FIELD: performing operations.
SUBSTANCE: invention relates to methods of separating and purifying mixtures of substances of organic and inorganic origin. Method for deep denitrogenation of liquefied natural gas, in which a stream of pre-purified natural gas with an admixture of nitrogen is liquefied and supercooled using a refrigerating circuit, expanded, and then subjected to rectification removal of nitrogen in a rectification column, hermetically separated into a stripping and concentration parts, characterized by that the supercooled stream of de-nitrated natural gas is supplied to the top of the stripping part of the rectification column, which acts as a reflux, and divided into a stream of nitrogen-methane mixture and a stream of commercial denitrogenated liquefied natural gas, the stream of nitrogen-methane mixture is used as a first additional internal cooling agent, is compressed, subjected to two-stage cooling by the first and second additional internal coolants, wherein after the first cooling stage the stream of nitrogen-methane mixture is divided into two streams, wherein first stream of nitrogen-methane mixture is expanded and supplied to bottom of concentration part of rectification column to create steam reflux, and the second stream of the nitrogen-methane mixture is additionally cooled at the second cooling stage, expanded and supplied to the concentration part of the rectification column as its feed stream, which in the concentration part of the rectification column is divided into a stream of concentrated nitrogen, further used as a second additional internal coolant in a two-stage cooling system, and a stream of partially denitrogenated liquefied natural gas, which after expansion is sent to the distillation part of the rectification column as raw material, and reflux of the concentration part of the rectification column is ensured by condensation of vapours of the nitrogen-methane mixture in a remote condenser placed in the stripping part of the rectification column and which is a reboiler for the stripping part of the rectification column.
EFFECT: increasing efficiency of the plant for liquefaction of natural gas with denitrogenation of liquefied natural gas and reducing power consumption for implementation of the process.
10 cl, 3 dwg, 1 tbl
