Method for separating air by means of cryogenic distillation

Abstract

In an air-distillation method, purified air is cooled in an exchange line and then sent to a distillation column of a system of columns, and oxygen- and nitrogen-rich fluids are extracted from a column of the system of columns only during the repressurization phase. A purified airflow, constituting between 3% and 20% of the air compressed in the compressor, is used to at least partially pressurize the adsorber completing the regeneration phase thereof, and the airflow compressed in the compressor during the adsorption phase is substantially equal to the airflow compressed in the compressor during the pressurization of the adsorber. A portion of the purified air is sent to a turbine where it is decompressed and then sent into the atmosphere an as to ensure that it is kept at least partially cold during the entire cycle, and the amount of decompressed airflow sent into the air during the pressurization of an adsorber is less than the amount sent into the air during the adsorption phase of the same adsorber.

1 - 13 . (canceled) 
     
     
         14 . A method for distilling air to produce an air gas selected from the group consisting of oxygen, nitrogen, argon, and combinations thereof, the method comprising the steps of:
 compressing the air to be distilled in a compressor;   purifying the air following compression using at least two adsorbers to form a purified air, wherein which each adsorber follows, offset, a cycle wherein succeed an adsorption phase, at a high pressure of the cycle (P ads ), and a regeneration phase at a low pressure P atmos  ending with a repressurization phase of the adsorber;   cooling the purified air in an exchange line and then sending the purified air to a distillation column of a system of columns;   withdrawing oxygen-rich and nitrogen-rich fluids a from a column ( 14 ) of the system of columns; and   sending a portion of the purified air to a turbine wherein the portion of the purified air is expanded and then sent to the atmosphere so as to provide at least partially the refrigeration requirements during the entire cycle and in that the flow of the expanded air sent to the atmosphere during the pressurization of the adsorber is lower than that sent to the atmosphere during the adsorption phase of the same adsorber,   wherein solely during the repressurization phase a purified air flow, constituting between 3 and 20% of the air compressed in the compressor, is used to pressurize, at least partially, the adsorber completing its regeneration phase,   wherein the air flow compressed in the compressor during the adsorption phase is substantially equal to the air flow compressed in the compressor during the pressurization of the adsorber.   
     
     
         15 . The method as claimed in  claim 14 , wherein the expanded air flow sent to the air during the pressurization of an adsorber is less than that sent to the air during the rest of the cycle beyond the pressurization phase. 
     
     
         16 . The method as claimed in  claim 14 , wherein the air flow compressed in the compressor during the adsorption phase of an adsorber is equal to the air flow compressed in the compressor during the pressurization of the adsorber. 
     
     
         17 . The method as claimed in  claim 14 , wherein the reduction of the air flow sent to the turbine and then to the air during the repressurization is equal to the air flow used during the repressurization in order to pressurize the adsorber completing its repressurization phase. 
     
     
         18 . The method as claimed in  claim 17 , wherein the quantity of air sent to the distillation is constant during the entire cycle. 
     
     
         19 . The method as claimed in  claim 14 , wherein the reduction in the air flow sent to the turbine and then to the air during the pressurization of an adsorber is less than the air flow used during the repressurization in order to pressurize the adsorber completing its repressurization phase. 
     
     
         20 . The method as claimed in  claim 19 , wherein during the repressurization phase the air flow compressed in the compressor increases in relation to the flow sent during the rest of the cycle and the quantity of air sent to the distillation remains equal to that sent during the rest of the cycle. 
     
     
         21 . The method as claimed in  claim 14 , wherein a liquid flow is produced as a final product. 
     
     
         22 . The method as claimed in  claim 14 , wherein the purification method is an adsorption of the PSA, TSA or TPSA type. 
     
     
         23 . The method as claimed in  claim 14 , wherein the air is expanded in a turbine and sent to a column of the system of columns. 
     
     
         24 . The method as claimed in  claim 14 , wherein the expanded air flow sent to the air during the pressurization of an adsorber is less than that sent to the air during the rest of the cycle beyond any pressurization phase. 
     
     
         25 . The method as claimed in  claim 14 , wherein the system of columns is constituted by a double column comprising a medium-pressure column and a low-pressure column. 
     
     
         26 . The method as claimed in  claim 25 , wherein an oxygen-rich flow is withdrawn from the low-pressure column and it is vaporized in the exchange line.