Method and device for obtaining compressed oxygen and compressed nitrogen by the low-temperature separation of air

Patent metadata

Field	Value
Publication number	US-9733014-B2
Application number	US-201113816809-A
Country	US
Kind code	B2
Filing date	Aug 9, 2011
Priority date	Aug 13, 2010
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

The invention relates to a method and device for obtaining compressed oxygen and compressed nitrogen by the low-temperature separation of air in a distillation column system for nitrogen-oxygen separation, said distillation column system having at least one high-pressure column ( 8 ) and one low-pressure column ( 460 ), wherein the low-pressure column ( 460 ) is in a heat-exchanging connection with the high-pressure column ( 8 ) by means of a main condenser ( 461 ) designed as a condenser-evaporator. Feed air is compressed in an air compressor ( 2 ). The compressed feed air ( 6, 734, 802, 840 ) is cooled down in a main heat exchanger ( 20 ) and at least partially introduced into the high-pressure column ( 8 ). An oxygen-enriched liquid ( 462, 465 ) is removed from the high-pressure column ( 8 ) and fed to the low-pressure column ( 460 ) at a first intermediate position ( 464, 467, 906 ). A nitrogen-enriched liquid ( 468, 470 ) is removed from the high-pressure column ( 8 ) and/or the main condenser ( 461 ) and fed to the head of the low-pressure column ( 460 ). A liquid oxygen flow ( 11, 12 ) is removed from the distillation column system for nitrogen-oxygen separation, brought to an elevated pressure in the liquid state ( 13 ), introduced into the main heat exchanger ( 20 ) at said elevated pressure, evaporated or pseudo-evaporated and heated to approximately ambient temperature in the main heat exchanger ( 20 ), and finally obtained as a gaseous compressed oxygen product ( 14 ). A high-pressure process flow ( 34, 734 ) is brought into indirect heat exchange with the oxygen flow in the main heat exchanger ( 20 ) and then depressurized ( 36, 38; 736, 738 ), wherein the depressurized high-pressure flow ( 37, 737 ) is introduced at least partially in the liquid state into the distillation column system for nitrogen-oxygen separation. A gaseous circuit nitrogen flow ( 18, 19 ) is drawn from the high-pressure column and at least partially ( 21 ) compressed in a circuit compressor ( 22 ). A first sub-flow ( 45, 46; 244, 242, 230; 845, 846 ) of the circuit nitrogen flow is removed from the circuit compressor ( 22, 322 ), cooled down in the main heat exchanger ( 20 ), at least partially condensed in the bottom evaporator ( 9, 209 ) of the high-pressure column ( 8 ) in indirect heat exchange with the bottom liquid of the high-pressure column ( 8 ), and conducted back into the distillation column system for nitrogen-oxygen separation. A second sub-flow of the circuit nitrogen flow is branched off upstream and/or downstream of the circuit compressor and/or from an intermediate stage of the circuit compressor at a product pressure (P, P 1 , P 2 , P 3 , P 4 ) and obtained as a compressed nitrogen product ( 27, 29, 53, 564, 565 ). The circuit compressor ( 22, 322 ) is designed as a hot compressor and is driven by means of external energy.

First claim

The invention claimed is:

1. A method of obtaining compressed oxygen and compressed nitrogen by separation of air in a distillation-column system for nitrogen-oxygen separation, said distillation-column system having at least one high-pressure column ( 8 ) with bottom evaporator ( 9 , 209 ) and a low-pressure column ( 460 ), wherein the low-pressure column ( 460 ) is in heat-exchanging communication with the high-pressure column ( 8 ) via a main condenser ( 461 ), configured as a condenser-evaporator, said high-pressure column ( 8 ) having a top and a bottom, and said low-pressure column ( 460 ) having a top and a bottom, said method comprising:
compressing feed air in an air compressor ( 2 ),
cooling the compressed feed air ( 6 , 734 , 802 , 840 ) in a main heat exchanger ( 20 ), and feeding the cooled and compressed feed air at least partially into said high-pressure column ( 8 ),
removing an oxygen-enriched liquid ( 462 , 465 ) from the high-pressure column ( 8 ), and supplying the oxygen-enriched liquid to said low-pressure column ( 460 ) at a first point ( 464 , 467 , 906 ) intermediate to said top and bottom of low-pressure column ( 460 ),
removing a nitrogen-enriched liquid ( 468 , 470 ) from said high-pressure column ( 8 ) and/or said main condenser ( 461 ), and delivering the nitrogen-enriched liquid to the top of said low-pressure column ( 460 ),
removing an oxygen stream ( 11 , 12 ) in the liquid state from said distillation-column system for nitrogen-oxygen separation, pressurizing the oxygen stream in the liquid state to an increased pressure ( 13 ), feeding the oxygen stream at the increased pressure into said main heat exchanger ( 20 ) wherein the oxygen stream is evaporated or pseudo-evaporated and warmed to form a gaseous compressed oxygen product ( 14 ), and removing the gaseous compressed oxygen product ( 14 ) from said main heat exchanger ( 20 ),
bringing a pressurized process stream ( 34 , 734 ) into indirect heat exchange with the oxygen stream in the main heat exchanger ( 20 ) wherein the pressurized process stream is cooled and the oxygen stream is evaporated or pseudo-evaporated and warmed , expanding the cooled pressurized process stream ( 36 , 38 ; 736 , 738 ) to form an expanded process stream, and then feeding the expanded process stream ( 37 , 737 ), at least partially in the liquid state, into said distillation-column system for nitrogen-oxygen separation,
withdrawing a gaseous circulation nitrogen stream ( 18 , 19 ) from said high-pressure column and compressing at least a portion ( 21 ) of the gaseous circulation nitrogen stream in a circulation compressor ( 22 ), wherein said circulation compressor ( 22 , 322 ) is a multistage compressor,
withdrawing a first partial stream ( 45 , 46 ; 244 , 242 , 230 ; 845 , 846 ) of the gaseous circulation nitrogen stream from the circulation compressor ( 22 , 322 ), cooling the first partial stream in said main heat exchanger ( 20 ), at least partially liquefying the first partial stream in said bottom evaporator ( 9 , 209 ) of said high-pressure column ( 8 ) by indirect heat exchange with bottom liquid of said high-pressure column ( 8 ), and recycling the first partial stream to said distillation-column system for nitrogen-oxygen separation,
branching off a second partial stream of the gaseous circulation nitrogen stream upstream and/or downstream of said circulation compressor and/or of an intermediate stage of said circulation compressor at a product pressure (P, P 1 , P 2 , P 3 , P 4 ) as compressed nitrogen product ( 27 , 29 , 53 , 564 , 565 ),
wherein said circulation compressor ( 22 , 322 ) operates with an inlet temperature that is above 250 K and is driven by means of external energy,
wherein a third partial stream of the gaseous circulation nitrogen stream is withdrawn from said circulation compressor ( 22 , 322 ) as a turbine stream ( 40 ; 242 ), expanded with performance of work ( 41 ), and fed at least partially into said distillation-column system for nitrogen-oxygen separation, and
wherein in a first operating mode a fourth partial stream ( 45 ) of the gaseous circulation nitrogen stream is withdrawn from an intermediate stage of said circulation compressor at a pressure (P 1 -GAN, P 2 -GAN) which is lower than the pressure at which said third partial stream is withdrawn from said circulation compressor ( 22 , 322 ), cooled in a passage of the main heat exchanger, and mixed with the expanded turbine stream ( 42 ), resulting from the expansion of the third partial stream, upstream of said bottom evaporator ( 9 ) and the resultant combined stream ( 30 ) is recycled to said the distillation-column system for nitrogen-oxygen separation.

