WO2015140197A2 - Procédé de liquéfaction d'un gaz naturel prétraité - Google Patents

Procédé de liquéfaction d'un gaz naturel prétraité Download PDF

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Publication number
WO2015140197A2
WO2015140197A2 PCT/EP2015/055636 EP2015055636W WO2015140197A2 WO 2015140197 A2 WO2015140197 A2 WO 2015140197A2 EP 2015055636 W EP2015055636 W EP 2015055636W WO 2015140197 A2 WO2015140197 A2 WO 2015140197A2
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Prior art keywords
refrigerant
cooling
lng
liquefaction
natural gas
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WO2015140197A3 (fr
Inventor
Pål Leo ECKBO
Tor Christensen
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GLOBAL LNG SERVICES Ltd
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GLOBAL LNG SERVICES Ltd
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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
    • F25J1/0002—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
    • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
    • F25J1/0097—Others, e.g. F-, Cl-, HF-, HClF-, HCl-hydrocarbons etc. or mixtures thereof
    • 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
    • F25J1/0212—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 single flow MCR 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
    • F25J1/02—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
    • 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
    • F25J1/0264—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams
    • F25J1/0265—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer
    • F25J1/0268—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer using a dedicated refrigeration means
    • 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
    • F25J1/0275—Construction and layout of liquefaction equipments, e.g. valves, machines adapted for special use of the liquefaction unit, e.g. portable or transportable devices
    • F25J1/0277—Offshore use, e.g. during shipping
    • F25J1/0278—Unit being stationary, e.g. on floating barge or fixed platform
    • 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.
    • F25J1/0296—Removal of the heat of compression, e.g. within an inter- or afterstage-cooler against an ambient heat sink
    • 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
    • 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
    • F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration

