CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority from U.S. Provisional Application No. 63/337,417, filed May 2, 2022, titled “NATURAL GAS LIQUEFACTION USING LIQUID AIR,” the entire contents of which are hereby incorporated by reference herein.

BACKGROUND

1. Field of the Invention

[0002] One or more embodiments relate to systems and methods for producing and using cryogenic liquids such as liquid air and/or liquid natural gas.

2. Description of Related Art

[0003] Cryogenic liquids typically have a boiling point below -130° F (-90 ⁰ C), and include, among others, liquid hy drogen (H2), liquid nitrogen (N2), liquid oxygen (O2), liquid natural gas (CH4), liquid propane, and liquid air (“LA”) which is a combination of mostly liquid nitrogen and liquid oxygen.

[0004] Conventional cryogenic liquefaction systems are configured to produce cryogenic liquids continuously at the average rate of demand for such cryogenic liquids.

[0005] Conventional liquid air energy storage (“LAES”) systems use energy (e.g., electricity) to produce LA, store that energy in LA vessels, and then use the stored LA to generate energy (e.g., via electricity into an electric grid). See Vecci et al., Liquid Air Energy Storage (LAES): A Review On Technology State-Of-The-Art, Integration Pathways And Future Perspectives, Advances in Applied Energy, ISSN: 2666-7924, Vol: 3, Page: 100047 (2021).

SUMMARY

[0006] One or more non-limiting embodiments provide an LAES system and method that is less expensive and/or more efficient (e.g., in terms of efficiency and/or cost per unit of energy storage).

[0007] One or more non-limiting embodiments provides a cryogenic system with a cryogenic storage vessel that that is oversized relative to an average rate of consumption of the cryogenic liquid from the vessel. One or more non-limiting embodiments provides a cryogenic system with a liquefaction system that is oversized (in terms of cryogenic liquid generation rate) relative to an average rate of consumption of the cryogenic liquid.

[0008] According to one or more embodiments, the oversized liquefaction system is operated discontinuously, for example only during hours when energy for powering the liquefaction system is relatively cheaper and/or more plentiful than during peak hours.

[0009] According to one or more embodiments, a cryogenic liquid, for example liquid air, produced by the oversized liquefaction system or another source is used to cool and liquefy another gas, for example natural gas, in a liquefaction plant.

[0010] One or more embodiments provide a method comprising: cryogenically liquifying a gas and providing a resulting cryogenic liquid within a cryogenic liquid storage vessel at an average rate X for a time period L, wherein the vessel has a cryogenic liquid storage capacity of V liters, and L is a discontinuous portion of a time period T. According to various embodiments, L > 1.25 T, 1.5 T, and/or 2 T. According to various embodiments, T > 48. T and L are measured in hours, and X is measured in liters of cryogenic liquid provided within the vessel per hour. According to various embodiments, an average cost of energy consumed by the liquefaction system during the time period L is lower than an average cost of energy over the time period T. According to various embodiments, V > (X x L).

[0011] According to one or more of these embodiments, the method further includes, over the time period T, using C liters of cryogenic liquid from the vessel.

[0012] According to one or more of these embodiments, using C liters of cryogenic liquid from the vessel comprises using C liters of cryogenic liquid from the vessel in a power generator to generate power from the cryogenic liquid.

[0013] According to one or more of these embodiments, using C liters of cryogenic liquid from the vessel comprises transferring C liters of cryogenic liquid from the vessel into one or more additional vessels.

[0014] According to one or more of these embodiments, V > C.

[0015] According to one or more of these embodiments, X > 2C/T.

[0016] According to one or more of these embodiments, throughout the time period T, an instantaneous rate U of said using of said cry ogenic liquid from the vessel is always less than X, 1//2 X, and/or */ ₄ X.

[0017] According to one or more of these embodiments, the gas comprises natural gas, and the cryogenic liquid comprises liquified natural gas. [0018] One or more embodiments provide a system that includes: a cry ogenic liquid storage vessel shaped and configured to store a cryogenic liquid; and a cryogenic liquefaction system operatively connected to the vessel and configured to cryogenically liquify a gas and provide a resulting cryogenic liquid into the vessel. According to one or more of these embodiments, the liquefaction system has a liquefaction rate that is at least 1.25, 1.5, and/or 2 times larger than the average consumption rate of the cryogenic liquid from the vessel.

