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
  • F25J1/0032—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
  • F25J1/0035—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by gas expansion with extraction of work
• • 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
  • F25J1/0032—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
  • F25J1/004—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by flash gas recovery
• • 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
  • F25J1/008—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
  • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
  • F25J1/0095—Oxides of carbon, e.g. CO2
• • 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
  • F25J1/0203—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 single-component refrigerant [SCR] fluid in a closed vapor compression cycle
  • F25J1/0204—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 single-component refrigerant [SCR] fluid in a closed vapor compression cycle as a single flow SCR 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
  • F25J1/0203—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 single-component refrigerant [SCR] fluid in a closed vapor compression cycle
  • F25J1/0208—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 single-component refrigerant [SCR] fluid in a closed vapor compression cycle in combination with an internal quasi-closed refrigeration loop, e.g. with deep flash recycle 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
  • 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
  • F25J1/0221—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 the cold stored in an external cryogenic component in an open refrigeration 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
  • 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
  • F25J1/0225—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 other external refrigeration means not provided before, e.g. heat driven absorption chillers
• • 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
  • F25J1/0225—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 other external refrigeration means not provided before, e.g. heat driven absorption chillers
  • F25J1/0227—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 other external refrigeration means not provided before, e.g. heat driven absorption chillers within a refrigeration 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
  • 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
  • F25J2210/00—Processes characterised by the type or other details of the feed stream
  • F25J2210/42—Nitrogen
• • 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
  • F25J2210/66—Landfill or fermentation off-gas, e.g. "Bio-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
  • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
  • F25J2230/30—Compression of 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
  • 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
  • F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
• • 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
  • F25J2270/908—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration by regenerative chillers, i.e. oscillating or dynamic systems, e.g. Stirling refrigerator, thermoelectric ("Peltier") or magnetic refrigeration

Definitions

• the present invention relates to a process for the liquefaction of a gas to be treated comprising at least 50% by volume of methane, the process comprising a purification of the gas to be treated to obtain a purified gas, a pre-cooling of the purified gas to obtain a pre-cooled, liquefying the pre-cooled gas to obtain a liquid stream, sub-cooling the liquid stream to obtain a sub-cooled liquid stream, and expanding the sub-cooled liquid stream to obtain a gas liquefied.
• the invention also relates to an installation suitable for implementing such a method.
• the gas to be treated is for example a biogas (resulting from the fermentation of organic matter).
• the relevant market is, for example, that of retail LNG (Liquefied Natural Gas), with final storage of the LNG produced at a pressure of less than 3 bar absolute. This market requires relatively low liquefied gas production capacities, typically less than 2000 Nm 3 /h of gas to be liquefied.
• a first category includes phase change cycles, often referred to as mixed refrigerant (MR) cycles.
• the cold is provided by evaporating a refrigerant fluid adapted to the level of cooling temperature required.
• the refrigerant is composed of a mixture that gradually evaporates throughout the target temperature range. Once completely vaporized, the refrigerant is condensed in stages using, on the one hand, several stages of compression and, on the other hand, pre-cooling on itself.
• phase change cycles due to their technical complexity, entail high costs.
• phase change cycles require a large succession of compressors, and a refrigerant mixture comprising sometimes explosive compounds, which requires specific compressor technologies.
• this type of cycle is too expensive for the small scales of production targeted.
• a second category includes inverted Brayton cycles.
• the cold is produced by expanding, using a turbine, a previously compressed refrigerant fluid.
• the big difference with the phase change cycle is that, precisely, in the inverted Brayton cycle, the refrigerant always remains gaseous.
• the cooling of gas to be treated takes place thanks to the difference in temperature between the gas to be treated and the expanded refrigerant.
• inverted Brayton cycles remain relatively complex. Like phase change cycles, they require a large succession of compressors and even greater capacities and powers than phase change cycles, due to their relative lack of energy efficiency. This results in a significant cost at the targeted production scales. Moreover, the key machine that is the cryogenic expansion turbine is expensive and is not available "off the shelf” at all scales, which increases its cost at the production scales concerned.
• a third category includes the Stirling cycles.
• the Stirling cycle resembles the reverse Brayton cycle in that it does not involve the evaporation of a refrigerant fluid.
