METHOD FOR OBTAINING ONE OR MORE AIR PRODUCTS, AND AIR FRACTIONATION PLANT

Abstract

A method for obtaining one or more air products, in which method an air fractionation plant is used which has a column system with a pressure column, wherein air is fedto the column system and is fractionated in the column system, wherein at least 90% of the total amount of air supplied to the column system is compressed, wherein nitrogen-rich gas is extracted from the pressure column, and wherein, at least in a first operating mode, further air is compressed to a pressure level above the base pressure level, is expanded, and is warmed without fractionation in the column system. It is provided that, at least in the first operating mode, a proportion of the nitrogen-rich gas extracted from the pressure column is fed to the further air upstream of the expansion.

Claims

1. A method for obtaining one or more air products, wherein an air fractionation plant is used which has a column system having a pressure column, wherein the pressure column is operated in a pressure range from 4 to 7 bar, wherein air is fed to the column system and fractionated in the column system, wherein at least 90% of the total air supplied to the column system is compressed to a base pressure level which is more than 5 bar above the pressure range at which the pressure column is operated, wherein nitrogen-rich gas is withdrawn from the pressure column, and wherein, at least in a first operating mode, further air is compressed to a pressure level above the base pressure level, is decompressed, and is warmed without fractionation in the column system, wherein, at least in the first operating mode, a portion of the nitrogen-rich gas withdrawn from the pressure column is fed into the further air upstream of the decompression.

2. The method according to claim 1, wherein the decompression of the further air is carried out in a decompression machine, in particular a decompression turbine.

3. The method according to claim 1, wherein, in a second operating mode as well, the further air is compressed to a pressure level above the base pressure level, is decompressed, and is warmed without fractionation in the column system, and wherein, in the second operating mode, none of the nitrogen-rich gas withdrawn from the pressure column is fed into the further air.

4. The method according to claim 3, wherein, in the third operating mode, no further air is compressed to a pressure level above the base pressure level, decompressed and warmed without fractionation in the column system, and in which, in the third operating mode, a portion of the nitrogen-rich gas withdrawn from the pressure column is decompressed and warmed instead of the further air.

5. The method according to claim 1, wherein the further air, at the pressure level above the base pressure level, is supplied to the warm side of a main heat exchanger of the air fractionation plant, is then removed from the main heat exchanger at a first intermediate temperature level, is then subjected to a first turbine decompression, is then supplied to the cold side of the main heat exchange, is then removed from the main heat exchanger at a second intermediate temperature level, is then subjected to a second turbine decompression, is then supplied to the main heat exchanger at a third intermediate temperature level, and is then withdrawn from the warm side of the main heat exchanger.

6. The method according to claim 5, wherein the portion of the nitrogen-rich gas withdrawn from the pressure column which is fed into the further air is fed to the cold side of the main heat exchanger together with the further air, is subjected to the second turbine decompression, is fed to the main heat exchanger at the third intermediate temperature level, and is withdrawn from the warm side of the main heat exchanger.

7. The method according to claim 5, wherein the portion of the nitrogen-rich gas withdrawn from the pressure column which is fed to the further air is supplied to the cold side of the main heat exchanger separately from the further air, is withdrawn from the warm side of the main heat exchanger, and is fed to the further air at the second intermediate temperature level and before the second turbine decompression.

8. The method according to claim 5, wherein the base pressure level is 16 to 24 bar, wherein the pressure level above the base pressure level to which the further air is compressed is 27 to 50 bar, wherein the pressure range in which the pressure column is operated is 4 to 7 bar, wherein the main heat exchanger is operated at a temperature level of 0 to 50° C. on the warm side, and at a temperature level of -150 to -177° C. on the cold side, wherein the first intermediate temperature level is -120 to -90° C., wherein the second intermediate temperature level is -20 to 30° C., wherein the third intermediate temperature level is -110 to -60° C., wherein the first turbine decompression is carried out to a pressure level of 4 to 7 bar, and wherein the second turbine decompression is carried out to a pressure level of 100 to 500 mbar above atmospheric pressure.