[0019] According to one or more of these embodiments, a storage capacity of the vessel at least 1.25, 1.5, and/or 2 times larger than a volume of cryogenic liquid used over a 24 hour period at the average consumption rate.

[0020] According to one or more of these embodiments, a storage capacity of the vessel is at least as large as an amount of cryogenic liquid producible by the liquefaction system in 48 hours.

[0021] According to one or more of these embodiments, the gas is air and the cryogenic liquid is liquid air.

[0022] According to one or more of these embodiments, the liquefaction system is powered by electricity.

[0023] According to one or more of these embodiments, the system includes a power generator (e.g., an electric generator) operatively connected to the vessel and configured to use cryogenic liquid from the vessel to generate power.

[0024] According to one or more of these embodiments, a cryogenic liquid consumption rate of the power generator is less than %, A, 1/3, and/or ^l A of the liquefaction rate of the liquefaction system.

[0025] According to one or more of these embodiments, the system includes a cryogenic separator operatively connected to or integrated into the vessel, the separator being shaped and configured to separate liquid oxygen from a remainder of the cryogenic liquid.

[0026] According to one or more of these embodiments, the system includes a cryogenic separator operatively connected to or integrated into the vessel, the separator being shaped and configured to separate liquid nitrogen from a remainder of the cryogenic liquid.

[0027] One or more embodiments provide a natural gas liquefaction method comprising: transferring liquid air into a cold side of a heat exchanger; transferring gaseous natural gas into a hot side of the heat exchanger; transferring heat from the natural gas in the hot side to the air in the cold side, resulting in the gasification of air in the cold side and liquefaction of natural gas in the hot side; transferring gaseous air out of the cold side; and transferring liquid natural gas out of the hot side.

[0028] According to one or more of these embodiments, the heat exchanger comprises a first heat exchanger, the method further comprises cooling said natural gas in a hot side of a second heat exchanger before said transferring of said gaseous natural gas into the hot side of the first heat exchanger, and the method further comprises transferring air from the cold side of the first heat exchanger to the cold side of the second heat exchanger, resulting in the transfer of heat from said natural gas to said air in the second heat exchanger.

[0029] According to one or more of these embodiments, the method also includes cooling said natural gas between when said natural gas is transferred out of the hot side of the second heat exchanger and when said natural gas is transferred into the hot side of the first heat exchanger.

[0030] According to one or more of these embodiments, said cooling of said natural gas between the first and second heat exchangers comprises expansion cooling said natural gas.

[0031] According to one or more of these embodiments, said cooling of said natural gas between the first and second heat exchangers comprises transferring heat from said natural gas to another fluid via a heat exchanger or active refrigeration unit.

[0032] One or more embodiments provides a natural gas liquefaction system comprising: a heat exchanger having a hot side with an inlet and outlet, and a cold side with an inlet and outlet; a source of liquid air connected to the inlet of the cold side to provide liquid air to the cold side; and a source of gaseous natural gas connected to the inlet of the hot side to provide gaseous natural gas to the hot side. According to one or more of these embodiments, the system is configured to transfer heat from the natural gas in the hot side to the air in the cold side, resulting in the gasification of air in the cold side and liquefaction of natural gas in the hot side.

[0033] According to one or more of these embodiments, the heat exchanger comprises a first heat exchanger, the system further comprises a second heat exchanger having a hot side with an inlet and outlet, and a cold side with an inlet and outlet, the inlet of the hot side of the second heat exchanger is connected to the source of gaseous natural gas, the outlet of the hot side of the second heat exchanger is connected to the inlet of the hot side of the first heat exchanger via a natural gas passageway such that the system is configured to provide natural gas from the source of gaseous natural gas to the hot side of the first heat exchanger by way of the hot side of the second heat exchanger, and the outlet of the cold side of the first heat exchanger is connected to the inlet of the cold side of the second heat exchanger, such that the system is configured to provide air from the source of liquid air to the second heat exchanger by way of the cold side of the first heat exchanger.

[0034] According to one or more of these embodiments, the system includes an expander disposed in the natural gas passageway between the hot sides of the first and second heat exchangers, the expander being configured to cool and expand natural gas received by the expander from the second heat exchanger.

[0035] According to one or more of these embodiments, the system includes a cooling system disposed in the natural gas passageway between the hot sides of the first and second heat exchangers, the cooling system being configured to transfer heat from the natural gas received by the cooling system to another fluid.

