Process for the separation of air by cryogenic distillation

Abstract

A process for separation of air by cryogenic distillation, including cooling a first purified feed air stream in a heat exchanger, thereby producing a cooled first feed stream, removing a first portion from the heat exchanger at a first intermediate temperature, and compressing the cooled first portion in a first booster compressor, cooling the compressed first portion in the heat exchanger, thereby producing a cooled first portion, removing a second portion from the heat exchanger at a second intermediate temperature, and compressing the cooled second portion in a second booster compressor, cooling the compressed second portion in the heat exchanger, thereby producing a cooled second portion, and vaporizing a pressurized liquid stream from the column system in the heat exchanger at a vaporization temperature to form a pressurized gaseous product stream, wherein, both the first discharge temperature and said second discharge temperature are below −55° C.

1 - 18 . (canceled) 
     
     
         19 . A process for separation of air by cryogenic distillation using a heat exchanger, a column system comprising a low pressure column and a high pressure column, the process comprising the steps of:
 a) cooling a purified air stream in the heat exchanger to produce a liquefied air stream, the heat exchanger having a warm end, a cold end, and an intermediate portion, wherein the purified air stream is at a pressure substantially greater than the high pressure column, wherein the liquefied air stream is at a temperature T c  when leaving the cold end of the heat exchanger;   b) introducing the liquefied air stream to the column system under cryogenic conditions configured to produce an oxygen rich stream and a nitrogen rich stream via cryogenic distillation within the column system;   c) withdrawing the oxygen rich stream from the column system and pressurizing the oxygen rich stream using a pump to produce a pressurized oxygen rich stream;   d) introducing the pressurized oxygen rich stream to the cold end of the heat exchanger; and   e) vaporizing the pressurized oxygen rich stream to produce a gaseous oxygen product stream at the warm end of the heat exchanger,   wherein step a) further includes the steps of:
 i) removing a first portion of the purified air stream from the intermediate portion of the heat exchanger and compressing the first portion in a first cold compressor to form a boosted first portion, wherein the first portion is at a temperature T i  when leaving the intermediate portion; 
 ii) cooling the boosted first portion in the heat exchanger to form a cooled first portion; 
 iii) removing the cooled first portion from the intermediate portion of the heat exchanger and compressing the cooled first portion in a second cold compressor to form a boosted second portion, wherein the cooled first portion is at a temperature T ii  when leaving the intermediate portion; and 
 iv) cooling the boosted second portion in the heat exchanger to form the liquefied air stream, 
   wherein the first cold compressor operate near the vaporization temperature of vaporizing oxygen;   wherein step b) further includes the steps of:
 i) removing a second portion of the purified air stream from the intermediate portion of the heat exchanger at a temperature T 2  and then expanding the second portion using a first turboexpander to form an expanded second portion; 
 ii) introducing the expanded second portion to a low pressure column of the column system; 
 iii) removing a third portion of the purified air stream from the intermediate portion of the heat exchanger at a temperature T 3  and then expanding the third portion using a second turboexpander to form an expanded third portion; and 
 iv) introducing the expanded third portion to a high pressure column of the column system. 
   
     
     
         20 . The process as claimed in  claim 19 , wherein the purified air stream is at a pressure between about 10 and about 20 bar absolute. 
     
     
         21 . The process as claimed in  claim 19 , wherein the purified air stream is at a pressure between about 14 and about 20 bar absolute. 
     
     
         22 . The process as claimed in  claim 19 , wherein T 2  is colder than T i  and T ii . 
     
     
         23 . The process as claimed in  claim 19 , wherein T 3  is colder than T i  and T ii . 
     
