Hydrocarbon fluid liquefaction system installation and system therefor

Abstract

One aspect of the invention relates to a hydrocarbons fluid liquefaction system, having a first heat-exchange module having a pre-cooling exchanger having a pre-cooling circuit and a plurality of pre-cooling refrigerant circuits for pre-cooling the feed stream through the circulation of an expanded first mixed-refrigerant stream, and a second heat-exchange module having a liquefaction exchanger having a liquefaction circuit and a liquefaction refrigerant circuit for liquefying the feed stream through the circulation of an expanded second mixed-refrigerant stream, wherein each heat-exchange module has thermally insulating walls and a framework that allows the module to be transported and secured, and allows the first heat-exchange module to be stacked on top of the second heat-exchange module.

Claims

1. A system for liquefying a hydrocarbons stream, comprising: a first heat-exchange module comprising: a pre-cooling exchanger, comprising: a. a first pre-cooling circuit comprising a hydrocarbons stream feed stream inlet, and a feed stream outlet, b. a plurality of pre-cooling refrigerant circuits for pre-cooling a feed stream through the circulation of an expanded first mixed-refrigerant stream, the plurality of pre-cooling refrigerant circuits each comprising an inlet and an outlet, at least one precooling expansion circuit, comprising: a. a precooling expansion device, b. a precooling expansion circuit inlet to receive a compressed first mixed-refrigerant stream, and c. a precooling expansion circuit outlet, connected to the inlet of the corresponding pre-cooling refrigerant circuit in order to transfer the expanded first mixed-refrigerant stream expanded by the expansion device, a second heat-exchange module comprising: a liquefaction exchanger comprising: a. a liquefaction circuit comprising a hydrocarbons stream feed stream inlet, and an outlet for a feed stream in the form of a flow of liquefied hydrocarbons, b. a liquefaction refrigerant circuit for liquefying the feed stream through the circulation of an expanded second mixed-refrigerant stream, the liquefaction refrigerant circuit comprising an inlet and an outlet for the expanded second mixed-refrigerant stream, a liquefaction expansion circuit, comprising: a. a liquefaction expansion device, b. a liquefaction expansion circuit inlet to receive a compressed second mixed-refrigerant stream, and c. a liquefaction expansion outlet, connected to the inlet of the liquefaction refrigerant circuit in order to transfer the expanded second mixed-refrigerant stream expanded by the expansion device, a first phase-separator module for the expanded first mixed-refrigerant stream, comprising a first phase separator per pre-cooling refrigerant circuit; each comprising: a first phase separator inlet connected to an outlet of the corresponding pre-cooling refrigerant circuit, and a first phase separator gas-phase outlet to be connected to a first compressor, a second phase-separator module comprising at least one second phase separator for the expanded liquefaction mixed-refrigerant stream, the at least one second phase separator comprising: at least one second phase separator inlet connected to an outlet of the liquefaction refrigerant circuit, and an at least one second phase separator gas-phase outlet to be connected to a second compressor, and wherein each separator module can be stacked and comprises at least a framework to allow it to be transported, secured, and stacked on top of or underneath another separator module, wherein each heat-exchange module comprises walls for thermally insulating, and a framework that allows the heat-exchange module to be transported and secured, and allows the first heat-exchange module to be stacked on top of the second heat-exchange module.

2. The liquefaction system according to claim 1, further comprising: a first pre-cooling compression module comprising a first compressor comprising an outlet coupled to the first heat-exchange module and one inlet per pre-cooling refrigerant circuit, each coupled to the outlet of the pre-cooling refrigerant circuit, a second liquefaction compression module comprising a second compressor comprising an outlet coupled to the second heat-exchange module and an inlet coupled to the outlet of the liquefaction refrigerant circuit, each compression module comprising a framework for transporting the module.

3. The liquefaction system according to claim 2, further comprising: a first cooler comprising an inlet coupled to the first pre-cooling compressor and an outlet to be coupled to the pre-cooling exchanger, a second cooler comprising an inlet coupled to the second compressor and an outlet to be coupled to the second liquefaction exchanger.

4. The liquefaction system according to claim 1, wherein the pre-cooling exchanger and the liquefaction exchanger each further comprise a first cooling circuit for cooling the corresponding compressed mixed-refrigerant stream, comprising an inlet to be coupled to an outlet of a compressor and one outlet per expansion circuit of the corresponding heat-exchange module, each coupled to an inlet of the corresponding expansion device.