[0036] One or more embodiments provide a natural gas liquefaction method comprising: transferring heat from argon to liquid air in a first heat exchanger to cool the argon; transferring the argon from the first heat exchanger to a second heat exchanger; and transferring heat from gaseous natural gas to the argon in the second heat exchanger, which causes gaseous natural gas in the second heat exchanger to liquefy.

[0037] One or more of these and/or other aspects of various embodiments of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. In one or more embodiments, the structural components illustrated herein are drawn to scale, but in other embodiments the drawings are not to scale. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. In addition, it should be appreciated that structural features shown or described in any one embodiment herein can be used in other embodiments as well. As used in the specification and in the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0038] All closed-ended (e.g., between A and B) and open-ended (greater than C) ranges of values disclosed herein explicitly include all ranges that fall within or nest within such ranges. For example, a disclosed range of 1-10 is understood as also disclosing, among other ranges, 2- 10, 1-9, 3-9, etc. Similarly, where multiple parameters (e.g., parameter C, parameter D) are separately disclosed as having ranges, the embodiments disclosed herein explicitly include embodiments that combine any value within the disclosed range of one parameter (e.g., parameter C) with any value within the disclosed range of any other parameter (e.g., parameter D).

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] For a better understanding of various embodiments as well as other objects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0040] FIG. 1 is a diagram of a liquefaction system according to one or more embodiments; and

[0041] FIG. 2 is a diagram of a liquefaction system that uses one cryogenic liquid (e.g., LA) to liquefy another fluid (e.g., gaseous natural gas).

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0042] One or more embodiments provide a system 10 and method for the cost-efficient liquefaction of gases such as air or natural gas. As shown in FIG. 1, the system 10 includes a cryogenic liquid storage vessel 20 shaped and configured to store a cryogenic liquid (e.g., LA, LNG), and a cryogenic liquefaction system 30 operatively connected to the vessel 20 and configured to cryogenically liquify a gas from a gas source 40 and provide a resulting cryogenic liquid into the vessel 20. The cryogenic liquid stored in the vessel 20 can then be used by a destination/ consumer 50 of the cryogenic liquid. As shown in FIG. 1, the source 40, liquefaction system 30, vessel 20, and destination 50 are interconnected by suitable passageways for transferring the working fluid (gas and/or liquid) between the components of the system 10. [0043] According to various embodiments, the source 40 is the ambient environment, such that the gas being liquefied is air. According to alternative embodiments, the source 40 comprises a source of gaseous natural gas.

[0044] According to various embodiments, the liquefaction system 30 comprises any suitable system, as is known in the art, for liquefying the working gas (e.g., air, natural gas). According to various embodiments, the liquefaction system 30 is oversized, relative to the average consumption rate by the destination/consumer 50. According to various embodiments, the liquefaction system 30 has a liquefaction rate that is at least 1.25, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, and/or 10 times larger than the average consumption rate of the destination/consumer 50. According to various embodiments, the system 30 is powered by electricity. [0045] According to various embodiments, the vessel 20 is similarly oversized relative to the average consumption rate by the destination/ consumer 50. According to various embodiments, the vessel 20 has a volumetric storage capacity that is that is at least 1.25, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 30, and/or 40 times larger than a volume of cryogenic liquid used by the destination/consumer 50 over a certain time period at the average consumption rate of the destination/consumer 50. According to various embodiments, the time period is 8, 12, 24, 36, 48, 60, 72, 96, 120, and/or 168 hours.

[0046] According to vanous embodiments, the volumetric storage capacity of the vessel 20 is at least as large as an amount of cryogenic liquid producible by the liquefaction system 30 in 8, 12, 24, 36, 48, 60, 72, 96, 120 and/or 168 hours.

[0047] According to various embodiments, the destination/consumer 50 comprises a power generator configured to use cryogenic liquid from the vessel 20 to generate power (e.g., mechanical power, electricity, etc.). According to various embodiments in which the working fluid of the system 10 is air, the power generator uses liquid air to generate electricity, as is known in the art. According to various embodiments, a maximum liquefaction rate of the system 30 is at least 1.5, 2, 3, 4, 5, 6, 7, 8, 9, and/or 10 times larger than a maximum instantaneous liquid consumption rate of the destination/consumer 50.

