Nitrogen rejection unit

摘要

Methods and systems for removing nitrogen during liquefaction of natural are provided. Methods of removing nitrogen include warming a predominantly methane stream in a methane cold box to provide a warmed predominantly methane stream; conducting at least a portion of the warmed predominantly methane stream from the methane cold box to a nitrogen removal unit comprising at least a first nitrogen removal column and a last nitrogen removal column, wherein the first nitrogen removal column is located upstream of the last nitrogen removal column; passing the warmed predominantly methane stream through the last nitrogen removal column to provide a refluxed warmed predominantly methane stream; and routing at least a portion of the refluxed warmed predominantly methane stream to the last nitrogen removal column.

主权项

1. A method of removing nitrogen from a natural gas stream comprising:
(a) routing the natural gas stream from a methane cold box of a main liquefaction process to a nitrogen rejection unit comprising: a first distillation column, a second distillation column, a third distillation column, and a condenser, wherein the main liquefaction process comprises: one or more refrigeration cycles external to the nitrogen rejection unit; (b) at least partially condensing the natural gas stream via the condenser, wherein the condenser utilizes a refrigerant used to transfer heat in the one or more refrigeration cycles to form a condensed natural gas stream, wherein the refrigerant is taken from the refrigeration cycle routed into a core-in-shell exchanger forming the condenser and returned to the refrigeration cycle without passing through the first distillation column; and (c) routing at least a portion of the condensed natural gas stream to the third distillation column to separate the at least a portion of the condensed natural gas stream into a third top fraction and a third bottom fraction, wherein the third top fraction comprises a predominantly nitrogen gas stream.