Process and apparatus for generating a pressurized product by low-temperature air fractionation

Abstract

The process serves for generating a pressurized product by low-temperature air fractionation. Feed air ( 1 ) is compressed ( 2 ), purified ( 4 ), cooled ( 9 ) and fed to a distillation column system ( 12 ) for nitrogen-oxygen separation ( 11, 23 ). A liquid product stream ( 13 ) is taken off from the distillation column system ( 12 ) for nitrogen-oxygen separation, brought ( 14 ) in the liquid state to an elevated pressure (PIV) and at this elevated pressure (PIV) vaporized or pseudovaporized ( 9 ). The (pseudo)vaporized product stream ( 16 ) is fed ( 17 ) as pressurized product to a gas pressure reservoir ( 19 ) which has a variable pressure (PA). The elevated pressure (PIV) is varied. The elevated pressure (PIV) is varied as a function of the pressure (PA) of the gas pressure reservoir ( 19 ).

1 . A process for generating a pressurized product by low-temperature air fractionation, said process comprising: 
 compressing ( 2 ), purifying ( 4 ), and cooling ( 9 ) feed air ( 1 ) and then feeding the feed air to a distillation column system ( 12 ) for nitrogen-oxygen separation ( 11 ,  23 ),    removing a liquid product stream ( 13 ) from said distillation column system ( 12 ) for nitrogen-oxygen separation, bringing ( 14 ) the liquid product stream ( 13 ), in the liquid state, to an elevated pressure (PIV), and at this elevated pressure (PIV) vaporizing or pseudovaporizing ( 9 ) the liquid product stream,    feeding ( 17 ) the vaporized or pseudovaporized product stream ( 16 ) as pressurized product to a gas pressure reservoir ( 19 ) which has a variable pressure (PA),    varying the elevated pressure (PIV), and    varying the elevated pressure (PIV) as a function of the pressure (PA) of the gas pressure reservoir ( 19 ).    
     
     
         2 . A process according to  claim 1 , further comprising compressing ( 20 ) a gaseous heat carrier stream ( 7 ,  21 ,  22 ) to a high pressure (PW), and vaporization or pseudovaporization of said liquid product stream ( 13 ,  15 ) is performed by indirect heat exchange ( 9 ) with said heat carrier stream which is at the high pressure, wherein the high pressure (PW) and/or the rate (MW) of the heat carrier stream is varied and the high pressure (PW) and/or the rate (MW) of the heat carrier stream is varied as a function of the pressure (PA) of the gas pressure reservoir ( 19 ).  
     
     
         3 . A process according to  claim 2 , wherein said gaseous heat carrier stream ( 7 ,  21 ,  22 ) is an air stream.  
     
     
         4 . A process according to  claim 1 , further comprising compressing ( 20 ) a gaseous heat carrier stream ( 7 ,  21 ,  22 ) to a high pressure (PW), and vaporization or pseudovaporization of said liquid product stream ( 13 ,  15 ) is performed by indirect heat exchange ( 9 ) with said heat carrier stream which is at the high pressure, wherein the high pressure (PW) and/or the rate (MW) of the heat carrier stream is varied and the high pressure (PW) and/or the rate (MW) of the heat carrier stream is varied as a function of the elevated pressure (PIV) of the liquid product stream ( 13 ).  
     
     
         5 . A process according to  claim 4 , wherein said gaseous heat carrier stream ( 7 ,  21 ,  22 ) is an air stream.  
     
     
         6 . A process according to  claim 3 , wherein said gaseous heat carrier stream is a compressed substream of the feed air which after being subjected to heat exchange with said liquid product stream is introduced into the distillation column system for nitrogen-oxygen separation.  
     
     
         7 . A process according to  claim 1 , wherein cold for the process is obtained in a cold generation system ( 26 ) and the amount of cold generated in the cold generation system ( 26 ) is varied as a function of the pressure (PA) of the gas pressure reservoir ( 19 ).  
     
     
         8 . A process according to  claim 7 , wherein said cold generation system comprises a substream of the feed air which is subjected to heat exhange with said liquid product stream, expanded, and then introduced into the distillation column system for nitrogen-oxygen separation.  
     
     
         9 . A process according to  claim 1 , wherein the operating parameters of the distillation column system are varied as a function of the pressure (PA) of the gas pressure reservoir ( 19 ).  
     
     
         10 . A process according to  claim 1 , wherein the elevated pressure (PIV) is only just above the pressure (PA) of the gas pressure reservoir ( 19 ).  
     
     
         11 . A process according to  claim 10 , wherein the difference (PIV−PA) between the elevated pressure (PIV) and the pressure (PA) of the gas pressure reservoir ( 19 ) is less than half the range of variation of the pressure of the gas pressure reservoir ( 19 ).  
     
     
         12 . A process according to  claim 10 , wherein the difference (PIV−PA) between the elevated pressure (PIV) and the pressure (PA) of the gas pressure reservoir ( 19 ) is less than one third the range of variation of the pressure of the gas pressure reservoir ( 19 ).  
     
     
         13 . A process according to  claim 10 , wherein the difference (PIV−PA) between the elevated pressure (PIV) and the pressure (PA) of the gas pressure reservoir ( 19 ) is less than one fifth the range of variation of the pressure of the gas pressure reservoir ( 19 ).  
     
     
         14 . A process according to  claim 1 , wherein an air stream ( 7 ,  21 ,  22 ) is compressed ( 20 ) to a high pressure (PW) and the liquid product stream ( 13 ,  15 ) is vaporized or pseudovaporized by indirect heat exchange ( 9 ) with said air stream at high pressure.  
     
     
         15 . A process according to  claim 1 , wherein said the distillation column system comprises a high-pressure column and a low-pressure column which are in a heat-exchange relationship via a shared condenser-evaporator.  
     
     
         16 . A process according to  claim 1 , wherein the elevated pressure (PIV) is set to a pressure which is 0.5 to 2 bar above the current the pressure (PA) of the gas pressure reservoir ( 19 ).  
     
     
         17 . An apparatus for generating a pressurized product by low-temperature air fractionation, said apparatus comprising: 
 a distillation column system for nitrogen-oxygen separation ( 12 ),    means ( 1 ,  3 ,  5 ,  6 ,  7 ,  10 ,  11 ,  21 ,  22 ,  23 ,  25 ,  27 ) for feeding compressed, purified and cooled feed air into said distillation column system ( 12 ) for nitrogen-oxygen separation,    means ( 13 ,  15 ) for taking off a liquid product stream from said distillation column system ( 12 ) for nitrogen-oxygen separation,    means ( 14 ) for bringing said liquid product stream in the liquid state to an elevated pressure (PIV),    means ( 9 ) for vaporizing or pseudovaporizing said liquid product stream at the elevated pressure (PIV),    means ( 16 ,  17 ) for feeding the vaporized or pseudovaporized product stream as pressurized product to a gas pressure reservoir ( 19 ),    means for varying said elevated pressure (PIV) and    a closed-loop or open-loop control unit which varies said elevated pressure (PIV) as a function of the pressure (PA) of the gas pressure reservoir ( 19 ).    
     
     
         18 . An apparatus according to  claim 17 , wherein said the distillation column system comprises a high-pressure column and a low-pressure column which are in a heat-exchange relationship via a shared condenser-evaporator.