[0048] According to various alternative embodiments, the working fluid received from the source 40 is air, and the system 10 further comprises a cryogenic separator operatively connected to or integrated into the vessel 20. The separator is shaped and configured to separate liquid oxygen from a remainder of the cryogenic liquid in the vessel 20. The system 10 then delivers separated cryogenic liquids to separate destinations/consumers 50 (e.g., delivering liquid oxygen to a first destination/consumer 50, and delivering liquid nitrogen to a second destination/consumer 50).

[0049] According to various embodiments, the destination/consumer 50 comprises one or more additional vessels 50 (e.g., vehicle-mounted vessel(s) 50 for transporting the liquid (e.g., liquid air, liquid nitrogen, liquid oxygen, liquid natural gas) to a distant destination/consumer 50).

[0050] Liquefying gas via the system 30 is an energy intensive process. According to various embodiments, by oversizing the liquefaction system 30 and vessel 20 relative to average demand by the destination/consumer 50, the liquefaction system 30 can operate discontinuously so as to operate when energy costs are lower (e.g., during off peak electricity demand hours). [0051] According to various embodiments, the system 10 can be used as follows to take advantage of abundant and/or less expensive energy during off-peak hours. The method of use includes cryogenically liquifying a gas via the system 30 and providing a resulting cryogenic liquid to the cryogenic liquid storage vessel 20 at an average rate X for a time period L. The vessel 20 has a cryogenic liquid storage capacity of V liters. Time period L is a discontinuous portion of a time period T. Time period T is at least 1.5, 2, 3, 4, 5, 6, 7, 8, 9, and/or 10 times larger than time period L. Time period T is at least 24, 48, 72, 96, 120, 144, and/or 168 hours. The rate X is measured in liters of cryogenic liquid provided by the system 30 to the vessel 20 per hour. According to various embodiments, an average cost of energy consumed by the liquefaction system 30 during the time period L is lower than an average cost of energy over the time period T. According to various embodiments, the storage capacity V of the vessel 20 is greater than the rate X multiplied by the time period L.

[0052] According to various embodiments, over the time period T, the destination/ consumer 50 consumes C liters of liquid from the vessel 20. According to various embodiments, V is larger than C. According to various embodiments, X is at least 1.5, 2, 3, 4, 5, 6, 7, 8, 9, and/or 10 times C/T.

[0053] According to vanous embodiments, throughout the time period T, X is always at least 1.5, 2, 3, 4, 5, 6, 7, 8, 9, and/or 10 times larger than an instantaneous rate U of consumption/use of said cryogenic liquid by the destination/consumer 50.

[0054] According to various embodiments, the system 10 liquefies air, and the destination/consumer 50 uses the liquid air to liquefy natural gas. For example, as shown in FIG. 2, the destination/consumer 50 may comprise a natural gas liquefaction plant 100, which consumes liquid air to help liquefy the natural gas.

[0055] As shown in FIG. 2, gaseous natural gas enters the plant 100 from a source 110 of gaseous natural gas (e.g., wellhead(s), vessel(s), pipe line(s)). The natural gas passes sequentially via suitable passageways/pipes/hoses through a mixer 120, a compressor 130, a refrigeration system 140, a heat exchanger 150, a refrigeration system 160, an expander 170, a heat exchanger 180, a Joule-Thompson valve 190, and into a LNG storage vessel 200. A passageway connects the vessel 200 to a downstream destination/consumer 210 of LNG. According to various embodiments, one or more of these components may be omitted without deviating from the scope of the present invention. For example, the interconnected heat exchangers 160, 220 and/or one of the heat exchangers 150 or 180 may be omitted according to various embodiments (e g., smaller scale plants 100 where the efficiency added by additional heat exchangers may not be warranted). According to various embodiments, the heat exchanger 150 may be disposed between the heat exchanger 160 and expander 170 along the pathway of the natural gas to be liquefied.

[0056] Natural gas that evaporates within the vessel 200 (or reached the vessel 200 in gaseous form) may be recycled by being transferred sequentially from the vessel 200 through a heat exchanger 220, a compressor 230, a refrigeration system 240, a passageway or valve 250, and back to the mixer 250, where the recycled natural gas and natural gas from the source 110 are mixed together for liquefaction in the plant 100.

[0057] As shown in FIG. 2, liquid air from a source 300 of liquid air (e.g., the system 10) passes, via suitable passageways/pipes/holes sequentially through the heat exchanger 180, the heat exchanger 150, and into a destination 310 (e.g., the ambient environment).