     
         24 . A process for separation of air by cryogenic distillation using a heat exchanger, a column system comprising a low pressure column and a high pressure column, the process comprising the steps of:
 a) cooling a purified air stream in the heat exchanger to produce a liquefied air stream, the heat exchanger having a warm end, a cold end, and an intermediate portion, wherein the purified air stream is at a pressure greater than the high pressure column, wherein the liquefied air stream is at a temperature T c  when leaving the cold end of the heat exchanger;   b) introducing the liquefied air stream to the column system under cryogenic conditions configured to produce an oxygen rich stream and a nitrogen rich stream via cryogenic distillation within the column system;   c) withdrawing the oxygen rich stream from the column system and pressurizing the oxygen rich stream using a pump to form a pressurized oxygen rich stream;   d) introducing the pressurized oxygen rich stream to the cold end of the heat exchanger; and   e) vaporizing the pressurized oxygen rich stream to produce a gaseous oxygen product stream at the warm end of the heat exchanger, wherein the pressurized oxygen rich stream provides at least part of the refrigeration to cool the purified air stream,   wherein step a) further includes the steps of:
 i) removing a first portion of the purified air stream from the intermediate portion of the heat exchanger and compressing the first portion in a first cold compressor to form a boosted first portion, wherein the first portion is at a temperature T i  when leaving the intermediate portion; 
 ii) cooling the boosted first portion in the heat exchanger to form a cooled first portion; 
 iii) removing the cooled first portion from the intermediate portion of the heat exchanger and compressing the cooled first portion in a second cold compressor to form a boosted second portion, wherein the cooled first portion is at a temperature T ii  when leaving the intermediate portion; and 
 iv) cooling the boosted second portion in the heat exchanger to form the liquefied air stream, 
   wherein T i  and T ii  are at about the same temperature and warmer than T c .   
     
     
         25 . The process as claimed in  claim 24 , wherein the first cold compressor and the second cold compressor operate near the vaporization temperature of vaporizing oxygen. 
     
     
         26 . The process as claimed in  claim 24 , wherein the first cold compressor and the second cold compressor operate within about 10° C. of the vaporization temperature of vaporizing oxygen. 
     
     
         27 . The process as claimed in  claim 24 , wherein the first cold compressor and the second cold compressor operate within about 5° C. of the vaporization temperature of vaporizing oxygen. 
     
     
         28 . The process as claimed in  claim 24 , wherein Ti and Tii are less than about −55° C. 
     
     
         29 . The process as claimed in  claim 24 , wherein the purified air stream is at ambient temperature conditions just prior to being cooled in the heat exchanger. 
     
     
         30 . The process as claimed in  claim 24 , further comprising the steps of:
 removing a second portion of the purified air stream from the intermediate portion of the heat exchanger at a temperature T 2  and then expanding the second portion using a first turboexpander to form an expanded second portion; and   introducing the expanded second portion to a low pressure column of the column system.   
     
     
         31 . The process as claimed in  claim 30 , wherein T 2  is colder than T i  and T ii . 
     
     
         32 . The process as claimed in  claim 24 , further comprising the steps of:
 removing a third portion of the purified air stream from the intermediate portion of the heat exchanger at a temperature T 3  and then expanding the third portion using a second turboexpander to form an expanded third portion; and   introducing the expanded third portion to a high pressure column of the column system.   
     
     
         33 . The process as claimed in  claim 32 , wherein T 3  is colder than T i  and T ii . 
     
     
         34 . The process as claimed in  claim 24 , further comprising compressing the purified air stream in a warm booster prior to step a). 
     
     
         35 . The process as claimed in  claim 24 , wherein the purified air stream is at a pressure between about 10 and about 20 bar absolute. 
     
     
         36 . The process as claimed in  claim 24 , wherein the pressurized oxygen rich stream is at a pressure of at least 50 bar abs. 
     
     
         37 . The process as claimed in  claim 24 , wherein the pressurized oxygen rich stream is at a pressure of at least 60 bar abs. 
     
     
         38 . The process as claimed in  claim 24 , wherein the pressurized oxygen rich stream is at a pressure of at least 70 bar abs. 
     
     
         39 . The process as claimed in  claim 24 , wherein the compression heat of the first cold compressor and the second cold compressor contributes to vaporizing the pressurized oxygen rich stream.