JP7624475B2 - Mixed refrigerant liquefaction system and method with pre-cooling - Google Patents

Description

Claiming priority
[0001] This application claims the benefit of U.S. Provisional Application No. 62/660,518, filed April 20, 2018, the contents of which are incorporated herein by reference.

[0002] The present invention relates generally to systems and methods for cooling or liquefying gases, and more particularly to a mixed refrigerant liquefaction system and method that includes a subsystem for fractionating a high pressure mixed refrigerant vapor into a liquid stream and a vapor stream using cold vapor separation, and for pre-cooling a feed gas stream and one or more mixed refrigerant streams using a second refrigerant.

[0003] Natural gas, primarily methane, and other gases are liquefied under pressure for storage and transportation. The reduction in volume resulting from liquefaction allows vessels of more practical and economical design to be used. Liquefaction is typically accomplished by chilling the gas by indirect heat exchange through one or more refrigeration cycles. Such refrigeration cycles are expensive, both in equipment cost and operation, due to the complexity of the equipment required and the required efficiency of the refrigerant performance. Therefore, there is a need for a gas cooling and liquefaction system with improved refrigeration efficiency and reduced operating costs due to reduced complexity.

[0004] The use of a mixed refrigerant in a refrigeration cycle for a liquefaction system increases efficiency in that the warming curve of the refrigerant more closely matches the cooling curve of the gas. The refrigeration cycle for a liquefaction system will typically include a compression system for conditioning or processing the mixed refrigerant. A mixed refrigerant compression system typically includes one or more stages, each stage including a compressor, a cooler, and a separation and liquid accumulator device. Vapor exiting the compressor is cooled in the cooler, and the resulting two-phase or mixed-phase stream is directed to a separation and liquid accumulator device from which the vapor and liquid exit for further processing and/or direction to a liquefaction heat exchanger.

[0005] The separated liquid and vapor phases of the mixed refrigerant from the compression system may be directed to a portion of a heat exchanger to provide more efficient cooling. Examples of such systems are provided in commonly owned U.S. Pat. No. 9,441,877 to Gushanas et al., U.S. Patent Application Publication No. US 2014/0260415 to Ducote et al., and U.S. Patent Application Publication No. US 2016/0298898 to Ducote et al., the contents of each of which are incorporated herein by reference.

[0006] Further increases in cooling efficiency and decreases in operating costs in gas cooling and liquefaction systems are desirable.

[0007] There are several aspects of the present subject matter that may be implemented separately or together in the methods, devices, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to exclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as discussed in the claims appended hereto.

[0008] In one embodiment, a system for cooling a gas with a pre-cooling refrigerant and a mixed refrigerant includes a pre-cooling heat exchanger having a feed gas inlet adapted to receive a feed gas flow, a feed gas outlet, a pre-cooling refrigerant inlet, a pre-cooling refrigerant outlet, a liquefied mixed refrigerant inlet, and a liquefied mixed refrigerant outlet. The pre-cooling heat exchanger is configured to use the pre-cooling refrigerant to cool the feed gas passing through the pre-cooling heat exchanger between the feed gas inlet and the feed gas outlet, and to cool the liquefied mixed refrigerant passing through the pre-cooling heat exchanger between the liquefied mixed refrigerant inlet and the liquefied mixed refrigerant outlet. A pre-cooling compressor system includes a pre-cooling compressor having an inlet in fluid communication with the pre-cooling refrigerant outlet of the pre-cooling heat exchanger. The pre-cooling compressor system further includes a pre-cooling condenser having an inlet in fluid communication with the outlet of the pre-cooling compressor. The pre-cooling condenser further includes an outlet in fluid communication with the pre-cooling refrigerant inlet of the pre-cooling heat exchanger. The liquefaction heat exchanger includes a liquefaction passage in fluid communication with the feed gas outlet of the pre-cooling heat exchanger, a primary cooling passage, a high pressure vapor cooling passage, and a cold separator vapor cooling passage, the cold separator vapor cooling passage having an outlet in fluid communication with the primary cooling passage. The mixed refrigerant compression system includes a mixed refrigerant compressor having an inlet in fluid communication with an outlet of the primary cooling passage, and a mixed refrigerant cooler having an inlet in fluid communication with an outlet of the mixed refrigerant compressor. The mixed refrigerant cooler further has an outlet in fluid communication with the liquefied mixed refrigerant inlet of the pre-cooling heat exchanger. The mixed refrigerant compression system further includes a high pressure accumulator having an inlet in fluid communication with the liquefied mixed refrigerant outlet of the pre-cooling heat exchanger and a vapor outlet in fluid communication with the inlet of the high pressure vapor cooling passage of the liquefaction heat exchanger. A cold vapor separator has an inlet in fluid communication with the outlet of the high pressure vapor cooling passage of the liquefaction heat exchanger, a vapor outlet in fluid communication with the inlet of the cold separator vapor cooling passage of the liquefaction heat exchanger, and a liquid outlet in communication with the primary cooling passage of the liquefaction heat exchanger.

[0009] In another aspect, a method for cooling a feed gas stream includes the steps of: pre-cooling the feed gas stream in a pre-cooling heat exchanger using a first refrigerant to form a pre-cooled feed gas stream; and cooling the pre-cooled feed gas stream by: i) cooling a high pressure second refrigerant stream in the pre-cooling heat exchanger to form a cooled high pressure second refrigerant stream; ii) separating the cooled high pressure second refrigerant stream to form a high pressure vapor stream and a high pressure liquid stream; iii) cooling the high pressure vapor stream in a liquefaction heat exchanger to form a mixed phase stream; iv) separating the mixed phase stream with a cold vapor separator to form a cold separator vapor stream and a cold separator liquid stream; and v) separating the mixed phase stream with a cold vapor separator to form a cold separator vapor stream and a cold separator liquid stream. ) condensing and flashing the cold separator vapor stream in a liquefaction heat exchanger using a second refrigerant to form a cold and warm refrigerant stream; vi) directing the cold and warm refrigerant stream to the liquefaction heat exchanger; vii) subcooling the high pressure liquid stream to form a subcooled high pressure liquid stream and combining it with the cold and warm refrigerant stream in the liquefaction heat exchanger; viii) subcooling the cold separator liquid stream to form a subcooled cold separator liquid stream and combining it with the cold and warm refrigerant stream in the liquefaction heat exchanger; and ix) further cooling the pre-cooled gas stream by thermally contacting the cold and warm refrigerant stream in the liquefaction heat exchanger.

