de T1, est totalement vaporisé, mais toujours à haute pression.Then, the completely vaporized nitrogen is, at the temperature T 2 , injected into the heat exchanger 20 of the cooling heat exchange zone 200, in which it circulates against the current of a part of the combustible gas which there is cooled between the pre-cooling temperature T1 up to the dew temperature T 2 . At the outlet of the heat exchanger 20, the nitrogen, at a temperature close to T 1 , is completely vaporized, but still at high pressure.

• Détente de l'azote liquide vaporisé :• Expanding the vaporized liquid nitrogen :

On détend ensuite l'azote vaporisé dans la turbine de détente 22 (typiquement d'une pression de 1,2 MPa à moins de 0,2 MPa, les valeurs précises dépendant du gaz combustible à refroidir). Cela permet d'obtenir un flux d'azote certes vaporisé, mais à une température cryogénique typiquement de l'ordre de -160°C (là encore les valeurs précises dépendent du cas étudié). Autrement dit, l'azote obtenu est à une température bien inférieure à T3 (qui est la température bulle du gaz à liquéfier) . Ainsi, on obtient de l'azote froid, complètement vaporisé et à basse pression, que l'on utilise pour liquéfier le reste du flux de combustible qui n'a pas été liquéfié. D'un point de vue conceptuel : c'est cette étape (qu'on peut qualifier de "soulagement" du seul refroidissement du gaz combustible par vaporisation d'azote liquide) qui permet d'économiser la quantité d'azote liquide globale.The vaporized nitrogen is then expanded in the expansion turbine 22 (typically from a pressure of 1.2 MPa to less than 0.2 MPa, the precise values depending on the fuel gas to be cooled). This makes it possible to obtain a flow of nitrogen that is certainly vaporized, but at a cryogenic temperature typically of the order of -160°C (here again the precise values depend on the case studied). In other words, the nitrogen obtained is at a temperature well below T 3 (which is the bubble temperature of the gas to be liquefied). This produces cold, completely vaporized, low-pressure nitrogen, which is used to liquefy the remainder of the fuel stream that has not been liquefied. From a conceptual point of view: it is this step (which can be described as "relief" from the sole cooling of the combustible gas by vaporization of liquid nitrogen) which makes it possible to save the overall quantity of liquid nitrogen.

B. Circulation du gaz combustible à traiter dans le circuit primaire 12. B. Circulation of the combustible gas to be treated in the primary circuit 12. • phase de pré-refroidissement 1000 • pre-cooling phase 1000

Au cours de cette phase 1000 de pré-refroidissement, le gaz combustible (de débit initial m) est refroidi de la température ambiante T0 à une température de pré-refroidissement T1 supérieure à la température de rosée T2 du gaz combustible, cette phase de pré-refroidissement étant réalisée par échange thermique avec un flux d'azote vaporisé et à basse pression circulant à contre-courant du flux de gaz combustible dans l'échangeur thermique 10 de la zone d'échange thermique 100 de pré-refroidissement.During this pre-cooling phase 1000, the combustible gas (of initial flow rate m) is cooled from the ambient temperature T 0 to a pre-cooling temperature T 1 greater than the dew point temperature T 2 of the combustible gas, this pre-cooling phase being carried out by heat exchange with a flow of vaporized and low-pressure nitrogen circulating countercurrent to the flow of combustible gas in the heat exchanger 10 of the pre-cooling heat exchange zone 100.

• première phase de redistribution 1050 • first phase of redistribution 1050

A la sortie de la zone d'échange thermique 10 de pré-refroidissement, le gaz combustible à liquéfier est réparti en deux sous-flux de débits respectifs m1 et m2=m-m1, cette première phase de redistribution 1050 étant réalisée dans une première zone de distribution intermédiaire 150.At the exit of the pre-cooling heat exchange zone 10, the combustible gas to be liquefied is distributed into two sub-flows of respective flow rates m 1 and m 2 =mm 1 , this first redistribution phase 1050 being carried out in a first intermediate distribution zone 150.

