METHOD AND UNIT FOR LOW-TEMPERATURE AIR SEPARATION

Abstract

The invention relates to a method for a low-temperature air separation in which an air separation unit is used comprising a first rectification column and a second rectification column. The first rectification column is operated at a first pressure level, and the second rectification column is operated at a second pressure level below the first pressure level. Fluid which is oxygen-enriched compared to atmospheric air is drawn from the first rectification column in the form of one or more first material flows. At least one fraction of the fluid which has been drawn from the first rectification column in the form of the one or more first material flows is heated in a heat exchanger; a fraction of the fluid which has been heated in the heat exchanger is compressed using a compressor and is returned to the first rectification column.

Claims

1. A method for low-temperature air separation, in which an air separation unit with a first rectification column and a second rectification column is used, wherein the first rectification column is operated at a first pressure level and the second rectification column is operated at a second pressure level below the first pressure level, fluid which is oxygen-enriched compared to atmospheric air is drawn from the first rectification column in the form of one or more first material flows, at least one fraction of the fluid drawn from the first rectification column in the form of the one or more first material flows is heated in a heat exchanger, a fraction of the fluid heated in the heat exchanger is compressed using a compressor and returned to the first rectification column, a first fraction of the head gas of the first rectification column is condensed in the heat exchanger, and a second fraction thereof is discharged from the air separation unit in the form of at least one nitrogen-rich air product, additional fluid containing oxygen, nitrogen, and argon is drawn from the first rectification column and used as a second material flow or to form a second material flow which is transferred to the second rectification column, and an oxygen-rich sump liquid is formed in the sump of the second rectification column, and at least one fraction thereof is discharged in the form of a third material flow from the air separation unit, wherein a third rectification column is used, wherein the second rectification column and the third rectification column are designed as parts of a double column, the third rectification column is arranged below the second rectification column, and the third rectification column is supplied with air.

2. The method according to claim 1, in which the air supplied to the third rectification column comprises compressed and cooled air which is expanded using an expansion machine.

3. The method according to claim 2, in which the second rectification column is operated with a condenser evaporator which is arranged in a sump region of the second rectification column and which is heated using fluid drawn from and/or supplied to the third rectification column.

4. The method according to claim 3, in which the air supplied to the third rectification column is at least partially liquefied in the condenser evaporator arranged in the sump region of the second rectification column and is returned to the third rectification column as a liquid return flow.

5. The method according to claim 3, in which a head gas is formed in the third rectification column and is liquefied at least in part in the condenser evaporator arranged in the sump region of the second rectification column and is returned as a return flow to the second and/or the third rectification column.

6. The method according to claim 3, in which a sump liquid is formed in the third rectification column and is at least in part fed into the second rectification column.

7. The method according to claim 1, in which a nitrogen-rich head gas is formed in the second rectification column, and at least one fraction thereof is discharged from the air separation unit as an additional nitrogen-rich air product, wherein a residual oxygen content of the head gas of the first rectification column is 1 ppb to 10 ppm, and a residual oxygen content of the head gas of the second rectification column is 10 ppb to 100 ppm.

8. The method according to claim 7, in which the second rectification column is equipped with 50 to 120 theoretical bottoms, and/or a nitrogen-rich liquid material flow is provided and added as a return flow to an upper region of the second rectification column.

9. The method according to claim 1, wherein fluid which has a higher argon content than the oxygen-rich sump liquid of the second rectification column is drawn from the second rectification column and used as a third material flow or to form a third material flow, a fourth rectification column is used into which the third material flow is fed, wherein an argon-rich fluid having a content of more than 95 mole percent argon is formed in the fourth rectification column.

10. The method according to claim 9, in which a fifth rectification column is used in which a liquid is formed having an oxygen content above an oxygen content of the oxygen-rich sump liquid formed in the sump of the second rectification column, and in which the fifth rectification column is used to form the third material flow using the fluid drawn from the second rectification column and having a higher argon content than the oxygen-rich sump liquid of the second rectification column.

11. The method according to claim 9, wherein a quantity of the argon product formed in the air separation unit comprises 1 to 85 percent of a total argon quantity supplied as a whole in the form of air to the air separation unit.

12. An air separation unit having a first rectification column and a second rectification column, which is configured: to operate the first rectification column at a first pressure level and the second rectification column at a second pressure level below the first pressure level, to draw fluid which is oxygen-enriched compared to atmospheric air, from the first rectification column in the form of one or more first material flows, to heat in a heat exchanger at least one fraction of the fluid drawn from the first rectification column in the form of the one or more first material flows, to compress using a compressor a fraction of the fluid heated in the heat exchanger and to return it to the first rectification column, a first fraction of the head gas of the first rectification column is condensed in the heat exchanger, and a second fraction thereof is discharged from the air separation unit in the form of at least one nitrogen-rich air product, to draw additional fluid containing oxygen, nitrogen, and argon from the first rectification column and to use it as a second material flow or to form a second material flow which is transferred to the second rectification column, and to form an oxygen-rich sump liquid in the sump of the second rectification column and to discharge at least one fraction thereof in the form of a third material flow from the air separation unit, wherein a third rectification column is provided, wherein the second rectification column and the third rectification column are designed as parts of a double column, and the third rectification column is arranged below the second rectification column, wherein the air separation unit is configured to supply the third rectification column with air.

