SYSTEM AND METHOD FOR EXTRACT COMPONENTS FROM GAS STREAM.

Abstract

A system for extracting selected components from a gas stream has a heat exchanger that includes a first cooling passage configured to receive a feed gas stream and provide a cooled feed gas stream. An expander receives at least a portion of the cooled feed gas stream. A separation device receives an expanded fluid stream from the expander and separates it into a liquid stream containing selected components and a purified vapor stream at a purified vapor temperature. A compressor receives the purified vapor stream at approximately the purified vapor temperature and produces a compressed vapor stream that is returned to the heat exchanger.

Description

SYSTEM AND METHOD FOR EXTRACT COMPONENTS FROM GAS STREAM 7001? ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Field of Invention The present invention relates in general to systems and methods for cooling or liquefying gases and, more particularly, to a system and method for extracting selected components from such gases. Background of the Invention Natural gas is frequently liquefied under pressure for storage, use, and transport. The reduction in volume resulting from liquefaction allows for the use of more practical and economical containers. Natural gas is typically obtained from underground deposits through drilling or similar operations. The resulting natural gas streams, while primarily containing methane, may also contain components such as heavy hydrocarbons (including, for example, butane, ethane, pentane and propane, benzenes, xylenes, heptanes, octanes, and heavier components), carbon dioxide, hydrogen, nitrogen, and water. Liquefaction is typically achieved by cooling natural gas through indirect heat exchange by one or more refrigeration cycles in one or more heat exchangers. If present, components such as heavy hydrocarbons in a gas stream during liquefaction Ref. 340305 liquefaction: such components can freeze and thereby impair the operation of the liquefaction heat exchanger. Recovering components as products may also be desirable. Furthermore, higher-purity liquefied natural gas produces fewer greenhouse gases, such as carbon dioxide, when burned as fuel. Summary of the Invention There are several aspects of the subject matter herein that may be incorporated separately or together into the methods, devices, and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects as a whole is not intended to preclude the use of these aspects separately or the claim of such aspects separately or in different combinations as set forth in the appended claims. In one aspect, a system for extracting selected components from a gas stream includes a heat exchanger having a first cooling passage configured to receive a feed gas stream and provide a cooled feed gas stream. An expander is configured to receive at least a portion of the cooled feed gas stream. A separation device is configured to receive an expanded fluid stream from the 7001? ίη / ZZΖΠZ / E / YΙΛΙ expander and to separate the expanded fluid stream into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature. A compressor is configured to receive the purified vapor stream at approximately the purified vapor temperature and to produce a compressed vapor stream that is returned to the heat exchanger. In another aspect, a system for liquefying a feed gas includes a heat exchanger having a first cooling passage and a second cooling passage. The first cooling passage is configured to receive a feed gas stream such that a cooled feed gas stream is formed. A mixed refrigerant compression system is in communication with the heat exchanger and configured to cool the first and second cooling passages. A liquefied gas outlet line is connected to an outlet of the second cooling passage. An expander is configured to receive at least a portion of the cooled feed gas stream from the first cooling passage. A separation device is configured to receive an expanded fluid stream from the expander and to separate the expanded fluid stream into a separate stream. 7001? Ln / Zznz / E / YIAI of liquid containing selected components and a purified vapor stream having a purified vapor temperature. A compressor is configured to receive the purified vapor stream at approximately the purified vapor temperature and to produce a compressed vapor stream. The second cooling passage is configured to receive and liquefy the compressed vapor stream. In another aspect, a process is provided for extracting selected components from a gas stream and includes the steps of cooling a feed gas stream to provide a cooled feed gas stream, expanding the cooled feed gas stream to provide an expanded gas stream, separating the expanded gas stream into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature; and compressing the purified vapor stream to provide a compressed vapor stream. In yet another aspect, a method of liquefying a gas feed stream includes the steps of cooling a gas feed stream to provide a cooled feed gas stream, expanding the cooled feed gas stream to provide an expanded gas stream, and separating the gas stream. 7001? ίη / ZZΖΠZ / E / YΙΛΙ expanded into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature, compressing the purified vapor stream to provide a compressed vapor stream and cooling the compressed vapor stream to form a liquefied gas stream. Brief Description of the Figures Figure 1 is a process flow diagram and schematic illustrating a first modality of the system description; Figure 2 is a process flow diagram and schematic illustrating a second modality of the system description; Figure 3 is a process flow diagram and schematic illustrating a third modality of the system description; Figure 4 is a process flow diagram and schematic illustrating a fourth modality of the system description; Figure 5 is a process flow diagram and scheme illustrating a fifth modality of the system description. Detailed Description of the Invention The mixed refrigerant liquefaction systems and methods, including the component extraction system modalities described, are illustrated in the Figures. 