In another aspect, a system for cooling a feed gas with a mixed refrigerant includes a pre-cooling heat exchanger having a pre-cooling refrigerant inlet configured to receive a flow of pre-cooling refrigerant, a pre-cooling refrigerant outlet, a liquefied mixed refrigerant inlet, and a liquefied mixed refrigerant outlet. The pre-cooling heat exchanger is configured to use the pre-cooling refrigerant to cool a liquefied mixed refrigerant passing through the pre-cooling heat exchanger between the liquefied mixed refrigerant inlet and the liquefied mixed refrigerant outlet. The liquefaction heat exchanger includes a liquefaction passage configured to receive a flow of the feed gas, a primary cooling passage, a high pressure vapor cooling passage, and a cold separator vapor cooling passage, the cold separator vapor cooling passage having an outlet in fluid communication with the primary cooling passage. The mixed refrigerant compression system includes a mixed refrigerant compressor having an inlet in fluid communication with the outlet of the primary cooling passage. The mixed refrigerant compression system further includes a mixed refrigerant cooler having an inlet in fluid communication with the outlet of the mixed refrigerant compressor. The mixed refrigerant cooler has an outlet in fluid communication with the liquefied mixed refrigerant inlet of the pre-cooling heat exchanger. The mixed refrigerant compression system further includes a high pressure accumulator having an inlet in fluid communication with the liquefied mixed refrigerant outlet of the pre-cooling heat exchanger and a vapor outlet in fluid communication with the inlet of the high pressure vapor cooling passage of the liquefaction heat exchanger. A cold vapor separator has an inlet in fluid communication with the outlet of the high pressure vapor cooling passage of the liquefaction heat exchanger, a vapor outlet in fluid communication with the inlet of the cold separator vapor cooling passage of the liquefaction heat exchanger, and a liquid outlet in communication with the primary cooling passage of the liquefaction heat exchanger.

[0011] In another aspect, a method for cooling a feed gas stream includes directing the feed gas stream into a liquefaction heat exchanger; cooling a high pressure mixed refrigerant stream in a pre-cooling heat exchanger to form a cooled high pressure mixed refrigerant stream; and cooling the feed gas stream in the liquefaction heat exchanger by the steps of: i) separating the cooled high pressure mixed refrigerant stream to form a high pressure vapor stream and a high pressure liquid stream; ii) cooling the high pressure vapor stream in the liquefaction heat exchanger to form a mixed phase stream; iii) separating the mixed phase stream with a cold vapor separator to form a cold separator vapor stream and a cold separator liquid stream; and iv) The method includes: condensing and flashing the cold separator vapor stream in a liquefaction heat exchanger to form a cold and warm refrigerant stream; v) directing the cold and warm refrigerant stream to the liquefaction heat exchanger; vi) subcooling the high pressure liquid stream in the liquefaction heat exchanger to form a subcooled high pressure liquid stream which is combined with the cold and warm refrigerant stream in the liquefaction heat exchanger; vii) subcooling the cold separator liquid stream to form a subcooled cold separator liquid stream which is combined with the cold and warm refrigerant stream in the liquefaction heat exchanger; and viii) cooling the gas stream in the liquefaction heat exchanger by thermally contacting the cold and warm refrigerant stream.

[0012] FIG. 1 is a process flow and schematic diagram illustrating a first embodiment of the system and method of the present disclosure. [0013] FIG. 2 is a process flow and schematic diagram illustrating a second embodiment of the system and method of the present disclosure. [0014] FIG. 1 is a process flow and schematic diagram illustrating a third embodiment of the system and method of the present disclosure. [0015] FIG. 1 is a process flow and schematic diagram illustrating a fourth embodiment of the system and method of the present disclosure. [0016] FIG. 11 is a process flow and schematic diagram illustrating a fifth embodiment of the system and method of the present disclosure.

[0017] Embodiments of the mixed refrigerant liquefaction system and method of the present disclosure are illustrated in Figures 1-5. Although the embodiments are illustrated and described below in the context of liquefying natural gas to produce liquefied natural gas, it should be noted that the present invention may be used to liquefy or cool other types of gases.

[0018] Embodiments of the present disclosure may use the mixed refrigerant liquefaction systems and processes described in commonly owned U.S. Patent No. 9,441,877 to Gushanas et al., U.S. Patent Application Publication No. 2014/0260415, U.S. Patent Application No. 14/218,949 to Ducote et al., and U.S. Patent Application No. 62/561,417 to Ducote et al., the contents of each of which are incorporated herein by reference.

[0019] It should be noted herein that passages and streams are sometimes both referred to by the same element number as displayed in the figures. Furthermore, as used herein and as known in the art, a heat exchanger is a device, or a section within a device, in which indirect heat exchange occurs between two or more streams at different temperatures, or between a stream and the environment. As used herein, the terms "communication,""communicating," and the like generally refer to fluid communication unless otherwise specified. Furthermore, although two fluids in communication may exchange heat based on mixing, such exchange would not be considered the same as heat exchange in a heat exchanger, even though such exchange may occur within the heat exchanger. As used herein, the term "reducing the pressure of" (or variations thereof) does not include a phase change, while the term "flash" (or variations thereof) includes a phase change, including even a partial phase change. As used herein, the terms "high,""medium,""moderate,""warm," and the like, are intended to refer to comparable flows, as is customary in the art.

[0020] Generally, referring to FIG. 1, a first embodiment, the system of the present disclosure includes a mixed refrigerant liquefaction system, generally designated at 8, including a multi-stream liquefaction heat exchanger, generally designated at 10, having a warm end 12 and a cold end 14. The heat exchanger receives a pre-cooled natural gas feed stream 16, which is cooled or liquefied in a liquefaction passage 18 by removal of heat by heat exchange with a cooled stream in the heat exchanger. As a result, a liquefied natural gas (LNG) product stream 20 is produced. The multi-stream design of the heat exchanger allows for convenient and energy-efficient consolidation of several streams into a single exchanger. Suitable heat exchangers include brazed aluminum heat exchangers, which may be purchased from Chart Energy & Chemicals, Inc. of The Woodlands, Texas. Such plate-and-fin multi-flow heat exchangers offer the added advantage of being physically compact.

