WO2021007548A1 - Systèmes et procédés permettant d'améliorer l'efficacité de systèmes frigorifiques en cascade et à composants multiples combinés - Google Patents

Systèmes et procédés permettant d'améliorer l'efficacité de systèmes frigorifiques en cascade et à composants multiples combinés Download PDF

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Publication number
WO2021007548A1
WO2021007548A1 PCT/US2020/041676 US2020041676W WO2021007548A1 WO 2021007548 A1 WO2021007548 A1 WO 2021007548A1 US 2020041676 W US2020041676 W US 2020041676W WO 2021007548 A1 WO2021007548 A1 WO 2021007548A1
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Prior art keywords
refrigerant
chilled
line
heat exchanger
feed gas
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PCT/US2020/041676
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English (en)
Inventor
David Ladd
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Bechtel Oil, Gas And Chemicals, Inc.
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Priority to AU2020311435A priority Critical patent/AU2020311435B2/en
Priority to US17/625,971 priority patent/US20220236004A1/en
Publication of WO2021007548A1 publication Critical patent/WO2021007548A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0211—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle
    • F25J1/0214—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a dual level refrigeration cascade with at least one MCR cycle
    • F25J1/0215—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a dual level refrigeration cascade with at least one MCR cycle with one SCR cycle
    • F25J1/0216—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a dual level refrigeration cascade with at least one MCR cycle with one SCR cycle using a C3 pre-cooling cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/0052—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/0052—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream
    • F25J1/0055—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream originating from an incorporated cascade
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
    • F25J1/008—Hydrocarbons
    • F25J1/0087—Propane; Propylene
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0262—Details of the cold heat exchange system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0291—Refrigerant compression by combined gas compression and liquid pumping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0292—Refrigerant compression by cold or cryogenic suction of the refrigerant gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/04—Mixing or blending of fluids with the feed stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/40—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/60—Expansion by ejector or injector, e.g. "Gasstrahlpumpe", "venturi mixing", "jet pumps"
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/90—Processes or apparatus involving steps for recycling of process streams the recycled stream being boil-off gas from storage
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/12—External refrigeration with liquid vaporising loop