13. The air separation unit according to claim 12, which is configured to carry out a method for low-temperature air separation, in which an air separation unit with a first rectification column and a second rectification column is used, wherein the first rectification column is operated at a first pressure level and the second rectification column is operated at a second pressure level below the first pressure level, fluid which is oxygen-enriched compared to atmospheric air is drawn from the first rectification column in the form of one or more first material flows, at least one fraction of the fluid drawn from the first rectification column in the form of the one or more first material flows is heated in a heat exchanger, a fraction of the fluid heated in the heat exchanger is compressed using a compressor and returned to the first rectification column, a first fraction of the head gas of the first rectification column is condensed in the heat exchanger, and a second fraction thereof is discharged from the air separation unit in the form of at least one nitrogen-rich air product, additional fluid containing oxygen, nitrogen, and argon is drawn from the first rectification column and used as a second material flow or to form a second material flow which is transferred to the second rectification column, and an oxygen-rich sump liquid is formed in the sump of the second rectification column, and at least one fraction thereof is discharged in the form of a third material flow from the air separation unit, wherein a third rectification column is used, wherein the second rectification column and the third rectification column are designed as parts of a double column, the third rectification column is arranged below the second rectification column, and the third rectification column is supplied with air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0106] FIGS. 1 to 31 each illustrate air separation units and parts of air separation units in an overall or partial illustration.

DETAILED DESCRIPTION OF THE DRAWINGS

[0107] In the following figures, air separation units of different embodiments of the present invention are illustrated and designated by 100 to 3100. The components of corresponding units are first explained with reference to FIG. 1 and the non-inventive air separation unit 100 illustrated therein. Elements which are present in the air separation units 200 to 3100 according to FIGS. 2 to 31 and each correspond to one another structurally or functionally will not explained repeatedly in that context.

[0108] FIG. 1 illustrates a non-inventive air separation unit 100 in the form of a schematic unit diagram.

[0109] A feed air flow a is supplied to the air separation unit 100 from a warm part of the air separation unit 100, which is illustrated schematically here as 110 and in particular comprises devices for purifying and compressing feed air. This feed air flow a is cooled in a main heat exchanger 1 of the air separation unit 100 and drawn from the main heat exchanger 1 near its cold end. The warm part 110 of the air separation unit can be of a customary design. For a non-limiting example of the present invention, reference is made to the explanations relating to FIG. 2.3A in Haring (see above).

[0110] The feed air flow a is subsequently divided into two partial flows b and c, wherein the partial flow b is fed directly into a first rectification column 11. In contrast, the partial flow c is conducted through a condenser evaporator 121 of a second rectification column 12 and then, in particular after combining with additional material flows as explained below, likewise fed into the first rectification column 11. The partial flows b and c are each fed into the first rectification column 11 at a suitable height.

[0111] In the first rectification column 11, which is operated at a previously explained “first” pressure level, a nitrogen-enriched or substantially nitrogen-containing head gas and an oxygen-enriched sump liquid are formed. Two material flows d and e are drawn from the first rectification column 11, and each comprise fluid which is oxygen-enriched compared to atmospheric air.

[0112] The material flow d is first cooled further in the main heat exchanger 1 and subsequently conducted through a heat exchanger 2 which, as explained below, is used to cool head gas of the first rectification column 11. The material flow e is first treated in a comparable manner to the material flow d, wherein a portion of the material flow e can be branched off as material flow e1 before the rest of the material flow e, which is further designated as e for the sake of simplicity, is supplied to the heat exchanger 2. Liquid nitrogen X can also be supplied externally to the material flow e if necessary. In the example shown, the material flow e is drawn from the sump of the first rectification column 11, whereas the material flow d is drawn from the first rectification column 11 from a position of a plurality of theoretical or practical bottoms above the sump. The material flows d and e are conducted through the heat exchanger 2 separately from one another.

[0113] The material flow e is subsequently partially heated in the main heat exchanger 1 and expanded in the form of two partial flows by means of an expansion machine 3 and optionally by means of a bypass valve which is not designated separately. These partial flows, subsequently combined with one another and with additional material flows, are heated in the main heat exchanger 1 and are discharged from the air separation unit in the form of a collection flow f, or are used in the warm part 110, for example for regenerating absorbers.