[0021] The system of FIG. 1, including the heat exchanger 10, may be configured to perform other gas processing options known in the art. These processing options may require the gas stream to exit and re-enter the heat exchanger one or more times, and may include, for example, natural gas liquids recovery or nitrogen rejection.

[0022] Heat removal is accomplished using a mixed refrigerant that is processed and reconditioned in a heat exchanger using a liquefaction system mixed refrigerant compressor system, generally designated at 22. The mixed refrigerant compressor system includes a first stage suction drum 24 that receives a mixed refrigerant vapor stream 26 from a primary cooling passage 28 of the heat exchanger 10. The vapor stream is compressed in a first stage compressor 32 (which may be an individual compressor or a single multi-stage compressor stage) and then cooled by a first stage heat exchanger or cooler 34. The resulting mixed refrigerant vapor stream proceeds to a second stage suction drum 35 and then to a second stage compressor 36 (which may be an individual compressor or a single multi-stage compressor stage) and, after compression, is cooled in a second stage heat exchanger or cooler 38.

[0023] As known in the art, the first and second stage suction drums 24 and 35, as well as the remaining suction drums mentioned below, are optional and protect those drums from liquid delivery to the subsequent compressor.

[0024] In addition to the liquefaction heat exchanger 10 and associated components described below and in U.S. Patent Application Serial No. 14/218,949 to Ducote et al., incorporated by reference above, and the mixed refrigerant compressor system 22, the system of FIG. 1 includes a pre-cooling system, generally designated at 40. The pre-cooling system includes a pre-cooling warm heat exchanger, generally designated at 42a, and a pre-cooling cold heat exchanger, generally designated at 42b. The warm and cold heat exchangers 42a and 42b may be, by way of example only, CORE-IN-KETTLE heat exchangers available from Chart Energy & Chemicals, Inc. of The Woodlands, Texas. Alternative types of heat exchangers may be used for the hot and cold heat exchangers 42a and 42b, including, but not limited to, shell and tube or thermosiphon type heat exchangers. The pre-cooling system may alternatively feature a single pre-cooling heat exchanger, or three or more pre-cooling heat exchangers.

[0025] The pre-cooling system further includes a compressor system, generally designated at 44, for processing and reconditioning a pre-cooling system refrigerant, such as propane, butane, ammonia, or a chlorofluorocarbon. Although the pre-cooling system in the embodiment described herein uses propane, alternative refrigerants may be used, including, but not limited to, butane, ammonia, or liquid fluorinated hydrocarbons.

[0026] The pre-cooling compressor system 44 includes a first stage suction drum 46 that receives a propane refrigerant vapor stream 48 from the cold heat exchanger 42b, as described in more detail below. A vapor stream 52 from the first stage suction drum proceeds to a pre-cooling compressor 54, and the resulting compressed stream proceeds to a pre-cooling condenser 56. The resulting propane refrigerant liquid stream proceeds to a pre-cooling refrigerant accumulator 62. A propane refrigerant liquid stream 64 proceeds from the accumulator to an expansion device 66, which causes a two-phase stream 72 to enter a shell 74 of the warm heat exchanger 42a. A liquid level sensor 76 controls the setting of the expansion device 66, which causes the proper liquid level to be maintained in the shell 74.

[0027] As in the case of all expansion devices mentioned herein, the expansion device 66 may be an expansion valve, such as a Joule-Thomson valve, or another type of expansion device, including, but not limited to, a turbine or an orifice.

[0028] The shell 74 of the pre-cooling warm heat exchanger 42a contains a core 78 that receives the natural gas feed stream 82. The warm feed gas heat exchanger core 78, and all such cores discussed below, may be, by way of example only, a brazed aluminum heat exchanger (BAHX) or other heat exchanger type such as microchannel or welded plate, tube or coil, printed circuit heat exchanger, etc. The natural gas stream is cooled within the core 78 by a propane liquid refrigerant, and the cooled natural gas stream exits the warm heat exchanger 42a as stream 84. In an alternative embodiment, if the natural gas stream 82 is colder than the warm heat exchanger 42a, the gas stream may be routed directly to the cold heat exchanger 42b, as indicated by dashed line 84' in FIG. 1. In such an embodiment, the core 78 may be omitted.

[0029] Warm propane refrigerant vapor stream 86 exits the shell 74 of the pre-cooling warm heat exchanger 42a and proceeds to the second stage suction drum 88 and to the inlet of the pre-cooling compressor 54.

[0030] Propane refrigerant liquid flow exits the shell of the warm heat exchanger as stream 92 and proceeds to an expansion device 94 which causes a two-phase flow 96 to enter the shell 98 of the pre-cooling cold heat exchanger 42b. A liquid level sensor 102 controls the setting of the expansion device 94 so that the proper liquid level is maintained in the shell 98.

[0031] The shell 98 of the cold heat exchanger 42b contains a core 104 that receives the natural gas feed stream 84 (or natural gas feed stream 84'). The natural gas stream 84 is further cooled (or cooled) in the core 104 by the propane liquid refrigerant, and the cooled natural gas stream exits the cold heat exchanger 42b as pre-cooled stream 16 and proceeds to the liquefaction passage 18 of the liquefaction heat exchanger 10. In an alternative embodiment, where the natural gas stream 82 is colder than both the warm heat exchangers 42a and 42b, the gas stream 84' of FIG. 1 may be routed directly to the liquefaction passage of the liquefaction heat exchanger. In such an embodiment, the core 104 may even be omitted.

[0032] The propane refrigerant vapor stream 48 exits the shell 98 of the pre-cooling cold heat exchanger 42b and proceeds to the first stage suction drum 46.

[0033] A high pressure mixed refrigerant stream 112 from the second stage compressor 36 and heat exchanger 38 of the mixed refrigerant compression system proceeds to a core 114 disposed within the shell 74 of the pre-cooling warm heat exchanger 42a. The mixed refrigerant flowing through the core 114 is cooled within the shell 74 with liquid propane refrigerant, and the resulting cooled mixed refrigerant stream 116 is directed to a cold mixed refrigerant core 118 disposed within the shell 98 of the pre-cooling cold heat exchanger 42b. The mixed refrigerant flowing through the core 118 is cooled within the shell 98 with liquid propane refrigerant, and the resulting mixed refrigerant (MR) mixed phase stream 122 is directed to a high pressure accumulator 124. Although an accumulator drum is illustrated as the high pressure accumulator 124, alternative separation devices may be used, including, but not limited to, another type of vessel, a cyclonic separator, a distillation unit, a coalescing separator, or a mesh or vane type mist eliminator. The same applies to the remaining separation devices or drums discussed herein.

