METHOD FOR NATURAL GAS LIQUEFACTION Russian patent published in 2023 - IPC F25J1/00 

FIELD: gas liquefaction.

SUBSTANCE: natural gas liquefaction method is intended for production of liquefied natural gas (hereinafter referred to as LNG), which ensures quality control of the produced LNG, and can be used at gas processing enterprises. The method for liquefying pre-treated and dried natural gas includes the following procedures: a) pre-cooling of natural gas, b) separation of pre-cooled natural gas, b) liquefaction of pre-cooled and separated natural gas, d) supercooling of natural gas with nitrogen, e) throttling of supercooled LNG, f ) LNG storage, g) compression of the total mixed refrigerant stream with intercooling and separation in the separator system into heavy liquid mixed refrigerant and light gaseous mixed refrigerant streams, h) subcooling the heavy mixed refrigerant stream, throttling and supplying to the pre-cooling heat exchanger as a refrigerant, i) cooling the light gaseous mixed refrigerant stream, condensing and subcooling the light gaseous mixed refrigerant stream, throttling and supplying the light mixed refrigerant stream to the liquefaction heat exchanger as a refrigerant, j) successively compressing nitrogen gas, expanding the nitrogen stream, while removing from the natural gas components of heavy hydrocarbons (hereinafter referred to as HHC) to an acceptable value that excludes the formation of solid hydrocarbon particles in procedures from c) to f), after performing procedure a), pre-cooled natural gas enters the first additional recuperative heat exchanger for post-cooling with a stream of separated gas and then before by performing the procedure b) it is throttled at the valve to ensure the following temperature and pressure parameters during separation: pressure in the range from 3.0 to 5.5 MPa with the condition of ensuring a value below the pseudo-critical pressure of the mixture of raw natural gas components; temperature in the range from minus 60 to minus 85°C with ensuring the pseudo-critical temperature of the mixture of raw natural gas components in the range of 85-105%, corresponding to the condensation of HHC.

EFFECT: proposed method for liquefying natural gas ensures the practical absence of heavy crystallized paraffinic and aromatic hydrocarbons in LNG, which reduce its quality and lead to risks of violating the LNG production technology.

5 cl, 2 dwg