TWO-STEP REMOVAL OF NITROGEN FROM LIQUEFIED NATURAL GAS Russian patent published in 2009 - IPC F25J3/02 

FIELD: heating.

SUBSTANCE: nitrogen is removed from liquefied natural gas (41) by two-step splitting implying first fractionation (23) of liquefied natural gas (41) to produce first flow (46) of the overhead fraction vapour rich in nitrogen and flow (19) of nitrogen-containing liquid sludge; afterwards at least part of above liquid sludge flow (19) is subject to the fractionation (25) to produce second flow (36) of the overhead fraction vapour rich in nitrogen and having lower purity than the above first overhead fraction vapour flow (46) and flow (50) of the purified liquefied natural gas. The first fractionation is carried out in distillation column (23) irrigated (45) by the nitrogen overhead fraction (43) which is condensed in condenser (24) set in evaporation drum (25) where the second fractionation is carried out. Provision of two flows (26, 36) containing nitrogen in different concentration allows for the control over the nitrogen content in fuel gas used in a natural gas liquefaction installation.

EFFECT: ensuring control over the nitrogen content in fuel gas used in a natural gas liquefaction installation.

15 cl, 5 dwg, 2 ex