BR102013008437A2 - method for drying and liquefying a natural gas stream, equipment for drying and liquefying a natural gas stream - Google Patents

Abstract

method for drying and liquefying a natural gas stream, equipment for drying and liquefying a natural gas stream a method and equipment for drying and liquefying a natural gas stream are described, wherein: (a) the supply stream of natural gas containing chilled authentic water, ü? The. cka stream feed cka cooled natural gas ëë dried and still cooled nwú? h (c) the anhydrous and heated cooled natural gas stream, (d) the anhydrous znatural cke gas stream. reheated and cooled and liquefied. and at least one indirect heat exchange compressed and cooled refrigerant feed stream countercurrent with an expanded cold refrigerant, and the current cn; currents c% â cold refrigerant. compressed are expanded, and that compressed are further cooled to provide said expanded cold refrigerant; wherein the cooling of the natural gas feed stream in step (a) and the heating of the cooled anhydrous natural gas stream in step (c) is by indirect thermal exchange between said two streams.

Description

METHOD FOR DRYING AND LIQUIDATING A NATURAL GAS CURRENT, EQUIPMENT FOR DRYING AND LIQUIDATING A NATURAL GAS CURRENT

Background to the Invention The present invention relates to a method and equipment for drying and liquefying a natural gas stream.

When a natural gas stream contains water, it is first necessary to dry the stream to remove all or substantially all of the water contained therein before liquefying the natural gas. In order to remove water (and other impurities, such as mercury) from natural gas, prior to liquefaction, it is very common to first cool the feed temperature below room temperature, especially when the room temperature is high.

An example of a liquefaction cycle that includes such a pre-cooling step is the pre-cooled propane mixed refrigerant ("C3MR") cycle. In such methods, propane (or a different liquid refrigerant from a vapor compression cycle) may be used to cool the natural gas feed to a desired temperature before the drying step occurs. The same liquid refrigerant may then be used at a lower pressure to further cool the already dry feed prior to said feed being introduced into the main cryogenic heat exchanger ("MCHE"). The refrigerant used for liquefaction, eg mixed refrigerant ("MR"), is also pre-cooled to approximately the same temperature. Therefore, all flows entering the hot end of the MCHE are at approximately the same temperature, thereby minimizing the thermal stresses in the MCHE. Pre-cooling a gas containing natural water may pose an additional problem. That is, if the temperature of natural gas during this cooling step is not tightly controlled, there may be a risk of hydrate formation. The use of a single component liquid refrigerant such as propane which is vaporized to pre-cool the natural supply gas allows good temperature control because at any given pressure the temperature at which such refrigerant vaporizes will not vary. (whereas, for example, with a mixed refrigerant stream the vaporization temperature will vary with any changes in the ratio of different refrigerants present in the stream as well as any changes in chain pressure).

An example of the prior art dealing with the formation of hydros in a C3MR cycle is that described in US Patent No. 4,755,200, the disclosure of which is incorporated herein by reference, wherein the natural gas feed is cooled by a single-component steam compression cycle prior to water removal. The resulting dry natural gas is further cooled by indirect heat exchange with the mixed refrigerant vapor from the MCHE before being fed to the MCHE.

However, a disadvantage with the C3MR process discussed in US Patent No. 4,755,200, and in other such processes wherein a single component liquid refrigerant in a vapor compression cycle is used to pre-cool the gas feed. The natural thing before liquefying natural gas in an MCHE that uses a mixed refrigerant is that they require the use of an additional cooling circuit (ie propane or other single component loop). This increases both the footprint and investment costs of the liquefaction facility.

There are also known natural gas liquefaction cycles that do not involve the use of propane to pre-cool the natural gas feed stream. These include the mixed refrigerant single cycle ("SMR"), such as, for example, that described in US Patent No. 6,347,531, the mixed refrigerant double cycle ("DMR"), for example, described in US Patent No. 6,119,479, and the nitrogen recycling cycle ("N2 recycle"), such as, for example, that described in US Patent 2010/0122551, the disclosures of which each of them are incorporated herein by reference.

In such methods a portion of the refrigerant (MR or gaseous nitrogen) may be removed from one of the main refrigerant circuits and used to cool the feed prior to water removal. Since MR, or a pure gaseous refrigerant such as nitrogen, provides cooling over a temperature range, it is difficult to control the temperature to prevent hydrate formation. In addition, the MR composition is optimized for cooling at lower temperatures, and the nitrogen recycle cycle (reverse Brayton cycle) is inherently inefficient at warmer temperatures. From an efficiency standpoint, pre-cooling work needs to be minimized. U.S. Patent No. 6,793,712, the disclosure of which is incorporated herein by reference, describes a cascade process wherein the water-containing natural gas feed is first dried and then expanded in an isentropic expander. The resulting cold natural gas is heated in a first heat exchanger and then in a second heat exchanger before the acid gas is removed. It is then cooled again by indirect heat exchange with the cold natural gas of the second heat exchanger before further removal of water, and then cooled again on the first heat exchanger, again by indirect heat exchange with the cold natural gas. The natural gas is then additionally cooled and liquefied. The disadvantage of such a process is that it requires at least one piece of rotating machinery (i.e. the isentropic expander) and two heat exchangers (or a parallel head heat exchanger), and the reduced feed pressure resulting from the expansion. in the isentropic expander reduces the efficiency of liquefaction.

There is thus a need in the art for alternative and / or improved natural gas liquefaction cycles (such as, but not limited to, SMR, DMR, and N2 recycle cycles) in situations where feed from Natural gas is required to be pre-cooled before water removal. It is an object of embodiments of the present invention to provide a liquefaction cycle where temperature differences at the bottom of the MCHE are minimized, and the overall efficiency of the liquefaction cycle is optimized. It is a further object of preferred embodiments of the present invention to provide good temperature control during the pre-cooling of the natural gas feed to prevent or minimize hydrate formation.

Brief Summary of the Invention According to a first aspect of the present invention a method for drying and liquefying a natural gas stream is provided, the method comprising: (a) cooling a water-containing natural gas stream to produce a cooled natural gas stream; (b) removing water and further cooling the cooled natural gas feed stream to produce an anhydrous cooled natural gas stream; (c) heating the anhydrous cooled natural gas stream to produce a reheated anhydrous natural gas stream; (d) cooling and liquefying the reheated anhydrous natural gas stream and cooling at least one compressed refrigerant feed stream by indirect heat exchange countercurrent with an expanded cold refrigerant to produce at least one liquefied natural gas product stream. a cold compressed refrigerant stream and an expanded heated refrigerant stream; and (e) further expanding and cooling the compressed liquid refrigerant stream or streams to provide said expanded cold refrigerant; wherein the cooling of the natural gas feed stream in step (a) and the heating of the anhydrous cooled natural gas stream in step (c) is by indirect thermal exchange between said two streams.

