Method for recovering a gaseous pressure product by low-temperature separation of air

Abstract

The invention relates to production of a pressurized gaseous oxygen product by low-temperature separation of air in a distillation column system, having a low-pressure column and a high-pressure column. A first partial stream of the purified feed air is work-expanded in a first expander, and at least partially introduced into the high-pressure column. A second partial stream is cooled in a main heat exchanger to an intermediate temperature, further compressed, cooled in the main heat exchanger where it is liquefied or pseudo-liquefied, and then introduced into the distillation column system. A third partial stream of the compressed feed air is work-expanded in a second expander. A liquid oxygen product stream, removed from the distillation column system, is brought to an elevated pressure, evaporated or pseudo-evaporated in the main heat exchanger, heated to approximately ambient temperature, and ultimately withdrawn as a pressurized gaseous oxygen product stream.

1 . A method for producing a gaseous oxygen pressure product by low-temperature separation of air in a distillation column system having at least one low-pressure column ( 90 ) and a high-pressure column ( 80 ), said method comprising:
 Compressing process feed air ( 1 ) in an air compressor ( 2 ),   Purifying the compressed feed air ( 3 ), at least in part, in a purification system ( 5 ),   Further compressing at least a part ( 7 ) of the purified feed air ( 6 ) in a warm booster compressor ( 8 ),   Depressurizing a first partial stream ( 11 ,  15 ) of the purified feed air ( 6 ) in a work-expansion manner in a first expander ( 16 ) and then at least partially introducing ( 17 ) the depressurized first partial stream into the high-pressure column ( 80 ) of the distillation column system,   Cooling a second partial stream ( 12 ) of the purified feed air ( 6 ) in a main heat exchanger ( 14 ) to an intermediate temperature, further compressing the cooled second partial stream in a cold compressor ( 19 ), further cooling the second partial stream in the main heat exchanger ( 14 ), whereby it is liquefied or pseudo-liquefied, and then introducing the liquefied or pseudo-liquefied second partial stream into the distillation column system ( 21 ,  23 ),   Depressurizing a third partial stream ( 13 ) of the compressed feed air ( 3 ) in a work-expansion manner in a second expander ( 25 ),   Removing a liquid oxygen product stream ( 30 ,  32 ) from the distillation column system, bringing the liquid oxygen product stream to an elevated pressure in a liquid state ( 34 ), evaporating or pseudo-evaporating the liquid oxygen product stream under this elevated pressure in the main heat exchanger ( 14 ), heating the evaporated or pseudo-evaporated oxygen product stream to approximately ambient temperature, and ultimately removing the evaporated or pseudo-evaporated oxygen product stream as a gaseous oxygen-pressure product stream ( 33 ),   Wherein the two expanders ( 16 ,  25 ) are each coupled to one of the two machines, the warm booster compressor ( 8 ) and the cold compressor ( 18 ,  19 ), and   Wherein at least one part of the work-expanded third partial stream ( 26 ) is returned to the air compressor ( 2 ).   
     
     
         2 . The method according to  claim 1 , wherein the air compressor ( 2 ) has a plurality of stages comprising at least a first and a last stage, whereby at least one part of the work-expanded third partial stream ( 26 ) is recycled to the air compressor ( 2 ) downstream from said first stage and upstream from said last stage ( 28 ). 
     
     
         3 . The method according to  claim 1 , wherein the third partial stream ( 13 ), upstream from the purification system ( 5 ), is branched-off from the compressed feed air ( 3 ). 
     
     
         4 . The method according to  claim 2 , wherein the third partial stream ( 13 ), upstream from the purification system ( 5 ), is branched-off from the compressed feed air ( 3 ). 
     
     
         5 . The method according to  claim 3 , wherein a part ( 6 ) of the compressed feed air ( 3 ), which comprises the first and second partial streams, is cooled upstream from the purification system ( 5 ) in a pre-cooling device ( 4 ), and the third partial stream ( 13 ) upstream from the pre-cooling device ( 4 ) is branched-off from the compressed feed air ( 3 ). 
     
     
         6 . The method according to  claim 4 , wherein a part ( 6 ) of the compressed feed air ( 3 ), which comprises the first and second partial streams, is cooled upstream from the purification system ( 5 ) in a pre-cooling device ( 4 ), and the third partial stream ( 13 ) upstream from the pre-cooling device ( 4 ) is branched-off from the compressed feed air ( 3 ). 
     
     
         7 . The method according to  claim 1 , wherein a part of the work-expanded third partial stream ( 26 ) is discharged into the atmosphere. 
     
     
         8 . The method according to  claim 1 , wherein the first and second partial streams are further compressed in the warm booster compressor ( 8 ), and the third partial stream ( 13 ) by-passes the warm booster compressor ( 8 ). 
     
     
         9 . The method according to  claim 1 , wherein the second partial stream is further compressed in the warm booster compressor ( 8 ), and the first partial stream by-passes the warm booster compressor. 
     
     
         10 . The method according to  claim 1 , wherein the third partial stream ( 13 ) is introduced into the second expander ( 25 ) at approximately the exit pressure of the air compressor ( 2 ). 
     
     
         11 . The method according to  claim 1 , wherein the air compressor ( 2 ) represents the only machine driven by external energy for compression of air. 
     
     
         12 . The method according to  claim 1 , wherein a liquid nitrogen product stream is removed from the distillation column system, brought to an elevated pressure in the liquid state, evaporated or pseudo-evaporated under this elevated pressure in the main heat exchanger, heated to approximately ambient temperature, and finally withdrawn as a gaseous pressurized nitrogen product stream.