• phase de refroidissement 2000 • cooling phase 2000

Au cours de cette phase de refroidissement 2000, le gaz combustible, une fois réparti en deux sous-flux de débits m1 et m2, est refroidi depuis la température de pré-refroidissement T1 jusqu'à la température de rosée T2 du gaz combustible, cette phase de refroidissement étant réalisée dans la zone d'échange thermique 200 de refroidissement comprenant l'échangeur thermique 20 et l'échangeur annexe 21, selon les étapes suivantes :

  • o injection 2001 du sous-flux de gaz combustible de débit m1 dans l'échangeur thermique 20 et injection 2002 du sous-flux de gaz de débit m2 dans l'échangeur annexe 21, un flux vaporisé circulant à contre-courant du flux de gaz combustible dans chacun des échangeurs (20, 21) de la zone d'échange thermique (200) de refroidissement ;
  • o à la température de rosée T2 du gaz combustible, réunion 2003 en un seul flux de débit m des deux sous-flux de gaz combustible de débits respectifs m1 et m2 sortant respectivement de chacun des échangeurs 20, 21 de la zone d'échange thermique 200 de refroidissement.
During this cooling phase 2000, the combustible gas, once distributed into two sub-flows of flow rates m 1 and m 2 , is cooled from the pre-cooling temperature T 1 to the dew point temperature T 2 of the combustible gas, this cooling phase being carried out in the cooling heat exchange zone 200 comprising the heat exchanger 20 and the annex exchanger 21, according to the following steps:
  • o injection 2001 of the sub-flow of combustible gas with flow rate m 1 in the heat exchanger 20 and injection 2002 of the sub-flow of gas with flow rate m 2 in the annex exchanger 21, a vaporized flow circulating counter-current to the flow of combustible gas in each of the exchangers (20, 21) of the cooling heat exchange zone (200);
  • o at the dew point temperature T 2 of the combustible gas, 2003 meeting in a single flow of flow rate m of the two sub-flows of combustible gas of respective flow rates m 1 and m 2 respectively leaving each of the exchangers 20, 21 of the heat exchange cooling zone 200.

• deuxième phase de redistribution 2050 • second phase of redistribution 2050

Au cours de cette phase, le flux de gaz combustible de débit m sortant de la zone d'échange thermique 200 de refroidissement, est redistribué en deux sous-flux de débits respectifs m3 et m4=m-m3, cette deuxième phase de redistribution 2050 étant réalisée dans une deuxième zone de distribution intermédiaire 250.During this phase, the flow of combustible gas with a flow rate m leaving the cooling heat exchange zone 200 is redistributed into two sub-flows with respective flow rates m 3 and m 4 = mm 3 , this second redistribution phase 2050 being carried out in a second intermediate distribution zone 250.

• phase de liquéfaction complète 3000 • complete liquefaction phase 3000

Au cours de cette phase de liquéfaction 3000, le gaz combustible réparti en deux sous-flux de débits respectifs m3 et m4 est complètement liquéfié par refroidissement jusqu'à une température T3 au moins aussi basse que la température bulle du gaz combustible. Cette phase de liquéfaction complète 3000 est réalisée dans la zone d'échange thermique 300 comme suit :