Definitions

  • the present disclosure generally relates to systems and methods for improving the efficiency of combined cascade and multicomponent refrigeration systems. More particularly, the systems and methods improve the efficiency of combined cascade and multicomponent refrigeration systems by utilizing one or more ejectors to reduce and/or eliminate compression stages.
  • the natural gas liquefaction process takes natural gas, primarily comprised of methane at high pressure and passes it through consecutive refrigeration cycles. These refrigeration cycles can be single or multi-component.
  • the present disclosure relates to multi- component refrigeration cycles. Two examples of such processes are presented in FIGS. 1 and 2.
  • FIG 1 a schematic diagram illustrates a conventional propane, pre-cooling system with mixed refrigerant liquefaction (hereinafter collectively the“C3MR system”).
  • Feed Gas 102 enters the system and is mixed with boil-off gas from line 104 that is recompressed.
  • the feed gas 102 is chilled by means of three consecutive heat exchangers (106, 108, 110).
  • the heat exchangers chill the feed gas to a temperature of approximately 23°F in line 111.
  • the chilled feed gas in line 111 is then distributed through two zones 112, 114 of a spiral-wound design heat exchanger, reaching a temperature of -about 262°F in line 116.
  • the propane pre-cooling system is comprised of a three-stage compressor 118, three flash drums 120, 122, 124 and a chiller 126 to reject heat.
  • Vapor propane is introduced into the first compression stage of compressor 118 and is compressed through three successive stages before being transferred through line 128 to the chiller 126.
  • the chiller 126 typically an air cooler or cooling water exchanger, chills the compressed propane to a temperature of about 100°F.
  • the outlet pressure in line 130 is equivalent to the pressure at which the refrigerant is liquid, which for propane is approximately 190 psia.
  • the liquid propane in line 130 is flashed through an expansion valve 132 to a pressure of approximately 80 psia and a temperature of about 41°F.
  • the outlet of the first heat exchanger 106 consists of a two-phase mixture of liquid and vapor propane.
  • the mixture is flashed in the high stage of flash drum 124.
  • the vapor is recompressed in the compressor 118.
  • the liquid is flashed to a lower pressure through a second expansion valve 134 to a temperature of approximately 25°F and 61 psia and is introduced into the second heat exchanger 108.
  • the outlet of the first heat exchanger 108 consists of a two-phase mixture of liquid and vapor propane.
  • the mixture is flashed in the middle stage flash drum 122.
  • the vapor is recompressed in the compressor 118.
  • the liquid is flashed to a lower pressure through a third expansion valve 136 to a temperature of approximately -35°F and 18 psia and is introduced into the third heat exchanger 110.
  • the propane is completely vaporized in the third exchanger 110 and is distributed into a compressor suction drum 120.
  • the mixed refrigerant system consists of a two-stage compressor 138, a refrigerant chiller 140 for heat rejection, a flash drum 142 for separating the mixed refrigerant into liquid and vapor phases and the spiral wound heat exchanger with two zones, 112 and 114. Vapor mixed refrigerant is introduced to the two-stage compressor 138.
  • the mixed refrigerant composition is variable and is designed to closely match the cooling curve of the feed gas 102. In this example, the mixed refrigerant composition is described in Table 1 below.
  • the mixed refrigerant is compressed to a pressure of approximately 601 psia and is then chilled to a temperature of 118°F by the mixed refrigerant chiller 140.
  • the mixed refrigerant chiller 140 can typically be an air cooler or cooling water exchanger.
  • the chilled mixed refrigerant in line 144 is introduced into the second and third heat exchangers 108, 110 and is subsequently chilled to about -30°F.
  • the refrigerant consists of a liquid and vapor mixture in line 146. In this example, the vapor molar fraction is approximately 43%.
  • the refrigerant is separated in flash drum 142 into liquid and vapor refrigerants and is then inserted into the top and bottom sections of the spiral wound heat exchanger. The refrigerant is then collected at the bottom of the spiral wound exchanger 112 and sent back to the suction of the two-stage compressor 138.
  • Liquefied gas in line 116 is flashed to atmospheric pressure via an expansion valve 148 as well as via the line losses in the transfer pipe and stored in a cryogenic liquefied natural gas (LNG) tank. Because the liquefied gas is subcooled, no vapor is generated.
  • Boil-off gas from the LNG tank is recompressed to pipeline pressure via a boil-off gas compressor 150 and chiller 152.
  • the chiller is typically an air cooler or cooling water exchanger.
  • FIG 2 a schematic diagram illustrates a conventional multi-component, integrated, propane pre-cooling system with single mixed refrigerant liquefaction (hereinafter collectively the“IPSMR system”).
  • Feed Gas 202 enters the system and is mixed with boil-off gas from line 204 that is recompressed.
  • the feed gas 204 is chilled by means of three consecutive heat exchangers (206, 208, 210).
  • the heat exchangers chill the feed gas to a temperature of approximately -35°F.
  • the chilled feed gas is then distributed through a brazed aluminum heat exchanger 212, reaching a temperature of about -265°F at the outlet in line 216.
  • the propane pre-cooling system is comprised of a three-stage compressor 218, three flash drums 220, 222, 224 and a chiller 226 to reject heat.
  • Propane in the vapor phase is introduced into the first compression stage of compressor 218 and is compressed through three successive stages before being transferred through line 228 to the chiller 226.
  • the outlet pressure in line 230 is equivalent to the pressure at which the refrigerant is liquid, which for propane is approximately 190 psia.
  • the liquid propane in line 230 is flashed through an expansion valve 232 to a pressure of approximately 80 psia and a temperature of about 41°F.
  • the outlet of the first heat exchanger 206 consists of a two-phase mixture of liquid and vapor propane.
  • the mixture is flashed in the high stage flash drum 224.
  • the vapor is recompressed in the compressor 218.
  • the liquid is flashed to a lower pressure through a second expansion valve 234 to a temperature of approximately 25°F and 61 psia and is introduced into the second heat exchanger 208.
  • the outlet of the first heat exchanger 208 consists of a two-phase mixture of liquid and vapor propane.
  • the mixture is flashed in the middle stage flash drum 222.
  • the vapor is recompressed in the compressor 218.
  • the liquid is flashed to a lower pressure through a third expansion valve 236 to a temperature of approximately -35°F and 18 psia and is introduced into the third heat exchanger 210.
  • the propane is completely vaporized in the third exchanger 210 and is distributed into a compressor suction drum 220.
  • the mixed refrigeration system consists of a brazed aluminum heat exchanger 212, three flash drums 242, 244, 246, a two-stage mixed refrigerant compressor 238, a mixed refrigerant chiller 240, and a mixed refrigerant pump 248.
  • Vapor mixed refrigerant 250 is introduced into the mixed refrigerant compressor 238.
  • the mixed refrigerant composition is variable and is designed to closely match the cooling curve of the feed gas 202. In this example, the mixed refrigerant composition is described in Table 2 below.
