Process for removing nitrogen from high-flow natural gas

Abstract

A process for separating the components of a gas mixture comprising methane, nitrogen, and at least one hydrocarbon having at least two carbon atoms, or a mixture of these hydrocarbons, including the following steps: a) introduction of a stream of the mixture to be treated into a demethanization of the gas mixture with at least N demethenization column; b) partial condensation of a gas mixture, comprising less than 1 mol % of hydrocarbons having at least two carbon atoms, extracted from the demethanization unit to obtain a liquid, at least a portion of which is treated in order to be extracted as denitrogenated natural gas and a second gas, c) introduction of the second gas into a nitrogen removal unit having N nitrogen removal columns.

1 - 6 . (canceled) 
     
     
         7 . A process for separating the components of a gas mixture to be treated comprising methane, nitrogen and at least one hydrocarbon having at least two carbon atoms, or a mixture of these hydrocarbons, comprising the following steps:
 a) introducing a stream of said gas mixture to be treated at a flow rate greater than or equal to 2 000 000 Nm 3 /h into a methane removal unit comprising N methane removal columns;   b) partially condensing a gas mixture, comprising less than 1 mol % of hydrocarbons having at least two carbon atoms, extracted from the methane removal unit in order to obtain a liquid, at least one part of which is treated in order to be extracted as denitrogenated natural gas product, and a second gas;   c) introducing said second gas into a nitrogen removal unit comprising N nitrogen removal columns obtained from which are a gas and a liquid, at least one part of which is treated in order to be extracted as denitrogenated natural gas product;   
       wherein said denitrogenated natural gas thus produced comprises less than 5 mol % of nitrogen and in that N is greater than or equal to 3. 
     
     
         8 . The process as claimed in  claim 7 , further comprising the additional step:
 d) treating said gas from step c) in a second nitrogen removal unit in order to produce a gaseous nitrogen stream comprising at most 2 mol % of methane and a gaseous methane stream comprising at most 5 mol % of nitrogen.   
     
     
         9 . The process as claimed in  claim 8 , wherein the second nitrogen removal unit (B) comprises at most N−1 nitrogen removal columns. 
     
     
         10 . The process as claimed in  claim 7 , wherein N is greater than or equal to 6. 
     
     
         11 . The process as claimed in  claim 10 , wherein the second nitrogen removal unit comprises between N−5 nitrogen removal columns and N−1 nitrogen removal columns. 
     
     
         12 . The process as claimed in  claim 7 , wherein the steps b) and c) are carried out at a temperature below −50° C. and the fluid is not reheated above −50° C. between step b) and step c).