Definitions

  • the present invention relates to improvements in methods and plants for liquefaction of natural gas to provide Liquefied Natural Gas (LNG) with improved economics and a reduction of the environmental impact including the elimination of the water intake of today's floating liquefaction plants. More specifically, the present invention relates to a method and plant for LNG production environmentally suited to locations offshore, or for locations near coastlines, with increased safety and liquefaction efficiency.
  • LNG Liquefied Natural Gas
  • Natural gas is becoming more important as the world's energy demand increases as well as its concerns about air and water emissions increase. Natural gas is readily available, in particular with the new technologies to utilize shale gas. It is much cleaner-burning than oil and coal, and does not have the hazard or waste deposition problems associated with nuclear power. The emission of greenhouse gases is lower than for oil, and only about one third of such emissions from coal.
  • LNG liquefied natural gas
  • the first step is gas pre-treatment to remove components that can solidify when cooled to cryogenic temperatures, mainly sour components and water. Trace elements, mainly mercury which can form amalgams - in particular with aluminum process components - are also removed from the gas. Heavy hydrocarbon fractions or Natural Gas Liquids (NGL) may be removed from the gas in the first or second of the two LNG processing steps.
  • the second processing step is mainly liquefaction of the purified gas, which then comprises mainly methane.
  • the entire FLNG plant can be built in a shipyard, which is efficient and improves quality control, cost control and reduces
  • FLNG's are also mobile and can be transferred to alternative locations if required.
  • both gas pre-processing and liquefaction will typically be located on the deck of the FLNG.
  • Space below deck is used for LNG storage and marine-specific equipment.
  • the area available on the FLNG deck is generally only about 20% of the area used for similar facilities onshore. This reduced process lay-out space presents safety issues, including proximity to living quarters and limited space for safety barriers. Significantly, it also limits the size of the processing plants and the possibilities to utilize economies of scale.
  • the liquefaction process generates large amounts of heat which must be transferred to the environment. Large amounts of sea water are needed for cooling purposes onboard the FLNG, water that is subsequently being discharged at a higher temperature.
  • CLSO Offloading
  • Oljeselskap AS now Statoil ASA
  • Air coolers are less efficient and require much larger space compared to seawater cooling. This presents a design challenge even with the extra deck space available on a CLSO. Furthermore, air cooled heat
  • design ambient air temperature may be relatively high such as 32°C (90°F) or higher, and it is anticipated that the approach temperature for the air cooled heat exchangers should be at least 10°C, preferably 15°C or more.
  • the deck space on a CLSO is severely limited. Therefore, the footprint of the air cooled exchangers must be minimized.
  • FIG. 1 shows typical air cooled exchanger plot area (footprint) for 100 MW cooling of hydrocarbons, with an ambient temperature of 40°C.
  • Figure 1 shows typical air cooled exchanger plot area (footprint) for 100 MW cooling of hydrocarbons, with an ambient temperature of 40°C.
  • higher hydrocarbon outlet temperature reduces the required plot area significantly.
  • higher hydrocarbon inlet temperature also reduces the plot area. Cooling to temperatures below ambient temperature of 40°C is not feasible in this example. In actual practice, cooling to low temperatures is almost always more difficult with air cooling than with water cooling.
  • Liquefaction processes are powered by compressors with inter-coolers and after-coolers, as shown much simplified in Figure 2.
  • Low pressure refrigerant enters the first compression stage, is compressed and cooled in an inter-cooler.
  • the refrigerant is then further compressed in a next compression stage, and cooled in an after-cooler.
  • the refrigerant now has high pressure and low enthalpy, and is returned to the liquefaction process. With air cooling, the coolers will have higher outlet temperatures. This increases compressor work by at least three mechanisms.
  • FIG. 3 illustrates the effect of increasing the pressure from e.g. 35 to 52 bara on the condensation temperature for the gas. At 35 bara cooling below 40 °C is necessary for condensation as shown with line a), whereas the condensation is complete at 70 °C at a pressure of 52 bara, as shown by line b).
  • Air cooling increases the overall cooling duty by 10 to 15%.
  • the air cooler footprint increases by roughly the same amount.
  • air coolers require power to drive air fans, typically about 2 to 3 MW for the examples in Table 1.