• its operating points are different, because the stages of expansion of the refrigerant and cooling of the gas to be treated are done at the same time, and the stages of compression of the refrigerant fluid and its cooling by an external source are also done simultaneously. same time.
• the overall system generally fits in a single relatively integrated and compact device, unlike other processes in which each step is carried out by dedicated equipment.
• Stirling cycles are difficult to implement for high capacities, in particular greater than 50 Nm 3 /h of gas to be treated which is rich in methane. They therefore have a high cost.
• Stirling cycles include isothermal compression and expansion, and therefore require a compact exchange line whose capacity cannot be increased easily.
• the heart of the cycle is often duplicated to increase capacity. Consequently, the specific cost does not really benefit from the increase in capacity (no economy of scale).
• Stirling cycles lack energy efficiency.
• a fourth category includes open cycles. Instead of creating the cold using mechanical energy, by the compression, then the expansion of a recycled fluid, we use a vector of cold, that is to say a consumable which brings the cold.
• a suitable vector is liquid nitrogen.
• the liquid nitrogen once vaporized, is released into the atmosphere, therefore lost, the cycle being open.
• Open cycles unfortunately present a lack of energy efficiency and a high operational cost.
• the consumption of the cold vector, for example liquid nitrogen, to achieve the cooling necessary for the liquefaction of the gas to be treated requires a mass flow rate of liquid nitrogen greater than twice that of the gas to be treated.
• An object of the invention is therefore to propose a liquefaction process making it possible to reduce the overall production cost, in particular for capacities of less than 2000 Nm 3 /h.
• the subject of the invention is a process for the liquefaction of a gas to be treated comprising at least 50% by volume of methane, the process comprising the following steps:
• pre-cooling of the purified gas to obtain a pre-cooled gas having a temperature less than or equal to -15°C, the pre-cooling being carried out by heat exchange with a pre-cooling refrigeration cycle,
• the liquefaction including a Stirling refrigeration cycle distinct from said pre-cooling refrigeration cycle and implementing a first refrigerant fluid, the Stirling refrigeration cycle comprising pre-cooling of the first refrigerant fluid by heat exchange with a second refrigerant fluid of a pre-cooling refrigeration cycle distinct from a Stirling cycle,
• the method comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:
• the single pre-cooling refrigeration cycle is a brine cycle, a CO2 cycle, an ammonia cycle, a freon cycle, or a propane cycle;
• the single pre-cooling refrigeration cycle comprises: cooling the second refrigerant fluid to produce a stream of cooled second refrigerant fluid; and a division of the stream of cooled second refrigerant fluid into at least two streams used respectively to carry out the pre-cooling of the first refrigerant fluid and the pre-cooling of the purified gas;
• the temperature of the pre-cooled gas is greater than or equal to -50°C;
• - sub-cooling includes: heat exchange with an open cycle using liquid nitrogen; and/or a heat exchange with a vapor produced by the expansion of the stream of subcooled liquefied gas;
• the method further comprising mixing the gas to be treated with at least a portion of the vapor to obtain a mixture;
• the method further comprises, prior to the liquefaction of the pre-cooled gas, an expansion of the pre-cooled gas;
• the invention also relates to an installation suitable for implementing a method as described above, comprising:
• a purification unit suitable for purifying a gas to be treated comprising at least 50% by volume of methane and obtaining a purified gas
• pre-cooling unit adapted to pre-cool the purified gas and to obtain a pre-cooled gas at a temperature less than or equal to -15°C
• liquefaction unit suitable for liquefying the pre-cooled gas and obtaining a stream of liquid, with subcooling of the stream of liquid less than or equal to 5°C at the outlet of the liquefaction unit
• the liquefaction unit including a Stirling refrigeration cycle distinct from said pre-cooling refrigeration cycle and being adapted to implement a first refrigerant fluid, the Stirling refrigeration cycle being adapted to carry out a pre-cooling of the first refrigerant fluid
• pre-cooling refrigeration cycle distinct from the Stirling refrigeration cycle and adapted to implement a second refrigerant fluid and to carry out a heat exchange with the first refrigerant fluid in order to obtain said precooling of the first refrigerant fluid, the pre-cooling refrigeration cycle being distinct from a Stirling cycle, - a liquid stream subcooling unit for obtaining a subcooled liquid stream, and
• FIG. 1 is a schematic view of an installation according to the invention adapted to implement a method according to the invention.