7001? ίη / ΖΖΠΖ / Ε / ΥΙΛΙ 1-5. It should be noted that, although the modalities are illustrated and described below in terms of systems for extracting frozen components and liquefying natural gas to produce liquefied natural gas, the technology described can be used with systems that liquefy or cool other types of gases. Furthermore, the technology described can be used to separate any selected component that freezes or condenses at temperatures warmer than the desired final temperature of liquefied natural gas or other product, but cooler than the inlet temperature of the gas stream. With reference to Figure 1, a system including a modality of the component extraction system described is indicated in general at 10. The system includes a selected component extraction system, indicated in general at 12, integrated into a liquefaction system, indicated in general at 14. The basic liquefaction system, including a mixed refrigerant compressor system, may be, by way of example only, as described in U.S. Patent No. 9,441,877 jointly owned by the inventors with Gushanas et al. or in U.S. Patent No. 10,480,851 by Ducote, Jr. et al., the contents of which are incorporated herein by reference. Generally, with reference to Figure 1, the system 7001? iP / 77Ω7 / B / YILI includes a multi-stream main heat exchanger, generally indicated at 16, having a hot-end portion 18 and a cold-end portion 20. The heat exchanger receives a high-pressure natural gas feed stream 22, which is cooled and liquefied in the main heat exchanger through heat extraction via heat exchange with the cooling streams. As a result, a product stream 24 of liquefied natural gas (LNG) is produced. The multi-stream design of the heat exchanger allows for convenient and energy-efficient integration of several streams into a single heat exchanger. Suitable heat exchangers, such as a welded aluminum heat exchanger (BAHX), can be purchased from Chart Energy & Chemicals, Inc. of Ball Ground, Georgia.The multi-stream plate and fin heat exchanger available from Chart Energy & Chemicals, Inc. offers the added advantage of being physically compact. Alternative designs and types of heat exchangers can be substituted for the BAHX illustrated in Figure 16. The system in Figure 1, including heat exchanger 16, can be configured to perform other gas processing options known in the prior art. These processing options may require the gas stream to exit and re-enter the heat exchanger once. 7001? Ln / 77Ω7 / B / YILI or more times and may include, as described in more detail below, the extraction of selected components and the recovery of natural gas liquids. Heat removal is performed in the heat exchanger using a mixed refrigerant that is processed and reconditioned using a mixed refrigerant compressor system, as generally indicated in 26. The mixed refrigerant compressor system includes a high-pressure accumulator 32 that receives and separates a mixed-phase stream of mixed refrigerant (MR) 34 after a final compression and cooling cycle. While an accumulator drum 32 is illustrated, alternative separation devices may be used, including, but not limited to, other vessel types, a cyclone separator, a distillation unit, a coalescing separator, or a mesh or vane-type mist eliminator. The high-pressure vapor refrigerant stream 36 exits the vapor outlet of the accumulator 32 and travels to the hot end portion 18 of the heat exchanger 16. The high-pressure liquid refrigerant stream 38 exits the liquid outlet of the accumulator 32 and also travels to the hot end of the heat exchanger. After cooling in the heat exchanger, it travels as a mixed-phase stream 40 to a vertical tube of 7001? ίη / ΖΖΠΖ / Ε / ΥΙΛΙ average temperature 42. After the high-pressure steam stream 36 from the accumulator 32 is cooled in the heat exchanger 16, a mixed-phase stream 44 flows to a cold steam separator 46. A resulting vapor-coolant stream 48 leaves the steam outlet of the separator 46 and, after being cooled in the heat exchanger 16, travels to the cold temperature riser 52 as a mixed-phase stream 54. The steam and liquid streams 56 and 58 leave the cold temperature riser 52 and are fed into the primary cooling passage 62 at the cold end 20 of the heat exchanger 16. A vaporized mixed refrigerant stream 63 exits the hot end 18 of the heat exchanger and, after passing through an optional suction drum 65, is directed to the inlet of a compressor for an initial compression and cooling cycle. A liquid stream 64 exits the cold vapor separator 46, is cooled in the heat exchanger 16, and exits the heat exchanger as a mixed-phase stream 66. The mixed-phase stream 66 is directed to the medium-temperature riser 42 and is combined with the mixed-phase stream 40 from the liquid outlet of the accumulator 32. Vapor and liquid streams 72 and 74 exit the medium-temperature riser and are fed into the primary cooling passage 62 as illustrated. 