5. The liquefaction system according to claim 1, wherein the pre-cooling exchanger further comprises a second precooling circuit for cooling the compressed second mixed-refrigerant stream, comprising an inlet to receive the compressed second mixed-refrigerant stream and an outlet coupled to the inlet of the expansion circuit of the second heat-exchange module.

6. The liquefaction system according to claim 1, wherein each expansion circuit comprises a phase separator comprising an inlet coupled to the outlet of the corresponding expansion device, a first, gas-phase, outlet and a second, liquid-phase, outlet, each coupled to the inlet of the corresponding pre-cooling circuit.

7. An installation of a mixed-refrigerant liquefaction system according to claim 1, wherein the first heat-exchange module is mounted on top of the second heat-exchange module.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

(2) FIG. 1 is a schematic diagram of a dual mixed-refrigerant hydrocarbon fluid liquefaction system according to one example of an embodiment of the invention.

(3) FIG. 2 is a schematic diagram depicting an installation of the dual mixed-refrigerant hydrocarbon fluid liquefaction system according to one example of an embodiment of the invention.

(4) FIG. 3 is a schematic diagram depicting an installation of the dual mixed-refrigerant hydrocarbon fluid liquefaction system according to one example of an embodiment of the invention.

(5) FIG. 4 is a schematic diagram depicting an installation of the dual mixed-refrigerant hydrocarbon fluid liquefaction system according to one example of an embodiment of the invention.

(6) FIG. 5 is a schematic diagram depicting an installation of the dual mixed-refrigerant hydrocarbon fluid liquefaction system according to one example of an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) FIG. 1 is a schematic diagram of a dual mixed-refrigerant hydrocarbon fluid liquefaction system according to one example of an embodiment of the invention.

(8) In FIG. 1, the dual mixed-refrigerant hydrocarbons fluid liquefaction system comprises a first heat-exchange module 1A comprising a heat exchanger, referred to hereinafter as the pre-cooling exchanger A1. The pre-cooling exchanger A1 comprises a pre-cooling circuit A1 for pre-cooling a hydrocarbons fluid feed stream NG, referred to hereinafter as the feed stream NG.

(9) The feed stream NG may be a stream of natural gas, which may be pretreated, in which one or several substances, such as sulphur, carbon dioxide, water, are reduced, so as to be compatible with cryogenic temperatures, as is known in the state of the art.

(10) The pre-cooling circuit A10 therefore comprises a feed stream inlet into which the feed stream NG is introduced at an initial temperature, and a feed stream outlet through which the feed stream is extracted at an intermediate temperature lower than the initial temperature. The feed stream NG is cooled, but not enough to be completely liquefied. Thus, hereinafter, this cooling of the feed stream NG is referred to as pre-cooled. The pre-cooling is explained hereinafter.

(11) The dual mixed-refrigerant hydrocarbons fluid liquefaction system further comprises a second heat-exchange module 2A comprising another heat exchanger, referred to hereinafter as liquefaction exchanger A2. The liquefaction exchanger A2 comprises a liquefaction circuit A20 for liquefying the feed stream NG.

(12) The liquefaction circuit A20 therefore comprises a feed stream inlet through which the feed stream NG is introduced at the intermediate temperature, and an outlet for a flow of liquefied hydrocarbon LNG. The flow of liquefied hydrocarbons LNG is extracted at a liquefaction temperature lower than the intermediate temperature. The flow of hydrocarbons NG is cooled enough to be completely or almost completely liquefied at the outlet. Thus, hereinafter, this cooling of the feed stream NG to a flow of liquefied hydrocarbons LNG is referred to as liquefaction.

(13) The first heat exchanger A1 and the second heat exchanger A2 are preferably each a brazed aluminium heat exchanger, but could also be a wound coil cryogenic exchanger.

(14) The heat exchangers are known from the prior art and may have various arrangements of their feed flows and refrigerant streams.

(15) When the flow of liquefied, or at least partially liquefied hydrocarbons LNG is liquefied natural gas, the temperature may be around −150° C. to −160° C.