• upstream and downstream generally extend relative to the normal direction of flow of a fluid.
• 1 Nm 3 /h means in this document one cubic meter per hour at a pressure of 101325 Pa and a temperature of 0°C.
• the installation is suitable for liquefying a gas to be treated 12 comprising at least 50% by volume of methane and obtaining a liquefied gas 14 (that is to say a liquid), for example with a view to its marketing on the LNG (Liquefied Natural Gas) retail.
• the liquefied gas 14 is advantageously stored at a pressure below 3 bar absolute (300 kPa).
• the gas to be treated 12 is for example a biogas, a network gas, a synthesis gas, or more generally a gas rich in methane.
• the gas to be treated 12 can contain up to 45% by volume of CO2 and therefore barely 50 to 55% by volume of methane.
• gas 12 to be treated is a fossil gas
• methane content before purification is generally greater than 70% by volume.
• the installation 10 comprises a compressor 16, followed by a cooler 18, and a purification unit 20 for purifying the gas to be treated 12 to obtain, in a manner known per se, a purified gas 22 which be liquefiable.
• the installation 10 is advantageously devoid of the compressor 16 and the cooler 18.
• the installation 10 comprises a pre-cooling unit 24 for pre-cooling the purified gas 22 and obtaining a pre-cooled gas 26 at a temperature less than or equal to -15°C, and advantageously greater than -50°C.
• the temperature of the pre-cooled gas 26 is between -45°C and -15°C.
• the installation 10 also includes an expansion unit 28 to expand the pre-cooled gas 26.
• the installation 10 comprises a liquefaction unit 30 suitable for liquefying the pre-cooled gas 26, and optionally expanded, and obtaining a stream of liquid 32, with sub-cooling of the stream of liquid less than or equal to 5° C., by example of about 3° C., at the outlet of the liquefaction unit 30.
• the installation 10 comprises a subcooling unit 34 for subcooling the liquid stream 32 to obtain a subcooled liquid stream 36, and an expansion unit 38 for expanding the subcooled liquid stream 36 and obtaining liquefied gas 14.
• the installation 10 comprises a single pre-cooling refrigeration cycle 40 to carry out, in the pre-cooling unit 24, a heat exchange with the purified gas 22, and to carry out, in the liquefaction unit 30, a precooling of a first refrigerant fluid 42 implemented by the liquefaction unit 30.
• cooling cycle is meant a set of pipes and elements (not shown), such as compressors or turbines, adapted to subject a fluid to a series of transformations with the aim of generating cold at a place of the cycle, in a manner known per se (see the preamble to this document).
• the installation 10 comprises two separate pre-cooling refrigeration cycles (whose fluids do not mix), one being adapted to provide cold to the unit of pre-cooling 24, and the other to the liquefaction unit 30.
• the expansion unit 38 also being suitable for producing a vapor 44 rich in methane, known as "flash gas"
• the installation 10 further comprises a mixer 46 suitable for mixing the gas with treat 12 with steam 44 to obtain a mixture 48. Put more simply, the steam is recycled in the gas to be treated upstream of the compression.
• the compressor 16, followed by the ambient temperature cooler 18, makes it possible to compress both the gas to be treated 12 and the vapor 44, for example between 19 and 40 bars absolute.
• the purification unit 20 makes the compressed gas liquefiable at cryogenic temperatures, typically below -80°C.
• the purification unit 20 is conventionally adapted to eliminate from the gas to be treated 12 the volatile compounds and the heavy hydrocarbons (known as “C6+”), for example thanks to activated carbons (not represented and known in themselves).
• the purification unit 20 comprises for example a condensation system (not shown).
• a membrane system (not shown) is for example used.
• molecular sieves can be used (not shown).
• the purified gas 22 comprises at least 90% by volume of methane if it comes from a fossil gas, or even 99% by volume and more if it comes from a biogas.
• the expansion unit 28 comprises for example a Joule-Thomson valve or a gas expansion turbine.
• the liquefaction unit 30 includes a Stirling refrigeration cycle 50 distinct from the pre-cooling refrigeration cycle 40 and implementing the first refrigerant fluid 42.
• the liquefaction unit 30 is adapted so that the liquid stream 32 has a temperature between -115°C and -90°C at the outlet of the liquefaction unit 30.