  • the mixed refrigerant is compressed to a pressure of approximately 718 psia and is then chilled via the mixed refrigerant chiller 240 to a temperature of about 95°F. At this state, the mixed refrigerant is approximately 70% vapor in line 252. The vapor and liquid mixed refrigerant is then transferred to a flash drum 246. The vapor and liquid are transferred through various sections of the brazed aluminum heat exchanger 212 and flashed through three separate let-down valves 254, 256, 258. The refrigerant is partially condensed in the brazed aluminum heat exchanger 212 and is then returned to flash drum 242. Liquid from the flash drum 242 is transferred to the middle stage flash drum 244 via a pump 248.
  • the middle stage flash drum 244 operates at a pressure of approximately 196 psia and a temperature of about 95°F. Liquid from the flash drum 244 is transferred to the brazed aluminum heat exchanger 212 and recycled back to flash drum 242. Vapor from the middle stage flash drum 244 is compressed in the mixed refrigerant compressor 238.
  • FIG. 1 is a schematic diagram illustrating a conventional C3MR system.
  • FIG. 2 is a schematic diagram illustrating a conventional IPSMR system.
  • FIG. 3 is a schematic diagram illustrating one embodiment of the present disclosure retrofitted in a pre-existing liquefied natural gas process.
  • FIG. 4 is a schematic diagram illustrating one embodiment of the present disclosure applied to a C3MR liquefied natural gas process.
  • FIG. 5 is a schematic diagram illustrating another embodiment of the present disclosure applied to an IPSMR liquefied natural gas process.
  • the present disclosure includes a system for chilling a feed gas, which comprises: i) a first heat exchanger enclosing a first portion of a feed gas line and a portion of a first chilled refrigerant line; ii) a first flash drum in fluid communication with the first chilled refrigerant line for receiving a two-phase refrigerant from the first heat exchanger, the first flash drum having a first vapor outlet line and a first liquid outlet line; iii) a second heat exchanger enclosing a second portion of the feed gas line and a portion of a second chilled refrigerant line; iv) a second flash drum in fluid communication with the second chilled refrigerant line for receiving a two-phase refrigerant from the second heat exchanger, the second flash drum having a second vapor outlet line and a second liquid outlet line; v) a third heat exchanger enclosing a third portion of the feed gas line and a portion of a third child
  • the present disclosure includes a method for chilling a feed gas, which comprises: i) introducing a feed gas stream through a first heat exchanger, a second heat exchanger and a third heat exchanger; ii) chilling the feed gas stream in the first heat exchanger by circulating a first chilled refrigerant stream adjacent the feed gas stream in the first heat exchanger using a compressor and a chiller to convert a first vapor refrigerant stream from a first flash drum into a liquid refrigerant stream and an ejector to convert the liquid refrigerant stream into the first chilled refrigerant stream; iii) chilling the feed gas stream in the second heat exchanger by circulating a second chilled refrigerant stream adjacent the feed gas stream in the second heat exchanger using a first liquid refrigerant stream from the first flash drum; iv) chilling the feed gas stream in the third heat exchanger by circulating a third chilled refrigerant stream adjacent the feed gas stream in the third heat exchanger using
  • FIG. 3 a schematic diagram illustrates one embodiment of the present disclosure retrofitted in a pre-existing liquefied natural gas process.
  • a vaporized refrigerant from the lowest stage drum 120 is taken through line 302 to an ejector 304 that is preferably a liquid motive ejector.
  • the motive for the ejector 304 is supplied via line 130 and is passed at saturated liquid conditions through a high-efficiency pump 306.
  • the propane chilling compressor 118 can comprise three stages or can employ two stages of compression and instead redirect the total flow of vaporized refrigerant from the lowest stage drum 120 through line 302. This facilitates a significant decrease in mass flow to the compressor 118, as depicted in Table 3 below, based on a HYSYSTM simulation.
  • the adjustment of the temperature profile differs by implementation, but generally is a reduction of about 2°F to about 4°F in the feed gas stream 102 and about 5°F to about 100°F in the supplemental refrigeration system 312.
  • the supplemental refrigeration system 312 produces one of a chilled feed gas stream and a liquified feed gas stream in line 116.
  • the supplemental refrigeration system 312 may be a mixed refrigeration system that includes a mixed refrigerant.
  • the boil-off gas recompression system can be eliminated in favor of another liquid motive ejector 310 that is controlled by means of the letdown valve 148. Pressure in the form of vapor suction through line 308 to the ejector 310 is monitored to ensure that the LNG tank does not reach vacuum pressure.
  • a small temperature increase of approximately 3-5°F is noted from HYSYS simulation models, but due to the significant subcooling of the chilled feed gas stream or the liquified feed gas stream at the letdown valve 148, no vapor generation occurs.
  • FIG. 4 a schematic diagram illustrates one embodiment of the present disclosure applied to a C3MR liquefied natural gas process.
  • the lowest compression stage from the drum 120 to the compressor 118 is eliminated.
  • the entire vaporized refrigerant from drum 120 is thus, diverted through line 302 to the liquid motive ejector 304.
  • the resultant effect is a reduction in the temperature in line 111 from about 23°F to about 19°F.
  • the temperature of the mixed refrigerant in line 146 is also reduced from about -30°F to about -34°F.
  • the vapor fraction in flash drum 142 is adjusted from about 43% to about 41%.
  • the inter-stage flashes conditions in the supplemental refrigeration system improve from about -162°F in the conventional C3MR liquefied natural gas process to about -190°F.
  • the temperature remains the same.
  • Table 4 (below) illustrates the impact of this embodiment applied to a natural gas liquefaction process for two cases, modeled using HYSYSTM.
  • One case maintains the natural gas feed rate to the natural gas liquefaction terminal.
  • the second case increases the feed rate to maintain the compressor 118 at a capacity like a conventional C3MR liquefied natural gas process.
  • An observed feed rate increase of nearly 17% is depicted when the terminal is revamped with the present embodiment. Additionally, a brake power reduction of nearly 22% is observed.
  • FIG. 4 (w/ increased
  • FIG. 5 a schematic diagram illustrates another embodiment of the present disclosure applied to an IPSMR liquefied natural gas process.
  • the lowest compression stage from the drum 220 to the compressor 218 is eliminated.
  • the entire vaporized refrigerant from drum 220 is thus, diverted through line 302 to the liquid motive ejector 304.
  • the increased capacity in the propane chilling system is used to cool the mixed refrigerant in line 501.
  • the mixed refrigerant passed through heat exchangers 206, 208 and 210 is chilled to a temperature of about -13°F in line 502.
  • the mixed refrigerant is then re-introduced into the brazed aluminum heat exchanger 212.
  • Table 5 illustrates the impact of this embodiment applied to a natural gas liquefaction process for two cases, modeled using HYSYSTM. One case only modifies the propane chilling system. The second case modifies both the propane chilling system and the mixed refrigeration system depicted in FIG. 5. Additionally, a brake power reduction of nearly 12% is observed.
  • FIG. 5 (w/MR
  • the systems and methods disclosed herein thus, improve the efficiency of combined cascade and multicomponent refrigeration systems by utilizing one or more ejectors to reduce and/or eliminate conventional compression stages.
  • the systems and methods change the temperature profile, which reduces the energy consumption of both the mixed refrigeration system and the pre-cooling system.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