  • on injecte 3004 le sous-flux de débit m3 dans l'échangeur thermique 30 de la zone d'échange thermique 300 de liquéfaction pour le liquéfier complètement et le refroidir jusqu'à la température T3, en y faisant circuler à contre-courant le flux d'azote au moins partiellement vaporisé sortant de la zone d'échange thermique 400 de sous-refroidissement ;
  • on injecte 3005 le sous-flux de débit m4 dans l'échangeur thermique annexe 31 de la zone d'échange thermique 300 de liquéfaction pour le liquéfier complètement et le refroidir jusqu'à la température T3, en y faisant circuler, à contre-courant du gaz combustible, le flux d'azote sortant de la turbine 22 ; à la température T3 du gaz combustible ;
  • on réunit 3006 les deux sous-flux de gaz combustible de débits respectifs m3 et m4 sortant respectivement de chacun des échangeurs thermiques 30, 31 de la zone d'échange thermique 300 de liquéfaction, pour les réinjecter dans la zone d'échange thermique 400 de sous-refroidissement.
During this liquefaction phase 3000, the fuel gas distributed into two sub-flows of respective flow rates m 3 and m 4 is completely liquefied by cooling to a temperature T 3 at least as low as the bubble temperature of the fuel gas. This complete liquefaction phase 3000 is carried out in the heat exchange zone 300 as follows:
  • the sub-flow of flow m 3 is injected 3004 into the heat exchanger 30 of the heat exchange zone 300 of liquefaction to liquefy it completely and cool it to the temperature T 3 , by circulating it countercurrently the flow of at least partially vaporized nitrogen leaving the subcooling heat exchange zone 400;
  • the flow sub-flow m 4 is injected 3005 into the heat exchanger annex 31 of the heat exchange zone 300 of liquefaction to liquefy it completely and cool it to the temperature T 3 , by circulating there, at counter-current of the combustible gas, the flow of nitrogen leaving the turbine 22; at the temperature T 3 of the combustible gas;
  • we combine 3006 the two sub-flows of combustible gas with respective flow rates m 3 and m 4 respectively leaving each of the heat exchangers 30, 31 of the heat exchange zone 300 of liquefaction, to reinject them into the heat exchange zone 400 subcooling.

• Détente 2004 de l'azote liquide vaporisé :• 2004 relaxation of vaporized liquid nitrogen :

Puis, on détend 2004 dans une turbine 22 le flux d'azote totalement vaporisé à la sortie de l'échangeur thermique 20 de la zone d'échange thermique 200 de refroidissement ; et on réinjecte l'azote vaporisé et détendu dans l'échangeur thermique annexe 31.Then, the flow of completely vaporized nitrogen at the outlet of the heat exchanger 20 of the cooling heat exchange zone 200 is expanded 2004 in a turbine 22; and the vaporized and expanded nitrogen is reinjected into the heat exchanger annex 31.

• Phase de sous-refroidissement 4000 • Subcooling phase 4000

Au cours de cette phase 4000, le gaz combustible liquéfié, sortant de la zone d'échange thermique 300 de liquéfaction, est sous-refroidi de la température T3 jusqu'à une température de sous-refroidissement T4, cette phase de sous-refroidissement 4000 étant réalisée dans la zone d'échange thermique 400 de sous-refroidissement comprenant au moins un échangeur thermique 40 par échange thermique avec le flux d'azote initialement complètement liquide circulant à contre-courant du flux de gaz combustible.During this phase 4000, the liquefied combustible gas, leaving the liquefaction heat exchange zone 300, is sub-cooled from the temperature T 3 to a sub-cooling temperature T 4 , this sub-cooling phase cooling 4000 being carried out in the subcooling heat exchange zone 400 comprising at least one heat exchanger 40 by heat exchange with the flow of initially completely liquid nitrogen circulating counter-current to the flow of combustible gas.

Sur cette étape, tout le gaz combustible est, par définition déjà liquéfié, et on cherche à le sous - refroidir encore ; sur cette étape la totalité du flux de GNL est sous-refroidi par le flux d'azote liquide haute pression qui se vaporise partiellement pour réaliser sa tâche.In this stage, all the combustible gas is, by definition already liquefied, and we seek to subcool it further; on this step the entire flow of LNG is subcooled by the flow of high pressure liquid nitrogen which partially vaporizes to carry out its task.

