DE10015602A1 - Method and device for obtaining a printed product by low-temperature separation of air - Google Patents

Abstract

For producing a pressurized product by low-temperature producing a pressurized product by low-temperature fractionation of air in a rectification system which has a high-pressure column (13) and a low-pressure column (14), a first feed airstream (12) is introduced into the high-pressure column (13), and an oxygen-rich fraction (38) from the low-pressure column (14) is brought (39) to pressure in the liquid state and introduced (41) into a mixing column (16). A second feed airstream (6, 15) is introduced into the lower region of the mixing column (16) and brought into countercurrent contact with the oxygen-rich fraction (41). The mixing column (16) is operated at a pressure (PM1S) which is lower than the operating pressure (pHDS) of the high-pressure column (13). A total airstream (1) which comprises the first and second feed airstreams is compressed (2) to a first pressure (p1) which is lower than the operating pressure (pHDS) of the high-pressure column (13) and is purified (3) at about this first pressure (p2) . The purified total airstream (4) is divided into the first (5) and the second (6) feed airstream. The first feed airstream (5) is further compressed (8) separately from the second feed airstream to a second pressure (P2) which is at least equal to the operating pressure (PHDS) of the high-pressure column (13).

Description

The invention relates to a method for obtaining a printed product by Cryogenic air separation to obtain a gaseous printed product from a mixing column according to claim 1. In the invention, the mixing column operated at a pressure lower than the operating pressure of the high pressure column of the two-pillar system that is used for nitrogen-oxygen separation.

The rectification system of the invention can be a two-column system, for example as classic double column system, be formed, but also as a three or Multi-column system. In addition to the columns for nitrogen-oxygen Separation of other devices for the extraction of other air components, especially noble gases (e.g. krypton, xenon and / or argon) exhibit.

The oxygen-rich fraction used as an insert for the mixing column points an oxygen concentration higher than that of air and for example 70 to 99.5 mol%, preferably 90 to 98 mol%. Under Mixing column is understood to be a countercurrent contact column in which a more volatile gaseous fraction of a less volatile liquid is sent to.

The method according to the invention is particularly suitable for the extraction of gaseous impure oxygen under pressure. An impure oxygen is used here Mixture with an oxygen content of 99.5 mol% or less, in particular of 70 to 99.5 mol%. The product pressures are, for example, 2.2 to 4.9 bar, preferably at 2.5 to 4.5 bar. Of course, the printed product if necessary, be compressed further in gaseous state.

A method and a device of the type mentioned at the outset are out EP 697576 A1 known. Here the total air is at about high pressure column pressure compresses and the mixing column air then to the operating pressure of the mixing column  relaxed, with the relaxation of part of the mixing column air performing work is carried out. As a result, the high pressure of this partial air flow can Cooling can be used. The known method is not in all Cases energetically favorable.

The invention has for its object a method of the type mentioned and to provide a corresponding device that is particularly small Have energy consumption.

This object is achieved in that a total air flow, which comprises at least the first and the second feed air flow, is compressed to a first pressure (p ₂ ), which is lower than the operating pressure (p _HDS ) of the high-pressure _column , and under approximately this first pressure (p ₁ ) is cleaned, that the cleaned total air flow is divided into the first and the second feed air flow and that the first feed air flow is further compressed separately from the second feed air flow to a second pressure (p ₁ ) which is at least equal to the operating pressure (p _HDS ) of the High pressure column.

The total air flow is not compressed to the highest pressure in the system, but to a lower value. The air part or parts that have a relatively high Require pressure - especially the high pressure column air - are deliberately separated further compressed. This allows you to use the least possible amount of energy Compress the feed air.

The least amount of equipment is required if the first pressure is about the same the operating pressure of the mixing column. The mixing column air (second Feed air flow) into the mixing column without any further pressure-changing measures be initiated.

Alternatively, the first pressure can be lower than the operating pressure (p _MiS ) of the mixing column. In this case, the second feed air stream is further compressed separately from the first feed air stream to a third pressure (p ₃ ) which is at least equal to the operating pressure (p _MiS ) of the mixing column.