9. The method according to claim 5, wherein the further air is compressed using one or two boosters to the pressure level above the base pressure level, wherein the one booster or at least one of the two boosters is or are driven using at least one of the decompression machines which are used in the first and second turbine decompression.

10. The method according to claim 1, wherein the column system further comprises a low-pressure column operated in a pressure range from 1 to 1.7 bar, and an argon gas recovery section having at least one further column.

11. The method according to claim 1, wherein the further air which is compressed to the pressure level above the base pressure level, is decompressed, and is warmed without fractionation in the column system, is compressed to the pressure level above the base pressure level together with air which is fed into the column system.

12. The method according to claim 11, wherein the air which is fed into the column system and which is compressed together with the further air to the pressure level above the base pressure level is cooled in a first fraction and fed into the column system without being subjected to the first and second decompression, and in a second fraction is separated in liquefied form after the first decompression and fed into the column system.

13. An air fractionation plant comprising a column system having a pressure column, wherein the air fractionation plant is designed to operate the pressure column in a pressure range from 4 to 7 bar, to supply air to the column system, and to fractionate it in the column system, and to compress at least 90% of the total air supplied to the column system to a base pressure level which is more than 5 bar above the pressure range at which the pressure column is operated, to remove nitrogen-rich gas from the pressure column, and, at least in a first operating mode, to compress further air to a pressure level above the base pressure level, to decompress it, and to warm it without fractionation in the column system, wherein the air fractionation plant is designed to feed, at least in the first operating mode, a portion of the nitrogen-rich gas withdrawn from the pressure column to the further air upstream of the decompression.

14. An air fractionation plant having means for carrying out the method features specified in claim 2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 shows a simplified illustration of an air fractionation plant which is not designed according to the invention.

[0042] FIG. 2 shows an air fractionation plant according to an embodiment of the invention in a simplified schematic representation.

[0043] FIG. 3 shows an air fractionation plant according to an embodiment of the invention in a simplified schematic representation.

[0044] In the figures, identical or comparable elements are in each case designated by identical reference signs and are not explained repeatedly for the sake of clarity. Components which are illustrated identically in multiple figures are sometimes not provided again with reference signs. Plant components can in each case also represent corresponding method steps, such that the following explanations regarding the air fractionation plants also relate to corresponding methods.

DETAILED DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 illustrates an air fractionation plant, not designed according to the invention, in the form of a simplified process flow diagram.

[0046] In the air fractionation plant according to FIG. 1, air from the atmosphere A is suctioned in by means of a main air compressor 1 via a filter 2 and compressed to the above-mentioned base pressure level. A compressed air stream a provided in this way is fed after cooling in heat exchangers (not designated separately) and a separation of water W to an adsorber station 3, and freed there of undesired components such as water and carbon dioxide. The compressed air flow a is divided into two partial streams b and c.

[0047] The partial stream b is fed to a main heat exchanger 4 at the hot end and removed at the cold end. The partial stream c is further compressed using two boosters 5 and 6 and then likewise fed to the main heat exchanger 4 at the hot end. A partial stream d of the partial stream c is again taken from the main heat exchanger 4 at the cold end. The partial streams b and d are decompressed via a throttle, are at least to some extent liquefied in the process, are combined, and are fed into a pressure column 11 of a column system 10 in the form of a material stream which is not designated separately.

[0048] In addition to the pressure column 11, the column system 10 has a low-pressure column 12 connected to the pressure column 11 in the form of a double column, and thermally coupled via a main condenser 13. As a further part of the column system 10, a supercooling countercurrent unit 14 and a conventional argon recovery part 15 are provided, by means of which pure argon X can be obtained. The latter can be operated as described in numerous examples in the technical literature. In both the pressure column 11 and the low-pressure column 12, a low-temperature rectification is carried out at a rectification pressure level.