According to a second aspect of the present invention, an equipment for drying and liquefying a natural gas stream is provided, the equipment comprising: an economizer heat exchanger for receiving a water-containing natural gas feed stream and a stream anhydrous cooled natural gas and to cool the water-containing natural gas feed stream and heat the anhydrous cooled natural gas stream by mutual indirect heat exchange to produce a water-containing cooled natural gas feed stream and a reheated anhydrous natural gas; removing water from the natural gas feed and natural gas feed cooling systems, in continuous communication with the economizer heat exchanger and mutually, to receive the cooled natural gas feed stream containing water from the economizer heat exchanger, further drying and cooling said stream, and returning the resulting anhydrous cooled natural gas stream to the economizer heat exchanger; a primary cryogenic heat exchanger for cooling and liquefying the reheated anhydrous natural gas stream and for cooling at least one indirect heat exchange compressed refrigerant feed stream countercurrent with an expanded cold refrigerant to produce a gas product stream liquefied natural, at least one cold compressed refrigerant stream, and one expanded heated refrigerant stream; a duct arrangement for transferring the reheated anhydrous natural gas stream from the economizer heat exchanger to the hot end of the main cryogenic heat exchanger, and for extracting the liquefied natural gas product stream from the cold end of the main cryogenic heat exchanger; and a refrigerant expansion system, in continuous communication with the main cryogenic heat exchanger, to receive at least one compressed cold refrigerant stream from the cold end of the cryogenic heat exchanger, further expanding and thereby cooling said cold refrigerant. , and return the expanded cold refrigerant to the cold end of the cryogenic heat exchanger.

Brief Description of the Drawings Figure 1 is a schematic flow chart of an apparatus and method for drying and liquefying a natural gas stream according to an embodiment of the present invention. Figure 2 is a schematic flowchart of a closed circuit mixed refrigerant system and process for use in equipment and method for drying and liquefying a natural gas stream shown in Figure 1. Figure 3 is a schematic flowchart of equipment and a method for drying and liquefying a natural gas stream according to another embodiment of the present invention.

Detailed Description of the Invention As described above, in the first aspect of the present invention a method for drying and liquefying a natural gas stream is provided comprising the above mentioned steps of (a) cooling a natural gas feed stream, (b ) removal of contained water and additional cooling of the natural gas supply stream, (c) heating of the anhydrous cooled natural gas stream, (d) cooling and liquefaction of the reheated anhydrous natural gas stream, and cooling of at least one feed stream indirect counter heat exchange compressed refrigerant with an expanded cold refrigerant, and (e) further expand and cool the compressed cold refrigerant stream or streams to provide said expanded cold refrigerant, wherein cooling of the feed stream natural gas in step (a) and heating the cooled natural gas stream to nidra in step (c) is by indirect heat exchange between said two currents.

As used herein, the term "expansion" refers to the reduction in pressure of the fluid in question by any suitable means, and in the case of a liquid may, unless otherwise indicated, involve at least partial vaporization or simply reduction in pressure.

As used herein, the term "anhydrous" refers to a fluid from which all or substantially all of the water has been removed. More specifically, this means that either all of the water is removed, or that the residual amount of remaining water is low enough to have a negligible effect on subsequent fluid processing. In particular, in the case of an "anhydrous natural gas stream" or water has been removed or any remaining residual water in the stream is present in a sufficiently low amount so as not to cause any operational problems in the subsequent cooling and liquefaction process due to separation freezing water.

As used herein, the phrase "indirect heat exchange" refers to the heat exchange between two fluids, where the two fluids are kept mutually separated by some form of physical barrier (for example, in a shell type heat exchanger). heat exchange occurs as the fluid on the pipe side is kept separate from the fluid on the shell side through the pipe walls). This is in contrast to "direct heat exchange" where fluids come in contact and may mix (such as in a wash column where mass transfer, in addition to heat transfer, may occur between countercurrent flowing currents). through the column).

In a preferred embodiment, in step (c), the anhydrous cooled natural gas stream is heated to approximately the same temperature as the temperature of at least one compressed refrigerant feed stream such that the temperatures of the reheated anhydrous natural gas stream, and at least one compressed refrigerant stream at the beginning of step (d) is approximately equal. Preferably, the natural gas feed stream is also about the same temperature as the temperatures of the reheated anhydrous natural gas stream and at least one compressed refrigerant feed stream at the beginning of step (d).

Preferably, in step (c), the anhydrous cooled natural gas stream is heated to a temperature which is the same or varying in the range of 20 ° C, more preferably in the range of 10 ° C, of the temperature of at least one stream. compressed refrigerant feed such that there is no temperature difference of less than 20 ° C, more preferably less than 10 ° C, between the reheated anhydrous natural gas stream and at least one compressed refrigerant feed stream in the beginning of step (d). Preferably, the temperature of the natural gas feed stream at the beginning of step (a) is also in the range of 20 ° C, more preferably in the range of 10 ° C, with respect to the temperatures of the reheated anhydrous natural gas stream. and at least one compressed refrigerant feed stream at the beginning of step (d).

In a preferred embodiment, step (d) is performed on a shell-tube cryogenic heat exchanger, more preferably on a serpentine heat exchanger.

In a preferred embodiment, in step (b) of the method the cooled natural gas feed stream is first dried to remove water and then further cooled to produce the anhydrous cooled natural gas stream. Alternatively, said steps may be performed in reverse order, where the feed stream is first cooled and then dried to produce the anhydrous cooled natural gas stream. However, this latter option is generally less preferred.

In one embodiment, the refrigerant in steps (d) and (e) is either of a mixed refrigerant (comprising, for example, a mixture of hydrocarbons and / or perfluorocarbons), in which case the cold compressed refrigerant stream or streams in step (d) are liquid or mixed phase streams and the expanded heated refrigerant stream in step (d) is a mixed phase or vapor phase stream, or is a gaseous refrigerant (such as, for example, a nitrogen or pure argon, for example at 99 mol% or more) which remains substantially in gaseous form during steps (d) and (e) (ie at most 12 mol%, more preferably at most 5 mol%, and very preferably no refrigerant is in liquid form at any point during steps (d) and (e)).

In preferred embodiments, the method further comprises the step of: (f) compressing and preferably cooling (e.g., by one or more interstages and / or after coolers), the expanded heated refrigerant stream to provide said at least a compressed refrigerant feed stream which is cooled in step (d). In one embodiment, step (f) comprises compressing and cooling the expanded heated refrigerant stream to provide at least one compressed refrigerant feed stream which is cooled in the step (d), and an additional compressed refrigerant stream, the method further comprising expanding said additional compressed refrigerant stream to further cool said stream and utilizing said further cooled refrigerant stream in step (b) to further cool down plus the indirect thermal exchange cooled natural gas supply stream. Preferably, step (f) comprises compressing, cooling and phase separating the expanded heated refrigerant stream to produce a compressed refrigerant vapor stream and a compressed refrigerant liquid stream, said vapor stream forming at least one refrigerant feed stream. which is cooled and at least partially liquefied in step (d), and at least a portion of said liquid stream forming the additional refrigerant stream which is expanded and then used in step (d) to further cool down the stream. natural gas supply cooled by indirect heat exchange.

In another embodiment, in step (d) the reheated anhydrous natural gas stream is cooled and liquefied to produce the liquefied natural gas product stream and an additional liquefied natural gas stream, said additional liquefied natural gas stream to be used in the production. step (b) to further cool the cooled natural gas feed stream. Preferably, in step (b), the cooled natural gas feed stream is further cooled by direct thermal exchange countercurrent with said additional liquefied natural gas stream.