7001? ίη / ΖΖΠΖ / Ε / ΥΙΛΙ An interstage separation device 76 receives and separates a mixed-phase stream of mixed refrigerant 78 after the initial compression and cooling cycle. While a separation drum 76 is illustrated, alternative separation devices may be used, including, but not limited to, other types of vessels, a cyclone separator, a distillation unit, a coalescing separator, or a mesh or paddle-type mist eliminator. A liquid stream 82 exits the liquid outlet of the interstage separation device, is cooled in the heat exchanger 16, and the resulting stream 84 expands and is directed to the primary cooling passage 62. A vapor stream 85 exits a vapor outlet of the interstage separation device and travels to the final compression and cooling cycle of the compression system.In alternative system configurations, the separation device between stages may include only a steam outlet, or it may be completely removed. According to the description, the component extraction system 12 receives a cooled gas feed stream 86, which is produced by cooling the feed gas stream 22 in a first cooling step 88a of the main heat exchanger 16. The cooled feed gas stream 86, after being withdrawn from the main heat exchanger 16, is 7001? Ln / 77Ω7 / B / YILI is directed to an optional suction drum 92. A vapor stream 94 from the suction drum travels to an expander 96, which is preferably an expansion turbine, so that the gas stream pressure is reduced below the critical pressure. This causes the components that would freeze and / or other components that would condense in the main heat exchanger to condense, forming a mixed-phase stream 98. This mixed-phase stream 98 travels to a separation device 102, where a liquid stream 104 containing the condensed freezing components and other selected components is removed from the bottom. While an expansion turbine such as the expander 96 is illustrated, alternative expansion devices could be used, including, but not limited to, expansion valves or orifices. Any liquid collected in the suction drum 92 can be directed into the mixed-phase stream 98 traveling to the separation device by opening a drain valve 106 on a liquid drain line 108 exiting the bottom of the suction drum. This prevents potential damage to the expander 96. Alternatively, the liquid from the suction drum can go directly into the separation device 102 after exiting valve 106. As previously stated, the 92 suction drum, and 7001? Ln / Zznz / E / YIAI In this way, the liquid line 108 and the drain valve 106 are optional and can thus be omitted with the feed stream removed from the main heat exchanger being directed directly to the inlet of the expander 96. Or, in an alternative embodiment, the stream directed to the inlet of the expander 96 can be slightly heated (such as by passing it through a portion of the heat exchanger 16 or a dedicated heat exchanger) to vaporize any liquid in the stream or in the hot gas bypass of the feed gas. A purified methane-rich steam stream 112 exits the top of the separation device 102 at purified steam temperature and is directed to a compressor (or compressors) 114, which can be powered by the expander 96 (in versions of the system where the expander is a turbine) or a motor 115, or a combination of both. Using the expander to power the compressor recovers energy from the high-pressure gas stream received by the expander. The ideal pressure for optimal efficiency of the stream returning to the heat exchanger for liquefaction (the return pressure) is a pressure corresponding to a temperature (the return temperature) that is nearly equal to the temperature of the suction drum or the outlet heat exchanger passage of stream 88a. Upon receiving the steam stream 112 in the 7001? ίη / ZZΖΠZ / E / YΙΛΙ purified vapor temperature (or approximately to the purified vapor temperature due to the potential incidental heating of the purified vapor stream as it flows from the separation device 102 to the compressor inlet), the compressor 114 cold-compresses the vapor stream 112 to a higher pressure and temperature, wherein the temperature of the compressed stream is approximately equal to or slightly lower than the temperature of the vapor in the suction drum 92 or in the cooled gas stream 86 withdrawn from the main heat exchanger. The return temperature of the vapor stream 118 leaving the compressor is ideally close to or below the temperature of the gas in the suction drum 92 (or stream 86) because the system does not heat the vapor leaving the separation device 102 before it enters the compressor 114.Furthermore, by introducing cold vapor into compressor 114, the pressure of the vapor exiting the compressor is higher and the temperature is lower than if the vapor from the separation device 102 were heated before entering the compressor (for the same compressor power level). As a result, the cooling power required for a given level of liquefied natural gas production is reduced, or conversely, higher liquefied natural gas production is achieved if the cooling power is kept constant. The compressed vapor stream 118 is returned to a second compressor. 7001? ίη / ZZΖΠZ / E / YΙΛΙ cooling passage 88b of heat exchanger 16 to a return pressure and return temperature at which it will liquefy so as to produce LNG product stream 24. While the first and second cooling passages 88a and 88b are illustrated in Figure 1 as part of a single heat exchanger 16, in alternative embodiments, passages 88a and 88b can be incorporated into separate heat exchangers arranged in series. Furthermore, passages running parallel to passage 88a can be formed in the same heat exchanger or in additional heat exchangers. The same applies to passage 88b (and to the passages corresponding to passages 88a and 88b in the remaining embodiments). The process shown is for a natural gas liquefaction process; however, the system and process illustrated in 12 can be used with any other process that requires separating at least part of the incoming feed gas at a lower pressure and temperature and benefits from the return of the feed gas at a higher pressure. As illustrated in Figure 2, the component extraction system 12 of Figure 1 can be implemented as part of a liquefaction process using a coiled heat exchanger (CWHX), generally indicated in 116. Such 7001? Ln / 77Ω7 / B / YILI heat exchangers are well known in the prior art and, as examples only, may be purchased from Linde Foot of Dublin, Ireland, or from Air Products and Chemicals, Inc. of Allentown, Pennsylvania. As illustrated in Figure 2, heat exchanger 116 receives a high-pressure natural gas feed