[0034] High pressure vapor refrigerant stream 126 exits the vapor outlet of accumulator 124 and proceeds to the warm end of heat exchanger 10.

[0035] High pressure liquid refrigerant stream 128 exits the accumulator 124 through a liquid outlet and proceeds to the warm end of the heat exchanger. After cooling in the heat exchanger 10 through the high pressure liquid cooling passage 125, the high pressure liquid refrigerant stream 128 is flashed at 129 and proceeds to the warm separator 131. From the warm separator 131, vapor stream 127 and liquid stream 133 proceed to the primary cooling passage 28 of the heat exchanger 10.

[0036] Heat exchanger 10 further receives and cools high pressure steam stream 126 from high pressure accumulator 124 by high pressure steam cooling passage 135, cooling high pressure steam stream 126 such that it is partially condensed. The resulting mixed phase cold separator feed stream 132 is provided to cold steam separator 134, which produces cold separator vapor stream 136 and cold separator liquid stream 138.

[0037] The cold separator vapor stream 136 is cooled in the heat exchanger 10 by the cold separator vapor cooling passage 141 to a liquid stream 142, condensed, flashed by the expansion device 144, and directed to the cold separator 146 to form a cold liquid stream 152 and a cold vapor stream 154, which are directed to the primary cooling passage 28 of the heat exchanger 10 as cold refrigerant streams.

[0038] Cold separator liquid stream 138 is cooled in heat exchanger 10 by cold separator liquid cooling passage 143 to form subcooled cold separator liquid 160, which is flashed at 162 and directed to intermediate temperature separator 164. The resulting liquid stream 166 and the resulting vapor stream 168 are directed to primary cooling passage 28 of heat exchanger 10.

[0039] The combined refrigerant streams from the warm separator 131, the intermediate separator 164, and the cold separator 146 provide cooling for liquefaction of the pre-cooled feed gas stream 16 in the liquefaction or cooling passage 18 of the heat exchanger 10 and exit the primary cooling passage 28 of the liquefaction heat exchanger as a combined return refrigerant stream 26, preferably in the vapor phase. The return refrigerant stream 26 flows to the suction drum 24, which results in a vapor mixed refrigerant stream 27, as previously mentioned.

[0040] A liquefied natural gas stream 172 exits the cold side of the heat exchanger and can optionally be expanded using expansion device 174 and sent to storage or a process.

[0041] The embodiment of FIG. 1 therefore shows a propane (C3) pre-cooled mixed refrigerant (MR) process in combination with a cold vapor separator (CVS) installed in the main liquefaction section of the process. The combination of C3 pre-cooling and MR with a CVS results in a process that is more efficient and with lower equipment costs than pre-cooling without a CVS, and also facilitates higher capacity. The combination of pre-cooling and CVS allows the C3 system to operate at significantly warmer temperatures, such as, by way of example only, approximately -5°C versus -35 to -40°C, with high efficiency, which reduces propane system costs and power consumption.

[0042] The process of FIG. 1 can be used with any MR liquefaction process that utilizes a CVS.

[0043] It should be noted that although FIG. 1 shows two stages of pre-cooling in pre-cooling system 40, one or more stages of pre-cooling may alternatively be used.

[0044] Furthermore, although FIG. 1 shows MR liquefaction system 8 featuring separate warm, medium, and cold separators, any of these separators may be combined or, in certain cases, separators may be eliminated. Furthermore, although the separators are illustrated as standpipes, alternative types of separators known in the art may be used.

[0045] Except as discussed below, the embodiments of Figures 2-4 feature the same mixed refrigerant compressor system, mixed refrigerant liquefaction system, and pre-cooling compressor system components and operation as described above with reference to Figure 1, and thus common reference numbers are used to refer to these portions of the systems and common components.

[0046] A second embodiment of the disclosed system is presented in FIG. 2. In this embodiment, two high pressure MR accumulators are used in place of the single high pressure MR accumulator 124 of FIG. 1. More specifically, stream 182 exiting the second stage compression and cooling cycle of the MR compressor system 22 is directed to the core 114 of the warm pre-cooling heat exchanger 42a. The core 114 cools stream 182 in the shell 74 using liquid propane refrigerant. The resulting cooled MR stream 186 proceeds to the first high pressure MR accumulator 188. The resulting vapor MR stream 192 proceeds to the core 194 disposed in the pre-cooling cold heat exchanger 42b, where the vapor MR stream 192 is cooled in the shell 98 by the liquid propane refrigerant. The resulting cooled stream 198 proceeds to the second high pressure MR accumulator 202.

[0047] The vapor stream 204 leaving the second high pressure MR accumulator 202 is cooled in the liquefaction heat exchanger 10 by passage 206 and directed to a cold vapor separator 208. The vapor stream exiting the cold vapor separator is treated as described above with respect to FIG. 1.

[0048] Liquid stream 212 leaving the second high pressure MR accumulator 202 is cooled in the liquefaction heat exchanger 10 by passage 214, flashed by expansion device 216, and directed to the intermediate temperature separator 164 where it is combined with the cooled flashed liquid stream from the cold vapor separator 208. The vapor and liquid streams exiting the intermediate temperature separator are directed to the primary cooling passage 28.

[0049] The liquid MR stream exiting the first high pressure MR accumulator 188 proceeds to a core 196 disposed in the pre-cooling cold heat exchanger 42b where it is cooled in the shell 98 by liquid propane refrigerant. The resulting cooled stream 218 is cooled in the liquefaction heat exchanger 10 by passage 220 and the resulting cooled liquid stream is flashed by expansion device 222 and delivered to the warm separator 131. The vapor and liquid streams exiting the warm separator are directed to the primary cooling passage 28.

2 embodiment, a pre-cooling system is used to cool the discharge stream 224 exiting the first stage compression and cooling cycle of the MR compressor system 22. More specifically, the pre-cooling warm heat exchanger 42a contains a core 226 that receives stream 224 through an interstage mixed refrigerant inlet and cools the stream 224 within the shell 74 using propane liquid refrigerant. The resulting cooled stream exits the core through an interstage mixed refrigerant outlet and proceeds to an interstage or MR low pressure accumulator 228. The resulting vapor stream 232 is directed to the inlet of the second stage compressor 36 of the MR compressor system 22. The liquid stream 234 exiting the MR low pressure accumulator 228 is received by a core 236 disposed within the shell 98 of the cold heat exchanger 42b. The resulting cooled stream 238 is cooled in passage 242 of the liquefaction heat exchanger 10, flashed by expansion device 244, and directed to the primary cooling passage 28 of the heat exchanger 10.

