Apparatus and method for separating air by cryogenic distillation

Abstract

Device for separating air comprises a pipe for withdrawing liquid oxygen from the low-pressure column and for sending it to a first pump, a pipe for sending liquid oxygen that has been pressurized to a pressure of below 9 bar as from the first pump to a vaporizer, a pipe for sending gaseous oxygen from the vaporizer to a main exchanger Where it is heated up, a pipe for sending liquid oxygen for purging from the vaporizer to a second pump to pressurize it and a pipe for sending the pressurized oxygen from the second pump to an exchanger where it vaporizes to form gaseous oxygen.

1 - 15 . (canceled) 
     
     
         16 . An apparatus for separating air, the apparatus comprising:
 a double column comprising a medium-pressure column and a low-pressure column;   a main exchanger;   a vaporizer; a main compressor;   means for sending all of the air to be treated in the double column to the main compressor in order to produce air substantially at the pressure P 1  of the medium-pressure column;   means for sending a portion of the air substantially at a high pressure P 2  to the main exchanger and then to the vaporizer;   a pipe for sending air at least partially condensed in the vaporizer to at least one of the columns;   a pipe for sending air at the pressure P 1  to the medium-pressure column;   means of pressurizing;   a pump;   a pipe for withdrawing liquid oxygen from the low-pressure column and for sending it to the means of pressurizing;   a pipe for sending the liquid oxygen that has been pressurized at a pressure below 9 bar abs from the means of pressurizing to the vaporizer;   a pipe for sending gaseous oxygen from the vaporizer to the main exchanger to be heated for forming a first flow of gaseous oxygen;   a purge pipe for sending the liquid purge oxygen from the vaporizer to the pump in order to pressurize the liquid purge oxygen; and   a pipe for sending the pressurized oxygen from the pump to an exchanger to be vaporized,   wherein the purge pipe is not connected to a purge liquid storage, and   wherein the exchanger is connected to a pipe for compressed air connected to the main compressor and to a pipe connected to the double column, thereby forming a second flow of gaseous oxygen.   
     
     
         17 . The apparatus as claimed in  claim 16 , wherein the exchanger connected to the oxygen purge pipe is the main exchanger. 
     
     
         18 . The apparatus as claimed in  claim 16 , wherein the exchanger connected to the oxygen purge pipe is an exchanger separate from the main exchanger. 
     
     
         19 . The apparatus as claimed in  claim 17 , wherein the exchanger comprises passages connected to a supply air inlet pipe and passages connected to a liquid refrigerant inlet pipe, possibly coming from the double column. 
     
     
         20 . The apparatus as claimed in  claim 16  further comprising a storage of pressurized gases connected to the exchanger for the vaporization of purge oxygen in order to collect the gaseous oxygen. 
     
     
         21 . A method for separating air in an apparatus comprising a double column having a medium-pressure column and a low-pressure column; a main exchanger; a vaporizer; a main compressor; means of pressurizing; a pump; the method comprising the steps of:
 sending all of the air to he treated in the double column to the main compressor to produce air substantially at the pressure P 1  of the medium-pressure column;   sending a portion of the air substantially at a high pressure P 2  to the main exchanger and then to the vaporizer;   sending air at least partially condensed in the vaporizer to at least one of the columns;   sending air at the pressure P 1  to the medium-pressure column;   withdrawing and pressurizing liquid oxygen from the low-pressure column to a pressure below  5  bar abs;   sending the liquid oxygen that has been pressurized at a pressure below 5 bar abs to the vaporizer;   sending a first flow of gaseous oxygen from the vaporizer to the main exchanger to be heated; and   pressurizing the liquid purge oxygen of the vaporizer in the pump, wherein the liquid purge oxygen is pressurized without having been stored and is then vaporized in an exchanger via heat exchange with the air, compressed in the main compressor and intended for the double column, thereby forming a second flow of gaseous oxygen.   
     
     
         22 . The method as claimed in  claim 21  further comprising pressurizing the purge oxygen at a pressure of at least 10 bars abs in the second pump. 
     
     
         23 . The method as claimed in  claim 21  further comprising pressurizing the purge oxygen at a pressure of at least 15 bars abs in the second pump. 
     
     
         24 . The method as claimed in  claim 21  further comprising pressurizing the purge oxygen at a pressure of at least 20 bars abs in the second pump. 
     
     
         25 . The method as claimed in  claim 21  further comprising vaporizing the purge oxygen in the main exchanger. 
     
     
         26 . The method as claimed in  claim 21  further comprising vaporizing the purge oxygen in an exchanger other than the main exchanger. 
     
     
         27 . The method as claimed in  claim 21  further comprising sending the second flow of gaseous oxygen to a storage of pressurized gases to be used for backup production. 
     
     
         28 . The method as claimed in  claim 21  further comprising mixing a variable quantity of the second flow of gaseous oxygen with the first flow of gaseous oxygen to produce a substantially constant mixed flow. 
     
     
         29 . The method as claimed in  claim 21 , wherein the liquid oxygen withdrawn from the low-pressure column contains at least 80% mol. oxygen. 
     
     
         30 . The method as claimed in  claim 29 , wherein the liquid oxygen withdrawn from the low-pressure column constitutes the only flow containing at least 80% mol. oxygen withdrawn from the low-pressure column. 
     
     
         31 . The method as claimed in  claim 21 , wherein the liquid oxygen withdrawn from the low-pressure column contains at most 98% mol. oxygen. 
     
     
         32 . The method as claimed in  claim 21 , further comprising an absence of fully condensing airflow in the exchanger wherein the purge oxygen is vaporized. 
     
     
         33 . The method as claimed in  claim 21 , further comprising an absence condensing airflow in the exchanger wherein the purge oxygen is vaporized.