As also described above, in the second aspect of the present invention, an equipment for drying and liquefying a natural gas stream is provided which comprises the above economizer heat exchanger, water removal systems contained in the natural gas feed. and natural gas feed cooling systems, main cryogenic heat exchanger, duct arrangement, and refrigerant expansion system. Said equipment is suitable for carrying out the method according to the first aspect. Accordingly, in a further preferred embodiment of the first aspect, the method according to the first aspect of the present invention is performed on equipment according to the second aspect.

In a preferred embodiment of the apparatus according to the second aspect, the main cryogenic heat exchanger is of the shell-tube type, and more preferably is a serpentine heat exchanger. The natural gas feed water removal system is preferably upstream of the natural gas feed cooling system such that the cooled natural gas containing water from the economizer heat exchanger is first dried in said water removal system, and the dried natural gas from said water removal system is then further cooled in said cooling system to produce anhydrous cooled natural gas which is then returned to the economizing heat exchanger. Alternatively, the order of said systems may be reversed such that the cooled natural gas containing water from the economizer heat exchanger is first further cooled in said cooling system and then dried in said water removal system. Again, however, the latter option is generally less preferred.

Optionally, where the natural gas supply water removal system is upstream of the natural gas supply cooling system, the anhydrous natural gas from the water removal system may be returned to the economizer heat exchanger and there again. cooled, before being sent to, and further cooled, the cooling system to produce anhydrous cooled natural gas which is then returned to the economizer heat exchanger.

In a preferred embodiment, the equipment further comprises a refrigerant compression system (which is preferably a refrigerant compression and cooling system, said cooling being, for example, provided by one or more interstages and / or after coolers), in continuous communication with the main cryogenic heat exchanger, to receive the expanded heated refrigerant stream from the hot end of the cryogenic heat exchanger, compress (and preferably cool) said refrigerant, and return at least one compressed refrigerant feed stream to the hot end of the cryogenic heat exchanger. The main cryogenic heat exchanger, refrigerant expansion system, and refrigerant compression system may form or be part of a closed loop refrigerant system, the contained and circulating refrigerant within said closed loop system comprising the said compressed and expanded refrigerant streams. As in the method according to the first aspect, said refrigerant may be, for example, a mixed refrigerant (comprising, for example, a mixture of hydrocarbons and / or perfluorocarbons), or a pure gaseous refrigerant such as, for example, nitrogen or argon (eg at 99 mol% or more).

In one embodiment, the natural gas feed cooling system is an indirect heat exchanger, and the equipment further comprises an additional expansion system, in continuous communication with the refrigerant compression and cooling system and the gas feed cooling system. natural gas, for receiving a compressed and cooled refrigerant stream from the refrigerant compression and cooling system and expanding said stream to further cool said stream, the natural gas feed cooling system utilizing said stream further cooled to further cool the cooled natural gas feed stream through indirect heat exchange. The refrigerant compression and cooling system may further comprise at least one phase separator for separating the compressed and cooled refrigerant in liquid and vapor phase form, said separator or separators being in continuous communication with the main cryogenic heat exchanger. and the additional expansion system, such that a compressed refrigerant vapor stream is fed to the hot end of the cryogenic heat exchanger and a compressed refrigerant liquid stream is fed to the additional expansion system.

In an alternative embodiment, the apparatus further comprises a duct arrangement for transferring an additional liquefied natural gas stream from the main cryogenic heat exchanger to the natural gas feed cooling system, said feed cooling system utilizing said stream. additional liquefied natural gas to further cool the cooled natural gas feed stream. For example, the natural gas feed cooling system may in this case be a system (such as, for example, a wash column), where the cooled natural gas feed stream is further cooled by direct heat exchange. countercurrent with said additional liquefied natural gas stream.