[0058] According to various embodiments, the expander 170 and compressor 230 are mechanically or otherwise linked so that energy generated by the expander 170 is used to drive the compressor 220.

[0059] According to various embodiments, the refrigeration systems 140, 160, 240 may comprise any suitable type of active or passive refrigeration system suitable for extracting heat from the natural gas at the temperature at which the natural gas enter such refrigeration system 140, 160, 240 (e.g., an active refrigeration system using an intermediate refrigerant, a heat exchanger, a passive system utilizing heat transfer fins). According to various embodiments, the refrigeration systems 140, 160, 240 transfer heat from the natural gas into the ambient environment (e.g., ambient air, an ambient body of water, etc.).

[0060] According to various embodiments, the heat exchanger 140 provides heat for a useful purpose (e.g., ORC, hot water recovery, low grade steam) instead of dumping the heat into the ambient environment.

[0061] According to various embodiments, the refrigeration system 160 is operatively connected to the heat exchanger 220 (e.g., via an intermediate working fluid/refrigerant) such that the refrigeration system 160 and heat exchanger 220 work together to transfer heat from the natural gas passing through the heat exchanger 150 to the natural gas passing through the heat exchanger 220. According to various embodiments, the refrigeration systems 160 and 220 together define a single, direct heat exchanger for transferring heat from the natural gas being liquefied to the gaseous natural gas being recycled.

[0062] Hereinafter, operation of the natural gas liquefaction plant 100 is described with reference to FIG. 2. According to various non-limiting embodiments, natural gas is transferred from the source 110 to the mixer 120 at a temperature of 80° F, a pressure of 594 psia, a vapor mole fraction of 100%, a molecular weight of 16.298 lb./lbmol., and a standard vapor volumetric flow rate of 200 MMSCFD. After mixing with recycled natural gas in the mixer 120, the combined natural gas stream enters the compressor 130 at a temperature of 80.9° F, a pressure of 594.3 psia, a vapor mole fraction of 100%, a molecular weight of 16.297 lb./lbmol., and a standard vapor volumetric flow rate of 220.24 MMSCFD. The natural gas is then compressed in the compressor 130, leaves the compressor 130, and enters the heat exchanger 140 at a temperature of 346° F, a pressure of 2750 psia, and a vapor mole fraction of 100%. The natural gas leaves the heat exchanger 140 and enters a hot side of the heat exchanger 150 at a temperature of 90° F, a pressure of 2745 psia, and a vapor mole fraction of 100%. The natural gas leaves the hot side of the heat exchanger 150 and enters the hot side of the heat exchanger 160 at a temperature of -26° F, a pressure of 2740 psia, and a vapor mole fraction of 100%. The natural gas leaves the hot side of the heat exchanger 160 and enters the expander 170 at a temperature of -35.5° F, a pressure of 2735 psia, and a vapor mole fraction of 100%. The natural gas leaves the expander 170 and enters the hot side of the heat exchanger 180 at a temperature of -206.56° F, a pressure of 110 psia, and a vapor mole fraction of 58.1% (i.e., a mixture of gas and liquid). The natural gas then leaves the hot side of the heat exchanger 180 and arrives at the valve 190 at a temperature of -230° F, a pressure of 105 psia, and a vapor mole fraction of 0% (i.e., mostly or entirely liquid). The natural gas leaves the valve 190 and enters the vessel at a temperature of -251.78° F, a pressure of 20 psia, and a vapor mole fraction of 8.75% (mostly liquid).

[0063] According to various embodiments, LNG is provided from the vessel 100 to the destination 210 at a temperature of -252.97° F, a pressure of 19 psia, a vapor mole fraction of 0%, a molecular weight of 16.298 lb./lbmol., a standard vapor volumetric flow rate of 200 MMSCFD, and a mass flow rate of 1.4221 e+06 TP A.