[0114] On the other hand, optionally after branching off and blowing off a partial flow into the atmosphere A, the material flow d is compressed in a compressor 5 which is coupled to one of the expansion machines 3 shown here, subsequently cooled, and returned to the first rectification column 11 in a manner comparable to the material flow c. As illustrated in the form of a dashed material flow dl, a bypass can also take place here. The compressor 5 is coupled to the expansion machine 3 and furthermore has an oil brake not designated separately here.

[0115] Head gas from the head of the first rectification column 11 is conducted through the heat exchanger 2 in the form of a material flow g and is at least partially liquefied there. This partially liquefied head gas can be partially returned to the first rectification column 11 in the form of a return flow, and an additional fraction thereof can be provided as liquid nitrogen product B. For this purpose, a portion can be supercooled in a sub-cooler 6 and discharged as a correspondingly supercooled liquid nitrogen product B. A fraction expanded in the sub-cooler 6 for cooling can be combined with the already mentioned material flow e. A portion of the material flow g can also be discharged as a so-called purge P. Further head gas can be heated in the form of a material flow h in the main heat exchanger 1 and discharged as gaseous nitrogen product C or used as sealing gas D. The gaseous nitrogen product C represents a “nitrogen-rich air product” previously explained with respect to different embodiments of the invention.

[0116] In the example illustrated in FIG. 1, a material flow i is conducted in liquid form from the first rectification column 11, is supercooled in the condenser evaporator 121 of the second rectification column, and added as a return flow to the second rectification column 12. From a region close to the head of the first rectification column 11, in any case significantly above the material flow i, an additional, correspondingly nitrogen-rich material flow i1 is withdrawn in liquid form and added as a return flow to the second rectification column 12 above the material flow i, in particular at the head.

[0117] From the sump of the second rectification column 12, a liquid oxygen-rich material flow k can be withdrawn, which can be pressurized by means of an internal compression pump 7 or by means of pressure buildup evaporation and can subsequently be heated in the main heat exchanger 1 and provided as an internally compressed oxygen pressure product E. A portion of the material flow k may also be provided as a liquid oxygen product F. Additional oxygen-rich liquid, but with a lower oxygen content, can analogously be withdrawn from the second rectification column 12 in the form of a material flow k1, pressurized by means of an additional internal compression pump 7a, and provided as an additional internally compressed oxygen pressure product E1. A fraction can optionally also be returned in the form of a material flow k2. A portion may also be provided as a liquid oxygen product F. In the example shown, a material flow l is withdrawn from the head of the second rectification column 12 and, after being combined with an additional material flow, can likewise be heated and, in the illustrated example, discharged to the atmosphere A. The material flows i and i1 are supercooled in a sub-cooler 9 against the material flow l before they are fed into the second rectification column 12.

[0118] From a central region of the second rectification column 12, in particular at the argon transition, a material flow m is withdrawn which is fed into a lower region of a rectification column 14 which is referred to as fourth rectification column 14 for consistency reasons (in the non-inventive embodiment illustrated here, the third rectification column 13 used according to the invention is not present). By means of a pump 8, an additional material flow n is withdrawn from the sump of the fourth rectification column 14 and returned to the second rectification column 12. A material flow o is withdrawn from the fourth rectification column 14 in an upper region, is conducted through a head condenser 141 of the fourth rectification column 141, is at least partially liquefied there, and is returned as a return flow to the fourth rectification column 14. A non-evaporated fraction may be discharged to the atmosphere A. A liquid argon product G is withdrawn in liquid form below the head of the fourth rectification column 14 in the form of a material flow p. A corresponding material flow p can also be at least partially pressurized by means of a pump and heated in the main heat exchanger 1 so that an internally compressed argon product can be provided in this way.

[0119] The head condenser 141 of the fourth rectification column 14 is cooled with liquid which can be supplied to the head condenser 141 in the form of the already mentioned material flow q. The material flow q can be formed using at least one portion of the likewise already mentioned material flow e1 and optionally the material flow k2. Fractions not used to form the material flow q can be combined in the form of a material flow q1 with the material flow c and fed into the first rectification column 11. A material flow r can be withdrawn from an evaporation chamber of the head condenser 141 of the fourth rectification column 14, which material flow r, after combining with the material flow l as explained with reference to this material flow l, can be heated in the main heat exchanger 1, preferably without back pressure or substantially without back pressure, and discharged from the unit. In this way, a low pressure can be adjusted in the evaporation chamber of the head condenser 141. Optionally, a fraction r1 of the material flow r can also be fed into the second rectification column 12. Liquid from the evaporation chamber of the head condenser 141 of the fourth rectification column 14 can, if necessary, be combined in the form of a material flow s with the partial flows of the material flow e before they are heated in the main heat exchanger 1.