stream 122, which is cooled and liquefied in the main heat exchanger through heat extraction via heat exchange with refrigeration streams. As a result, a product stream 124 of liquefied natural gas (LNG) is produced. A compression system provides mixed refrigerant streams and receives a mixed refrigerant flow 128 from the heat exchanger 116 and conditions the mixed refrigerant in the same manner as the compression system 26 of Figure 1. As known in the prior art, the CWHX 116 heat exchanger includes a shell 132 that receives the conditioned mixed refrigerant streams 134, 136, 138, and 140. The mixed refrigerant stream 134 is formed by cooling and expanding the vapor stream 142 from the cold vapor separator 144. The mixed refrigerant stream 136 is formed by cooling and expanding the liquid stream 146 from the cold vapor separator 144. The mixed refrigerant stream 138 is formed by cooling and expanding the liquid stream 148 from the high-pressure accumulator 152. 7001? ίη / ZZΖΠZ / E / YΙΛΙ of mixed refrigerant 140 is formed by cooling and expanding the liquid stream 154 from the interstage separation device 156. The cooling passages 188a and 188b of the heat exchanger 116, and the passages used to cool the mixed refrigerant, are formed by tube bundles wrapped around a core or mandrel and placed inside the heat exchanger shell 132. As a result, the outer surfaces of the tube bundles are exposed to the mixed refrigerant streams 134, 136, 138, and 140 entering the shell. Similar to the system and process in Figure 1, the component extraction system 12 receives a cooled gas feed stream 186, which is produced by cooling the feed gas stream 122 in a first cooling passage 188a of the main heat exchanger 116. The cooled gas feed stream 186 is processed in the component extraction system 12 in the same manner described above with reference to Figure 1, and a compressed steam stream 190 is returned to a second cooling passage 188b of the heat exchanger 116 to be liquefied to produce the LNG product stream 124. An alternative modality of the component extraction system is generally indicated in Figure 3. 7001? ίη / ZZΖΠZ / E / YΙΛΙ liquefaction system 14 works in the same manner as illustrated in Figure 1 and therefore also includes a main heat exchanger 16 which includes the first and second cooling passages 88a and 88b. As explained below, the component extraction system 200 in Figure 3 uses a stripping gas to extract light components from the freezing components and other selected components so that the light components are added to the LNG product stream. With reference to Figure 3, and as in previous embodiments, a natural gas feed stream 202 is cooled and liquefied in the main heat exchanger 16 through heat extraction via heat exchange with cooling streams. As a result, a product stream 204 of liquefied natural gas (LNG) is produced. The component extraction system 200 receives a cooled gas feed stream 206, which is produced by cooling the feed gas stream 202 in the first cooling passage 88a of the main heat exchanger 16. The cooled feed gas stream 206, after being withdrawn from the main heat exchanger 16, is directed to an optional suction drum 208. A stream 7001? ίη / ZZΖΠZ / E / YΙΛΙ of steam 210 from the suction drum travels to an expander 212, which is preferably an expansion turbine, so that the gas stream pressure is reduced below the critical pressure. This causes selected components that would freeze and / or other components that would condense in the main heat exchanger to condense, forming a mixed-phase stream 214. While an expansion turbine is illustrated as the expander 212, alternative expansion devices including, but not limited to, expansion valves or orifices could be used. This mixed-phase stream 214 travels to a separation column, generally indicated as 216. The column 216 includes a separation section 218 and a stripping section 220. As is known in the prior art, the stripping section 220 may include mesh pads, trays, packing, and similar components. The mixed-phase stream 214 enters the separation section 218 of the column and is separated into vapor and liquid portions. The liquid portion flows down into the stripping section 220 directly and / or through an internal or external distribution arrangement that includes, for example, the distribution line 224 and the distribution device 226. A depletion gas is supplied through the line 7001? ίη / ZZΖΠZ / E / YΙΛΙ of exhaust gas 228 which directs a portion of the feed gas stream 202 to the bottom of the exhaust section 220 under the control of valve 230. Alternatively, the exhaust gas can be removed from stream 88a at a cooler temperature. A liquid stream 232 containing the condensed freezing components and other selected components is withdrawn from the bottom of column 216. Any liquid collected in the suction drum 208 can be directed to the stripping section 220 of the column 216 by opening a drain valve 236 in a liquid line 234 leading from the bottom of the suction drum. This prevents potential damage to the expander 212. The suction drum 208, and consequently the liquid line 234 and drain valve 236, are optional and can therefore be omitted with the feed stream removed from the main heat exchanger and directed straight to the expander inlet 212. A steam stream rich in purified methane 238 exits the top of the separation column 216 and is directed to a compressor 242, which can be powered by the expander 212 (in versions of the system where the expander is a turbine) or a motor 244, or a combination of both. Upon receiving the steam stream at the temperature of the separation device, the compressor 242 performs cold compression. 