[0051] It should be understood with respect to the embodiment of FIG. 2 that pre-cooling the discharge stream (224) of the first compression and cooling stage of the MR compressor system 22 prior to compression in the second stage and the incorporation of the first and second MR high pressure accumulators (188 and 202) into the process are separate and independent and may be utilized in combination or separately.

[0052] Furthermore, the pre-cooled liquid stream 224 from the first compression and cooling stage may be introduced separately into the MR liquefaction system 8 as shown in FIG. 2, or may be combined with any of the other cooled streams in a separator of the MR liquefaction system 8, or in some cases without any separator.

[0053] A third embodiment of the system of the present disclosure is presented in FIG. 3. In this embodiment, a warm mixed refrigerant (MR) pre-cooling system, generally designated 252, is used in place of the propane pre-cooling system of FIGS. 1 and 2.

[0054] The MR pre-cooling system includes a warm MR pre-cooling heat exchanger, generally designated 254, that includes a pre-cooling passage 256 that receives the natural gas feed stream 82.

[0055] The MR pre-cooling system further includes a pre-cooling compressor system 262 including a first stage suction drum 264 that receives a pre-cooled MR vapor stream 266 from a pre-cooling primary cooling passage 268 of the heat exchanger 254. A vapor stream 272 from the first stage suction drum proceeds to an inlet of the pre-cooling compressor 272 and the resulting compressed stream proceeds to a pre-cooling condenser 274. The resulting MR liquid stream proceeds to a pre-cooling MR accumulator 276. The vapor stream from the accumulator 276 can either be discharged by a valve 278 or directed by a second valve to a second stage suction drum 284. A vapor stream 286 from the second stage suction drum 284 proceeds to an inlet of the pre-cooling compressor 272.

[0056] From the accumulator 276, the liquid pre-cooled MR stream 292 travels through the cooling passage 294 of the heat exchanger 254, and the resulting cooled liquid stream travels to an expansion device 296 where it is flashed and the resulting mixed phase stream enters the pre-cooled cold separator 302. A portion of the cooled liquid stream leaving the heat exchanger passage 294 (or all of it) can be directed to the secondary pre-cooled cooled passage 304 of the heat exchanger using a valve 298, depending on the system temperature and load needs. The vapor stream 306 exiting the secondary pre-cooled cooled passage 304 is directed to the second stage suction drum 284. Both the vapor pre-cooled MR stream and the liquid pre-cooled MR stream (308 and 312, respectively) from the pre-cooled cold separator 302 are directed to the pre-cooled primary cooled passage 268 of the heat exchanger 254.

[0057] The natural gas feed stream flowing through pre-cooling passages 256 of pre-cooling heat exchanger 254 is pre-cooled by cooling passages 268 and 304 of the heat exchanger, and the resulting cooled natural gas stream 314 is directed to liquefaction heat exchanger 10 for liquefaction.

[0058] Liquefaction compressor system 316, similar to the embodiment of Figures 1 and 2, features a first stage compression and cooling cycle that produces a first stage liquefied MR stream 318, and a second stage compression and cooling cycle that produces a second stage liquefied MR stream 322. Liquefied MR streams 318 and 322 are further cooled in pre-cooling heat exchanger 254 by passages 324 and 326, with the resulting mixed phase stream 328 exiting passage 324 proceeding to liquefied MR low pressure accumulator 332, while the resulting mixed phase stream 334 proceeds to liquefied MR high pressure accumulator 336.

[0059] Liquefied MR vapor stream 338 proceeds from liquefied MR low pressure accumulator 332 to second stage suction drum 342 of liquefied compressor system 316, where the resulting vapor stream is directed to the second stage compression and refrigeration cycle. Liquefied MR liquid stream 344 from liquefied MR low pressure accumulator 332 is cooled in passage 346 of liquefied heat exchanger 350, flashed by expansion device 348, and directed to primary cooling passage 352 of heat exchanger 350.

[0060] The liquefied MR vapor stream 354 leaving the liquefied MR high pressure accumulator 336 is cooled in the liquefaction heat exchanger 350 by passage 356 and directed to a cold vapor separator 358. The vapor stream exiting the cold vapor separator may be processed as described above with respect to FIG. 1.

[0061] Liquid stream 362 leaving liquefied MR high pressure accumulator 336 is cooled in liquefied heat exchanger 350 by passage 364, flashed by expansion device 366, and directed to intermediate temperature separator 368 after combining liquid stream 362 with the cooled and flashed liquid stream from cold vapor separator 358 (which is functionally equivalent to combining the streams in the intermediate temperature separator as indicated in FIG. 2). The vapor and liquid streams exiting the intermediate temperature separator are directed to the primary cooling passage 352 of heat exchanger 350.

[0062] With respect to the embodiment of FIG. 3, it should be noted that pre-cooling the liquefied MR compression system 316 first stage discharge (318) prior to compression in the second stage is an optional feature and may be utilized in combination with other features or not used at all. Additionally, the mixed refrigerant used in the pre-cooling system and the liquefaction system may be of the same or different composition.

[0063] Additionally, it should be noted that the MR pre-cooling system illustrated at 262 in FIG. 3 is merely an example of a suitable MR system, and that other MR systems and non-mixed refrigerant systems known in the art may alternatively be used as the pre-cooling system.

[0064] The system embodiment illustrated in Figure 4 is essentially the same as the embodiment of Figure 1, including a propane pre-cooling system, generally designated at 370, with the exception of the configuration of the pre-cooling heat exchanger. More specifically, in the system embodiment illustrated in Figure 4, the pre-cooling system 370 includes a pre-cooling hot heat exchanger, generally designated at 372a, and a pre-cooling cold heat exchanger, generally designated at 372b. The hot and cold heat exchangers 372a and 372b may be, by way of example only, CORE-IN-KETTLE heat exchangers available from Chart Energy & Chemicals, Inc. of The Woodlands, Texas. Alternative types of heat exchangers may be used, including, but not limited to, shell-and-tube or thermosiphon type heat exchangers.