[0120] As already mentioned, the material flows i and/or i1 can be supercooled against the material flow l in sub-coolers, designated 9 in each case, against the material flow l. The same also applies optionally to the material flow q with respect to the material flow r. A plurality of sub-coolers 9 can also be combined in one common apparatus.

[0121] In FIG. 2, another non-inventive air separation unit is illustrated in the form of a schematic unit diagram and is designated by 200 as a whole.

[0122] In contrast to the air separation unit 100 illustrated in FIG. 1, a partial flow a1 of the feed air flow a is drawn from the main heat exchanger 1 at an intermediate temperature level, is expanded by means of an expansion machine 201 coupled to a generator, and is otherwise used like the material flow c according to FIG. 1. If a corresponding expansion machine is present and is used for the same or a comparable purpose, it is also designated as 201 in the following figures. The features deviating from the air separation unit 100 can be provided individually or together and/or combined with any features described above and below.

[0123] In FIG. 3, another non-inventive air separation unit is illustrated in the form of a schematic unit diagram and is designated by 300 as a whole.

[0124] As illustrated here, a material flow corresponding to the material flow a1 of FIG. 2, after it has been expanded in the expansion machine 201, can also be resupplied to the main heat exchanger 1, be heated there, and blown off to the atmosphere A. With regard to further details, reference is expressly made to the explanations relating to the preceding figures. The features deviating from the preceding figures can also be provided individually or together here and/or be combined with any features described above and below.

[0125] In FIG. 4, another non-inventive air separation unit is illustrated in the form of a schematic unit diagram and is designated by 400 as a whole.

[0126] In contrast to the air separation units 100 to 300 illustrated in the preceding figures, a material flow corresponding to the material flow i1 is not used here. With regard to further details, reference is expressly made to the explanations relating to the preceding figures. The features deviating from the preceding figures can also be provided individually or together here and/or be combined with any features described above and below.

[0127] In FIG. 5, an air separation unit according to an embodiment of the present invention is shown in the form of a schematic unit diagram and is designated overall as 500.

[0128] The air separation unit 500 according to FIG. 5 differs from the previously explained embodiments in particular in that the second rectification column 12 is formed as part of a double column which additionally has the third rectification column 13 already mentioned. A fraction, previously designated a1 and correspondingly treated, of the feed air flow a is fed into a lower region of this third rectification column 13.

[0129] A material flow q2, which is otherwise further used in a manner comparable to the material flow q of the preceding figures and is therefore also designated here as q further downstream, is formed in the air separation unit 500 using sump liquid of the third rectification column 13, of the partial flow e2, and optionally of the material flow k2. Head gas of the third rectification column 13 is at least partially liquefied in the form of a material flow u in the condenser evaporator 121 and is subsequently used in the form of a partial flow u1 as a return flow to the third rectification column 13, and in the form of a partial flow u2 as a return flow to the second rectification column 12.

[0130] Nitrogen-rich liquid is drawn from the third rectification column 13 in the form of a material flow v via a side offtake and conveyed into the first rectification column 11 by means of a pump 501.

[0131] With regard to further details, reference is expressly made to the explanations relating to the preceding figures. The features deviating from the preceding figures can also be provided individually or together here and/or be combined with any features described above and below.

[0132] In FIG. 6, another non-inventive air separation unit is illustrated in the form of a schematic unit diagram and is designated by 600 as a whole. The illustration in FIG. 6 and the subsequent figures deviates slightly from those in FIGS. 1 to 5, but a part of the function of the shown elements is identical or comparable with regard to the technical function and is therefore indicated with identical reference signs.

[0133] From a warm part, which is also summarized here as 110, a feed air flow a, which is formed from atmospheric air L, is also supplied here to the air separation unit 600. In the warm part 110, a filter 111 via which feed air L is drawn in, a main air compressor 112 with aftercoolers not separately designated, a direct contact cooler operated with water W, and an absorber set 115 are inter alia illustrated here. The feed air flow a is also cooled here in a main heat exchanger 1 of the air separation unit 600 and drawn from the main heat exchanger 1 near its cold end.

[0134] As before, the feed air flow a is divided into two partial flows b and c, wherein the partial flow b is fed directly into the first rectification column, also designated here by 11. The second partial flow c is in turn conducted through a condenser evaporator 121 of a second rectification column 12 which is also designated here by 12 but is subsequently discharged here from the air separation unit 600 as explained below. In contrast to the condenser evaporator 121 illustrated in FIGS. 1 to 5, the flow routing in the condenser evaporator 121 according to FIG. 6 is not illustrated as being crossed.