• Stirling refrigeration cycle 50 is meant here a refrigeration cycle implemented by a Stirling machine 51 known in itself to those skilled in the art.
• the Stirling machine 51 is a thermomechanical device configured to carry out a regenerated, closed, alternating, single-phase thermodynamic cycle.
• the cycle successively comprises phases of compression and expansion of the working fluid, here the first refrigerant fluid 42, at different temperature levels.
• the cycle is said to be “regenerated”, because the first refrigerant fluid 42 passes through a regenerator (not shown) whose purpose is to cool or heat the first refrigerant fluid 42 according to its direction of transit.
• the cycle is said to be "closed", because the movement of the first refrigerant fluid 42 is entirely controlled by the variation of internal volumes of the Stirling machine 51, without recourse to organs for isolating the different parts occupied by the first refrigerant fluid 42 , that is to say in particular without the use of valves.
• the cycle is said to be “alternative” because, at each point of the internal volumes occupied by the first refrigerant fluid 42, at least one thermodynamic characteristic of the fluid, such as the temperature or the pressure, is not stationary during the cycle.
• the cycle is said to be “single-phase”, in the sense that the first refrigerant fluid 42 remains single-phase during the cycle.
• a refrigeration cycle is "distinct from a Stirling cycle" if it is not implemented by a Stirling machine or does not have one of the properties stated above.
• the Stirling refrigeration cycle 50 is further adapted to carry out a precooling of the first refrigerant fluid 42 by heat exchange with a second refrigerant fluid 52 implemented by the pre-cooling refrigeration cycle 40, the second refrigerant fluid 52 heating up for example by less than 5° C. during this heat exchange.
• the Stirling refrigeration cycle 50 is advantageously adapted to pre-cool the first refrigerant fluid 42 to a temperature less than or equal to -15°C.
• the pre-cooling refrigeration cycle 40 used is not a Stirling cycle.
• the pre-cooling refrigeration cycle 40 is for example a brine cycle, a CO2 cycle, an ammonia cycle, a freon cycle, or a propane cycle, known per se and which will not be described in detail. retail.
• the pre-cooling refrigeration cycle 40 comprises a cooling module 54 to produce a stream of cooled second refrigerant fluid 56, and a divider 57 to divide the stream of cooled second refrigerant fluid 56 into two streams 58, 60 used respectively to perform the pre-cooling of the first refrigerant fluid 42 and the pre-cooling of the purified gas.
• the pre-cooling refrigeration cycle 40 comprises for example a mixer 62 adapted to mix the two streams 58, 60 after their respective passages through the liquefaction unit 30 and into the pre-cooling unit 24 and to reconstitute a stream of second fluid refrigerant 64 directed to cooling module 54.
• the cooling module 54 is adapted to cool the flow of second refrigerant fluid 64 and produce the stream of cooled second refrigerant fluid 56.
• the sub-cooling unit 34 is for example adapted to cool the liquid stream 32 by heat exchange with an open cycle 66 implementing liquid nitrogen.
• the sub-cooling unit 34 is adapted to cool the liquid stream 32 by heat exchange with the vapor 44 produced by the expansion unit 38.
• the expansion unit 38 advantageously comprises an expansion module 68 suitable for expanding the stream of subcooled liquid 36 and obtaining an expanded subcooled stream 70 at a pressure of less than 3 bars absolute, for example a pressure of 2 bars absolute .
• the expansion unit 38 comprises for example a flash drum 72 to separate the expanded subcooled stream 70 into the liquefied gas 14, for example received in a storage 74, and the steam 44 recycled upstream of the compressor 16.
• the gas to be treated 12 and the vapor 44 from the flash drum are mixed by the mixer 46 to form the mixture 48.
• the gas to be treated 12, within the mixture 48 is compressed in the compressor 16, then cooled to approximately ambient temperature, for example 20° C., in the cooler 18. Then the gas to be treated 12, in the example at within the mixture 48, is purified in the purification unit 20 to form the purified gas 22.
• the purified gas 22 is pre-cooled in the pre-cooling unit 24 to a temperature below -15° C., by heat exchange with the second refrigerant fluid 56, in the example with the flow 60.
• the pre-cooled gas 26 is expanded in the expansion unit 28 to obtain a pre-cooled and expanded gas 76.