7001? iη / ZZΖΠZ / E / YILI the steam stream 238 at a higher pressure and temperature, wherein the temperature of the compressed gas stream is ideally approximately equal to or slightly lower than the temperature of the steam in the suction drum 208 or the cooled gas stream 206 withdrawn from the main heat exchanger. The outlet temperature of the steam stream 246 leaving the compressor is close to or below the temperature of the gas in the suction drum 208 (or stream 206) because the system does not heat the steam leaving the separation column 216 before it enters the compressor 242. Furthermore, by allowing the cooled steam to enter the compressor 242, the pressure of the steam leaving the compressor is higher than if the steam from the separation column 216 were heated before entering the compressor (for the same compressor power level).As a result, the cooling energy required for a given level of liquefied natural gas production is reduced, or conversely, higher liquefied natural gas production is achieved if the cooling power is fixed. The compressed vapor stream 246 is returned to the second cooling passage 88b of the heat exchanger 16 to be liquefied to produce the LNG product stream 204. An alternative version of the system in Figure 3, where a reboil service has been added for the stripping section of the separation column, is presented in the 7001? ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Figure 4. More specifically, a component extraction system, generally indicated as 300 in Figure 4, includes a separation column 302, which has a separation section 304 and a stripping section 306. A liquid stream 308 containing the condensed freezing components and other selected components is withdrawn from the bottom of column 302. In addition, a reboil service, which includes the reboil heat exchanger 312, receives a reheater liquid stream 314 from the stripping section 306 of the column. The heat exchanger 312 also receives and cools a launch gas stream 316, which branches off the primary natural gas feed stream 318 entering the liquefaction system.As a result, the liquid stream 314 from the column is at least partially vaporized, and the resulting vapor stream 322 is returned to the stripping section 306 of the column for use as stripping gas. The cooled pitch gas stream 324 exits the reheater heat exchanger 312 and is directed to the optional suction drum 326. In embodiments where the suction drum 326 is omitted, the cooled pitch gas stream 324 can be combined with the vapor stream 328 entering the expander 332. In an alternative embodiment, stream 316 can be replaced by a stream taken from stream 88a. 7001? ίη / ZZΖΠZ / E / YΙΛΙ (Figure 1) or any other heating medium. The remaining aspects of the contamination system 300, the separation column 302, and the liquefaction system 14 in Figure 4 operate in the same manner as described above with reference to Figure 3. An alternative modality of the component extraction system is generally indicated at 400 in Figure 5. The liquefaction system 14 operates in the same manner as illustrated in Figure 1. The remaining aspects of the system in Figure 5 are the same as those of the system in Figure 3 with the exception of the treatment of the compressor 414 outlet stream 412. The compressor outlet stream treatment of Figure 5 can be used in any of the modalities described above. System 400 includes a main heat exchanger 406 comprising a hot-end portion 406, a cold-end portion 410, and the first and second cooling passages 408a and 408b. As illustrated in Figure 5, the second cooling passage 408b is configured as a high-pressure passage that passes at least partially through the hot-end and cold-end portions 406 and 410 of the heat exchanger. In the mode shown in Figure 5, the compressor suction remains at approximately the purified vapor temperature where, as in the previous modes, the temperature 7001? Ln / 77Ω7 / B / YILI of purified steam is the temperature of the steam stream 416 exiting the top of the separation device 418. The compressor discharge pressure, and thus the pressure of stream 412, is increased (compared to the modes described above) to the point where stream 412 is hotter than the temperature of stream 422 entering the expander 424 (or optional suction drum 426). As a result, the gas stream 412 is hotter than in the previous modes, and thus stream 412 is directed to the high-pressure gas passage 408b. In this mode, it may be necessary to power the compressor with an optional motor 428 (either on its own or in addition to the power supplied by the expander turbine 424).Additionally, an optional 430 compressor discharge conditioning heat exchanger can be provided to condition (which can be either cooling or heating) the 412 stream and provide thermal integration with the liquefaction, condensate, or other process system before it enters the heat exchanger. The component extraction system methods presented above recompress a gas from a separation device, where the selected components are extracted from the gas without heating it, so the compressor suction is cold. 7001? Ln / 77Ω7 / B / YILI, that is, at the temperature of the separation device. The power required for the compressor's compression and discharge temperatures is proportional to the suction temperature. Therefore, cold compression allows for a higher compressor discharge pressure and a lower temperature than if the suction were heated first, with a fixed power supply, and the desired return temperature and pressure to the main heat exchanger. As a result, the cooling energy required for a given level of liquefied natural gas production is reduced, or conversely, a higher liquefied natural gas production is achieved if the cooling energy is fixed. While preferred embodiments of the invention have been shown and described, it will be evident to those skilled in the art that changes and modifications can be made to them without departing from the spirit of the invention, the scope of which is defined by the appended claims. It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.