The liquid-pressurized oxygen-rich fraction is preferably added before the Feed on the mixing column in indirect heat exchange with an overheated one Airflow warmed up. The superheated airflow is caused, for example, by part of the Feed air is formed, which is at high pressure column pressure. This is at a Intermediate temperature from the main heat exchanger, in the feed air to about Dew point is cooled, removed and without further temperature changing Measures for indirect heat exchange with the oxygen-rich liquid brought. In this way, the temperature of the liquid on the mixing column is optimally given to the conditions in countercurrent mass transfer adjusted within the mixing column.

Cold is generated in the process in a favorable manner by a third The air flow is relieved from work and introduced into the low pressure column. As a result, the "natural" pressure drop between the first pressure or a other process pressure can be used to compensate for insulation losses and if necessary, liquefy some of the products.

The third feed air stream is preferably used before the work-related relaxation post-condensed, particularly during work-related relaxation mechanical energy is used to drive the post-compression. This can a turbine-booster combination can be used in the expansion turbine and post-compressor are mechanically coupled via a common shaft.

The third feed air flow can be combined with the first and second on the first Pressure compressed and cleaned. Then it either becomes immediate led to post-compression or together with the first feed air flow post-compressed.

As an alternative to blowing in the third feed air flow into the low pressure column the second feed air flow after it has been further compressed and before it is fed in the mixing column can be relaxed while working. The further compression then takes place to a second pressure that is significantly higher than the mixing column pressure.

The invention also relates to a device according to claim 9.  

The invention and further details of the invention are described below of exemplary embodiments illustrated in the drawings. Here demonstrate:

Fig. 1, a method and a device with work softly tender expanding part of the compressed air to the first pressure,

Fig. 2 is a modified process to work tender slightest expansion of a portion of said compressed air to said second pressure,

Fig. 3 shows a process with relaxation of the mixing column air and work

Fig. 4 shows another variant of Fig. 1 without recompression of the turbine air.

In the example shown in FIG. 1 process, feed air 1 is introduced into a two-stage air compressor 2 after cooled to a first pressure p ₁ of, for example 2.7 to 3.7 bar, preferably approximately 3.2 bar and brought occurs under this pressure in a cleaning device 3 , which is preferably formed by a pair of molecular sieve adsorbers. The cleaned total air 4 is divided into three partial streams 5 , 6 , 7 .

The first feed air stream 5 is in a first booster 8 to a second pressure p ₂ of for example 4,4 to 7,0 bar, preferably approximately 5.7 bar is further compressed and flows into a main heat exchanger 10 to after-cooling. 9 The first feed air stream leaves the main heat exchanger 10 via line 11 at approximately dew point temperature and is fed via line 12 into a high-pressure column 13 . The operating pressure p _{HDS of} the high pressure column 13 is, for example, 4.3 to 6.9 bar, preferably about 5.6 bar. The rectification system also has a low pressure column 14 which is operated under, for example, 1.3 to 1.7 bar, preferably about 1.5 bar.

The second feed air stream 6 is likewise passed through the main heat exchanger 10 at approximately the first pressure p ₁ (minus line losses and pressure losses in the cleaning device) and finally flows via line 15 to the mixing column. The feed point is located directly above the bottom of the mixing column 16 .

The third partial stream 7 is post-compressed from about the first pressure p ₁ in a second post-compressor 17 to a third pressure p ₃ of, for example, 3.8 to 5.6 bar, preferably about 4.7 bar, and after post-cooling 18 via line 19, the warm one End of the main heat exchanger supplied. However, it is only cooled to an intermediate temperature and drawn off from the main heat exchanger 10 again via line 50 before the cold end and expanded in a turbine 20 to perform work. The relaxed air 21 is blown into the low pressure column 14 . Post-compressor 17 and turbine 20 are directly mechanically coupled.

In the exemplary embodiments, the rectification system is designed as a classic Linde double-column apparatus with a condenser-evaporator 22 as the main condenser. However, the invention can also be used in rectification systems with a different capacitor and / or column configuration.