  • the increased refrigerant temperature from compressor after-coolers significantly increases the amount of heat that must be transferred within the LNG heat exchangers where pre-processed natural gas is liquefied. This is because more heat must be transferred from the incoming, pressurized refrigerant in the LNG exchanger to the expanded, cold refrigerant in order to get sufficient pre-cooling of the pressurized refrigerant before expansion. This pre-cooling duty is therefore much larger, resulting in a larger LNG exchanger. There is an upper limit to the size of LNG exchangers.
  • An object of the present invention is to provide a method and a system for generation of LNG from natural gas on Coastal Liquefaction, Storage and Offloading (CLSO) facilities that allows for minimized LNG exchanger duty and hence maximum production using air coolers, while at the same time minimizing any safety concerns.
  • CLSO Coastal Liquefaction, Storage and Offloading
  • Other objects will be clear for the skilled person reading the present description and claims. Accordingly, an efficient base load liquefaction system should be employed, with safe air cooling where flammable refrigerants are confined to a small, safe area, where air cooling does not increase the LNG exchanger duty compared to similar water cooled systems, and with all gas pre-processing located on separate platforms or floaters, or on shore.
  • the present invention relates to a method for liquefaction of a pre- processed natural gas to produce LNG, where pre-processed natural gas and a liquefied and/or cooled primary refrigerant are introduced separately into a LNG heat exchanger where the pre-processed natural gas is liquefied by cooling against the evaporating and/or heating primary refrigerant , where evaporated and/or heated primary refrigerant is withdrawn from the LNG heat exchanger and re-liquefied and/or compressed by compression in a series of compressor steps, where the compressed gas from each compression step is cooled by means of heat exchangers, wherein an aqueous cooling medium cooled in an array of air coolers, is used for cooling of the primary refrigerant.
  • the evaporated primary refrigerant is compressed to a pressure of 45 to 65 bara and condensed at said pressure. Operation at said pressure, makes it possible to complete the condensation at temperatures from about 60 °C, at about 70 °C, or higher, which makes it possible to use air coolers even in hot climate, where the ambient temperature may exceed 40 °C, temperatures which makes it impossible to use air coolers in conventional plants at pressures of e.g. 35 bara, where temperatures lower than 40 °C is needed for condensation. See figure 3.
  • the compressed and cooled refrigerant is further cooled by means of a secondary refrigerant in coolers 16, 16'. Further cooling after compression and cooling by means of an aqueous refrigerant reduces the duty of the LNG heat exchanger, or makes it possible to produce / liquidize more LNG at the same LNG heat exchanger duty.
  • the secondary refrigerant cools the primary refrigerant by evaporation in the coolers (16, 16'), and the secondary refrigerant is compressed, cooled in an array of air coolers before being expanded before being expanded for further cooling of the secondary refrigerant.
  • the secondary refrigerant operates in a heat pump circuit where additional cooling effect from air coolers are obtained for further cooling of the primary refrigerant to reduce the duty of the LNG heat exchanger by creating cooling efficiency that would else be possible only by means of water cooling or by air cooling in cold climate.
  • Figure 1 is a plot of air cooled exchanger footprint for obtaining a set hydrocarbon outlet temperature after cooling at different hydrocarbon inlet temperatures
  • Figure 2 is an illustration of a compressor train comprising two
  • Figure 3 is an illustration of the condensation temperature and pressure for an exemplary refrigerant
  • Figure 4 is an illustration of a natural gas liquefaction plant with air cooling using circulating water as cooling medium for cooling at high temperatures and non-flammable, non-toxic and non-ozone depletion refrigerant as cooling medium for cooling at lower temperatures, and
  • Figure 5 is an illustration of a natural gas liquefaction plant with air cooling using circulating water as cooling medium for cooling at high temperatures and non-flammable, non-toxic and non-ozone depletion refrigerant as cooling medium for cooling at lower temperatures including cooling of pre- processed natural gas.
  • LNG plants according to the present invention will be located on offshore floaters.
  • the floaters will receive pre-treated natural gas from a remote location, which may be pre-treatment facilities on an offshore terminal, a barge or other floater, or land based facilities.
  • the full pre-treatment of the natural gas at the remote location normally comprises but is not limited to:
  • NGL extraction and processing i.e. separation of the NGL from the gas, and optional fractionation of the NGL into saleable products, which depending on the NGL composition might be Liquefied Petroleum Gas (LPG) consisting mainly of propane and butane, and a heavier C5+ fraction.
  • LPG Liquefied Petroleum Gas
  • the pretreated gas is liquefied by cooling to about - 163°C.
  • the liquefaction plants as such will be based on known
  • refrigerants for LNG such as hydrocarbons or nitrogen
  • a circuit comprising compressors, compressor inter-coolers and after-coolers, and LNG exchangers.
  • refrigerants may or may not condense in the compressor coolers before being routed to the LNG exchangers.
  • FIG. 4 illustrates an embodiment of the present invention.
  • Single mixed refrigerant (SMR) liquefaction process is assumed.
  • Pre-treated natural gas arrives to the floater and is introduced into the LNG plant onboard the floater in a gas pipe 1.
  • the gas in line 1 is introduced into a LNG heat exchanger 2.
  • the LNG heat exchanger 2 the gas is cooled, liquefied and sub-cooled by heat exchanging with a cold refrigerant as will be further described below.
  • the liquefied and sub-cooled gas exits the LNG exchanger in pipe 3, where it has an enthalpy close to the enthalpy of LNG at atmospheric pressure. The pressure is then reduced to near
  • Compressed, cooled and fully or partly condensed refrigerant in a cold refrigerant line 17 is introduced to LNG exchanger 2, where it is further cooled and, if required, fully condensed. Following this cooling, the refrigerant is expanded in valve 7, which further reduces the temperature, and, most importantly, enables boiling at low temperatures.
  • the cold and expanded refrigerant flows via pipe 8 through LNG exchanger 2. In this process, the refrigerant is gasified and heated.
  • the heated and gasified refrigerant is withdrawn from the LNG exchanger in refrigerant pipe 9, which routes the refrigerant to serially arranged main compressors 10, 10 ' and 10 " in which the refrigerant is compressed in a series of compressions. Due to the heating caused by compression heat exchangers 1 1 , 1 1 ' and 1 1 ", are arranged after each compressor to cool the compressed refrigerant to a temperature of e.g. about 70°C.
  • the heat exchangers are normally located in an area comprising equipment containing hydrocarbons, i.e. LNG and / or the pre-treated natural gas for LNG production, an area which is classified as a hazardous area.
  • a non-flammable, non-toxic high heat capacity liquid such as water
  • a cooling medium for the heat exchangers 1 1 , 1 ⁇ and 1 1 " is preferably used as a cooling medium for the heat exchangers 1 1 , 1 ⁇ and 1 1 " .
  • This cooling medium is withdrawn from the heat exchangers 1 1 , 1 1 ' , 1 1 " in a cooling medium recycle pipe 27 and is introduced into an array of air coolers 14 that are arranged in a non-hazardous area.
  • the cooling medium is cooled to the lowest possible temperature allowed by space available for air coolers 14, air cooler efficiency and air temperature. Cooling medium from air cooler 14 is pumped in pump 15 to overcome frictional pressure losses, and re-distributed to each of the heat exchangers 1 1 , 1 1 ' and 1 1 " in cooling medium recycle pipe 27'.
  • Knock-out drums 12, 12' are arranged downstream of the coolers 1 1 , 1 1 'in the path of the gasified refrigerant to remove liquid from the gaseous phase to avoid two-phase flow in the compressors 10 ' , 10 " and 10 " ' .
  • the liquid removed from the gas phase in the knock-out drums is pumped in pumps 13 and 13' and is subsequently mixed with the refrigerant exiting the last compressor stage 10 " via a liquid bypass pipe 28.
  • a two stage refrigeration system which cools the compressed refrigerant in heat exchangers 16 and 16' is arranged in the path of the refrigerant downstream of cooler 1 1 ".
  • Coolers 16 and 16' use a non-flammable, non-toxic and non-ozone depletion and low global warming potential refrigerant, similar to some refrigerants used in buildings.
  • This refrigerant is called "secondary refrigerant” in the following, to distinguish it from the primary refrigerant used in the LNG exchanger.
  • the secondary refrigerant will work in about the same pressure and temperature range as residential air conditioning systems. Examples of refrigerants applicable as secondary refrigerants are R-410A and R-407C and others under development, replacing the familiar ozone depleting R-22.
  • the secondary refrigerant is compressed as will be described below, and is cooled in an array of air coolers 20 where cooling, condensation and sub-cooling take place. These air coolers can be located outside safe areas since the secondary refrigerant is non-flammable or nearly nonflammable. Most of the heat is removed from the secondary refrigerant in the condensation process, which occurs at a nearly constant and relatively high temperature such as about 70°C. This gives a relatively high air cooler LMTD, even in warm climates, enabling efficient cooling.