(16) The liquefaction of the feed stream NG is performed using a circulating mixed-refrigerant stream or fluid MPR expanded in several pre-cooling refrigerant circuits A11 for pre-cooling the feed stream NG, in this instance three circuits, situated in the pre-cooling exchanger A1, and using a second circulating expanded mixed-refrigerant stream MR circulating in a liquefaction refrigerant circuit A21 situated in the liquefaction exchanger A2.

(17) The first circulating mixed-refrigerant stream MPR and the second circulating refrigerant stream MR are preferably selected from the group comprising nitrogen, methane, ethane, ethylene, propane, propylene, butane, etc. The composition of the mixed refrigerant can vary according to the conditions and parameters desired for the pre-cooling exchanger A1 or the liquefaction exchanger A2, as is known in the prior art. The composition of the first circulating mixed-refrigerant stream MPR and of the second circulating refrigerant stream MR may be identical or different.

(18) The first heat-exchange module 1A comprises one expansion circuit A3 per pre-cooling refrigerant circuit A11, namely, in this example, three expansion circuits A3.

(19) Each expansion circuit A3 comprises an expansion device A30, an inlet to receive the compressed mixed-refrigerant stream and an outlet connected to the inlet of the corresponding pre-cooling refrigerant circuit A11 in order to transfer to it the mixed-refrigerant stream MPR expanded by the expansion device A30.

(20) In this embodiment, each expansion circuit A3 further comprises a separator A32 comprising an inlet coupled to the outlet of the corresponding expansion device A30, a first, gas-phase, outlet and a second, liquid-phase, outlet, each coupled to the inlet of the corresponding pre-cooling refrigerant circuit A11.

(21) Furthermore, in this example of this embodiment, the pre-cooling exchanger A1 further comprises a first cooling circuit A13 for the circulation of the first mixed-refrigerant stream MPR in a compressed state, comprising an inlet to receive the compressed first mixed-refrigerant stream MPR and an outlet coupled to the inlet of each expansion circuit A3.

(22) The first heat exchanger A1 may further comprise a phase separator A15 comprising an inlet to receive the compressed first mixed-refrigerant stream MPR, and an outlet coupled to the inlets of the expansion circuits A3. According to this example, the phase separator A15 has its outlet connected to the inlet of the cooling circuit A13 for cooling the first mixed-refrigerant stream MPR.

(23) The first circulating mixed-refrigerant stream MPR in this example therefore enters the phase separator A15 of the first heat exchanger A1 compressed, and re-emerges therefrom compressed and pre-cooled, then, in the compressed state, enters each expansion circuit A3 in which each expansion device A30 expands it, allowing the circulating first mixed-refrigerant stream MR to evaporate in each pre-cooling refrigerant circuit A11 each situated in the heat exchanger A1 in order to produce cold and thus cool the feed stream sweeping over the walls of the casings of the exchanger in which the pre-cooling refrigerant circuits A11 are situated.

(24) The second heat-exchange module A2 also comprises an expansion circuit A3′ comprising an expansion device A30′, an inlet to receive the compressed second mixed-refrigerant stream MR and an outlet coupled to the inlet of the liquefaction refrigerant circuit, allowing the mixed-refrigerant stream MR expanded by the expansion device A30′ to be transferred to it. In the same way as the expansion circuit A3 of the first heat-exchange module, in this embodiment, the expansion circuit A3′ further comprises a separator A32′ comprising an inlet coupled to the outlet of the expansion device A30′, a first, gas-phase, outlet and a second, liquid-phase, outlet, each coupled to the inlet of the liquefaction refrigerant circuit A21.

(25) Furthermore, in this embodiment, the liquefaction heat exchanger A2 further comprises a first cooling circuit A23 for the circulation of the second mixed-refrigerant stream MR in a compressed state, comprising an inlet to receive the compressed second mixed-refrigerant stream MR and an outlet coupled to the inlet of the expansion circuit A3′.

(26) In this example of this embodiment, in order to reduce the temperature difference between the second mixed-refrigerant stream MR in a compressed state and the liquefaction exchanger A2, the pre-cooling exchanger A1 further comprises a second cooling circuit A12 for cooling the compressed second mixed-refrigerant stream MR, comprising an inlet to receive the compressed second mixed-refrigerant stream MR and an outlet coupled to the inlet of the expansion circuit A23 of the liquefaction exchanger 2A of the second heat-exchange module A2.

