Method for producing a pressurised air gas by means of cryogenic distillation

Abstract

The invention relates to a method for separating air by means of cryogenic distillation in a system of columns, in which two single-stage air superchargers are connected in series and coupled to two turbines, which expand the air that was not supercharged. The superchargers supercharge the cooled high-pressure air in an exchange line in which the oxygen from the system of columns is vaporized.

1 - 15 . (canceled) 
     
     
         16 . A method for separating air by means of cryogenic distillation in an installation comprising a system of columns, of which one column operating at the highest pressure called the medium pressure wherein:
 all of the air is brought to a high pressure, at least 3 bars higher than the medium pressure, purified at this pressure in a purification unit and air is sent at the output temperature from the purification unit to an exchange line;   all of the purified air is cooled in the exchange line and a portion constituting between 10% to 35% of the purified air is boosted by means of at least one first single-stage booster ( 15 ) and sucking at a first intermediate temperature of the exchange line;   at least one portion of the boosted air in the first booster is cooled in the exchange line, boosted by means of at least one second single-stage booster and sucking at a second intermediate temperature of the exchange line and is sent back into the exchange line where it is cooled, then is liquefied, possibly at the cold end of the exchange line and is sent into the system of columns after expansion;   another portion of the high-pressure purified air, constituting possibly between 65% and 90% of the high-pressure purified air, is cooled in the exchange line then at least partially expanded in at least two turbines having one or more intake temperatures which is an intermediate temperature or which are intermediate temperatures of the exchange line then sent to the system of columns in order to be separated;   the work generated by the expansion of the air is used at least partially for the cryogenic compression carried out by the first and/or the second booster by coupling the first booster to one of the two turbines and the second booster to the other of the two turbines; and   liquid oxygen is vaporized in the exchange line,   wherein all of the air purified in the purification unit is sent at the output temperature of the purification unit to an exchange line, the liquid oxygen is pressurized at a pressure below or equal to 16 bars in order to be vaporized in the exchange line, an energy dissipating device is coupled to at least one of the boosters, the first temperature differs from the second temperature by at most 10° C. and the first and second temperatures are between −145° C. and −165° C.   
     
     
         17 . The method as claimed in  claim 16 , wherein the two turbines have different intake temperatures, constituted by the third intermediate temperature and a fourth intermediate temperature of the exchange line. 
     
     
         18 . The method as claimed in  claim 17 , wherein the third temperature is lower than the first temperature. 
     
     
         19 . The method as claimed in  claim 17 , wherein the third temperature differs from the fourth temperature by at most 20° C. 
     
     
         20 . The method as claimed in  claim 17 , wherein the third temperature differs from the fourth temperature by at most 10° C. 
     
     
         21 . The method as claimed in  claim 16 , wherein the first temperature is higher than the second temperature. 
     
     
         22 . The method as claimed in  claim 16 , wherein the first temperature is lower than or equal to the second temperature. 
     
     
         23 . The method as claimed in  claim 16 , wherein a portion of the energy generated by at least one of the turbines is dissipated. 
     
     
         24 . The method as claimed in  claim 23 , wherein a portion of the energy is dissipated by means of an oil valve system connected to the turbine. 
     
     
         25 . The method as claimed in  claim 16 , wherein all of the air boosted in the first booster is sent to the second booster. 
     
     
         26 . The method as claimed in  claim 16 , wherein all of the air purified in the purification unit is sent to the exchange line at the output pressure of the purification unit. 
     
     
         27 . The method as claimed in  claim 16 , wherein the system comprises a double column for separating air comprising a first column and a second column operating at a lower pressure than the first and wherein the air expanded in the two turbines is sent to the first column. 
     
     
         28 . The method as claimed in  claim 16 , wherein all of the air intended for the separating is sent to the hot end of the exchange line. 
     
     
         29 . The method as claimed in  claim 16 , wherein the first temperature is colder than the output temperature of the second booster. 
     
     
         30 . The method as claimed in  claim 16 , wherein the output temperature or temperatures of the first and/or of the second booster is/are between −110° C. and −150° C. 
     
     
         31 . The method as claimed in  claim 16 , wherein the output temperature or temperatures of the first and/or of the second booster is/are between −125° C. and −145° C. 
     
     
         32 . The method as claimed in  claim 16 , wherein the liquid oxygen is pressurised at a pressure between 10 and 16 bars.