Process and apparatus for the separation of air by cryogenic distillation

Abstract

In a process for the separation of air by cryogenic distillation using a cryogenic distillation unit comprising at least a double column ( 1 ) including a high pressure column ( 2 ) and a low pressure column ( 3 ), in which air is compressed in a compressor (C) to a first pressure, cooled and purified air at the first pressure is compressed in first and second booster compressors ( 8, 11 ) to a second pressure and then cooled in a heat exchanger ( 5 ), at least part of the air at the second pressure is cooled and expanded in a first turbine ( 12 ) having a first inlet temperature, a first part of the air expanded in the first turbine is sent to the high pressure column and a second part of the air expanded in the first turbine is sent to the heat exchanger to be warmed, the warmed second part of the air is expanded in a second turbine ( 9 ), returned to the heat exchanger and further warmed and a portion of the air is compressed in the first booster compressor ( 8 ) to a pressure intermediate to the first and second pressures, sent to the heat exchanger, cooled, liquefied, and sent to at least one column of the double column.

1 . A process for the separation of air by cryogenic distillation using a cryogenic distillation unit comprising at least a double column including a high pressure column and a low pressure column, in which air is compressed in a compressor to a first pressure, cooled and purified, air at the first pressure is compressed in first and second booster compressors to a second pressure and then cooled in a heat exchanger, at least part of the air at the second pressure sent to the heat exchanger is cooled, liquefied and sent to at least one column of the double column and at least a portion of the air is compressed in the first booster compressor to a pressure intermediate the first and second pressures, is cooled and expanded in a first turbine having a first inlet temperature, a first part of the air expanded in the first turbine is sent to the high pressure column and a second part of the air expanded in the first turbine is sent to the heat exchanger to be warmed, the warmed second part of the air is expanded in a second turbine, returned to the heat exchanger and further warmed.  
   
   
       2 . The process of  claim 1 , in which all the air compressed to the intermediate pressure and then cooled without further compression is sent to the first turbine.  
   
   
       3 . The process of  claim 1 , in which at least one liquid product is produced.  
   
   
       4 . The process of  claim 1 , in which the first booster compressor is coupled to the first turbine and the second booster compressor is coupled to the second turbine.  
   
   
       5 . An apparatus for the separation of air by cryogenic distillation, the apparatus comprising a double column comprising a high pressure column and a low pressure column, a compressor, first and second turbines, first and second booster compressors and a heat exchanger, a conduit for sending air at a first pressure from the compressor to the first and second booster compressors connected in series, conduits for sending air at a second pressure from the outlet of the second booster to the heat exchanger and thence to at least one column of the double column, a conduit for removing air from the first booster compressor and a conduit for sending the air removed from the first booster to the heat exchanger and thence to the first turbine, a conduit for sending air from the first turbine to the high pressure column, a conduit for sending air from the first turbine to a cold end of the heat exchanger, a conduit for removing the air sent from the first turbine to the heat exchanger from an intermediate point of the heat exchanger, a conduit for sending the removed air to a second turbine and a conduit for returning air from the second turbine to the heat exchanger.  
   
   
       6 . The apparatus of  claim 5 , in which the outlet of the first booster compressor is connected only to inlet of the first turbine.  
   
   
       7 . The apparatus of  claim 5 , in which the first booster compressor is coupled to the first turbine and the second booster compressor is coupled to the second turbine.