Au final, le procédé selon l'invention comporte 5 grands paramètres de pilotage du procédé :

  • le débit d'azote liquide mN2,
  • la pression de pompage de l'azote liquide PN2HP, la détente de l'azote totalement vaporisé et donc sa pression en fin de détente PN2BP, et les deux phases de répartition 1050 et 2050 du débit de gaz combustible d'une part entre les phases de pré-refroidissement et d'autre part entre les phases de refroidissement et de liquéfaction.
Ultimately, the process according to the invention includes 5 major process control parameters:
  • the liquid nitrogen flow m N2,
  • the pumping pressure of the liquid nitrogen P N2HP , the expansion of the totally vaporized nitrogen and therefore its pressure at the end of expansion P N2BP , and the two distribution phases 1050 and 2050 of the flow of combustible gas on the one hand between the pre-cooling phases and on the other hand between the cooling and liquefaction phases.

EXEMPLESEXAMPLES

Les exemples suivants illustrent l'invention sans toutefois en limiter la portée. Il s'agit de simulations numériques réalisée à l'aide de l'outil de simulation aspen hysys V7.3 sur la base du modèle thermodynamique SRK LK - 1 (Soave Redlich-Kwong Lee Kesler 1). Ces simulations ont permis de calculer les paramètres suivants :

  • la puissance mécanique utilisée par le procédé en kW ;
  • la consommation spécifique en kWh/t de GNL produit (ratio de la puissance mécanique et du débit massique de GNL produit) ;
  • le ratio massique d'azote liquide utilisé par rapport au GNL produit d'azote liquide ;
  • le gain de consommation d'énergie par rapport au procédé connu de l'art antérieur avec un cycle ouvert à l'azote liquide ;
par comparaison avec les résultats que l'on obtiendrait avec un procédé connu selon l'art antérieur comportant un cycle ouvert à l'azote liquide tel qu'illustré à la figure 3 :
Ces simulations numériques ont été réalisées dans les conditions suivantes :
  • Gaz d'entrée (gaz combustible à refroidir) :
    • o Pression : 48 bar
    • o Température : 30°C
    • o Débit massique : 10,18 t/h
    • o Composition (% molaire) :
      • ▪ N2 : 0,79%
      • ▪ C1 : 91,21%
      • ▪ C2 : 7,89%
      • ▪ C3 : 0,11%
      • ▪ C4+ :0
  • Température minimale de refroidissement du réfrigérant avec le milieu ambiant : 30°C
  • Hypothèses de rendement polytropique de compresseur : 85%
  • Température de sous-refroidissement du GNL : -158°C.
The following examples illustrate the invention without limiting its scope. These are numerical simulations carried out using the aspen hysys V7.3 simulation tool on the basis of the SRK LK - 1 thermodynamic model (Soave Redlich-Kwong Lee Kesler 1). These simulations made it possible to calculate the following parameters:
  • the mechanical power used by the process in kW;
  • the specific consumption in kWh/t of LNG produced (ratio of mechanical power and mass flow of LNG produced);
  • the mass ratio of liquid nitrogen used relative to the LNG produced from liquid nitrogen;
  • the gain in energy consumption compared to the process known from the prior art with an open cycle with liquid nitrogen;
by comparison with the results that would be obtained with a process known according to the prior art comprising a cycle open to liquid nitrogen as illustrated in Figure 3 :
These numerical simulations were carried out under the following conditions:
  • Input gas (combustible gas to be cooled):
    • o Pressure: 48 bar
    • o Temperature: 30°C
    • o Mass flow: 10.18 t/h
    • o Composition (molar %):
      • ▪ N 2 : 0.79%
      • ▪ C 1 : 91.21%
      • ▪ C 2 : 7.89%
      • ▪ C 3 : 0.11%
      • ▪ C 4+ :0
  • Minimum cooling temperature of the refrigerant with the ambient environment: 30°C
  • Compressor polytropic efficiency assumptions: 85%
  • LNG subcooling temperature: -158°C.

