Method and device for generating an oxygen product by low-temperature separation of air

Abstract

The method and device serve for generating an oxygen product by low-temperature separation of air having a distillation column system for nitrogen-oxygen separation that comprises a high-pressure column ( 6 ) and a low-pressure column ( 7 ) which contain mass-transfer sections. Liquid that drains off from the lowest mass-transfer section ( 32 ) of the low-pressure column ( 7 ) is introduced into a main condenser ( 8 ) constructed as a bath evaporator and condenser-evaporator. Between the bottom end of the lowest mass-transfer section ( 32 ) of the low-pressure column ( 7 ) and the main condenser ( 8 ) there is arranged a liquid buffer ( 33 ). In the event of a reduction in load, liquid is introduced into the liquid buffer ( 33 ) and is stored there. In the event of an increase in load, liquid stored in the liquid buffer ( 33 ) is introduced ( 34 ) into the main condenser ( 8 ).

1 . A method for the variable generation of an oxygen product by low-temperature separation of air using a distillation column system for nitrogen-oxygen separation that comprises a high-pressure column ( 6 ) and a lower-pressure column ( 7 ), which each contain mass-transfer sections, said method comprising:
 cooling a feed air stream ( 1 ,  3 ,  5 ) in a main heat exchanger ( 2 ) and introducing the cooled feed air stream into a high-pressure column ( 6 ),   removing an oxygen-enriched stream ( 28 ) from the lower region of a low-pressure column ( 7 ), warming the oxygen-enriched stream in said main heat exchanger ( 2 ), and obtaining warmed the oxygen-enriched product stream as oxygen product ( 29 ),   introducing liquid drained off from the lowest mass-transfer section ( 32 ) of said low-pressure column ( 7 ) into a main condenser ( 8 ) that is constructed as a bath evaporator and condenser-evaporator, and partially vaporizing said liquid drained off from the lowest mass-transfer section ( 32 ) in said main condenser,   introducing non-vaporized liquid from the main condenser ( 8 ) into a column bottom ( 35 ), and   providing a liquid buffer ( 33 ), constructed for storage of liquid, between the bottom end of said lowest mass-transfer section ( 32 ) of said low-pressure column ( 7 ) and the main condenser ( 8 ),   wherein during a reduction in load, liquid from said column bottom ( 35 ) of said main condenser is introduced into said liquid buffer ( 33 ) and is stored there and, thereby the storage contents of said liquid buffer ( 33 ) are increased, and   wherein during an increase in load, at least some of the liquid stored in said liquid buffer ( 33 ) is introduced ( 34 ) said main condenser ( 8 ) and, thereby the storage contents of said liquid buffer ( 33 ) are decreased.   
     
     
         2 . The method according to  claim 1 , wherein the liquid from said column bottom ( 35 ) of said main condenser is introduced by a liquid pump ( 36 ) into said liquid buffer ( 33 ). 
     
     
         3 . The method according to  claim 2 , wherein said main condenser ( 8 ) is constructed as a multistorey bath evaporator. 
     
     
         4 . The method according to  claim 3 , wherein said main condenser ( 8 ) is constructed as a cascade evaporator. 
     
     
         5 . The method according to  claim 3 , wherein said oxygen-enriched stream ( 28 ) has an oxygen concentration of less than 98%. 
     
     
         6 . The method according to  claim 4 , wherein said oxygen-enriched stream ( 28 ) has an oxygen concentration of less than 98%. 
     
     
         7 . An apparatus for generating an oxygen product by low-temperature separation of air, said apparatus comprising:
 a distillation column system for nitrogen-oxygen separation comprising a high-pressure column ( 6 ) and a low-pressure column ( 7 ), which each contain mass-transfer sections,   a main heat exchanger ( 2 ) for cooling a feed air stream ( 1 ,  3 ,  5 ),   means for introducing cooled feed air stream from said main heat exchanger into said high-pressure column ( 6 ),   means for removing an oxygen-enriched stream ( 28 ) from the lower region of said low-pressure column ( 7 ) and means for introducing the oxygen-enriched stream ( 28 ) into said main heat exchanger ( 2 ),   an oxygen product line for obtaining the warmed product stream as oxygen product ( 29 ) from said main heat exchanger ( 2 ),   a main condenser ( 8 ) constructed as a bath evaporator and condenser-evaporator,   means for introducing liquid that drains off from the lowest mass-transfer section ( 32 ) of said low-pressure column ( 7 ) into said main condenser ( 8 )   a column bottom ( 35 ) for collecting non-vaporized liquid from said main condenser ( 8 ),   a liquid buffer ( 33 ) arranged between the bottom end of said lowest mass-transfer section ( 32 ) of said low-pressure column ( 7 ) and said main condenser ( 8 ),   means for introducing liquid into said liquid buffer ( 33 ),   means for introducing ( 34 ) at least some of the liquid stored in said liquid buffer ( 33 ) into said main condenser ( 8 ), and   control means constructed in such a manner that during a reduction in load, liquid from said column bottom ( 35 ) of said main condenser is introduced into said liquid buffer ( 33 ) and is stored there and, in this case, the storage contents of said liquid buffer ( 33 ) are increased, and that during an increase in load, at least some of the liquid stored in said liquid buffer ( 33 ) is introduced ( 34 ) into said main condenser ( 8 ) and, in this case, the storage contents of said liquid buffer ( 33 ) are decreased.   
     
     
         8 . The apparatus according to  claim 7 , further comprising a liquid pump ( 36 ) for transporting liquid from said column bottom ( 35 ) of said main condenser into said liquid buffer ( 33 ). 
     
     
         9 . The apparatus according to  claim 8 , wherein said main condenser ( 8 ) is constructed as a multistorey bath evaporator. 
     
     
         10 . The apparatus according to  claim 8 , wherein said main condenser ( 8 ) is constructed as a cascade evaporator.