Accordingly, the present invention includes the following aspects, numbered 1 to 20: 1. A method for drying and liquefying a natural gas stream, the method comprising: (a) cooling a natural gas feed stream containing water , to produce a cooled natural gas stream; (b) removing water and further cooling the cooled natural gas feed stream to produce an anhydrous cooled natural gas stream; (c) heating the anhydrous cooled natural gas stream to produce a reheated anhydrous natural gas stream; (d) cooling and liquefying the reheated anhydrous natural gas stream and cooling at least one compressed refrigerant feed stream by indirect heat exchange countercurrent with an expanded cold refrigerant to produce at least one liquefied natural gas product stream. a cold compressed refrigerant stream and an expanded heated refrigerant stream; and (e) further expanding and cooling the compressed liquid refrigerant stream or streams to provide said expanded cold refrigerant; wherein the cooling of the natural gas feed stream in step (a) and the heating of the anhydrous cooled natural gas stream in step (c) is by indirect thermal exchange between said two streams. A method according to 1, wherein in step (c), the anhydrous cooled natural gas stream is heated to a temperature that is the same or varies in the range of 20 ° C relative to the temperature of at least one stream. refrigerant feed stream such that there is a temperature difference of 20 ° C or less between the reheated anhydrous natural gas stream and at least one compressed refrigerant feed stream at the beginning of step (d), 3. A method according to 2, wherein the temperature of the natural gas feed stream at the beginning of step (a) is also the same or varies within a range of 20 ° C relative to the temperatures of the reheated anhydrous natural gas stream and at least a compressed refrigerant feed stream at the beginning of step (d). 4. A method according to any one of 1 to 3, wherein step (d) is performed on a serpentine cryogenic heat exchanger. 5. A method according to any of 1 to 4, wherein in step (b) the cooled natural gas feed stream is first dried to remove water from it, then further cooled to produce the gas stream. natural cold anhydrous. A method according to any of 1 to 5, wherein the refrigerant in steps (d) and (e) is one or another of a mixed refrigerant, the cold refrigerant stream or streams compressed in step (d) are currents. liquid or mixed phase and the heated refrigerant stream expanded in step (d) is a mixed phase or vapor phase stream, or is a gaseous refrigerant that remains in substantially gaseous form during steps (d) and (e) . A method according to any one of 1 to 6, wherein the method further comprises: (f) compressing the expanded heated refrigerant stream to provide said at least one compressed refrigerant feed stream that is cooled in step (d). ). A method according to 7, wherein step (f) comprises compressing and cooling the expanded heated refrigerant stream to provide at least one compressed refrigerant feed stream, which is cooled in step (d), and an additional compressed refrigerant stream, the method also comprising expanding said additional compressed refrigerant stream to further cool said stream and using said further cooled additional refrigerant stream in step (b) to further cool the stream natural gas supply by means of indirect heat exchange. A method according to 8, wherein step (f) comprises compressing, cooling and phase separating the expanded heated refrigerant stream to produce a compressed refrigerant vapor stream and a compressed refrigerant liquid stream, said vapor stream. forming at least one compressed refrigerant feed stream which is cooled and at least sparingly liquefied in step (d), and at least a portion of said liquid stream forming the additional refrigerant stream which is expanded and then used in step (b). ) to further cool the cooled natural gas feed stream by indirect heat exchange. 10. A method according to any one of 1 to 7, wherein in step (d) the reheated anhydrous natural gas stream is cooled and liquefied to produce the liquefied natural gas product stream and an additional liquefied natural gas stream, at said additional liquefied natural gas stream being used in step (b) to further cool the cooled natural gas feed stream. 11. A method according to 10, wherein in step (b), the cooled natural gas feed stream is further cooled by direct heat exchange countercurrent with said additional liquefied natural gas stream. 12. An apparatus for drying and liquefying a natural gas stream, the equipment comprising: a heat exchanger and receiver for receiving a natural gas feed stream containing water. and an anhydrous chilled natural gas stream, and to cool the water-containing natural gas feed stream and heat the anhydrous chilled natural gas stream by indirect heat exchange therebetween to produce a chilled natural gas feed stream containing water and a reheated anhydrous natural gas stream; natural gas feed water removal systems and natural gas feed cooling systems, in continuous communication with the economizer heat exchanger and mutually, to receive the cooled natural gas feed stream containing water from the economizer heat exchanger drying and further cooling said stream and returning the resulting anhydrous cooled natural gas stream to the heat exchanger and quencher; a primary cryogenic heat exchanger for cooling and liquefying the reheated anhydrous natural gas stream and for cooling at least one indirect heat exchange compressed refrigerant feed stream countercurrent with an expanded cold refrigerant to produce a gas product stream liquefied natural, at least one cold compressed refrigerant stream, and one expanded heated refrigerant stream; a duct arrangement for transferring the reheated anhydrous natural gas stream from the economizer heat exchanger to the hot end of the main cryogenic heat exchanger, and for extracting the liquefied natural gas product stream from the cold end of the main cryogenic heat exchanger, and a refrigerant expansion system, in continuous communication with the main cryogenic heat exchanger, to receive at least one compressed cold refrigerant stream from the cold end of the cryogenic heat exchanger, further expanding and thereby cooling said cold refrigerant. , and return the expanded cold refrigerant to the cold end of the cryogenic heat exchanger. 13. An apparatus according to 12, wherein the main cryogenic heat exchanger is a serpentine heat exchanger. 14. Equipment according to 12 or 13, wherein the natural gas supply water removal system is upstream of the natural gas supply cooling system, such that the cooled natural gas containing water from the heat exchanger The economizer is first dried in said water removal system, and the anhydrous natural gas from said water removal system is then further cooled in said cooling system to produce anhydrous cooled natural gas which is then returned to the economizer heat exchanger. . An apparatus according to any one of 12 to 14, wherein the equipment additionally comprises: a refrigerant compression system, in continuous communication with the main cryogenic heat exchanger, for receiving the expanded heated refrigerant stream from the hot end. from the cryogenic heat exchanger, compress said refrigerant, and return at least one compressed refrigerant feed stream to the hot end of the cryogenic heat exchanger. 16. An apparatus according to 15, wherein the main cryogenic heat exchanger, refrigerant expansion system, and refrigerant compression system form or are part of a closed circuit refrigerant system, the contained and circulating refrigerant in the inside said closed loop system comprising said compressed and expanded refrigerant streams, said refrigerant being a mixed refrigerant or nitrogen or pure argon. 17. An apparatus according to 15 or 16, wherein the refrigerant compression system compresses and cools the expanded heated refrigerant, and the natural gas supply cooling system is an indirect heat exchanger, and wherein the apparatus comprises an additional expansion system further communicating with the refrigerant compression system and the natural gas supply cooling system for receiving a compressed and cooled refrigerant stream from the refrigerant compression system and expanding said stream to further cool said stream, the natural gas feed cooling system utilizing said still cooler stream to further cool the cooled natural gas feed stream by indirect heat exchange. 18. An apparatus according to 17, wherein the refrigerant compression system further comprises at least one phase separator for separating the liquid and vapor phase cooled compressed refrigerant, said phase separator or separators being in Communication continues with the main cryogenic heat exchanger and the additional expansion system such that a compressed refrigerant vapor stream is fed to the hot end of the cryogenic heat exchanger and a compressed refrigerant liquid stream is fed to the additional expansion system. 19. An apparatus according to any of 12 to 16, wherein the apparatus additionally comprises a duct arrangement for transferring an additional liquefied natural gas stream from the main cryogenic heat exchanger to the gas supply cooling system. natural, the feed cooling system using said additional liquefied natural gas stream to further cool the cooled natural gas feed stream. 20. An apparatus according to 19, wherein the natural gas feed cooling system is a flush column, wherein the cooled natural gas feed stream is further cooled by direct thermal exchange countercurrent with said stream. of additional liquefied natural gas.

By way of example only, certain specific embodiments of the invention will now be described with reference to the accompanying drawings.

Referring to Figure 1, an exemplary apparatus and method for drying and liquefying a natural gas stream according to an embodiment of the present invention is described. Water-containing natural gas feed stream 10 is first cooled in an economizer heat exchanger 11. The resulting water-containing cooled natural gas feed stream 12 is fed to the natural gas feed water removal system 13 for cooling drying. the stream, thereby producing the anhydrous natural gas stream 14. There may be a phase separator in stream 12 (not shown for simplicity) to remove any condensed water from said stream prior to its introduction into the water removal system. 13. The anhydrous natural gas stream 14 is re-cooled in the natural gas feed cooling system (feed chiller) 15 to produce the anhydrous cooled natural gas stream 16. The anhydrous cooled natural gas stream 16 is then reheated. on the economizer heat exchanger 11 by indirect countercurrent heat exchange with the water-containing natural gas feed stream 10 to produce the reheated anhydrous natural gas stream 17. Thus, in economizer heat exchanger 11 the water-containing natural gas feed stream 10 is cooled, and the gas stream natural cooled anhydrous 16 is heated by indirect thermal exchange between the two currents. The reheated anhydrous natural gas stream 17 is then sent to the master cryogenic heat exchanger (MCHE) 1 for further cooling and liquefaction. The economizer heat exchanger 11 may be any type of heat exchanger suitable for indirectly countercurrent thermal exchange between the water containing natural gas feed stream 10 and the anhydrous cooled natural gas feed stream 16; such as, for example, a shell-tube, fin-plate or printed circuit heat exchanger. The water removal system 13 may be any type of system suitable for drying / dewatering a water-containing natural gas stream. Various types of water removal systems are known in the art, including both absorption systems; such as, for example, glycol dehydrating system or adsorption system, such as, for example, molecular sieves and activated alumina. Feed chiller 15 utilizes a cooler than room temperature stream to further cool the natural gas stream. The feeder chiller 15 may be, for example, an indirect heat exchanger that uses as said current at a temperature colder than room temperature, a refrigerant stream from the same refrigerant loop that is also used to provide the work. MCHE 1, an example of such an arrangement being described in Figure 2, which will be described in more detail below. Alternatively (and preferably less), such a current at a temperature colder than room temperature may, for example, form part of a separate refrigerant circuit, such as where the feeder cooler 15 is a cooler assembly that uses its own circuitry. cooling separately. In either case, either case, power chiller 15 may be of any flow arrangement; such as in co-current or boiler, and type, such as shell, vane, or diffusion, to effect indirect thermal exchange between the natural gas stream and the stream at a temperature colder than ambient temperature.