Les résultats des simulations sont présentés dans le tableau 1 ci-après : Tableau 1 Procédé connu avec un cycle ouvert à l'azote liquide (tel qu'illustré sur la figure 2) Procédé selon l'invention consommation d'énergie mécanique en kW 0 0 la consommation spécifique en kWh/t de GNL produit 0 0 le ratio massique d'azote liquide utilisé par rapport au GNL produit d'azote liquide 2,05 1,85 le gain en consommation d'énergie par rapport au procédé connue de l'art antérieur avec un cycle ouvert à l'azote liquide - -9,8 % The results of the simulations are presented in Table 1 below: <u>Table 1</u> Known process with an open cycle with liquid nitrogen (as illustrated in the figure 2 ) Process according to the invention mechanical energy consumption in kW 0 0 the specific consumption in kWh/t of LNG produced 0 0 the mass ratio of liquid nitrogen used compared to LNG produced from liquid nitrogen 2.05 1.85 the gain in energy consumption compared to the process known from the prior art with an open cycle with liquid nitrogen - -9.8%

Ces résultats montrent que, par rapport à un procédé à cycle ouvert simple à l'azote liquide, le procédé selon l'invention permet de réduire la consommation d'azote liquide de presque 10%, ce qui constitue la principale source de coûts opérationnels d'un procédé à cycle ouvert.These results show that, compared to a simple open cycle process with liquid nitrogen, the process according to the invention makes it possible to reduce the consumption of liquid nitrogen by almost 10%, which constitutes the main source of operational costs of an open cycle process.

Claims (7)

