PROCESS AND APPARATUS FOR GENERATING A PRESSURIZED PRODUCT BY LOW-TEMPERATURE AIR FRACTIONATION
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.