  • the condensed and sub-cooled secondary refrigerant cooled in coolers 29, is led to the LNG system safe area in a secondary refrigerant pipe 31 , and expanded in valve 21 , for example to a pressure of about 14 bara. At this pressure, the boiling point of the secondary refrigerant is much lower, such as 35°C.
  • the secondary refrigerant is then used as cooling medium in heat exchanger 16, where primary (LNG) refrigerant is cooled to intermediate temperatures such as 45°C. In this process, the secondary refrigerant is only partly vaporized, such as about 50%.
  • refrigerant line 30 is expanded in valve 22 to lower the pressure such as to about 5 bara and introduced into a heat exchanger 16' for further cooling of the primary refrigerant.
  • the boiling point of the secondary refrigerant might be about 0°C, which is sufficient to cool the primary (LNG) refrigerant to about 15 °C.
  • Vaporized secondary refrigerant from heat exchanger 16' is withdrawn through a refrigerant line 30' and is optionally introduced into a liquid knock-out drum 19'. Normally, there will be no liquid from knock-out drum 19'.
  • the gaseous refrigerant in line 30' is introduced into a compressor 18', either directly from line 30' or via the knock-out drum 19', and is compressed typically to a pressure of about 14 bara.
  • Table 2 shows examples for the first embodiment of the present invention.
  • the first column in Table 2 shows equipment reference numerals, which correspond to numerals in Figure 4.
  • the second column describes the equipment.
  • the third and fourth columns show variables and units, respectively.
  • Results are shown for four cases.
  • the first case shows main compressor, item 10 in Figure 4, after-cooler discharge temperature of 45°C.
  • This is a reference case obtainable either with the present invention or with direct cooling of the LNG refrigerant in air coolers.
  • the next three cases show results with successive reduction of the main compressor after-cooler discharge temperature to 30, 15 and 0°C, respectively. With an ambient temperature of 32°C, none of these temperatures would be obtainable by direct cooling of the LNG refrigerant in air coolers.
  • the LNG exchanger total duty is 346.3 MW. Reduction of this temperature to 30, 15 and 0°C lowers this duty to 302.4, 264.0 and 233.1 MW, respectively.
  • This lower duty can be used to increase the liquefaction capacity, bringing the duty back up to the maximum value of 346.3 MW.
  • the increased liquefaction rate has a significant and positive economic impact. [0047] As shown in Table 2, this advantage is achieved without increase in air cooler total footprint or increase in total compressor power. At the same time, the safety of the liquefaction system is significantly improved in that no flammable fluid is routed out of the liquefaction plant safe area.
  • a second embodiment of the present invention is shown in Figure 5.
  • the second embodiment differs from the first embodiment in that a part of the refrigerant in line 30 downstream of valve 22, is withdrawn via a gas cooler line 25 and led into a gas cooler 23 arranged on the gas pipe 1 to cool the incoming gas.
  • Gasified refrigerant is withdrawn from the gas cooler 23 in a refrigerant return line 25 and is combined with the gas in line 30' and compressed in compressor 18' as described above, optionally after liquid separation in knock-out drum 19'.
  • Table 3 shows examples for the second embodiment of the present
  • the examples are based on the liquefaction of pre-processed natural gas with composition 98.0 mole% methane, 1.5 mole% ethane and 0.5 mole% propane.
  • the gas flow is 400 metric tons per hour.
  • Temperature of ambient air is 32°C in all cases.
  • the first column in Table 3 shows equipment reference numerals, which correspond to numerals in Figure 5.
  • the second column describes the equipment.
  • the third and fourth columns show variables and units, respectively.
  • Results are shown for two cases.
  • the first case shows main compressor, item 10 in Figure 5, after-cooler discharge temperature of 15°C.
  • the next case shows results when the after-cooler 16 discharge temperature is reduced to 0°C.
  • second embodiment of the present invention With both main compressor discharge temperature, line 17, and natural gas feed temperature, line 1 , are 15°C, the LNG exchanger total duty is 257.2 MW. Reduction of these temperatures 0°C lowers this duty to 191.2 MW. This lower duty can be used to increase the liquefaction capacity, bringing the duty back up to the maximum value of 346.3 MW (Table 2). The increased liquefaction rate has a significant and positive economic impact.
  • heat exchangers 1 1 , 1 1 ', 1 1 " can be substituted with air cooler(s) for direct cooling at these locations.