  1. A method for liquefying a fuel gas comprising predominantly methane, wherein said fuel gas circulates in a primary circuit (12) from a source of fuel gas (1) toward a tank for liquefied gas (2), and a refrigerant consisting of nitrogen in a liquid or at least partly vaporized state circulates in an open secondary circuit (34) from a liquid nitrogen tank (3) to be released into the atmosphere (4), said method comprising the following phases:
    • a pre-cooling phase (1000) during which the initial flow rate m of fuel gas is cooled from the ambient temperature T0 to a pre-cooling temperature T1 greater than the dew temperature T2 of the fuel gas, this pre-cooling phase being carried out by heat exchange with a flow of totally vaporized nitrogen at a temperature close to T1 at low pressure circulating in counter-current to the flow of fuel gas in at least one heat exchanger (10) of a pre-cooling heat exchange region (100);
    • a first phase (1050) of redistributing the fuel gas at the outlet of the pre-cooling heat exchange region (100) into two sub-flows of respective flow rates m1 and m2 = m-m1, this first redistribution phase (1050) being carried out in a first intermediate distribution region (150), then
    • a cooling phase (2000) during which the fuel gas is cooled from the pre-cooling temperature T1 to the dew temperature T2 of the fuel gas, this cooling phase being carried out in a cooling heat exchange region (200) comprising a heat exchanger (20) and an auxiliary exchanger (21), according to the following steps:
    o injecting (2001) the sub-flow of flow rate m1 into the heat exchanger (20) and injecting (2002) the gas sub-flow of flow rate m2 into the auxiliary exchanger (21),
    o a flow of completely vaporized nitrogen circulating in counter-current to the flow of fuel gas in the heat exchanger (20) of the cooling heat exchange region (200), at the outlet of the heat exchanger (20) of the cooling heat exchange region (200), the nitrogen forming a flow of totally vaporized nitrogen at a temperature close to T1 at high pressure;
    o a flow of completely vaporized nitrogen at a temperature close to T2 and at low pressure circulating in counter-current to the flow of fuel gas in the auxiliary exchanger (21) of the cooling heat exchange region (200), at the outlet of the auxiliary exchanger (21) of the cooling heat exchange region (200), the nitrogen forming the flow of totally vaporized nitrogen at a temperature close to T1 at low pressure;
    o at the dew temperature T2 of the fuel gas, combining (2003) the two sub-flows of fuel gas of respective flow rates m1 and m2 leaving each of the heat exchangers (20, 21) of the cooling heat exchange region (200), respectively, into a single flow of flow rate m;
    • a complete liquefaction phase (3000) during which the single flow of fuel gas leaving the cooling heat exchange region (200) is completely liquefied by cooling to a temperature T3 at least as low as the bubble temperature of the fuel gas; this complete liquefaction phase (3000) being carried out in a liquefaction heat exchange region (300) comprising at least one heat exchanger (30);
    • a subcooling phase (4000) during which the liquefied fuel gas leaving the liquefaction heat exchange region (300) is subcooled from the temperature T3 to a subcooling temperature T4, this subcooling phase (4000) being carried out in a subcooling heat exchange region (400) comprising at least one heat exchanger (40) by heat exchange with the initially completely liquid nitrogen from the liquid nitrogen tank (3) and circulating in counter-current to the flow of fuel gas, the nitrogen being partly vaporized and forming a flow of partly vaporized nitrogen;
    said method further comprises, between the cooling phase (2000) and complete liquefaction phase (3000), a second phase (2050) of redistributing the fuel gas flow of flow rate m leaving the cooling heat exchange region (200) into two sub-flows of respective flow rates m3 and m4 = m-ms; this second redistribution phase (2050) being carried out in a second intermediate distribution region (250);
    and an additional step consisting of expanding (2004), in a turbine (22), the flow of totally vaporized nitrogen at a temperature close to T1 at high pressure and the nitrogen forming a flow of completely vaporized nitrogen at low pressure; then the flow of completely vaporized nitrogen at low pressure is injected into the auxiliary heat exchanger (31);
    wherein the complete liquefaction phase (3000) further comprises additional intermediate steps (3004, 3005, 3006, 3007) between the dew temperature T2 of the fuel gas and the temperature T3:
    • the sub-flow of flow rate m3 is injected (3004) into the heat exchanger (30) of the liquefaction heat exchange region (300) in order to completely liquefy and cool it to the temperature T3 by circulating therein the flow of partly vaporized nitrogen leaving the subcooling heat exchange region (400), the nitrogen being totally vaporized in the heat exchanger (30) of the liquefaction heat exchange region (300) and forming the flow of completely vaporized nitrogen;
    • the sub-flow of flow rate m4 is injected (3005) into an auxiliary heat exchanger (31) of the liquefaction heat exchange region (300) in order to completely liquefy and cool it to the temperature T3 by causing the flow of completely vaporized nitrogen at low pressure leaving the turbine (22) to circulate in counter-current to the fuel gas, and the nitrogen at the outlet of the auxiliary heat exchanger (31) of the liquefaction heat exchange region (300) forming the flow of completely vaporized nitrogen at a temperature close to T2 at low pressure;
