PROCESS AND PLANT FOR LOW-TEMPERATURE FRACTIONATION OF AIR

Abstract

A SPECTRA process for low-temperature fractionation of air, in which bottoms liquid from an additional second rectification column used to obtain oxygen is evaporated in a second condenser-evaporator. In this second condenser-evaporator, gas that has been evaporated beforehand in a first condenser-evaporator, which is used for condensation of tops gas from a first rectification column, is condensed at the pressure level of the previous evaporation. The invention likewise provides a corresponding plant.

Claims

1-13. (canceled)

14. A process for the low-temperature fractionation of air, in which an air fractionation plant having a first rectification column, a second rectification column, a first condenser evaporator, and a second condenser evaporator is used, wherein the process comprises that the first rectification column is fed with air and operated at a first pressure level, and the second rectification column is fed from the first rectification column and operated at a second pressure level below the first pressure level, wherein tops gas of the first rectification column is obtained as a nitrogen product and discharged from the air fractionation plant, and bottoms liquid of the second rectification column is obtained as an oxygen product and discharged from the air fractionation plant, a first and a second material stream below the first pressure level are subjected to evaporation in the first condenser evaporator, and further tops gas of the first rectification column is condensed in the first condenser evaporator and returned to the first rectification column as a return flow, the first material stream is formed using liquid taken from the first rectification column with a first oxygen content, and the second material stream is formed using liquid taken from the first rectification column with a second oxygen content above the first oxygen content, gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator is partially or completely subjected to recompression to the first pressure level and fed into the first rectification column, and gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator is subjected to work-performing expansion and discharged from the air fractionation plant, and bottoms liquid of the second rectification column is evaporated in the second condenser evaporator, and gas of the first or second material stream after its evaporation or partial evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator and fed at least in part to the liquid taken from the first rectification column with the first or second oxygen content and used in the formation of the first or second material stream, or fed into a lower region of the first rectification column, wherein the gas of the first or second material stream, which is subjected to condensation in the second condenser evaporator after its evaporation or partial evaporation in the first condenser evaporator, is subjected to condensation in the second condenser evaporator at a pressure level at which it was previously subjected to evaporation or partial evaporation in the first condenser evaporator.

15. The process according to claim 14, in which a first portion of the first material stream after its evaporation in the first condenser evaporator is subjected to recompression to the first pressure level, and in which a second portion of the first material stream after its evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator.

16. The process according to claim 14, in which a first portion of the second material stream after its evaporation in the first condenser evaporator is subjected to work-performing expansion, and in which a second portion of the second material stream after its evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator.

17. The process according to claim 14, in which one or more compressors is or are provided for the recompression of the gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator, and in which, for the expansion of the gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator, one or more expansion machines are provided which is or are coupled to the one or more compressors.

18. The process according to claim 14, in which the gas of the first or second material stream, which after evaporation or partial evaporation in the first condenser evaporator is subjected to condensation in the first condenser evaporator, is transferred into the second condenser evaporator using a gas line that without a compressor couples the first condenser evaporator and the second condenser evaporator.

19. The process according to claim 14, in which at least a portion of a condensate formed during condensation in the first condenser evaporator is by use of a pump subjected to an increase in pressure in the liquid state.

20. The process according to claim 19, in which the pressure increase to the first pressure level is carried out in the liquid state.

21. The process according to claim 14, in which the tops gas of the first rectification column has a content of in each case less than 1 ppb oxygen, carbon monoxide, and/or hydrogen and a content of less than 10 ppm argon on a volume basis.

22. The process according to claim 14, in which the bottoms liquid of the second rectification column has a content of less than 10 ppb argon and/or 5 ppm methane on a volume basis.

23. The process according to claim 14, in which the first pressure level is 7 to 14 bar absolute pressure and in which the second pressure level is 1.2 to 5 bar absolute pressure.

24. The process according to claim 14, in which all of the cooled compressed air to be fractionated in the process is fed into the first rectification column in gaseous form.