In Figure 1, the water removal system 13 is located upstream of the feed chiller 15 such that the cooled natural gas supply stream containing water from the economizer heat exchanger 11 is dried by the water removal system. before it is cooled again in the power cooler. If the feed chiller 15 is downstream of the water removal system 13 (as shown in Figure 1), then the current that is colder than the ambient temperature used by the feed chiller 15 cools an already anhydrous gas stream. with the resulting cooled and anhydrous natural gas stream 16 thereafter being used in the economizer heat exchanger 11 to cool the water-containing natural gas feed stream 10 as required prior to water removal. This is particularly advantageous where the current at a temperature colder than the ambient temperature used by the feed chiller 15 is a mixed refrigerant or a pure gaseous refrigerant (such as nitrogen), as may be the case where the current is at a temperature colder than room temperature is a refrigerant stream from the same refrigerant loop that is also used to provide cooling work for MCHE 1 since cooling of the natural gas-containing water stream 10 The economizer heat exchanger 11 thus provides better control over the temperature of the natural gas-containing water supply stream 10 during cooling than if a mixed refrigerant or a pure gaseous refrigerant (such as nitrogen) were used to cool said cooling stream. natural gas feed containing 10 water directly. Therefore, cooling the water-containing natural gas feed stream 10 in this way can reduce the risk of hydrate formation in the water-containing natural gas feed stream during cooling before water removal.

In an alternative arrangement (not described) the feed chiller 15 may instead be placed upstream of the water removal system 13. However, where the feed chiller 15 uses a mixed refrigerant or a pure gaseous refrigerant there will also be a greater risk of hydrate formation in the water-containing natural gas feed stream during cooling (in said feed chiller 15) prior to the removal of water. If the power chiller 15 is instead a chiller assembly that uses a separate cooling circuit comprising, for example, a pure liquid refrigerant (or an azeotropic mixture) in a vapor compression cycle, then there should be no risk. hydrate formation, but the requirements for an additional cooling circuit (ie, the chiller assembly) will increase the capital investment and plant footprint costs.

Thus, positioning of the water removal system 13 upstream of the feed chiller 15 is generally preferred. The reheated anhydrous natural gas stream 17 exiting the economizer heat exchanger 11 is, as mentioned above, introduced into the hot end of the master cryogenic heat exchanger (MCHE) 1 being cooled and liquefied to produce the liquefied natural gas product stream 18. , which is extracted from the cold end of the heat exchanger 1. MCHE 1 is part of a cooling system 2, such as a closed loop cooling system (using, for example, a mixed refrigerant or pure gaseous refrigerant), to cool and liquefy the reheated anhydrous natural gas stream 17. In said system, one or more compressed refrigerant feed streams 3 are also cooled in MCHE 1 to produce one or more compressed cold refrigerant streams, which are then extracted from MCHE 1 and expanded to further cool the refrigerant, the expanded cold refrigerant is then returned to MCHE 1 to provide cooling work. cooling and liquefying the reheated anhydrous natural gas stream 17 and cooling the compressed cold refrigerant streams 3. The expanded heated refrigerant resulting from countercurrent thermal exchange with said reheated anhydrous natural gas stream 17 and compressed refrigerant streams 3 , is then taken from the compressed MCHE 1 and returned to the MCHE 1 as one or more compressed refrigerant feed streams 3.

In the example illustrated in Figure 1, two compressed refrigerant feed streams 3 are introduced into the hot end of MCHE 1, with one stream being cooled and extracted as a cold compressed refrigerant stream coming from the cold end of MCHE 1, and the other being cooled and extracted as a compressed cold refrigerant stream from an intermediate site of the MCHE 1. The compressed cold refrigerant stream withdrawn from the cold end is then expanded through regulator valve 38, whose adiabatic (isenthalic) expansion further cools the refrigerant, thus providing an expanded cold refrigerant that is returned to the cold end of MCHE 1 to provide cooling work. Likewise, the compressed cold refrigerant stream withdrawn from the intermediate site is expanded through the regulating valve 39, whose adiabatic (isenthalic) expansion further cools the refrigerant, thereby providing an expanded cold refrigerant that is returned to the cold end of MCHE 1 to provide the cooling job. The expanded cold refrigerant flows through the MCHE in the opposite direction relative to the reheated anhydrous natural gas stream 17 and compressed refrigerant feed streams 3, cooling said currents by indirect countercurrent heat exchange. Additional aspects of a representative cooling system 2, of which MCHE 1 forms a part, will be described in more detail below with reference to Figure 2.

Although in Figure 1, the regulating valves 38 and 39 are used to expand the cooled compressed refrigerant streams, in the present invention any type of device or system for expanding (i.e., reducing pressure) of said streams in order to reducing the temperature of said currents may be used. Thus, any device or system for adiabatically expanding said streams may be used, including centrifugal or reciprocating expanders that expand the refrigerant stream when producing external work (ie, where isentropic rather than isenthalic expansion of the refrigerant occurs). ). For example, where refrigerated compressed refrigerant streams are liquid streams, hydraulic turbines (dense fluid expanders) that expand the refrigerant isentropically may be used.

As described in Figure 1, MCHE 1 is a serpentine heat exchanger (or other shell-tube heat exchanger) containing two beams (the intermediate location from which one of the two compressed cold refrigerant streams is between the two beams), the reheated anhydrous natural gas stream 17 is, for example, cooled and optionally partially or fully liquefied in the first beam, and fully liquefied (if not already) and / or subcooled in the second beam. Likewise, however, other types of heat exchanger arrangements may be used. For example, where the MCHE is a serpentine (or other shell-type) heat exchanger, it may contain fewer beams, and the beams may be located on the same or different hulls (interconnected by suitable ducts in the case of the latter). The MCHE can also be any other type of cryogenic heat exchanger suitable for indirect countercurrent heat exchange. For example, the MCHE may be of the sheet metal type. However, the use of a serpentine type MCHE is generally preferred. The reheated anhydrous natural gas stream 17 and the compressed refrigerant feed stream or streams 3 preferably enter MCHE 1 at the same or similar temperature so as to minimize any relative temperature change between the streams entering the hot end of the stream. MCHE. Preferably, the reheated anhydrous natural gas stream 17 and the stream or streams 3 are in a mutual range of 10 ° C. Typically, the water-containing natural gas feed stream 10 is also at a temperature similar to those of streams 17 and 3, and thus is also within the range of 10 ° C from the temperatures of streams 17 and 3. The use of economizer heat exchanger 11, arranged and operating as described above, provides a number of advantages. Cooling has a number of advantages. Cooling the water-containing natural gas stream 10 in the economizer heat exchanger 11 results in a colder natural gas stream (stream 12) being fed to the water removal system 13 which would otherwise be the case if the natural gas stream containing water 10 were fed directly to the water removal system 13, which in turn allows for a more optimal removal of water from said natural gas stream. More specifically, cooling the water-containing natural gas stream prior to its introduction into the water removal system 13 may reduce the burden on the water removal system (as when cooling results in part of the water in the stream being condensed and removed prior to introduction). current in the water removal system) and / or increase the efficiency with which said system removes water (such as where the water removal system is an adsorption system, where the adsorbent may adsorb more water at lower temperatures). Cooling the water-containing natural gas stream prior to its introduction into the water removal system 13 also allows the temperature of the natural gas to be fed to the water removal system 13 to be controlled, thereby preventing operational difficulties as might otherwise. result from the natural gas temperature remaining above the temperature at which the water removal system 13 is designed to function (which may result in insufficient water removal from the natural gas in system 13, and consequently at unacceptable levels of water in the natural gas leaving that system).