La présente invention concerne des systèmes et des procédés permettant d'améliorer l'efficacité de systèmes frigorifiques en cascade et à composants multiples combinés en utilisant un ou plusieurs éjecteurs pour réduire et/ou éliminer des étapes de compression. Les systèmes et les procédés modifient le profil de température, ce qui réduit la consommation d'énergie à la fois du système frigorifique mixte et du système de pré-refroidissement.
PCT/US2020/041676 2019-07-10 2020-07-10 Systèmes et procédés permettant d'améliorer l'efficacité de systèmes frigorifiques en cascade et à composants multiples combinés WO2021007548A1 (fr)

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AU2020311435A AU2020311435B2 (en) 2019-07-10 2020-07-10 Systems and methods for improving the efficiency of combined cascade and multicomponent refrigeration systems
US17/625,971 US20220236004A1 (en) 2019-07-10 2020-07-10 Systems and Methods for Improving the Efficiency of Combined Cascade and Multicomponent Refrigeration Systems

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US201962872317P 2019-07-10 2019-07-10
US62/872,317 2019-07-10

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US11725858B1 (en) 2022-03-08 2023-08-15 Bechtel Energy Technologies & Solutions, Inc. Systems and methods for regenerative ejector-based cooling cycles

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US20220236004A1 (en) 2022-07-28
AU2020311435B2 (en) 2023-01-19

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