• the pre-cooled and expanded gas 76 (or the pre-cooled gas 26, in the absence of the optional expansion) is liquefied by the liquefaction unit 30, with a minimal undercooling, less than or equal to 5 °C, for example about 3°C.
• the temperature of the liquid stream 32 leaving the liquefaction unit 30 is 3° C. below the bubble temperature of the pre-cooled and expanded gas 76 (or of the pre-cooled gas 26, in l absence of the optional trigger).
• the temperature of the liquid stream 32 leaving the liquefaction unit 30 is preferably between -115°C and -90°C.
• the liquefaction unit 30 implements the Stirling refrigeration cycle 50, which brings the cold allowing the liquefaction of the pre-cooled gas 26.
• the Stirling refrigeration cycle 50 performs in particular a pre-cooling of the first refrigerant fluid 42 to a temperature below ⁇ 15° C., by heat exchange with the flow 58 of second refrigerant fluid. During this heat exchange, the second refrigerant fluid 52 heats up by less than 5°C.
• liquid stream 32 is then subcooled in the subcooling unit 34, expanded in the expansion module 68 to, for example, 2 bars absolute, and sent to the flash tank 72.
• the liquefied gas 14 is for example recovered at the bottom of flash tank 72 and sent to storage 74.
• liquid stream 32 is cooled by heat exchange with open cycle 66 using liquid nitrogen. In other words, liquid nitrogen is vaporized and gives up its cold to the sub-cooling unit 34.
• the vapor from the flash tank 72, as indicated above, is recycled in the gas to be treated 12.
• the second refrigerant stream 64 is cooled by the cooling module 54 to produce the second cooled refrigerant stream 56.
• the second cooled refrigerant stream 56 is divided into the two stream 58, 60.
• the stream 60 passes through the pre-cooling unit 24 to yield cold to the purified gas 22 and carry out the pre-cooling of the purified gas.
• the flow 58 passes through the liquefaction unit 30 to yield cold to the Stirling refrigeration cycle 50 and carry out the pre-cooling of the first refrigerant fluid 42. After their respective passages through the liquefaction unit 30 and into the pre-cooling unit cooling 24, the two flows 58, 60 are mixed to reconstitute the flow of second refrigerant fluid 64.
• the pre-cooling of the purified gas 22 and the pre-cooling of the first refrigerant fluid 42 are therefore carried out in parallel by the single pre-cooling refrigeration cycle 40.
• the gas 12 to be treated is compressed between 19 and 40 bars absolute, for example at 40 bars absolute.
• the purified gas 22 is pre-cooled between -15°C and -50°C, for example at -35°C, by the pre-cooling unit 24.
• the temperature of the liquid stream 32 leaving the liquefaction unit 30 is between -115°C and -90°C, for example -90°C.
• the liquid stream 32 is subcooled by the subcooling unit 34 to a temperature making it possible to obtain a molar evaporation rate in the flash drum 72 comprised between 20% and 50%, preferably between 20% and 25%.
• the method makes it possible to reduce the overall production cost of the liquefied gas 14, in particular for production capacities of less than 2000 Nm 3 /h.
• the pre-cooling of the purified gas 22 down to a temperature between -15° C. and -50° C., and the sub-cooling of the liquid stream 32 are carried out by dedicated systems (separate from the liquefaction unit 30) and at low cost.
• the Stirling refrigeration cycle 50 is itself pre-cooled to a temperature below -15° C. by a separate pre-cooling refrigeration cycle 40, which is not a Stirling cycle. . This improves the performance of the Stirling 50 refrigeration cycle.
• the subcooling of the liquid stream 32 which occurs in the liquefaction unit 30 is advantageously reduced to 5°C or less.
• the real sub- cooling is carried out in the dedicated sub-cooling unit 34, and not by the Stirling refrigeration cycle 50 of the liquefaction unit 30.
• the liquefaction unit 30 minimizes the thermal expenditure of the liquefaction unit 30, which alone concentrates half of the overall energy expenditure in the prior art.
• the liquefaction is carried out by the refrigeration cycle of Stirling 50, which is not very complex. This cycle is well suited to targeted cooling and advantageously integrates all the elements of independent cooling in a single machine.

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• 2021
  • 2021-12-06 FR FR2113017A patent/FR3130018B1/fr active Active
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