(27) Each heat-exchange module 1A and 2A comprises walls for thermally insulating the corresponding heat exchanger (pre-cooling exchanger 1A and liquefaction exchanger 2A) with respect to the outside, and comprises a framework that allows the heat-exchange module 1A and 2A to be transported and secured, and potentially allows the first heat-exchange module 1A to be stacked on top of the second heat-exchange module 2A.

(28) The framework may be made of bars made of stainless steel in order to reduce the effects of thermal diffusion. Furthermore, this framework may take the form of a container, thus forming the edge corners of a rectangular parallelepiped, also referred to as a right cuboid. Thus it is simple to transport. The framework of the first heat-exchange module 1A may further comprise feet and the framework of the second heat-exchange module 2A may comprise receiving elements that accept the feet of the first heat-exchange module 1A in order to facilitate installation if the first heat-exchange module 1A is being stacked on top of the second heat-exchange module 2A. The receiving elements may be housings or projections to guide and retain the feet of the first heat-exchange module 1A.

(29) In this example of this embodiment, the outlet of the second cooling circuit A12 may comprise a means of connection directly to the inlet of the first cooling circuit A23 for cooling the compressed second mixed-refrigerant stream MR, so as to simplify assembly.

(30) The system for liquefying hydrocarbon fluid using refrigerant further comprises a first phase-separator module 1B for the expanded pre-cooling mixed-refrigerant stream MPR, comprising one phase separator 1B0 per pre-cooling refrigerant circuit A13, namely, in this example, three phase separators 1B0.

(31) The system further comprises a first pre-cooling compression module 1C comprising a first compressor 1C0 comprising an outlet coupled to the first heat-exchange module, in this instance in this example to the inlet of the phase separator A15, and three inlets (one per pre-cooling refrigerant circuit A3) each connected to a gas-phase outlet of the corresponding phase separator 1B0 of the phase-separator module 1B.

(32) Each phase separator 1B0 comprises an inlet connected to an outlet of the corresponding pre-cooling refrigerant circuit A13 and a gas-phase outlet to be connected to the compressor 1C0 of the system.

(33) The first mixed-refrigerant stream MPR therefore circulates in a closed pre-cooling circuit comprising a line in the compressed state from the compressor 1C0 to the pre-cooling refrigerant circuit A13, and parallel lines in the compressed state which separate the flow of the mixed-refrigerant stream MPR for each corresponding expansion device A30, in this instance three parallel lines in the compressed state, then parallel lines in the expanded state, in this instance three of them, each extending from the outlet of the corresponding expansion device A30 to the corresponding inlet of the compressor 1C0.

(34) Each parallel line in the compressed state has a temperature distinct from the others, allowing the feed stream to be pre-cooled progressively in the pre-cooling exchanger A1.

(35) Furthermore, in this example of this embodiment, the system comprises a first cooler 1D comprising an inlet coupled to the first pre-cooling compression module 1C, in this instance connected to the outlet of the compressor 1C0 and an outlet to be connected to the first heat-exchange module 1A, in this instance connected to the phase separator A15.

(36) The system further comprises a second separator module 2B comprising at least one phase separator 2B0 for the expanded liquefaction mixed-refrigerant stream MR, and a second liquefaction compression module 2C comprising a second compressor 2C0 comprising an outlet coupled to the second heat-exchange module 2A, in this instance to the inlet of the first cooling circuit A23, via the second cooling circuit A12 of the first heat-exchange module 1A. The second compressor 2C0 comprises an inlet coupled to the outlet of the liquefaction refrigerant circuit A21 via the phase separator 2B0, to receive the mixed-refrigerant stream MR in the expanded state in order to compress same.

(37) The phase separator 2B0 therefore comprises an inlet connected to an outlet of the liquefaction refrigerant circuit A21 and a gas-phase outlet to be connected to the compressor 2C0.

(38) The second circulating mixed-refrigerant stream MR therefore circulates in a closed liquefaction circuit comprising a line for a compressed stream which therefore enters the first heat-exchange module 1A in the compressed state, and leaves same pre-cooled, then enters the first cooling circuit A23 of the second heat-exchange module 2A and leaves same cooled until it enters the expansion device of the expansion circuit A3′. The closed liquefaction circuit next comprises an expanded-stream line in which the expansion device A30′ expands the stream to allow the second circulating mixed-refrigerant stream MR to evaporate in the second liquefaction refrigerant circuit A21 situated in the liquefaction exchanger A2 to produce cold, then enter the separator module 2B and finally enter the compressor 2C0.