[0065] In the embodiment of FIG. 4, a core 374 (which may be, by way of example only, a brazed aluminum heat exchanger (BAHX) or other heat exchanger type such as microchannel or welded plate, etc.) extends through an internal head 376 between the shells 378 and 382 of the hot and cold heat exchangers 372a and 372b, such that the process stream, which is the discharge stream 384 from the second compression and cooling stage of the liquefaction MR compressor system 386, is continuous through the core 374. The benefit of this arrangement is that the cooled and partially condensed process stream is not susceptible to two-phase flow maldistribution that adversely affects system performance, which maldistribution may be encountered if the heat exchanger design were multiple cores piped in series as shown in FIG. The arrangement of FIG. 4 reduces process power consumption in either the propane or liquefaction system, or both, that may be due to maldistribution, or simplifies equipment count and reduces costs to eliminate maldistribution effects.

[0066] It should be noted that the hot and cold heat exchangers 372a and 372b can utilize any shape of internal head 376, including flat plates. Furthermore, while FIG. 4 shows a propane (C3) pre-cooled MR process, the embodiment of FIG. 4 can be used with any process that utilizes at least two boiling refrigerant cooling steps. Additionally, while propane (C3) is described as the coolant for the pre-cooling system of FIG. 4, any refrigerant can be used, such as, but not limited to, butane, ammonia, or liquid fluorinated hydrocarbons, etc. Furthermore, while the system of FIG. 4 shows two stages of pre-cooling, two or more stages of cooling can be used. Additionally, while FIG. 4 shows separate feed exchangers, the feed exchangers can be combined with the MR exchangers.

[0067] In the embodiment illustrated in FIG. 5, a chilled water cooling system, generally designated 402, is used to pre-cool the discharge stream 404 from the second compression and cooling stage of the liquefied MR compressor system 406. More specifically, water is pumped by pump 412 to a coolant heat exchanger 414. The heat exchanger in turn receives and cools the MR discharge stream 404. The chilled water is water or a water/glycol mixture that is cooled in a pre-cooling refrigerant system, which may be, but is not limited to, a mechanical chiller or an adsorption chiller or a thermoelectric chiller or a thermoacoustic refrigerator, and is always colder than the temperature that can be achieved by either air cooling or water evaporative cooling.

[0068] The cooled MR stream 416 then flows to the high pressure accumulator 124 and the resulting liquid and vapor streams are directed to the liquefaction heat exchanger 420 of the MR liquefaction system 408 as in the previous embodiment.

[0069] Although a single chiller heat exchanger 414 is illustrated in FIG. 5, multiple chiller heat exchangers in parallel or in series may be used instead.

[0070] As in the previous embodiment, the liquefaction MR compressor system provides refrigerant to the MR liquefaction system 408, which includes a cold vapor separator (CVS) 410. The combination of pre-cooling by a chilled water cooling system and MR with a CVS results in a process that is more efficient and with lower equipment costs than pre-cooling without a CVS, and also facilitates higher plant capacity. The combination of pre-cooling and CVS allows the chilled water cooling system to operate at significantly warmer temperatures, approximately -5°C versus -35 to -40°C. The combination also allows the chiller equipment to be located away from the hydrocarbon containing equipment, which reduces system costs and provides site planning flexibility. The process may be used with any MR liquefaction process that utilizes a CVS.

[0071] Although FIG. 5 shows a chilled water pre-cooled MR process, any chilled cooling fluid may be used, such as, but not limited to, ammonia, water, water glycol mixtures, lithium bromide solutions, liquid fluorinated hydrocarbons, liquid hydrocarbons, and the like. Additionally, while FIG. 5 shows a shell-and-tube heat exchanger for the pre-cooling system heat exchanger 414, any heat exchanger type may be used. Furthermore, while FIG. 5 shows separate hot, medium, and cold standpipes 422, 424, and 426, any of these standpipes may be combined, or in certain cases the standpipes may be eliminated. Although not explicitly shown, the chilled water cooling system may also be used to cool the feed gas and/or cool the first stage discharge as shown in FIG. 2, or provide cooling for the turbine inlet air for the gas turbine driver, or to cool multiple liquefaction systems.

[0072] There are several aspects of the present subject matter that may be implemented separately or together in the methods, devices, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to exclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as discussed in the claims appended hereto.

[0073] While preferred embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications can be made in those embodiments without departing from the spirit of the invention, the scope of which is defined by the appended claims.

Claims (30)