In addition (and as shown in the following Examples), the inventors have found that by cooling the water-containing natural gas stream 10 in the economizer heat exchanger 11 against the anhydrous cooled natural gas feed stream 16 the overall process efficiency drying and liquefying can be improved. Use of the economizer heat exchanger 11 significantly reduces the required cooling work of the gas supply cooling system 15, since a significant proportion of the cooling work to cool the water-containing natural gas stream 10 prior to water removal in the water removal system 13 it is in this case supplied by the recovery of the cold from the cooled anhydrous natural gas (ie from stream 16) after the removal of the water. Although this also means that the natural gas stream (i.e. reheated natural gas stream 17) that is fed to the MCHE 1 is warmer than would otherwise be the case if the anhydrous cooled natural gas stream 16 occurred. Instead of being fed directly to the MCHE 1, the inventors have found that the total process power consumption is still reduced (particularly when the refrigerant used by the power cooling system 15 is a refrigerant stream from the same refrigerant loop). which is used to provide cooling work in MCHE 1). Where the power cooling system 15 is a chiller assembly that utilizes its own separate cooling circuit, the reduction in cooling work required from the power cooling system 15 may also allow a smaller chiller assembly to be used, thereby saving money. in investment costs.

In addition, heating the anhydrous cooled natural gas stream 16 in the economizer heat exchanger 11 to provide a reheated anhydrous natural gas (i.e. stream 17) at a temperature similar to that of the compressed refrigerant (i.e. streams 3) which also entering the hot end of the MCHE 1 allows any temperature mismatch between the currents entering the hot end of the MCHE 1 to be minimized. This in turn minimizes mechanical stresses that may otherwise occur (particularly in a coil-type heat exchanger) due to the thermal expansion differential of the components at the hot end of MCHE 1, and minimizes the potential for damage to MCHE 1. as a result. In certain types of MCHE, such as a welded aluminum serpentine type MCHE, a possible alternative arrangement (not in accordance with the present invention) to avoid such temperature mismatch may be to introduce the anhydrous natural gas stream into the MCHE at a higher temperature. than that of the compressed refrigerant streams and at a different location, further to the cold end of the exchanger, through a so-called side head instead of using an economizer heat exchanger to reheat the natural gas flow after having been dried. However, the use of side heads makes the manufacture of such MCHE more complicated and therefore this is also undesirable.

Referring now to Figure 2, an exemplary closed loop cooling system and process (indicated as system 2 in Figure 1) is described which can be employed in the system described in Figure 1. The closed loop system and process, in this case, contain and utilize a mixed refrigerant, and comprise, in addition to MCHE 1, regulating valves 38 and 39 and supply chiller 15 (all as described above), a refrigerant compression and cooling system (comprising refrigerant compressor 21, chiller 22 and phase separator 23) and additional regulating valves 28 and 29.

In this case, the two compressed refrigerant feed streams 3 which are introduced into the hot end of the MCHE 1 are a mixed refrigerant liquid stream 27 and a mixed refrigerant vapor stream 24. The vapor stream 24 is partially and fully liquefied and cooled. taken as a cold compressed (liquid or mixed phase) refrigerant stream from the cold end of MCHE 1, and the liquid stream is cooled and extracted as a cold compressed (liquid) refrigerant stream from the intermediate location of MCHE 1. then expanded adiabatically through the regulating valves 38 and 39, respectively, to provide expanded cold refrigerant streams (which may be at least partially vaporized as a result of said expansion) which are returned to the cold end and intermediate location, respectively, MCHE 1. Expanded cold mixed refrigerant flows through MCHE (ie through the hull side in the case of a coil-core or other type heat exchanger such as shell-tube) being heated (and, if still in the liquid or mixed phase, vaporized) by indirect heat exchange with natural gas stream 17 and compressed mixed refrigerant in streams 3. Expanded heated refrigerant (ie mixed refrigerant, obtained after it has undergone thermal exchange with natural gas in stream 17 and mixed refrigerant compressed in streams 3) is collected and extracted from the hot end of the heat exchanger as stream 20. Ά stream 20 is compressed in refrigerant compressor 21, cooled in refrigerant cooler 22, and separated as a liquid stream 25 ( MRL) and steam current 24 (MRV) in phase separator 23. Although in the illustrated embodiment refrigerant chiller 22 is described as a separate aftercooler from refrigerant compressor 21, compressor d and refrigerant 21 may be a multi-stage compressor and in this case refrigerant cooler 22 may comprise one or a series of intercoolers, additionally or in place of a post-cooler. Refrigerant cooler 22 may, for example, also comprise a pre-cooler for cooling current 20 prior to compression in refrigerant compressor 21. Steam stream 24 from phase separator 23 is then introduced into the cold end of MCHE 1 as said vapor stream from the compressed mixed refrigerant (which is cooled and partially or fully liquefied in MCHE 1 and extracted from its cold end). The liquid stream 25 from the phase separator 23 is divided into the liquid stream 27 (for the most part) and the liquid stream 26. The liquid stream 27 is introduced at the cold end of the MCHE 1 as the mentioned liquid stream of the compressed mixed refrigerant (ie. MCHE 1 and removed from an intermediate location). The mixed refrigerant liquid stream 26 expands through the regulating valve 28 to further cool (and in this case at least partially vaporize) the stream, and this re-cooled stream is used in the feed cooler 15 to provide cooling (through heat exchange). indirect cooling) for additional cooling of anhydrous natural gas stream 14 to produce anhydrous cooled natural gas stream 16. The resulting (and now fully vaporized) mixed mixed refrigerant stream leaving the supply chiller 15 may optionally be repressurized by the valve 29, and then be recombined in the suction of the refrigerant compressor 21 with the expanded heated refrigerant stream 20 drawn from the hot end of the MCHE 1.