25. An air fractionation plant having a first rectification column, a second rectification column, a first condenser evaporator, and a second condenser evaporator and configured to feed the first rectification column with air and to operate it at a first pressure level, and to feed the second rectification column from the first rectification column and to operate it at a second pressure level below the first pressure level, to obtain tops gas of the first rectification column as a nitrogen product and discharge it from the air fractionation plant, and to obtain bottoms liquid of the second rectification column as an oxygen product and discharge it from the air fractionation plant, to subject a first and a second material stream below the first pressure level to evaporation in the first condenser evaporator, and to condense further tops gas of the first rectification column in the first condenser evaporator and to return it to the first rectification column as a return flow, to form the first material stream using liquid taken from the first rectification column with a first oxygen content, and to form the second material stream using liquid taken from the first rectification column with a second oxygen content above the first oxygen content, to partially or completely subject gas of the first material stream, after its evaporation or partial evaporation in the first condenser evaporator, to recompression to the first pressure level and to feed it into the first rectification column, and to subject gas of the second material stream, after its evaporation or partial evaporation in the first condenser evaporator, to expansion and to discharge it from the air fractionation plant, to evaporate bottoms liquid of the second rectification column in the second condenser evaporator, and to subject gas of the first or second material stream, after its evaporation or partial evaporation in the first condenser evaporator, to condensation in the second condenser evaporator and to feed it at least in part to the liquid taken from the first rectification column with the first or second oxygen content and used in the formation of the first or second material stream, or to feed it into a lower region of the first rectification column, wherein for the recompression of the gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator, one or more compressors are provided, and for the expansion of the gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator, one or more expansion machines mechanically coupled to the one or more compressors are provided, wherein the first condenser evaporator and the second condenser evaporator are arranged in such a way that the gas of the first or second material stream, which is subjected to condensation in the second condenser evaporator, is subjected to condensation at a pressure level at which it was previously subjected to evaporation in the first condenser evaporator.

26. Air fractionation plant according to claim 25, having means which are configured to carry out a process for the low-temperature fractionation of air, in which an air fractionation plant having a first rectification column, a second rectification column, a first condenser evaporator, and a second condenser evaporator is used, wherein the process comprises that the first rectification column is fed with air and operated at a first pressure level, and the second rectification column is fed from the first rectification column and operated at a second pressure level below the first pressure level, wherein tops gas of the first rectification column is obtained as a nitrogen product and discharged from the air fractionation plant, and bottoms liquid of the second rectification column is obtained as an oxygen product and discharged from the air fractionation plant, a first and a second material stream below the first pressure level are subjected to evaporation in the first condenser evaporator, and further tops gas of the first rectification column is condensed in the first condenser evaporator and returned to the first rectification column as a return flow, the first material stream is formed using liquid taken from the first rectification column with a first oxygen content, and the second material stream is formed using liquid taken from the first rectification column with a second oxygen content above the first oxygen content, gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator is partially or completely subjected to recompression to the first pressure level and fed into the first rectification column, and gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator is subjected to work-performing expansion and discharged from the air fractionation plant, and bottoms liquid of the second rectification column is evaporated in the second condenser evaporator, and gas of the first or second material stream after its evaporation or partial evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator and fed at least in part to the liquid taken from the first rectification column with the first or second oxygen content and used in the formation of the first or second material stream, or fed into a lower region of the first rectification column, wherein the gas of the first or second material stream, which is subjected to condensation in the second condenser evaporator after its evaporation or partial evaporation in the first condenser evaporator, is subjected to condensation in the second condenser evaporator at a pressure level at which it was previously subjected to evaporation or partial evaporation in the first condenser evaporator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] FIG. 1 shows an air fractionation plant according to an embodiment of the invention.

[0062] FIG. 2 shows an air fractionation plant according to an embodiment of the invention.

[0063] FIG. 3 shows an air fractionation plant according to an embodiment of the invention.

[0064] In the figures, elements corresponding functionally or structurally to one another are indicated by identical reference signs and only for the sake of clarity are not repeatedly explained below.

DETAILED DESCRIPTION OF THE DRAWINGS

[0065] FIG. 1 illustrates an air fractionation plant 100 in the form of a schematic plant diagram. The central component is a distillation column system having a first rectification column 11, a second rectification column 12, a first condenser evaporator 111, and a second condenser evaporator 121. The first rectification column 11 is operated at a first pressure level, and the second rectification column 12 is operated at a second pressure level below the first pressure level.