[0135] In the first rectification column 11, which is also operated at the previously explained “first” pressure level here, a nitrogen-enriched or substantially nitrogen-containing head gas and an oxygen-enriched sump liquid are formed. Two material flows d and e are also drawn from the first rectification column 11 here and respectively comprise fluid which is oxygen-enriched compared to atmospheric air.

[0136] The material flow d is first cooled further in the main heat exchanger 1 and subsequently conducted through a heat exchanger 2 which, as explained below, is used to cool head gas of the first rectification column 11. The material flow e is first treated in a comparable manner to the material flow d, wherein the material flow e is first combined here with the material flow c, and an additional material flow q3 is subsequently branched off therefrom. Only then is this material flow, still designated by e for the sake of simplicity, further cooled in the main heat exchanger 1 and supplied to the heat exchanger 2. The material flow q3 is designated by q hereinafter for comparability with the previous figures and because of its corresponding use.

[0137] Liquid nitrogen X can be fed to the material flow e as before, if necessary. In the example shown, the material flow e is drawn from the sump of the first rectification column 11, whereas the material flow d is drawn from the first rectification column 11 from a position of a plurality of theoretical or practical bottoms above the sump. The material flows d and e are conducted through the heat exchanger 2 separately from one another.

[0138] The material flow e is subsequently partially heated in the main heat exchanger 1 and expanded in the form of two partial flows by means of an expansion machine 3 and optionally an expansion valve or via a bypass. These partial flows are subsequently combined with one another and with additional material flows, are heated in the main heat exchanger 1, and are discharged from the air separation unit in the form of a collection flow f or are used in the warm part 110 of the air separation unit 600, for example for regenerating the absorber of the absorber set 114.

[0139] On the other hand, after branching off and blowing off a partial flow to the atmosphere A, the material flow d is optionally compressed in a compressor 5 which is coupled to one of the expansion machines 3 shown here, subsequently cooled, and returned to the first rectification column. As illustrated in the form of a dashed material flow dl, a bypass can also take place here. The compressor 5 is coupled to the expansion machine 3 and furthermore has an oil brake not designated separately here. Any other combinations are also possible.

[0140] Head gas from the head of the first rectification column 11 is conducted through the heat exchanger 2 in the form of a material flow g and is at least partially liquefied there. This partially liquefied head gas can be partially returned to the first rectification column in the form of a return flow, and an additional fraction thereof can be provided as liquid nitrogen product B. For this purpose, a portion can be supercooled in a sub-cooler 6 and discharged as a correspondingly supercooled liquid nitrogen product B. A fraction expanded in the sub-cooler 6 for cooling can be combined with the already mentioned material flow e. A portion can also be discharged as a so-called purge P. Further head gas can be heated in the form of a material flow h in the main heat exchanger 1 and discharged as gaseous nitrogen product C or used as sealing gas D.

[0141] Also in the example illustrated in FIG. 6, a material flow i is discharged in liquid form from the first rectification column 11, is supercooled in the condenser evaporator 121 of the second rectification column 120, and supplied as a return flow to the second rectification column 12.

[0142] From the sump of the second rectification column 12, a liquid oxygen-rich material flow k can be withdrawn, which is fed here in liquid form into a tank system 101. From the tank system 101 or another tank, a corresponding liquid oxygen-rich material flow, here designated by k3, may be withdrawn, and may subsequently be heated in the main heat exchanger 1 and provided as gaseous oxygen product U. The second rectification column 12 can in particular be designed and operated in such a way that an ultrahigh-purity oxygen product U with the specifications explained above can be provided by means of said rectification column. This does not have to be the case with the second rectification columns 12 of the air separation units 100 to 500.

[0143] Additional oxygen-rich liquid can be withdrawn from the second rectification column 12 analogously in the form of a material flow k1, pressurized by means of an internal compression pump 7a, and provided as an internally compressed oxygen pressure product E1. In the example shown, a material flow l is withdrawn from the head of the second rectification column 12 and is also used here to form the already mentioned material flow f.

[0144] A material flow m is withdrawn from a central region of the second rectification column 12, in particular at the argon transition, and is fed into a lower region of a fourth rectification column also designated by 14 here. As above, an additional material flow n is withdrawn from the sump of the fourth rectification column 14 by means of a pump 8 and returned to the second rectification column 12. From the head of the fourth rectification column 14, head gas rises into a condensation chamber of a head condenser 141, is at least partially liquefied there, and returned as a return flow to the fourth rectification column 14. A non-evaporated fraction may be discharged to the atmosphere A. A material flow p is withdrawn in liquid form below the head of the fourth rectification column 14. The material flow p is pressurized by means of a pump 7b and is subsequently heated in the main heat exchanger 1 so that an internally compressed argon product l can be provided in this way.