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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)
  • Ocean & Marine Engineering (AREA)
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Abstract

La présente invention concerne un procédé de liquéfaction d'un gaz naturel prétraité pour produire du GNL, le procédé comprenant l'introduction du gaz naturel prétraité dans un échangeur de chaleur pour GNL dans lequel le gaz naturel prétraité est liquéfié par refroidissement au moyen d'un réfrigérant primaire d'évaporation, le retrait du réfrigérant primaire évaporé de l'échangeur de chaleur pour GNL, le réfrigérant primaire étant ensuite re-liquéfié par compression dans une série d'étapes de compression, le refroidissement du gaz comprimé issu de chaque étape de compression au moyen d'échangeurs de chaleur, et l'utilisation d'un milieu de refroidissement aqueux refroidi dans un ensemble de refroidisseurs d'air pour refroidir le réfrigérant primaire.
PCT/EP2015/055636 2014-03-18 2015-03-18 Procédé de liquéfaction d'un gaz naturel prétraité Ceased WO2015140197A2 (fr)

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NO20140358A NO20140358A1 (no) 2014-03-18 2014-03-18 Kystnær LNG produksjon

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WO2018209399A1 (fr) * 2017-05-18 2018-11-22 Woodside Energy Technologies Pty Ltd Barge et procédé de refroidissement d'eau d'une installation de production de gnl
WO2019222815A1 (fr) * 2018-05-25 2019-11-28 Woodside Energy Technologies Pty Ltd Installation hybride modulaire de production de gnl
WO2020002613A1 (fr) * 2018-06-28 2020-01-02 Global Lng Services As Procédé de production de gnl sur support flottant, à grande échelle, refroidie à l'air avec un gaz de liquéfaction comme seul agent réfrigérant
US11959700B2 (en) 2018-06-01 2024-04-16 Steelhead Lng (Aslng) Ltd. Liquefaction apparatus, methods, and systems
JP2025506286A (ja) * 2022-02-28 2025-03-07 ハーキュレス プロジェクト カンパニー リミテッド ライアビリティー カンパニー 単一混合冷媒ｌｎｇ製造プロセス

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AU2021370108A1 (en) * 2020-10-26 2023-05-04 Shell Internationale Research Maatschappij B.V. Compact system and method for the production of liquefied natural gas

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Publication number Priority date Publication date Assignee Title
DE19517116C1 (de) * 1995-05-10 1996-06-20 Linde Ag Verfahren zur Verringerung des Energieverbrauchs
FR2932876B1 (fr) * 2008-06-20 2013-09-27 Inst Francais Du Petrole Procede de liquefaction d'un gaz naturel avec pre-refroidissement du melange refrigerant
FR2957140B1 (fr) * 2010-03-08 2014-09-12 Total Sa Procede de liquefaction de gaz naturel utilisant de l'azote enrichi en tant que fluide frigorigene

Cited By (10)

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Publication number Priority date Publication date Assignee Title
WO2018209399A1 (fr) * 2017-05-18 2018-11-22 Woodside Energy Technologies Pty Ltd Barge et procédé de refroidissement d'eau d'une installation de production de gnl
AU2018203513B2 (en) * 2017-05-18 2022-07-14 Woodside Energy Technologies Pty Ltd A barge for and method of water cooling an lng production plant
WO2019222815A1 (fr) * 2018-05-25 2019-11-28 Woodside Energy Technologies Pty Ltd Installation hybride modulaire de production de gnl
US11959700B2 (en) 2018-06-01 2024-04-16 Steelhead Lng (Aslng) Ltd. Liquefaction apparatus, methods, and systems
US12111103B2 (en) 2018-06-01 2024-10-08 Steelhead Lng (Aslng) Ltd. Methods of manufacturing apparatus and systems for liquefaction of natural gas
US12158301B2 (en) 2018-06-01 2024-12-03 Steelhead Lng (Aslng) Ltd. Apparatus and systems for liquefaction of natural gas
US12158302B2 (en) 2018-06-01 2024-12-03 Steelhead Lng (Aslng) Ltd. Apparatus and systems for liquefaction of natural gas
US12163735B2 (en) 2018-06-01 2024-12-10 Steelhead Lng (Aslng) Ltd. Systems for liquefaction of natural gas
WO2020002613A1 (fr) * 2018-06-28 2020-01-02 Global Lng Services As Procédé de production de gnl sur support flottant, à grande échelle, refroidie à l'air avec un gaz de liquéfaction comme seul agent réfrigérant
JP2025506286A (ja) * 2022-02-28 2025-03-07 ハーキュレス プロジェクト カンパニー リミテッド ライアビリティー カンパニー 単一混合冷媒ｌｎｇ製造プロセス

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