1. A system for cooling a gas with a pre-cooling refrigerant and a mixed refrigerant, comprising:
a pre-cooling heat exchanger having a feed gas inlet adapted to receive a feed gas stream, a feed gas outlet, a pre-cooled refrigerant inlet, a pre-cooled refrigerant outlet, a liquefied mixed refrigerant inlet, and a liquefied mixed refrigerant outlet, wherein the pre-cooling heat exchanger is configured to use the pre-cooling refrigerant to cool the feed gas passing through the pre-cooling heat exchanger between the feed gas inlet and the feed gas outlet, and to cool the liquefied mixed refrigerant passing through the pre-cooling heat exchanger between the liquefied mixed refrigerant inlet and the liquefied mixed refrigerant outlet;
b. i) a pre-cooling compressor having an inlet in fluid communication with the pre-cooling refrigerant outlet of the pre-cooling heat exchanger;
ii) a pre-cooling compressor system including a pre-cooling condenser having an inlet in fluid communication with an outlet of the pre-cooling compressor and further having an outlet in fluid communication with the pre-cooling refrigerant inlet of the pre-cooling heat exchanger;
c) a liquefaction heat exchanger including a liquefaction passage in fluid communication with the feed gas outlet of the pre-cooling heat exchanger, a primary cooling passage, a high pressure steam cooling passage, and a cold separator steam cooling passage, the cold separator steam cooling passage having an outlet in fluid communication with the primary cooling passage;
d. i) a mixed refrigerant compressor having an inlet in fluid communication with an outlet of the primary cooling passage;
ii) a mixed refrigerant cooler having an inlet in fluid communication with an outlet of the mixed refrigerant compressor and an outlet in fluid communication with the liquefied mixed refrigerant inlet of the pre-cooling heat exchanger;
iii) a mixed refrigerant compression system including a high pressure accumulator having an inlet in fluid communication with the liquefied mixed refrigerant outlet of the pre-cooling heat exchanger and a vapor outlet in fluid communication with an inlet of the high pressure vapor cooling passage of the liquefaction heat exchanger;
a cold vapor separator having an inlet in fluid communication with an outlet of the high pressure vapor cooling passage of the liquefaction heat exchanger, a vapor outlet in fluid communication with an inlet of the cold separator vapor cooling passage of the liquefaction heat exchanger, and a liquid outlet in communication with the primary cooling passage of the liquefaction heat exchanger;
The pre-cooling heat exchanger is
a shell having the pre-cooled refrigerant inlet and the pre-cooled refrigerant outlet;
a feed gas core disposed within the shell, the feed gas core having the feed gas inlet and the feed gas outlet;
a liquefied mixed refrigerant core disposed within the shell and having the liquefied mixed refrigerant inlet and the liquefied mixed refrigerant outlet;
Including,
system. The system of claim 1, wherein the pre-cooling heat exchanger includes a hot pre-cooling heat exchanger and a cold pre-cooling heat exchanger. The system of claim 2, wherein each of the hot pre-cooling heat exchanger and the cold pre-cooling heat exchanger includes a shell that receives the pre-cooling refrigerant, and at least one of the hot pre-cooling heat exchanger and the cold pre-cooling heat exchanger includes a supply gas core that receives the supply gas. The system of claim 2, wherein each of the hot pre-cooling heat exchanger and the cold pre-cooling heat exchanger includes a liquefied mixed refrigerant core configured to cool the liquefied mixed refrigerant passing through the pre-cooling heat exchanger between the liquefied mixed refrigerant inlet and the liquefied mixed refrigerant outlet. The system of claim 4, wherein a single liquefied mixed refrigerant core extends through both the hot pre-cooling heat exchanger and the cold pre-cooling heat exchanger shells and is configured to cool the liquefied mixed refrigerant passing through the pre-cooling heat exchanger between the liquefied mixed refrigerant inlet and the liquefied mixed refrigerant outlet. The system of claim 5, wherein an internal head extends between the interior spaces of the shells of the hot pre-cooling heat exchanger and the cold pre-cooling heat exchanger, and the single liquefied mixed refrigerant core extends through the internal head. 2. The system of claim 1, wherein the mixed refrigerant compression system further comprises a mixed refrigerant second compressor or compression stage having an inlet in fluid communication with the outlet of the mixed refrigerant cooler, and a second mixed refrigerant cooler having an inlet in fluid communication with an outlet of the mixed refrigerant second compressor or compression stage, the second mixed refrigerant cooler having an outlet in fluid communication with the liquefied mixed refrigerant inlet of the pre-cooling heat exchanger. 8. The system of claim 7, wherein the pre-cooling heat exchanger includes an interstage mixed refrigerant inlet and an interstage mixed refrigerant outlet, the mixed refrigerant compressor having an outlet in fluid communication with the interstage mixed refrigerant inlet of the pre-cooling heat exchanger, the interstage mixed refrigerant outlet of the pre-cooling heat exchanger in fluid communication with an interstage accumulator having a vapor outlet in fluid communication with the inlet of the mixed refrigerant second compressor or compression stage and a liquid outlet in fluid communication with the primary cooling passage of the liquefaction heat exchanger. The system of claim 1, wherein the high pressure accumulator has a liquid outlet, and the liquefaction heat exchanger further comprises a high pressure liquid cooling passage having an inlet in fluid communication with the liquid outlet of the high pressure accumulator and an outlet in fluid communication with the primary cooling passage of the liquefaction heat exchanger. The system of claim 1, wherein the pre-cooling refrigerant is propane, butane, ammonia, or a chlorofluorocarbon. The system of claim 1, wherein the pre-cooling refrigerant is a mixed refrigerant. The system of claim 11, wherein the liquefaction heat exchanger is a plate-and-fin heat exchanger. 1. A method for cooling a feed gas stream, comprising:
a. pre-cooling the feed gas stream in a pre-cooling heat exchanger using a first refrigerant to form a pre-cooled feed gas stream;
b. subjecting the pre-cooled feed gas stream to
i) cooling a high pressure second refrigerant stream in said pre-cooling heat exchanger to form a cooled high pressure second refrigerant stream;
ii) separating the cooled high pressure second refrigerant stream to form a high pressure vapor stream and a high pressure liquid stream;
iii) cooling the high pressure vapor stream in a liquefaction heat exchanger to form a mixed phase stream;
iv) separating the mixed-phase stream with a cold vapor separator to form a cold separator vapor stream and a cold separator liquid stream;
v) condensing and flashing the cold separator vapor stream in the liquefaction heat exchanger with the second refrigerant to form a cold refrigerant stream;
vi) directing said cold refrigerant stream to said liquefaction heat exchanger;
vii) subcooling said high pressure liquid stream to form a subcooled high pressure liquid stream which is combined with said cold refrigerant stream in said liquefaction heat exchanger;
viii) subcooling the cold separator liquid stream to form a subcooled cold separator liquid stream which is combined with the warm and cold refrigerant stream in the liquefaction heat exchanger;
ix) further cooling the pre-cooled feed gas stream in the liquefaction heat exchanger by thermal contacting the pre-cooled feed gas stream with a cold refrigerant stream;
The pre-cooling heat exchanger is
a shell having a pre-cooled refrigerant inlet and a pre-cooled refrigerant outlet;