[0049] A further partial stream e of the partial stream c is taken from the main heat exchanger 4 at an intermediate temperature level, decompressed in a decompression turbine 7 coupled to the booster 5, thereby partially liquefied, and fed into a separator 9, where a liquid phase and a gas phase form. The liquid phase is conveyed in the form of a material stream f through the supercooling countercurrent unit 14, and then fed into the low-pressure column 12. The gas phase is divided into two partial streams g and h.

[0050] The partial stream g is fed into the pressure column 11. The partial stream h, on the other hand, is fed to the main heat exchanger 4 at the cold end and removed from the latter close to the hot end. It is subsequently decompressed in a decompression turbine 8 coupled to the booster 6, fed back to the main heat exchanger 4 at an intermediate temperature level, removed from the main heat exchanger at the hot end, and discharged from the plant. This is the so-called excess air - here also denoted by H. Since the partial stream h already comprises purified air, it can be compressed again, for example, in the main air compressor 2 and used to form the compressed air flow a in order to reduce the purification effort.

[0051] At the top of the pressure column 11, a nitrogen-rich top gas is formed, one part of which is warmed in gaseous form in the form of a material stream i in the main heat exchanger 4 and discharged as a compressed product I from the air fractionation plant. A further part is at least partially condensed in the main condenser 13. A first part (not designated) of the condensate is recycled as a return flow to the pressure column 11; a second part is provided in the form of a stream k, as an internally compressed nitrogen product K; and a third part is conveyed in the form of a material stream m through the supercooling countercurrent unit 14 and is fed at the top thereof to the low-pressure column 12 as a return flow.

[0052] The low-pressure column 12 is primarily fed with the bottoms liquid of the pressure column 11, which is withdrawn therefrom in the form of a material stream o. In the example shown, the bottoms liquid of the pressure column 11 is used for cooling top condensers in the argon recovery section 15, and is partially evaporated there. Evaporated and unevaporated fractions are transferred, as illustrated here in the form of material streams p, into the low-pressure column 12. The argon recovery section 15 is materially connected to the low-pressure column 12 by material streams q, not explained in more detail here. Furthermore, liquid air in the form of a material stream n is fed into the low-pressure column 12, and withdrawn directly below the feed point for the material streams b and d from the pressure column 11 and conveyed through the supercooling countercurrent unit 14.

[0053] Bottoms liquid from the low-pressure column 12 can be withdrawn therefrom in the form of a material stream r and provided in part in the form of a material stream S as liquid nitrogen S, and can be further used in part in the form of a material stream t to provide internal compression products T1, T1. Gaseous nitrogen can be drawn off from the top of the low-pressure column 12 in the form of a material stream u, and liquid nitrogen can be drawn off in the form of a material stream v. The latter can be provided as liquid nitrogen V, and a partial stream of the material stream M can be provided as pressurized liquid nitrogen M.

[0054] FIG. 2 shows an air fractionation plant according to an embodiment of the invention in a simplified schematic representation. This is denoted as a whole by 100 and comprises all components of the air fractionation plant illustrated in FIG. 1.

[0055] In the air fractionation plant, as illustrated here in the form of a material stream w, a partial stream of the material stream i can be fed into the material stream h, at least in one operating mode, and can be warmed and decompressed with it in the manner described. In other operating modes, the formation of the material stream w can also be prevented, or the material stream w can completely replace the material stream h.

[0056] FIG. 3 shows an air fractionation plant according to a further embodiment of the invention in a simplified representation. It is denoted as a whole by 200, and comprises all components of the air fractionation plant 100 illustrated in FIG. 2; however, a generator G is provided instead of the booster 6. The partial stream c is thus only compressed by means of the booster 5.

[0057] FIG. 4 shows an air fractionation plant according to a further embodiment of the invention, in a simplified representation. It is denoted as a whole by 300 and comprises all components of the air fractionation plant 100 illustrated in FIG. 2; however, in contrast thereto, instead of the material stream w there at the warm side of the main heat exchanger 4, a material stream x is branched off from the material stream i and is fed to the material stream h.