[0145] The head condenser 141 of the fourth rectification column 14 is also cooled with liquid here, which can be fed to the head condenser 141 in the form of the already mentioned material flow q3, which is hereinafter designated by q. A material flow r can be withdrawn from an evaporation chamber of the head condenser 141 of the fourth rectification column 14, which material flow r, after combining with the material flow l and the material flow s (explained below) as explained with reference to this material flow l, can preferably be heated in the main heat exchanger 1 without back pressure or substantially without back pressure and discharged from the air separation unit. In this way, a low pressure can be adjusted in the evaporation chamber of the head condenser 141. Liquid from the evaporation chamber of the head condenser 141 of the fourth rectification column 14 is withdrawn here in the form of the material flow s.

[0146] In FIG. 7, an air separation unit according to another embodiment of the present invention is shown in the form of a schematic unit diagram and is designated by 700 as a whole.

[0147] In contrast to the air separation unit 600 illustrated in FIG. 6, a partial flow of the feed air flow a, which is designated by a1 as in FIG. 2 for the first time, is drawn here from the main heat exchanger 1 at an intermediate temperature level and expanded by means of an expansion machine designated by 201 as above.

[0148] The remainder of the feed air flow a is at least partially fed into the first rectification column, wherein a cross connection a2 is provided between the partial flow a1 and the material flow a.

[0149] The air separation unit 700 illustrated in FIG. 7 is furthermore characterized in that the second rectification column 12 is designed as part of a double column which additionally has a third rectification column 13. The fraction of the feed air flow a designated by a1 and expanded is fed into a lower region of this third rectification column 13.

[0150] A material flow which is otherwise further used in a manner comparable to the material flow q of the preceding figures and is therefore also designated here by q is formed in the air separation unit 700 using sump liquid of the third rectification column 13. Head gas of the third rectification column 13 is at least partially liquefied in the form of a material flow u in the condenser evaporator 121 and is subsequently used in the form of a partial flow u1 as return flow to the third rectification column 13 and in the form of a partial flow u2 as return flow to the second rectification column 12.

[0151] Nitrogen-rich liquid is drawn from the third rectification column 13 in the form of a material flow v via a side offtake and conveyed into the first rectification column 11 by means of a pump 501. An additional material flow k4 is withdrawn from the second rectification column 12 in gaseous form and combined with the material flows l and r to form a material flow designated here by f1. Like the material flow f, the material flow f1 is heated in the main heat exchanger 1 and used correspondingly. In the shown example, the material flows q, i, and u2 are supercooled in a common sub-cooler 9 against the material flow l.

[0152] With regard to further details, reference is explicitly made to the explanations relating to the preceding figures, in particular to FIGS. 5 and 6. The features deviating from the preceding figures can also be implemented individually or together here.

[0153] In FIG. 8, an air separation unit according to another embodiment of the present invention is shown in the form of a schematic unit diagram and is designated by 800 as a whole.

[0154] The air separation unit 800 according to FIG. 8 differs from the previously shown and explained air separation units 100 to 700 in particular in that a fifth rectification column 15 is used which is configured as a rectification column for providing high-purity oxygen.

[0155] Furthermore, in the air separation unit 800, the material flow i is fed into the third rectification column 13, and a material flow w is drawn in liquid form in a region of this feed and fed into the second rectification column 12. Here, the material flow i is thus fed into the second rectification column 12 “via the detour” of the third rectification column 13. Furthermore, a portion of the sump liquid from the third rectification column 13 is fed directly into the second rectification column 12 in the form of a material flow q4. This amounts to a bypass of the head condenser 141 of the fourth rectification column 14, which is only fed with the remaining remainder.

[0156] A material flow m1 is drawn from the second rectification column 12 and fed into an upper part 15a of the fifth rectification column 15, which is separated from a lower part 15b by a barrier bottom 15c. Liquid segregating on the barrier bottom 15c is returned into the second rectification column 12 in the form of a material flow n1. The already explained material flows r and s are fed back into the second rectification column 12. The upper part 15a of the fifth rectification column 15 serves in particular for discharging argon, the predominant portion of which is transferred via a material flow m2 into the fourth rectification column 14. The material flow m2 also comprises head gas of the lower part 15b of the fifth rectification column 15. The sump liquid of the fourth rectification column 14 is conducted in the form of a material flow m2 to the head of the upper and lower parts 15a, 15b of the fifth rectification column 15.

[0157] The fifth rectification column 15 is provided with a condenser evaporator 151, which is operated with a nitrogen-rich gas that is withdrawn from the third rectification column 13 in the form of a material flow x, at least partially liquefied in the condenser evaporator 151, and returned into the third rectification column 13.