Claims

1. A system for extracting selected components from a gas stream, characterized in that it comprises: a) a heat exchanger including a first cooling passage configured to receive a feed gas stream and provide a cooled feed gas stream; b) an expander configured to receive at least a portion of the cooled feed gas stream; c) a separation device configured to receive an expanded fluid stream from the expander and separate the expanded fluid stream into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature; and d) a compressor configured to receive the purified vapor stream at approximately the purified vapor temperature and to produce a compressed vapor stream that is returned to the heat exchanger.

2. The system according to claim 1, characterized in that it further comprises a second cooling passage configured to receive the compressed steam stream 7001? Ln / Zznz / E / YIAI and wherein the heat exchanger includes a single main heat exchanger comprising the first and second cooling passages.

3. The system according to claim 1, characterized in that it further comprises a second cooling passage configured to receive the compressed steam stream and wherein the heat exchanger includes a first heat exchanger including the first cooling passage and a second heat exchanger including the second cooling passage.

4. The system according to claim 1, characterized in that it further comprises a second cooling passage configured to receive the compressed steam stream, a third cooling passage arranged in parallel with the first cooling passage such that the first and third cooling passages receive the feed gas stream and provide a cooled feed gas stream to the expander, and a fourth cooling passage arranged in parallel with the second cooling passage such that the second and fourth cooling passages receive the compressed steam stream.

5. The system according to claim 4, characterized in that the first and second cooling passages are in a first heat exchanger and the third and fourth cooling passages are in a second heat exchanger.

6. The system according to claim 1, characterized in that it further comprises a conditioning heat exchanger configured to receive compressed steam from the compressor and to direct the conditioned compressed steam to the heat exchanger.

7. The system according to claim 1, characterized in that it further comprises a suction drum configured to receive the cooled feed gas stream from the first cooling passage of the heat exchanger, the suction drum having a suction drum steam outlet configured to direct at least a portion of the cooled feed gas stream to the expander.

8. The system according to claim 7, characterized in that the suction drum has a suction drum liquid outlet and further comprises a liquid drain line configured to direct a fluid stream towards the separation device.