Referring now to Figure 3, exemplary alternative equipment and a method of drying and liquefying a natural gas stream are described, which are modified from those described in Figure 1 in two main respects (either of such modifications to the md of Figure 1 can be done independently as well as in combination as shown in Figux'a 3). The first modification is that, in the apparatus and method illustrated in Figure 3, the anhydrous natural gas stream exiting the water removal system 13 from the natural gas feed is first returned to the economizer heat exchanger 11 for further cooling therein. be sent to the natural gas supply cooling system. Thus, as shown in Figure 3, the water-containing natural gas feed stream 10 is first cooled in an economizer heat exchanger 11 to produce the water-containing chilled natural gas feed stream 12 which is then extracted from the intermediate location. economizer heat exchanger 11. The chilled water-containing natural gas feed stream 12 is fed to the water removal system 13 to cool the said stream, thereby producing the anhydrous natural gas stream 14, which is then returned the intermediate location of the economizer heat exchanger 11 as current 30 and sent to the natural gas supply cooling system. The second modification is that, in the apparatus and method described in Figure 3, the natural gas feed cooling system utilizes a liquefied natural gas stream 34 obtained from MCHE 1 as the stream that is at a colder temperature than room temperature to cool the anhydrous natural gas stream 14/30. The natural gas cooling system may again be an indirect heat exchange system, but in this arrangement, it is preferred that said natural gas feed cooling system comprises a wash column 31 (or other system in which the gas stream be further cooled by direct countercurrent thermal exchange with liquefied natural gas, thereby also allowing mass transfer between countercurrent currents to occur). This allows the method to be applied to a situation where there is a need to remove heavy components from the natural gas feed prior to liquefaction, as the wash column 31 can remove these components in addition to natural gas cooling1.

More specifically, the anhydrous natural gas stream 30, which has already been cooled in the economizer heat exchanger 11, enters the wash column 31 (which in this example is a simple rectifier) and is directly countercurrented with a reflux current from the liquefied natural gas, which both cools down further and removes heavy components from stream 30. The bottom heavy product is removed as stream 32. The lighter top product, which constitutes anhydrous cooled natural gas stream 33, is then (as before), reheated in the economizer heat exchanger 11 and enters the hot end of the MCHE as a reheated anhydrous natural gas stream 17. The reheated anhydrous natural gas stream 17 is partially liquefied (for example, in the first coil beam of the MCHE) to produce a mixed phase natural gas stream 34 that is extracted from an intermediate site of the MCHE. This mixed phase stream 34 is then separated into a reflux drum 35 or other phase separator into a natural gas liquid stream 36 and a natural gas vapor stream 37. The liquid stream 36 is then returned to the flow column. wash 31 to provide reflux as described above. Steam stream 37 is returned to the intermediate site of the MCHE being cooled and liquefied (for example, in a second MCHE coil bundle) to produce the Liquefied Natural Gas (LNG) product stream 18.

In a possible modification of the system / equipment and method illustrated in Figure 3, the MCHE 1 may be, for example, a serpentine heat exchanger, which has three beams (instead of the two shown), one for pre-cooling the feed to generate reflux for the wash column, one for its liquefaction, and one for its subcooling.

It will be apparent to those of ordinary skill in the art that the methods and equipment illustrated in Figures 1 to 3 represent only some of the possible arrangements. Different mixed refrigerant (MR) arrangements according to the present invention may involve multiple phase separators, multiple compression stages, liquid pumps and so on. Any mixed refrigerant (MR) liquid stream may be used by the supply chiller 15 and returned fully or partially vaporized to different locations within the closed loop MR system. In a closed loop nitrogen recycling cycle, a portion of the gaseous refrigerant may also be used for the same purpose.

Example Referring to Figure 1, the water-containing natural gas feed stream 10 comprising 0.8% nitrogen, 88.2% methane, 6.9% ethane, 2.5% propane and hydrocarbon equilibrium heavy, saturated with water, and at a pressure of 7060 kPa (1024 psi) and a temperature of 48.1 ° C (118.6 ° F) is to be liquefied. The natural gas stream 12 leaves the economizer heat exchanger 11 at 22 ° C (71.60 F). The natural gas stream 14 leaves the anhydrous water removal system 13 at 26.8 ° F (26 ° C) (slightly warmer due to heat absorption). It is then cooled in the power chiller to 18.9 ° C (15 to 66.1 ° F). The cooling utility fluid used in the supply chiller 15 is a portion of the MR drawn from the main MR circuit. The MR enters the feed chiller 15 as a two-phase stream comprising 52.5% steam at -60.1 ° C (-76.2 ° F). It comes out as a fully vaporized stream at 13.9 ° C (57.0 ° F). It contains 1.7% nitrogen, 24.5% methane, 43.7% ethane, 13.7% propane and 17.1% isopentane. The anhydrous cooled natural gas stream 16 is reheated in the economizer heat exchanger 11 at 46.1 ° C (115.0 ° F). THE

reheated anhydrous natural gas stream 17 enters MCHE 1 and exits as a liquefied stream 18 at -155.5 ° C (-247.9 ° F).

Mixed refrigerant (MR) streams (in this case an MR steam stream and a liquid MR stream) 3, comprising nitrogen, methane, ethane, propane and isopentane, enter the hot end of the MCHE at 47 ° C (116.6 ° F), a temperature close to the temperature of the reheated anhydrous natural gas stream 17.

Table 1 Table 1 compares the present invention with. a conventional arrangement of existing art. Case 1 is a conventional SMR cycle that produces about 2 million tons per year of LNG, without feed heat exchanger and the feed chiller (necessarily) upstream of the water removal system. Case 2 is the configuration (as shown in Figure 1 of this application), described in the example above. As can be seen in the present invention, the feed chiller work (i.e. the required cooling work of the feed chiller 15) is reduced by about 73%, and the need for liquefying power (i.e. Total power required by operation of both MCHE 1 and power chiller 15) is reduced by 2.4%. The quantitative result shown in Table 1 is almost exactly the same if in the method according to the present invention the feeder chiller 15 is placed upstream rather than downstream of the water removal system 13. In this case the gas stream natural 12 leaves the economizer heat exchanger 11 at 28.8 ° C (83.9 ° F) being cooled in the power chiller to 22 ° C (15-71.6 ° F) before being fed to the heat removal system. 13, and the anhydrous cooled natural gas stream 16 again enters the economizer heat exchanger 11 at 26 ° C (78.8 ° F). The same savings in feed and liquefying chiller work (as compared to existing technique arrangements) are achieved. However, the configuration shown in figure 1 is best suited to avoid hydrate formation in the feed since the feed chiller 15 (and thus the mixed refrigerant from the refrigerant circuit that also provides MCHE cooling work) is in the configuration of Figure 1, not being used to cool the natural gas stream before the drying step occurs.