a feed gas core disposed within the shell, the feed gas core having a feed gas inlet and a feed gas outlet;
a liquefied mixed refrigerant core disposed within the shell and having a liquefied mixed refrigerant inlet and a liquefied mixed refrigerant outlet;
Including,
method. The method of claim 13, wherein the high pressure liquid stream and the cold separator liquid stream are subcooled in the liquefaction heat exchanger. The method of claim 13, wherein step b. further comprises: cooling a low-pressure mixed refrigerant stream in the pre-cooling heat exchanger; separating the cooled low-pressure mixed refrigerant stream to form a low-pressure mixed refrigerant vapor stream and a low-pressure mixed refrigerant liquid stream; compressing the low-pressure mixed refrigerant vapor stream to form a high-pressure mixed refrigerant stream; and then cooling the high-pressure mixed refrigerant stream to form the cooled high-pressure mixed refrigerant stream. The method of claim 15, wherein the high pressure mixed refrigerant stream is cooled in the pre-cooling heat exchanger to form the cooled high pressure mixed refrigerant stream. The method of claim 15, wherein the high pressure mixed refrigerant stream is cooled in both the pre-cooling heat exchanger and the liquefaction heat exchanger to form the cooled high pressure mixed refrigerant stream. The method of claim 13, wherein the first refrigerant is propane, butane, ammonia, or a chlorofluorocarbon. The method of claim 13, wherein the first refrigerant is a mixed refrigerant. The method of claim 13, wherein step a. includes a first pre-cooling stage using a hot pre-cooling heat exchanger and a second pre-cooling stage using a cold pre-cooling heat exchanger. 1. A system for cooling a supply gas with a mixed refrigerant, comprising:
a pre-cooling heat exchanger having a feed gas inlet adapted to receive the feed gas , a feed gas outlet, a pre-cooling refrigerant inlet configured to receive a flow of a pre-cooling refrigerant, a pre-cooling refrigerant outlet, a liquefied mixed refrigerant inlet, and a liquefied mixed refrigerant outlet, wherein the pre-cooling refrigerant is configured to use the pre-cooling refrigerant to cool the feed gas passing through the pre-cooling heat exchanger between the feed gas inlet and the feed gas outlet, and to cool the liquefied mixed refrigerant passing through the pre-cooling heat exchanger between the liquefied mixed refrigerant inlet and the liquefied mixed refrigerant outlet;
b. a liquefaction heat exchanger configured to receive a flow of the feed gas, the liquefaction heat exchanger including a liquefaction passageway, a primary cooling passageway, a high pressure steam cooling passageway, and a cold separator steam cooling passageway, the cold separator steam cooling passageway having an outlet in fluid communication with the primary cooling passageway;
c.
i) a mixed refrigerant compressor having an inlet in fluid communication with an outlet of the primary cooling passage;
ii) a mixed refrigerant cooler having an inlet in fluid communication with an outlet of the mixed refrigerant compressor and an outlet in fluid communication with the liquefied mixed refrigerant inlet of the pre-cooling heat exchanger;
iii) a mixed refrigerant compression system including a high pressure accumulator having an inlet in fluid communication with the liquefied mixed refrigerant outlet of the pre-cooling heat exchanger and a vapor outlet in fluid communication with an inlet of the high pressure vapor cooling passage of the liquefaction heat exchanger;
a cold vapor separator having an inlet in fluid communication with an outlet of the high pressure vapor cooling passage of the liquefaction heat exchanger, a vapor outlet in fluid communication with an inlet of the cold separator vapor cooling passage of the liquefaction heat exchanger, and a liquid outlet in fluid communication with the primary cooling passage of the liquefaction heat exchanger;
The pre-cooling heat exchanger is
a shell having the pre-cooled refrigerant inlet and the pre-cooled refrigerant outlet;
a feed gas core disposed within the shell, the feed gas core having the feed gas inlet and the feed gas outlet;
a liquefied mixed refrigerant core disposed within the shell and having the liquefied mixed refrigerant inlet and the liquefied mixed refrigerant outlet;
Including,
system. 22. The system of claim 21, wherein the pre-cooling heat exchanger further includes a feed gas inlet adapted to receive a feed gas flow and a feed gas outlet, and the pre-cooling heat exchanger is configured to use the pre-cooling refrigerant to cool the feed gas passing through the pre-cooling heat exchanger between the feed gas inlet and the feed gas outlet. The system of claim 21, wherein the pre-cooling heat exchanger includes multiple heat exchangers connected in series or parallel. 22. The system of claim 21, wherein the pre-cooling refrigerant is selected from the group consisting of propane, butane, ammonia, water, water-glycol mixtures, lithium bromide solutions, liquid fluorinated hydrocarbons, and liquid hydrocarbons. 22. The system of claim 21, further comprising a pump configured to pump a flow of pre-cooled refrigerant to the pre-cooled refrigerant inlet of the pre-cooled heat exchanger. 22. The system of claim 21, further comprising a pre-cooling refrigerant system selected from the group consisting of a mechanical chiller, an adsorption chiller, a thermoelectric chiller, and a thermoacoustic cooling device, the pre-cooling refrigerant system configured to cool the pre-cooling refrigerant. 1. A method for cooling a feed gas stream, comprising:
a. directing the feed gas stream into a liquefaction heat exchanger;
b. cooling the high pressure mixed refrigerant stream in a pre-cooling heat exchanger to form a cooled high pressure mixed refrigerant stream;
c. cooling the feed gas stream in the liquefaction heat exchanger;
i) separating the cooled high pressure mixed refrigerant stream to form a high pressure vapor stream and a high pressure liquid stream;
ii) cooling the high pressure vapor stream in the liquefaction heat exchanger to form a mixed phase stream;
iii) separating the mixed-phase stream with a cold vapor separator to form a cold separator vapor stream and a cold separator liquid stream;
iv) condensing and flashing the cold separator vapor stream in the liquefaction heat exchanger to form a cold refrigerant stream;
v) directing said cold refrigerant stream to said liquefaction heat exchanger;
vi) subcooling the high pressure liquid stream in the liquefaction heat exchanger to form a subcooled high pressure liquid stream which is combined with the cold refrigerant stream in the liquefaction heat exchanger;
vii) subcooling the cold separator liquid stream to form a subcooled cold separator liquid stream which is combined with the warm and cold refrigerant stream in the liquefaction heat exchanger;
viii) cooling said feed gas stream in said liquefaction heat exchanger by thermal contact with said cold refrigerant stream;
The pre-cooling heat exchanger is
a shell having a pre-cooled refrigerant inlet and a pre-cooled refrigerant outlet;
a feed gas core disposed within the shell, the feed gas core having a feed gas inlet and a feed gas outlet;
a liquefied mixed refrigerant core disposed within the shell and having a liquefied mixed refrigerant inlet and a liquefied mixed refrigerant outlet;
Including,
method. 28. The method of claim 27, further comprising pre-cooling the feed gas stream in the pre-cooling heat exchanger prior to step a. 28. The method of claim 27, wherein step b. is performed using a pre-cooled refrigerant that is cooled using a pre-cooled refrigerant system selected from the group consisting of a mechanical chiller, an adsorption chiller, a thermoelectric chiller, and a thermoacoustic cooling device. The method of claim 29, wherein the pre-cooled refrigerant is cooled to a temperature colder than can be achieved by either air cooling or water evaporative cooling.

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