2. The method as claimed in claim 1 , wherein a total amount of compressed nitrogen product (PN) is obtained, said total amount of compressed nitrogen product being formed by the sum of all streams that are branched from the circulation nitrogen stream upstream and/or downstream of the circulation compressor and/or of an intermediate stage of the circulation compressor at a product pressure (P, P 1 , P 2 , P 3 , P 4 ) removed as compressed nitrogen product ( 27 , 29 , 53 , 564 , 565 ), wherein in a first loading case
a first total amount of compressed nitrogen product PN 1 is obtained,
the first partial stream is fed at a first amount TS 1 through the bottom evaporator ( 9 , 209 ) of the high-pressure column ( 8 ) and
the feed air is fed at a first amount EL 1 into the air compressor ( 2 ), and wherein in a second loading case
a second, higher total amount of compressed nitrogen product PN 2 is obtained, wherein PN 2 >PN 1 ,
the first partial stream is fed at a second amount TS 2 through the bottom evaporator ( 9 , 209 ) of the high-pressure column ( 8 ), wherein TS 2 >TS 1 , and
the feed air is fed at a second amount EL 2 into the air compressor ( 2 ), wherein the first amount of feed air EL 1 , the second amount of feed air EL 2 , the first total amount of compressed nitrogen product PN 1 , and the second total amount of compressed nitrogen product PN 2 satisfy the following equation (EL 2 −EL 1 )/EL 1 <0.2·(PN 2 −PN 1 )/PN 1 .

3. The method as claimed in claim 1 , wherein a liquid fraction from an intermediate point of the high-pressure column ( 8 ) is fed at the operating pressure of the high-pressure column into an intermediate condenser-evaporator ( 10 ) of the high-pressure column, and there, in indirect heat exchange with at least one part of the work-performing expanded turbine stream, is evaporated at least partially, and the stream resulting from the at least partial evaporation of said liquid fraction is recycled at least partially to the high-pressure column ( 8 ).

4. The method as claimed in claim 1 , wherein said third partial stream of the circulation nitrogen stream is withdrawn from an intermediate stage of the circulation compressor and then supplied to the work-performing expansion.

5. The method as claimed in claim 4 , wherein a partial stream of the gaseous circulation nitrogen stream is withdrawn from the circulation compressor at a pressure which is higher than the pressure at which said third partial stream is withdrawn from said circulation compressor, and is then used as said pressurized process stream ( 34 ).

6. The method as claimed in claim 1 , wherein in a second operating mode a part of the work-performing expanded turbine stream ( 42 ) is warmed in the main heat exchanger and is supplied to the circulation compressor at an intermediate stage thereof.

7. The method as claimed in claim 1 , wherein said oxygen stream ( 411 , 412 ) is withdrawn from a lower region of the low-pressure column ( 460 ).

8. The method as claimed in claim 1 , wherein a liquid stream ( 465 ,

Assignees

• Schwenk Dirk
• Alekseev Alexander
• Masterson Frances
• Goloubev Dimitri
• Linde Ag

Inventors

• Schwenk Dirk
• Alekseev Alexander
• Masterson Frances
• Goloubev Dimitri

Classifications

• F25J2240/10

  the fluid being air · CPC title

• F25J3/04884

  Arrangement of reboiler-condensers · CPC title

• F25J3/04084 Primary

  of nitrogen · CPC title

• F25J3/04175

  at a pressure of substantially more than the highest pressure column · CPC title

• F25J2200/52

  in the high pressure column of a double pressure main column system · CPC title