It will be appreciated that the invention is not limited to the details described above with reference to preferred embodiments, and that numerous modifications and variations may be made without departing from the spirit or scope of the invention as defined in the following claims. - CLAIMS -

Claims (20)

1. Method for drying and liquefying a natural gas stream, the method comprising: (a) cooling a natural gas feed stream containing water to produce a cooled natural gas stream; (b) removing water and further cooling the cooled natural gas feed stream to produce an anhydrous cooled natural gas stream; (c) heating the anhydrous cooled natural gas stream to produce a reheated anhydrous natural gas stream; (d) cooling and liquefying the reheated anhydrous natural gas stream and cooling at least one compressed refrigerant feed stream by indirect heat exchange countercurrent with an expanded cold refrigerant to produce at least one liquefied natural gas product stream. a cold compressed refrigerant stream and an expanded heated refrigerant stream; and (e) further expanding and cooling the compressed liquid refrigerant stream or streams to provide said expanded cold refrigerant; wherein the cooling of the natural gas feed stream in step (a) and the heating of the anhydrous cooled natural gas stream in step (c) is by indirect thermal exchange between said two streams. Method according to claim 1, characterized in that in step (c), the anhydrous cooled natural gas stream is heated to a temperature which is the same or varies in the range of 20 ° C with respect to the temperature of at least a compressed refrigerant feed stream such that a temperature difference of 20 ° C or less exists between the reheated anhydrous natural gas stream and at least one compressed refrigerant feed stream at the beginning of step (d). Method according to claim 2, characterized in that the temperature of the natural gas feed stream at the beginning of step (a) is also the same or varies within a range of 20 ° C relative to the temperatures of the reheated anhydrous natural gas stream. and at least one compressed refrigerant feed stream at the beginning of step (d). Method according to any one of claims 1 to 3, characterized in that step (d) is performed in a serpentine-type cryogenic heat exchanger. Method according to any one of claims 1 to 4, characterized in that in step (b) the cooled natural gas feed stream is first dried to remove water therefrom and further cooled to produce the stream. of anhydrous cooled natural gas. Method according to any one of claims 1 to 5, characterized in that the refrigerant in steps (d) and (e) is either of a mixed refrigerant, the cold refrigerant stream or streams compressed in step (d). are liquid or mixed phase streams and the expanded heated refrigerant stream in step (d) is a mixed phase or vapor phase stream, or is a gaseous refrigerant that remains in substantially gaseous form during steps (d) and ( and). A method according to any one of claims 1 to 6, characterized in that the method further comprises: (f) compressing the expanded heated refrigerant stream to provide said at least one compressed refrigerant feed stream which is cooled in step (d). Method according to claim 7, characterized in that step (f) comprises compressing and cooling the expanded heated refrigerant stream to provide at least one compressed refrigerant feed stream which is cooled in step (d). and an additional compressed refrigerant stream, the method further comprising expanding said further compressed refrigerant stream to further cool said stream and using said further cooled additional refrigerant stream in step (b) to further cool the stream. natural gas supply stream cooled by indirect heat exchange. Method according to claim 8, characterized in that step (f) comprises compression, cooling and phase separation of the expanded heated refrigerant stream to produce a compressed refrigerant vapor stream and a compressed refrigerant liquid stream, said vapor stream forming at least one compressed refrigerant feed stream which is cooled and at least partially liquefied in step (d), and at least a portion of said liquid stream forming the additional refrigerant stream which is expanded and then used in step (b) to further cool the cooled natural gas feed stream by indirect heat exchange. Method according to any one of claims 1 to 7, characterized in that in step (d) the reheated anhydrous natural gas stream is cooled and liquefied to produce the liquefied natural gas product stream and an additional liquefied natural gas stream. , said additional liquefied natural gas stream being used in step (b) to further cool the cooled natural gas feed stream. Method according to Claim 10, characterized in that in step (b), the cooled natural gas feed stream is further cooled by direct heat exchange countercurrent with said additional liquefied natural gas stream. 12. EQUIPMENT FOR DRYING AND LIQUIDATING A NATURAL GAS CURRENT, the equipment comprises: an economizer heat exchanger for receiving a natural gas feed stream containing water and an anhydrous cooled natural gas stream and for cooling the feed stream natural gas containing water and heating the anhydrous cooled natural gas stream by indirect thermal exchange between them to produce a chilled natural gas feed stream and a reheated anhydrous natural gas stream; natural gas feed water removal systems and natural gas feed cooling systems, in continuous communication with the economizer heat exchanger and mutually, to receive the cooled natural gas feed stream containing water from the economizer heat exchanger drying and further cooling said stream, and returning the resulting anhydrous cooled natural gas stream to the economizer heat exchanger; a primary cryogenic heat exchanger for cooling and liquefying the reheated anhydrous natural gas stream and for cooling at least one indirect heat exchange compressed refrigerant feed stream countercurrent with an expanded cold refrigerant to produce a gas product stream liquefied natural, at least one cold compressed refrigerant stream, and one expanded heated refrigerant stream; a duct arrangement for transferring the reheated anhydrous natural gas stream from the economizer heat exchanger to the hot end of the main cryogenic heat exchanger, and for extracting the liquefied natural gas product stream from the cold end of the main cryogenic heat exchanger, and a refrigerant expansion system, in continuous communication with the main cryogenic heat exchanger, to receive at least one compressed cold refrigerant stream from the cold end of the cryogenic heat exchanger, further expanding and thereby cooling said cold refrigerant. , and return the expanded cold refrigerant to the cold end of the cryogenic heat exchanger. Equipment according to Claim 12, characterized in that the main cryogenic heat exchanger is a serpentine heat exchanger. Equipment according to claim 12 or 13, characterized in that the natural gas supply water removal system is upstream of the natural gas supply cooling system such that the cooled natural gas containing water from the exchanger The heat-saving heat is first dried in said water removal system, and the anhydrous natural gas from said water removal system is then further cooled in said cooling system to produce anhydrous cooled natural gas which is then returned to the heat exchanger. heat saving. Equipment according to any one of claims 12 to 14, characterized in that the equipment further comprises: a refrigerant compression system, in continuous communication with the main cryogenic heat exchanger, for receiving the expanded heated refrigerant stream from the hot end of the cryogenic heat exchanger, compress said refrigerant, and return at least one compressed refrigerant feed stream to the hot end of the cryogenic heat exchanger. Equipment according to claim 15, characterized in that the main cryogenic heat exchanger, the refrigerant expansion system, and the refrigerant compression system form or are part of a closed circuit refrigerant system, the contained refrigerant and circulating within said closed loop system comprising said compressed and expanded refrigerant streams, said refrigerant being a mixed refrigerant or nitrogen or pure argon. Equipment according to claim 15 or 16, characterized in that the refrigerant compression system compresses and cools the expanded heated refrigerant, and the natural gas supply cooling system is an indirect heat exchanger, and where the equipment further comprising an additional expansion system, in continuous communication with the refrigerant compression system and the natural gas supply cooling system, for receiving a cooled and compressed refrigerant stream from the refrigerant compression system and expanding said refrigerant compression system. stream to further cool said stream, the natural gas feed cooling system utilizing said still cooler stream to further cool the cooled natural gas feed stream by indirect heat exchange. Apparatus according to claim 17, characterized in that the refrigerant compression system further comprises at least one phase separator for separating the liquid and vapor phase cooled refrigerant, said phase separator or separators being in communication. continues with the main cryogenic heat exchanger and the additional expansion system such that a compressed refrigerant vapor stream is fed to the hot end of the cryogenic heat exchanger and a compressed refrigerant liquid stream is fed to the added expansion system 1. Equipment according to any one of claims 12 to 16, characterized in that the equipment additionally comprises a duct arrangement for transferring an additional liquefied natural gas stream from the main cryogenic heat exchanger to the feed cooling system. natural gas, the feed cooling system using said additional liquefied natural gas stream to further cool the cooled natural gas feed stream. Equipment according to claim 19, characterized in that the natural gas feed cooling system is a flush column, wherein the cooled natural gas feed stream is further cooled by direct thermal exchange countercurrent with the said additional liquefied natural gas stream.