[0066] By means of a main air compressor 1 of the air fractionation plant 100, air is sucked in from the atmosphere A via a filter (not separately designated) and compressed. After cooling in an aftercooler (likewise not designated separately) downstream of the main air compressor 1, the feed air stream a formed in this way is further cooled in a direct contact cooler 2 operated with water W. The feed air stream a is then subjected to cleaning in an adsorber unit 3. For further explanations in this context, reference is made to the technical literature, for example in connection with FIG. 2.3A in Haring (see above).

[0067] After cooling in the main heat exchanger 4, the feed air stream a is fed into the first rectification column 11. In a conventional process, a portion of the feed air stream a would be fed into the first rectification column 11, whereas a further portion would be routed through the second condenser evaporator 121, which is arranged in a lower region of the second rectification column 12, and evaporated by means of the bottoms liquid of the second rectification column 12. This further portion would be condensed in the second condenser evaporator 121 and then likewise fed into the first rectification column 11. As mentioned, this is not the case in the embodiments of the invention.

[0068] Tops gas of the first rectification column 11 is discharged from the air fractionation plant 300 in the form of a material stream d as a nitrogen product B or sealing gas C. In contrast, bottoms liquid of the second rectification column 12 is discharged in the form of a material stream e as an oxygen product D. It is also possible, for example, to feed into so-called run tanks for later evaporation for the provision of an internally compressed oxygen product D.

[0069] In the first condenser evaporator 111, a first material stream g and a second material stream h below the first pressure level (for this purpose, a corresponding expansion in particular takes place in valves which are not designated separately) are subjected to evaporation. Further tops gas of the first rectification column 11 is condensed in the form of a material stream i in the first condenser evaporator 111 and returned to the first rectification column 11 as a return flow. As illustrated here in the form of a material stream k, a portion can also be supercooled in a supercooler 5 and provided as liquid nitrogen F. A material stream I heated thereby is treated as explained in more detail below. A further discharge in the form of a purge stream m or P may also be provided.

[0070] The first material stream g is formed using liquid taken from the first rectification column 11 with a first oxygen content, and the second material stream h is formed using liquid (in particular bottoms liquid) taken from the first rectification column 11 with a second oxygen content above the first oxygen content.

[0071] After its evaporation or partial evaporation in the first condenser evaporator 111, gas of the first material stream g is subjected in a compressor 6 to recompression to the first pressure level and fed into the first rectification column 11. A portion indicated by a dashed line can also be returned to compression in the compressor 6. A portion of the material stream g can also be discharged into the atmosphere A in the form of a material stream n.

[0072] After its evaporation or partial evaporation in the first condenser evaporator 111, gas of the second material stream h is subjected to parallel further expansion in expansion machines 7 and 8, combined with tops gas, which is taken in the form of a material stream o from the second rectification column 12, and, after heating in the main heat exchanger 4, used as regeneration gas in the adsorber unit 3 or discharged to the atmosphere A and thus discharged from the air fractionation plant 300.

[0073] The expansion machine 7 is coupled to the compressor 6, and the expansion machine 8 is coupled to a generator G. In each case, a different number of corresponding machines or a different type of coupling may also be used. An (oil) brake (not separately designated) may also be provided.

[0074] The second rectification column 12 is fed with a side stream p of the first rectification column 11, which is passed through the second condenser evaporator 121 and fed into the second rectification column in an upper region. In addition, gas of the second material stream h after its evaporation or partial evaporation in the first condenser evaporator 111 is conducted as a partial stream b through the condenser evaporator 121 and subjected to condensation. A correspondingly formed liquid, further designated by b, has its pressure increased by means of a pump 9 and is subsequently recombined with the second material stream h prior to its evaporation.

[0075] In the otherwise substantially identical or comparable air fractionation plant 200 according to FIG. 2, the liquid formed in the condenser evaporator 121 by condensation of gas of the second material stream h in the form of the material stream b also has its pressure increased by means of the pump 9 but is then fed into the first rectification column 11 in a lower region.

[0076] A partial stream of the first material stream g can also be used accordingly, as illustrated in FIG. 3 with a material stream c. The air fractionation plant 300 according to FIG. 3 can otherwise be substantially identical or comparable. The liquid formed in the second condenser evaporator 121 by condensation of gas of the first material stream g has its pressure increased by means of the pump 9 and is then recombined with the first material stream g before evaporation in the first condenser evaporator 111.