[0064] According to various embodiments, the vessel 200 acts as a separation vessel 200 for separating gaseous natural gas from liquid natural gas (e.g., gas that flashed as a result of passing through the JT valve 190). The gaseous natural gas in the vessel 200 leaves the vessel 200 and enters the heat exchanger 220 at a temperature of -252.97° F, a pressure of 19 psia, a vapor mole fraction of 100%, and a standard vapor volumetric flow rate of 20.239 MMSCFD. The natural gas then leaves the heat exchanger 220 and enters the compressor 230 at a temperature of -48.265° F, a pressure of 14 psia, and a vapor mole fraction of 100%. The natural gas leaves the compressor 230 and enters the heat exchanger 240 at a temperature of 737.38° F, a pressure of 599.3 psia, and a vapor mole fraction of 100%. According to various embodiments, the natural gas may leave the compressor 230 at lower temperatures (which may result in a more efficient process), for example as a result of using a multi-stage intercooled compressor 230. The natural gas then leaves the heat exchanger 240 and enters the recycler 250 and mixer 120 at a temperature of 90° F, a pressure of 594.3 psia, and a vapor mole fraction of 100%.

[0065] According to various embodiments, liquid air leaves the source 300 and enters the cold side of the heat exchanger 180 at a temperature of -308.8° F, a pressure of 25 psia, a vapor mole fraction of 0% (e.g., mostly or entirely liquid), a molecular weight of 28.85 lb./lbmol., and a mass flow rate of 2.7974e+05 kg/h. Air leaves the cold side of the heat exchanger 180 and enters the cold side of the heat exchanger 150 at a temperature of -307.74° F, a pressure of 20 psia, and a vapor mole fraction of 100% (mostly or entirely gaseous). As a result, according to various embodiments, liquid air evaporates in the heat exchanger 180 and natural gas condenses in the heat exchanger 180. This natural gas liquefaction process in the heat exchanger 180 works well because the boiling point of liquid air at the pressure on the cold side of the heat exchanger 180 is lower than the boiling point of natural gas at the pressure on the hot side of the heat exchanger 180. Evaporation of the air is therefore able to sufficiently cool the natural gas so as to condense the natural gas into LNG.

[0066] The air leaves the cold side of the heat exchanger 150 and enters the destination

310 at a temperature of -33.364° F, a pressure of 15 psia, and a vapor mole fraction of 100%. [0067] In the illustrated plant 100, liquid air is used to cool the gas being liquefied. However, according to various alternative embodiments, other cryogenic liquids can be used instead (e.g., liquid argon) to cool the gas being liquefied. Similarly, in the illustrated system 100, the gas being liquefied is natural gas. However, according to various alternative embodiments, other gases can be liquefied using the system 100. According to various embodiments, the boiling point of the cryogenic liquid being used by the system 100 to cool the gas being liquefied has a boiling point lower than the boiling point of the gas being liquefied by the system 100 so that the heat exchanger 300 can take advantage of the difference in boiling points to help liquefy the gas.

[0068] In the plant 100, liquid air from the source 300 is used directly to liquefy natural gas via heat exchangers 180, 150, with air and natural gas passing through separated hot and cold sides of the heat exchangers 180, 150. However, in order to avoid having air and natural gas being disposed in the same heat exchanger (and potentially intermix if there is a leak in the heat exchanger), an intermediate inert fluid such as argon or nitrogen can be added. According to such an alternative embodiment, liquid air is used to cool/liquefy the intermediate fluid via a heat exchanger (not shown), and then that intermediate liquid from the source 300 is passed through the heat exchangers 180, 150 instead of liquid air, to cool and liquefy the natural gas. The intermediate fluid from the destination 310 can then be recycled by reliquefying it using liquid air and transferred back to the source 300 of liquid intermediate fluid. As a result, liquid air is indirectly used in the natural gas liquefaction system 100.

[0069] While the illustrated plant 100 utilizes a particular combination of temperature and pressure controlling components arranged in accordance with a particular liquefaction cycle, it should be understood that alternative plants in accordance with alternative embodiments of the present invention may utilize different combinations of pressure and/or temperature controlling components without deviating from the scope of the present invention. Indeed, according to various embodiments, liquid air cooling of the gas being liquefied in a liquefication plant may be added to any conventional liquefaction system in addition to and/or in the alternative to cooling steps in such plants, e g., by use of the heat exchanger 180 alone or in combination with the second heat exchanger 150.

[0070] All vessels 20, 210 and passageways, pipes, hoses, etc. may be insulated and rated for the temperature and pressure ranges of the fluids disposed therein.

[0071] The foregoing illustrated embodiments are provided to illustrate the structural and functional principles of various embodiments and are not intended to be limiting. To the contrary, the principles of the present invention are intended to encompass any and all changes, alterations and/or substitutions thereof (e.g., any alterations within the spirit and scope of the following claims).