    • at the temperature T3 of the fuel gas, the two sub-flows of fuel gas of respective flow rates m3 and m4 leaving each of the heat exchangers (30, 31) of the liquefaction heat exchange region (300) are recombined (3006) in order to reinject them into the subcooling heat exchange region (400).
  2. The method according to claim 1, wherein:
    - the flow rate m1 of the sub-flow of fuel gas injected into the heat exchanger (20) of the cooling heat exchange region (200) is at least 80%, and preferably at least 85%, of the initial flow rate m of fuel gas; and
    - the flow rate m3 of the sub-flow of fuel gas injected into the heat exchanger (30) of the liquefaction heat exchange region (300) is at least 60% of the initial flow rate m of fuel gas, and at the most the value of m1.
  3. The method according to either claim 1 or claim 2, wherein the liquid nitrogen from the liquid nitrogen tank (3) is pumped at a pressure of at least 1.2 MPa.
  4. The method according to claim 1, wherein the at least partly vaporized nitrogen at the outlet of the heat exchanger (20) of the cooling heat exchange region (200) is expanded, in the turbine (22), at a pressure of less than or equal to 0.2 MPa.
  5. The method according to any of claims 1 to 4, wherein the gas to be liquefied contains methane in a molar proportion of at least 80%.
  6. A facility for liquefying a fuel gas for carrying out the method as defined according to any of claims 1, 2, 4 and 5, said facility comprising a primary circuit (12) connected to a source (1) of fuel gas and to a tank for liquefied gas (2), an open secondary circuit (34) connected to a liquid nitrogen tank (3), and four heat exchange regions (100, 200, 300, 400) arranged in cascade for cooling and liquefying the fuel gas circulating in the primary circuit (12), each of said heat regions (100, 200, 300, 400) being crossed by the primary circuit (12) and secondary circuit (34) arranged so that the fuel gas and the nitrogen circulate there in counter-current mode according to the following configuration:
    - a pre-cooling heat exchange region (100) comprising at least one heat exchanger (10),
    - a cooling heat exchange region (200) comprising a heat exchanger (20) and an auxiliary exchanger (21), the cooling heat exchange region (200) being connected, in the primary circuit (12), to the pre-cooling heat exchange region (100) by
    - a first intermediate distribution region (150) which is suitable for distributing, at the outlet of the pre-cooling heat exchange region (100), the fuel gas into two sub-flows of respective flow rates m1 and m2 = m-m1, and injecting them into the heat exchanger (20) and the auxiliary exchanger (21) of the cooling heat exchange region (200), respectively,
    - a liquefaction heat exchange region (300) comprising at least one heat exchanger (30), and
    - a subcooling heat exchange region (400) comprising at least one heat exchanger (40),
    said facility further comprises:
    - an auxiliary heat exchanger (31) in the liquefaction heat exchange region (300),
    - a turbine (22) which is arranged, in the secondary circuit (34), between the outlet of the heat exchanger (20) of the cooling heat exchange region (200) and the inlet of the auxiliary heat exchanger (31) of the liquefaction heat exchange region (300) in order to expand and cool the at least partly vaporized nitrogen leaving the heat exchanger (20) of the cooling heat exchange region (200) before injecting it into the auxiliary heat exchanger (31) of the liquefaction heat exchange region (300), a second intermediate distribution region (250) connecting, in the primary circuit (12), the cooling heat exchange region (200) and the liquefaction heat exchange region (300), the second intermediate distribution region (250) being suitable for combining, into a single flow, the two sub-flows of fuel gas leaving the heat exchangers (20, 21) of the cooling heat exchange region (200) and redistributing them into two other sub-flows of fuel gas of respective flow rates m3 and m4 = m-m3 in order to inject them respectively into the heat exchanger (30) and the auxiliary heat exchanger (31) of the liquefaction heat exchange region (300), the expanded and cooled nitrogen from the turbine (22) circulating in the auxiliary heat exchanger (31) in counter-current to the sub-flow of gas of flow rate m4.
  7. The facility according to claim 6 for carrying out the method as defined in claim 3, further comprising a pump which is configured to pump at a pressure of at least 1.2 MPa.
EP16834023.0A 2015-12-17 2016-12-16 Hybrid method for liquefying a fuel gas and facility for implementing same Active EP3390938B1 (en)

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FR1562705A FR3045796A1 (en) 2015-12-17 2015-12-17 HYBRID PROCESS FOR THE LIQUEFACTION OF A COMBUSTIBLE GAS AND INSTALLATION FOR ITS IMPLEMENTATION
FR1650632A FR3045794B1 (en) 2015-12-17 2016-01-26 HYBRID LIQUEFACTION PROCESS OF A FUEL GAS AND INSTALLATION FOR ITS IMPLEMENTATION
PCT/FR2016/053523 WO2017103535A1 (en) 2015-12-17 2016-12-16 Hybrid method for liquefying a fuel gas and facility for implementing same

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