9. The system according to claim 8, characterized in that the liquid drain line includes a drain valve.

10. The system according to claim 1, characterized in that the expander is an expansion turbine. 7001? Ln / 77Ω7 / B / YILI 11. The system according to claim 10, characterized in that the compressor is powered by the expansion turbine.

12. The system according to claim 11, characterized in that the compressor is powered by the expansion turbine and a motor.

13. The system according to claim 1, characterized in that the expander is powered by a motor.

14. The system according to claim 1, characterized in that the separation device includes a separation column having a separation section and a stripping section, wherein the separation section is configured to receive the expanded fluid stream from the expander, direct the liquid to the stripping section, and direct the purified vapor stream to the compressor, and the contaminant liquid stream exits the stripping section; and further comprising a stripping gas line configured to receive a portion of the feed gas stream and to direct the portion of the feed gas stream to the stripping section for use as a stripping gas.

15. The system according to claim 14, characterized in that the exhaust gas line includes an inlet configured to receive fluid from the 7001? Ln / 77Ω7 / B / YILI first cooling passage of the heat exchanger.

16. The system according to claim 14, characterized in that it further comprises a suction drum configured to receive the cooled feed gas stream from the first cooling passage of the heat exchanger, the suction drum having a suction drum vapor outlet configured to direct at least a portion of the cooled feed gas stream to the expander and a suction drum liquid outlet configured to direct a fluid stream to the exhaust section.

17. The system according to claim 1, characterized in that the separation device includes a separation column having a separation section and a stripping section, wherein the separation section is configured to receive the expanded fluid stream from the expander, direct the liquid to the stripping section, and direct the purified vapor stream to the compressor, and wherein the liquid stream containing the selected components exits the stripping section; and further comprising: a reheater heat exchanger configured to receive a reheater liquid stream from the stripping section to vaporize at least partially the reheater liquid stream and direct a resulting stripping gas stream to the stripping section.

18. The system according to claim 17, characterized in that it further comprises a launch gas line configured to receive a portion of the feed gas stream and to direct the portion of the feed gas stream to the reheater heat exchanger wherein the portion of the feed gas stream is cooled as the reheater liquid stream is heated and vaporized and wherein the reheater heat exchanger is configured to direct at least a portion of the cooled portion of the feed gas stream to the expander.

19. The system according to claim 1, characterized in that it further comprises a second cooling passage configured to receive the compressed steam stream, wherein the first and second cooling passages are positioned within the heat exchanger in a parallel configuration.

20. The system according to claim 19, characterized in that the heat exchanger includes a hot end portion and a cold end portion with the second cooling passage forming a high-pressure passage passing at least partially through both the hot and cold end portions of the heat exchanger, and wherein the first cooling passage passes through at least a portion of the hot end portion of the heat exchanger.

21. The system according to claim 20, characterized in that it further comprises a conditioning heat exchanger configured to receive compressed steam from the compressor and to direct the conditioned compressed steam to the high-pressure passage.

22. A feed gas liquefaction system, characterized in that it comprises: a. a heat exchanger having a first cooling passage and a second cooling passage, the first cooling passage being configured to receive a feed gas stream so as to form a cooled feed gas stream; b. a mixed refrigerant compression system in communication with the heat exchanger and configured to cool the first and second cooling passages; c. a liquefied gas outlet line connected to an outlet of the second cooling passage; d. an expander configured to receive at least a portion of the cooled feed gas stream from the first cooling passage; e.a separation device configured to receive an expanded fluid stream from the expander and to separate the expanded fluid stream into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature; f. a compressor configured to receive the purified vapor stream at approximately the purified vapor temperature and to produce a compressed vapor stream; g. the second cooling passage configured to receive and liquefy the compressed vapor stream.

23. The system according to claim 22, characterized in that the heat exchanger includes a single main heat exchanger comprising the first and second cooling passages.

24. The system according to claim 22, characterized in that the heat exchanger includes a first heat exchanger including the first cooling passage and a second heat exchanger including the second cooling passage.

25. The system according to claim 22, characterized in that it further comprises a third cooling passage arranged in parallel with the first cooling passage, such that the first and third cooling passages receive the feed gas stream and provide a cooled feed gas stream 7001? Ln / 77Ω7 / B / YILI to the expander, and a fourth cooling passage arranged in parallel with the second cooling passage such that the second and fourth cooling passages receive and liquefy the compressed vapor stream.

26. The system according to claim 25, characterized in that the first and second cooling passages are in a first heat exchanger and the third and fourth cooling passages are in a second heat exchanger.