[0158] The example shown here, a material flow k is drawn from the sump of the second rectification column 12 and transferred into a tank system 101. However, internal compression by means of a pump 7c subsequently takes place here. Furthermore, ultrahigh-purity oxygen in the form of a material flow k5 is drawn from the fifth rectification column 5. This material flow k5 is transferred to a tank system 102, temporarily stored there, evaporated in the main heat exchanger 1, and provided as an ultrahigh-purity oxygen product U1. Temporary storage of the argon product in a tank system 103 is also possible.

[0159] With regard to further details, reference is explicitly made to the explanations relating to the preceding figures, in particular to FIGS. 5 and 7. The features deviating from the preceding figures can also be implemented individually or together here.

[0160] FIGS. 9 to 28 illustrate a number of further variants of air separation units according to embodiments of the invention and according to non-inventive embodiments. Although other designations are used for certain material flows and apparatuses in some cases than in the preceding figures, they may also correspond to one another.

[0161] FIG. 9 illustrates, only as a basis for the explanations relating to the following figures, a non-inventive air separation unit with an oxygen column next to the first rectification column 11, i.e., a second rectification column 12, but without additional rectification columns, and designated overall by 900. The predominant fraction of the components illustrated in FIG. 9 has already been explained several times. As illustrated in FIG. 9, another storage tank 104 may be used, and the material flow l may be conducted separately through the main heat exchanger 1.

[0162] In FIG. 10, an air separation unit is illustrated and designated by 1000, which represents likewise non-inventive variant of the air separation unit 900 according to FIG. 9 and in which a material flow k6 is drawn from the second rectification column 12 via an intermediate extraction and is optionally, after temporary storage in a buffer tank 105 and internal compression in an internal compression pump 7d and heating in the main heat exchanger 1, discharged as a corresponding oxygen product U2.

[0163] FIG. 11 illustrates another non-inventive air separation unit and is designated by 1100, which represents another variant of the units 900 and 1000 according to FIGS. 9 and 10. The air separation unit 1100 comprises a fourth rectification column 14 from which the material flow p, explained several times, is drawn in liquid form. Corresponding argon can be temporarily stored in a buffer tank 103 and, after internal compression in an internal compression pump 7b and heating in the main heat exchanger 1, can be discharged as a corresponding argon product l.

[0164] As illustrated here with 1101, a cross-connection between the material flows f and l may be provided on the cold side of the main heat exchanger 1. This cross-connection can be activated, in particular, in the case of a failure of one or more rectification columns in order to not have to shut down the air separation unit 1100 altogether in this way.

[0165] In this embodiment, as illustrated by 1102, liquid nitrogen provided externally and a liquid, nitrogen-rich material flow i1 from the first rectification column can also be supplied in this embodiment at the head of the second rectification column 12. Said material flow i1 has a lower nitrogen content than the head gas of the second rectification column 12. An additional separating section in the second rectification column 12 is designated by 1103.

[0166] A material flow k7 is drawn from the second rectification column 12, combined with the material flow l, and discharged or supplied to the warm part 110 in the form of this material flow, further designated by l for the sake of simplicity. In this way, the yield of gaseous, internally compressed argon (material flow p or product l) can be increased overall. The material flow l is fed to the material flow r, whereas the material flow s is used to form the material flow f.

[0167] In FIG. 12, another non-inventive air separation unit is illustrated and designated by 1200, which in particular represents a variant of the air separation unit 1100 according to FIG. 11. The air separation unit 1200 comprises the additional expansion machine 201. The partial flow a1 is expanded in this additional expansion machine 201 and used as explained several times.

[0168] The remainder of the material flow a not expanded in the expansion machine 201 is treated comparably to the material flow comparably to the material flow b explained above and is therefore correspondingly designated. Furthermore, a sub-cooler 9 already explained several times is shown here. The second rectification column 12 is arranged with its lowest point in particular more than 6 m above the lowest point of the first rectification column 11.

[0169] In FIG. 13, an air separation unit is illustrated and designated by 1300, which in particular represents a variant of the air separation unit 1200 according to FIG. 12 but in contrast thereto represents an embodiment of the present invention.

[0170] The air separation unit 1200 has the third rectification column 13 explained several times and the fifth rectification column 15, which have already been explained in more detail with reference to FIG. 8. With respect to the unit 900, reference is therefore explicitly made to the statements regarding the air separation unit 800 according to FIG. 8.

[0171] In deviation from the air separation unit 800 according to FIG. 8, an external liquid nitrogen X is in particular fed into the second rectification column 12, and a partial flow of the material flow r is combined with the material flow l and the material flow k3. This is the case in particular because there is no need for the complete return flow in the second rectification column 12, or an optimum prevails in this respect. As illustrated, the material flow i is supercooled here in the condenser evaporator 121 before being fed into the second rectification column 12.

[0172] In FIG. 14, an air separation unit is illustrated and designated by 1400, which in particular represents a variant according to the invention of the air separation unit 1300 according to FIG. 13. The air separation unit 1400 is configured to provide another compressed nitrogen product D1.