(39) The second separator module 2B in this example further comprises a cooler 2B1 and a separator 2B2 mounted in series. The cooler comprises an inlet connected to the second compressor 2C0 and the separator 2B2 comprises an outlet connected to an inlet of the second compressor 2C0. That allows the second mixed-refrigerant stream MR to be cooled while it is being compressed.

(40) According to another example, the cooler 2B1 and the separator 2B2 are situated in the second compressor module 2C.

(41) The system furthermore comprises in this example a second cooler 2D comprising an inlet coupled to the second pre-cooling compression module, in this instance connected to the outlet of the compressor 2C0 and an outlet to be coupled to the second heat-exchange module A2, in this instance connected to the second cooling circuit A12 for cooling the second mixed-refrigerant stream MR.

(42) Each compression module 1C, 2C comprises a framework for transporting the module.

(43) Each separator module 1B and 2B can be stackable on one another and comprises at least a framework to allow it to be transported, secured, and stacked on top of or underneath the other separator module 1B, 2B.

(44) In this way, the system can be installed with various different layouts of the modules.

(45) FIG. 2 is a schematic depiction of a dual mixed-refrigerant hydrocarbon fluid liquefaction system installation according to one example of an embodiment of the invention.

(46) In this installation, the first heat-exchange module 1A is mounted on top of the second heat-exchange module 2A placed on the ground/floor of an environment. The tubular connections for the circuits between the first heat-exchange module 1A and the second heat-exchange module 2A may be direct connections to one another by means of tubular connections.

(47) In this installation, the first phase-separator module 1B forms, with the first pre-cooling compression module 1C, a first alignment of pre-cooling modules, and the second phase-separator module 2B forms, with the liquefaction compression module 1C, a second alignment of liquefaction modules. The two alignments of modules are juxtaposed on the ground/floor in such a way that the space between the centres of the two alignments is aligned with the stack of the first heat-exchange module 1A on the second heat-exchange module 2a.

(48) This FIG. 2 also schematically shows the pipes or pipework between each module.

(49) Thus it may be seen that, for installing the closed pre-cooling circuit of this example of this system, all that is required is to couple a pipe 1CA to couple the first compression module 1C to the first heat-exchange module 1A, piping 1AB, in this instance having three pipes or channels, to connect the first heat-exchange module 1A to the first phase-separator module 1B, and piping 1BC, in this instance having three pipes or channels, to connect the first phase-separator module 1B to the first pre-cooling compression module 1C.

(50) In this example, the system comprises no cooler 1D or, in another example, this is incorporated into the first compression module 1C or into the first heat-exchange module 1A.

(51) Thus it may also be seen that, for installing the closed liquefaction circuit of this example of this system, all that is required is to couple a pipe 2C1A to couple the second compression module 2C to the first heat-exchange module 1A, to couple a pipe 2AB to connect the second heat-exchange module 2A to the second phase-separator module 2B, and piping or a pipe 2BC to connect the first phase-separator module 2B to the first pre-cooling compression module 2C.

(52) In this example, the system comprises no cooler 2D or, in another example, this is incorporated into the second compression module 2C or into the first heat-exchange module 1A.

(53) In this example, the piping 2BC in this instance has three pipes or channels, to connect the compressor 2C0 to the cooler 2B2 and to the separator 2B1 and to the separator 2B0. In the case of a system without a cooler 2B2 and without a separator 2B1, or in the case where the cooler 2B2 and the separator 2B1 are incorporated into the second compressor module 2C, the piping 2BC may be a single-channel pipe,

(54) Thus, the modules of the system can be coupled using just six pipes.

(55) FIG. 3 is a schematic depiction of another dual mixed-refrigerant hydrocarbon fluid liquefaction system installation according to the preceding example, but not depicting the piping or pipes.

(56) This installation is identical to that of FIG. 2, except for the fact that the first heat-exchange module 1A is placed on the ground/floor of the environment aligned with the first alignment and for the fact that the second heat-exchange module 2A is aligned with the second alignment.

(57) This installation therefore further comprises a feed pipe between the two heat-exchange modules 1A, 2A and a pipe for connecting the second cooling circuit A12 to the first cooling circuit A23.