27. The system according to claim 22, characterized in that it further comprises a conditioning heat exchanger configured to receive compressed steam from the compressor and to direct the conditioned compressed steam to the heat exchanger.

28. The system according to claim 22, characterized in that it further comprises a suction drum configured to receive the cooled feed gas stream from the first cooling passage of the heat exchanger, the suction drum having a suction drum steam outlet configured to direct at least a portion of the cooled feed gas stream to the expander.

29. The system according to claim 28, characterized in that the suction drum has a suction drum liquid outlet and further comprises a liquid drain line 7001? Ln / 77Ω7 / B / YILI configured to direct a fluid stream towards the separation device.

30. The system according to claim 29, characterized in that the liquid drain line includes a drain valve.

31. The system according to claim 22, characterized in that the expander is an expansion turbine.

32. The system according to claim 31, characterized in that the compressor is powered by the expansion turbine.

33. The system according to claim 31, characterized in that the compressor is powered by the expansion turbine and a motor.

34. The system according to claim 22, characterized in that the compressor is powered by a motor.

35. The system according to claim 22, characterized in that the separation device includes a separation column having a separation section and a stripping section, wherein the separation section is configured to receive the expanded fluid stream from the expander, direct the liquid to the stripping section, and direct the purified vapor stream to the compressor, and wherein the liquid stream containing the selected components exits the stripping section; 7001? Ln / 77Ω7 / B / YILI, and further comprising a stripping gas line configured to receive a portion of the feed gas stream and to direct the portion of the feed gas stream to the stripping section for use as stripping gas.

36. The system according to claim 35, characterized in that the exhaust gas line includes an inlet configured to receive fluid from the first cooling passage of the heat exchanger.

37. The system according to claim 35, characterized in that it further comprises a suction drum configured to receive the cooled feed gas stream from the first cooling passage of the heat exchanger, the suction drum having a suction drum vapor outlet configured to direct at least a portion of the cooled feed gas stream to the expander and a suction drum liquid outlet configured to direct a fluid stream to the exhaust section.

38. The system according to claim 22, characterized in that the separation device includes a separation column having a separation section and a stripping section, wherein the separation section is configured to receive the expanded fluid stream from the expander, direct the liquid to the stripping section, and direct the purified vapor stream to the compressor, and wherein the liquid stream containing components exits the stripping section; and further comprising: a reheater heat exchanger configured to receive a reheater liquid stream from the stripping section for heating and at least partially vaporizing the reheater liquid stream and directing a resulting stripping gas stream to the stripping section.

39. The system according to claim 38, characterized in that it further comprises a launch gas line configured to receive a portion of the feed gas stream and to direct the portion of the feed gas stream to the reheater heat exchanger wherein the portion of the feed gas stream is cooled as the reheater liquid stream is heated and partially vaporized and wherein the reheater heat exchanger is configured to direct at least a portion of the cooled portion of the feed gas stream to the expander.

40. The system according to claim 22, characterized in that the heat exchanger includes a hot end portion and a cold end portion with the second cooling passage forming a high-pressure passage that passes at least partially through both the hot and cold end portions of the heat exchanger and wherein the first cooling passage passes through at least a portion of the hot end portion of the heat exchanger.

41. The system according to claim 40, characterized in that it further comprises a conditioning heat exchanger configured to receive compressed steam from the compressor and to direct conditioned compressed steam to the high-pressure passage.

42. A method for extracting selected components from a gas stream, characterized in that it comprises the steps of: a. cooling a feed gas stream to provide a chilled feed gas stream; b. expanding the cooled feed gas stream to provide an expanded gas stream; c. separating the expanded gas stream into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature; and d. compressing the purified vapor stream after receiving the purified vapor stream at approximately the purified vapor temperature to provide a compressed vapor stream.

43. The method according to claim 42, characterized in that the gas stream is a natural gas stream.

44. A method for liquefying a gas feed stream, characterized in that it comprises the steps of: a. cooling a feed gas stream to provide a chilled feed gas stream; b. expanding the chilled feed gas stream to provide an expanded gas stream; c. separating the expanded gas stream into a liquid stream containing selected components and a purified vapor stream having a purified vapor temperature; d. compressing the purified vapor stream after receiving the purified vapor stream to approximately the purified vapor temperature to provide a compressed vapor; and e. cooling the compressed vapor stream to form a liquefied gas stream.

45. The method according to claim 44, characterized in that the gas stream is a natural gas stream.

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