Oxygen-enriched liquid 23 from the sump of the high-pressure column 13 is cooled in a first supercooling counterflow 24 and, after throttling 25, is fed to the low-pressure column 14 at an intermediate point 26 . Gaseous nitrogen 27 from the top of high pressure column 13 may be heated to a part 28 in the main heat exchanger 10 and recovered as nitrogen product pressure 29th The rest 30 is essentially completely condensed in the main condenser 22 . The liquid nitrogen 31 obtained in this way is fed at least in part 32 as a return to the high-pressure column 13 . If necessary, another part 33 can be drawn off as a liquid product. After supercooling 24 and throttling 35, an intermediate liquid (impure nitrogen) of the high pressure column 34 serves as a return for the low pressure column. Gaseous impure nitrogen 36 from the top of the low pressure column is warmed in the heat exchangers 24 and 10 and finally withdrawn via line 37 . As shown, it can be used as a regeneration gas for the cleaning device 3 .

Liquid oxygen 38 is drawn off from the bottom of the low-pressure column, brought to a pressure of, for example, 5.7 to 6.5 bar, preferably about 6.1 bar in a pump 39, heated in a second supercooling countercurrent 40 and finally upside down the mixing column 16 abandoned ( 41 ). In the second subcooling counterflow 40 , in particular, an overheated airflow 42 is cooled, which is branched off from the first feed airflow upstream of the cold end of the main heat exchanger, at an intermediate temperature that is lower than the inlet temperature of the turbine 20 . After cooling, this air stream is combined again via line 43 with the first feed air stream 11 . The amount of the air flow flowing through the second supercooling counterflow is set via the valve 44 .

Gaseous impure pressurized oxygen 51 is drawn off from the top of the mixing column 16 , warmed in the main heat exchanger 10 and obtained as product 52 . Bottom liquid 45 and an intermediate liquid 46 are removed from the mixing column and fed to the low-pressure column 14 at a suitable point via lines 47 and 48, respectively.

FIG. 2 differs only from FIG. 1 in that the third feed air flow 207 is further compressed together with the second feed air flow in the first post-compressor 108 . As a result, a higher inlet pressure is reached at the turbine 20 and correspondingly more cold is generated.

In the variant of FIG. 3, the cleaning device is operated under a first pressure p ₁ ', which is higher than the operating pressure p _{MiS of} the mixing column. The first pressure p ₁ 'is here, for example, 2.7 to 3.7 bar, preferably about 3.2 bar. Here, the second feed air stream 306 is expanded upstream of its feed into the mixing column. A third feed air stream that is blown into the low pressure column does not exist. The second feed air stream 306 is further compressed downstream of its branch from the cleaned total air in the second post-compressor 317 , which is driven by the turbine 320 . The second feed air flow 349 , which is further compressed to, for example, 3.8 to 5.6 bar, preferably about 4.7 bar, is fed to the turbine 320 via line 350 and is expanded there to perform work to approximately mixing column pressure p _MiS .

Similarly as in Fig. 3, the cleaning 3 is in the procedure of Fig. 4 at a very low first pressure p ₁ "of, for example 2.7 to 3.7 bar, preferably approximately 3.2 bar operated. The turbine 420 is as applied in Fig. 1 with a third feed air stream 407, 450, which is, however, not densified here, but directly from about p to the first pressure from the low pressure column pressure is work expanded ₁ "to about. The turbine-driven post-compressor 418 is used here to further compress the second feed air flow to the second pressure p ₂ , which is approximately equal to the operating pressure p _{MiS of} the mixing column.

In all exemplary embodiments, the air compressor and the post-compressor 8 , 108 are preferably designed together as a three-stage machine. In other words, the further compression of the first feed air stream is carried out in the third stage of a machine, the first and second stages of which are used for air compression upstream of the cleaning unit 3 . As an alternative to this, this machine can also be constructed in four stages, in which case the first three stages are arranged in front of the cleaning device 3 .