(58) Furthermore, in this example of this installation, the first heat-exchange module 1A can be positioned against the first separator module 1B so that these can be connected to one another directly, thus omitting the piping 1AB.

(59) Furthermore, in this example of this installation, the second heat-exchange module 2A can be positioned against the second separator module 2B so that these can be connected to one another directly, thus omitting the piping 2AB.

(60) FIG. 4 is a schematic depiction of another dual mixed-refrigerant hydrocarbons fluid liquefaction system installation according to the preceding example, but not depicting the piping or pipes.

(61) This installation is identical to that of FIG. 2, except for the fact that the first separator module 1B is mounted on top of the second separator module 1B, and for the fact that the stack of the separator modules 1B, 2B is aligned with the stack of the heat exchanger modules 1A, 2A.

(62) This installation makes it possible to have the same amount of piping or number of pipes but to reduce the footprint of the installation.

(63) FIG. 4 is a schematic depiction of another dual mixed-refrigerant hydrocarbon fluid liquefaction system installation.

(64) according to the preceding example, but not depicting the piping or pipes.

(65) This installation is identical to that of FIG. 2, except for the fact that the first alignment is aligned with the second alignment and for the fact that the stack of the first and second separator modules 1B, 2B is aligned between the two alignments.

(66) Furthermore, according to one example of this installation, the second separator module 2B is positioned against the second heat-exchange module 2A. According to one example, the second separator module 2B is directly connected to the second heat-exchange module 2A thus omitting the pipe 2AB.

(67) FIG. 5 is a schematic depiction of another dual mixed-refrigerant hydrocarbon fluid liquefaction system installation according to the preceding example, but not depicting the piping or pipes.

(68) This installation is identical to that of FIG. 2, except for the fact that the first and second compressor modules 1C, 2C are not respectively aligned with the first and second separator modules 1B, 2B.

(69) The first and second separator modules 1B, 2B are positioned as in the installation of FIG. 4, namely aligned with the stack of heat-exchange modules 2A, 2B.

(70) Furthermore, according to one example of this installation, the second separator module 2B is positioned against the second heat-exchange module 2A. According to one example, the second separator module 2B is directly connected to the second heat-exchange module 2A thus omitting the pipe 2AB.

(71) This installation makes it possible to have the same or a lesser amount of piping or number of pipes or the same or a lesser length of piping or pipes and to reduce the lengthwise footprint of the installation.

(72) Unless specified to the contrary, the same element appearing in different figures has the same unique reference.

(73) Each expansion circuit may comprise one or ore expansion devices in series or in parallel.

(74) What is meant by an element is a module, or a compressor, or an expansion device, or a circuit of a module, or a cooler, or a separator.

(75) What is meant by connections, are a tube or pipework that may be insulated or uninsulated and may comprise valves or restrictors.

(76) What is meant by a stream is one or more fluids, that may be in liquid phase or gas phase or both, circulating through elements of the system.

(77) What is meant by an inlet is a point at which fluid enters, therefore giving the stream a direction of circulation. In other words, an inlet of a second element is coupled downstream of an outlet of a first element.

(78) What is meant by an outlet is a point at which fluid leaves an element, therefore giving the stream a direction of circulation. In other words, an outlet of a first element is coupled upstream of an inlet of a second element.

(79) Coupled means coupled for the transporting of a fluid, for example an inlet coupled to an element implies that a fluid can pass from the element to the inlet either directly or via other elements.

(80) Connected means a connection between two elements (the outlet of one element to an inlet of another element) for transporting fluid using connections, or connected directly to one another (an outlet directly coupled to an inlet of an element (without pipework)). In other words, there are no other elements between the two elements.

(81) Secured means one element being mounted physically to another element in order to fix the one to the other.

(82) An expanded stream means the stream downstream of an expansion circuit and upstream of a compressor.

(83) A compressed stream means the stream upstream of an expansion circuit and downstream of a compressor.

(84) A temperature substantially equal to another temperature means a temperature that s equal to within plus or minus 5° C.

(85) The liquefied natural gas resulting from the method that forms the subject of the present invention can thereafter for example be transferred to a storage or transport device.

(86) The method that forms the subject of the present invention notably affords optimization of investment expenditure. Specifically, having a modular system makes it possible to propose a plurality of layouts for the modules and thus reduce installation research costs and the cost of manufacture since each system is no longer a one-off.

(87) It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.