Process for the production of a subcooled liquefied natural gas stream from a natural gas feed stream, and associated installation

摘要

A process for the production of a subcooled liquefied natural gas stream from a natural gas feed stream. Passing a first natural gas feed stream through a first heat exchanger for precooling by heat exchange with a first stream of gaseous refrigerant produced in a first refrigeration cycle comprising a first dynamic expansion turbine. Passing the precooled feed stream through a second heat exchanger for liquefying by heat exchange with a second stream of gaseous refrigerant produced in a second refrigeration cycle comprising a second dynamic expansion turbine. Passing the liquefied natural gas stream through a third heat exchanger for subcooling the liquefied gas by heat exchange with a third refrigerant stream produced in a third refrigeration cycle comprising a third dynamic expansion turbine separate from the first turbine and the second turbine. An installation includes devices for conveying the natural gas stream, the heat exchangers and the turbines and compression devices cooling the refrigerants for the heat exchangers.

主权项

1. A process for the production of a subcooled liquefied natural gas stream from a natural gas feed stream, the method comprising the following steps:
precooling the natural gas feed stream by passing the natural gas feed stream through a first heat exchanger for obtaining a feed stream precooled to a temperature below −20° C.; liquefying the precooled feed stream by passing the precooled feed stream through a second heat exchanger for obtaining at least one liquefied natural gas stream at a temperature below −80° C.; subcooling the liquefied natural gas stream by passing the liquefied natural gas stream through a third heat exchanger for obtaining a liquefied natural gas stream subcooled to a temperature below −120° C.; during the precooling, placing the natural gas feed stream in a heat exchange relationship in the first heat exchanger with a first stream of substantially gaseous refrigerant and producing the substantially gaseous refrigerant in a first refrigeration cycle from a first gaseous stream of expanded refrigerant fluid issuing from a first dynamic gas expansion turbine; during the liquefying, placing the precooled feed stream in a heat exchange relationship in the second heat exchanger with a second stream of gaseous refrigerant circulating in a second refrigeration cycle, producing the second gaseous refrigerant stream from a second gaseous stream of expanded fluid issuing from a second dynamic gas expansion turbine separate from the first dynamic gas expansion turbine; during the subcooling, placing the liquefied natural gas stream in a heat exchange relationship in the third heat exchanger with a third refrigerant stream circulating in a third refrigeration cycle, producing the third refrigerant stream at least partly from a third gaseous stream of expanded fluid issuing from a third dynamic expansion turbine separate from the first and the second dynamic gas expansion turbines; conveying a first stream of heated refrigerant obtained at an outlet of the first heat exchanger to a first compression device without passing the first stream of heated refrigerant through the second or the third heat exchangers; conveying a second stream of heated refrigerant issuing from the second heat exchanger to a second compression device without passing the second stream of heated refrigerant through the first or the third heat exchangers; and conveying a third stream of heated refrigerant issuing from the third heat exchanger to a third compression device without passing the third stream of heated refrigerant through the first or the second heat exchangers.