Claims (9)

1. A method for obtaining a printed product by low-temperature separation of air in a rectification system having a high-pressure column ( 13 ) and a low-pressure column ( 14 ), in which

• a first feed air stream ( 12 ) is introduced into the high pressure column ( 13 ),
• an liquid-rich fraction ( 38 ) from the low-pressure column ( 14 ) is pressurized liquid ( 39 ) and applied ( 41 ) to a mixing column ( 16 ),
• a second feed air stream ( 6 , 15 , 306 , 406 ) is introduced into the lower region of the mixing column ( 16 ) and brought into countercurrent contact with the oxygen-rich fraction ( 41 ),
• - The mixing column ( 16 ) is operated under a pressure (p _MiS ) which is lower than the operating pressure (p _HDS ) of the high pressure column ( 13 ), and at which
• a gaseous top product ( 51 ) is removed from the upper region of the mixing column ( 16 ) and obtained as a pressure product ( 52 ),

characterized in that

• - A total air flow ( 1 ), which contains the first and the second feed air flow, is compressed ( 2 ) to a first pressure (p ₁ ), which is lower than the operating pressure (p _HDS ) of the high-pressure column ( 13 ), and below this first pressure (p ₁ ) is cleaned ( 3 ) that
• - The cleaned total air flow ( 4 ) in the first ( 5 ) and the second ( 6 , 306 , 406 ) feed air flow is divided and that
• - The first feed air stream ( 5 ) is further compressed ( 8 , 108 ) separately from the second feed air stream to a second pressure (p ₂ ), which is at least equal to the operating pressure (p _HDS ) of the high pressure column ( 13 ).

2. The method according to claim 1, characterized in that the first pressure (p ₁ ) is approximately equal to the operating pressure (p _MiS ) of the mixing column ( 16 ). 3. The method according to claim 1, characterized in that the first pressure is lower than the operating pressure (p _MiS ) of the mixing column ( 16 ) and that the second feed air stream ( 306 , 406 ) separated from the first feed air stream to a third pressure (p ₃ ) is further compressed ( 317 , 417 ), which is at least equal to the operating pressure (p _MiS ) of the mixing column ( 16 ). 4. The method according to any one of claims 1 to 3, characterized in that the liquid-pressurized oxygen-rich fraction is heated to an indirect heat exchange ( 40 ) with an overheated air stream ( 42 ) before being fed ( 41 ) onto the mixing column ( 16 ). 5. The method according to any one of claims 1 to 4, characterized in that a third feed air stream ( 7 , 50 , 207 , 407 , 450 ) work relaxed ( 20 , 420 ) and in the low pressure column ( 14 ) is introduced ( 21 ). 6. The method according to any one of claims 1 to 5, characterized in that the third feed air stream ( 7 ) before the work relaxation ( 20 ) is post-compressed ( 17 ), in particular in the work relaxation ( 20 ) generated mechanical energy for post-compression ( 17th ) is used. 7. The method according to any one of claims 1 to 6, characterized in that the third feed air flow is formed by part of the total air flow ( 4 ) downstream of the cleaning ( 3 ) and directly or after joint further compression ( 108 ) with the first feed air flow of the post-compression ( 17 ) is fed ( 7 , 207 ). 8. The method according to any one of claims 1 to 4, characterized in that the second feed air stream ( 306 , 349 , 350 ) is relaxed to perform work ( 320 ) before it is introduced into the mixing column. 9. Device for obtaining a printed product by low-temperature separation of air with a rectification system, which has a high-pressure column ( 13 ) and a low-pressure column ( 14 ), and with

• - a first feed air line ( 5 , 11 , 12 ) leading into the high pressure column ( 13 ),
• a liquid line ( 38 , 41 ) for removing an oxygen-rich fraction from the low-pressure column ( 14 ), which contains means ( 39 ) for increasing the pressure and leads to a mixing column ( 16 ),
• - A second feed air line ( 6 , 15 ), which leads into the lower region of the mixing column ( 16 ), and with
• an oxygen product line, which is connected to the upper region of the mixing column ( 16 ),

characterized in that

• - A total air line, which leads through an air compressor ( 2 ) and a cleaning device ( 3 ) and is connected downstream to the first and second feed air lines and through
• - A post-compressor ( 8 , 108 ) which is arranged in the first feed air line ( 5 , 11 , 12 ).