[0173] For this purpose, the head flow of the second rectification column 12 is obtained with higher purity than before the material flow l. The latter is therefore designated by l1 here. This is achieved by withdrawing an additional material flow l2 from the second rectification column 12 below the head. Furthermore, the second rectification column is provided here with an additional separating section 12a. The illustrated embodiment also has a positive effect on the yield and purity of argon.

[0174] The material flows combined with the material flow l in the air separation unit 1300 according to FIG. 13 are now combined with the material flow l2 into a material flow designated again by l for the sake of simplicity. The material flow l1 is partially compressed in an external compressor 1401 after being heating in the main heat exchanger 1. Another portion passes into the warm part 110. Further details in this respect are also illustrated in more detail in FIGS. 27 and 28.

[0175] In FIG. 15, an air separation unit is illustrated and designated by 1500 as a whole, which in particular represents a variant according to the invention of the air separation unit 1400 according to FIG. 14.

[0176] The sump liquid of the third rectification column 13 which is used in the air separation unit 1400 according to FIG. 14 only to form the material flow q is partially used here to form a material flow q4 (see also the air separation unit 800 according to FIG. 8 in this respect) which is supplied to the second rectification column 12. The second rectification column 12 and the feed point of the material flow i are adapted accordingly.

[0177] In FIG. 16, an air separation unit is illustrated and designated by 1600, which in particular represents a variant according to the invention of the air separation unit 1500 according to FIG. 15.

[0178] The material flow x formed in the previously explained units 800 and 1300 to 1500 is not correspondingly used here. Instead, a material flow x1 is branched off as partial flow of the head gas drawn from the third rectification column 13 and, as previously the material flow x, is in part liquefied in the condenser evaporator 151 and returned to the third rectification column 13 as a return flow. Another portion is heated in the form of a material flow x2 and is at least in part discharged as an additional nitrogen product D2 from the air separation unit 1600.

[0179] In FIG. 17, an air separation unit is illustrated and designated by 1700, which in particular represents a variant according to the invention of the units according to the previous figures in which a fifth rectification column 15 is used. However, said fifth rectification column 15 is present here in modified form and is designated by 15a as before.

[0180] The rectification column 15a corresponds to the upper part 15a of the fifth rectification column 15 of the previous figures. From its head, a material flow m3 is transferred into the fourth rectification column 14 and is fed into a region above the sump which functionally corresponds to the lower part 15b of the fifth rectification column 15 of the previous figures and which is therefore designated by 15b′ here. Liquid accumulating here is pumped back to the rectification column 15a in the form of a material flow n3 by means of a pump not designated separately. By means of the embodiment according to FIG. 17, it is possible in particular to achieve the absence of non-ferrous metals in the oxygen product U because, as a result of this arrangement, the fluid which is conducted to the partial column 15b′ does not come into contact with an impeller of a pump which usually consists of bronze.

[0181] In FIGS. 18 and 19, variants of units are illustrated and designated by 1800 and 1900, in which the warm part 110 and the routing of the material flows are substantially modified by the main heat exchanger 1. Only this warm part 110 and a section of the main heat exchanger 1 as well as material flows required for understanding this variant are shown in FIGS. 18 and 19.

[0182] According to FIG. 18, the cooled and purified air compressed in the main air compressor 112 is divided into partial flows a2 and a3, of which the partial flow a2 is conducted through the main heat exchanger 1 from the warm end to the cold end. By contrast, the material flow a3 is further compressed by means of a compressor or a compressor stage 112a, which is coupled to the main air compressor 112, and is then treated like the material flow a of the previous figures. In particular, a partial flow, designated by a1 here as before, is expanded in the expansion machine 201 and then combined with the material flow a2. As illustrated in the variant according to FIG. 19, an expansion machine 201 and the formation of the material flow a1 can also be dispensed with.

[0183] By using the measures illustrated in FIGS. 18 and 19, energy consumption can be reduced since not all of the air but only the fraction of the material flow a3 needs to be brought to a high pressure.

[0184] In FIG. 20, a variant of an air separation unit according to the invention is illustrated and designated by 2000, which has commonalities with the air separation unit 800 according to FIG. 8 and other units described above, in particular with regard to the treatment of the material flows i and w. As a result, the third rectification column 13 can be used to separate the material flow i, and a higher fraction of nitrogen product can be obtained. Reference is made to the above explanations, and only a few material flows are individually designated here and below.

[0185] The embodiment according to FIG. 20 (and according to FIG. 8) has the particular advantage that the condenser evaporator 121 can be simplified, and a likewise simplified regulation can be used. The material flow w can be regulated in particular like a conventional Joule-Thomson flow.

[0186] In a variant thereof according to the invention, which is illustrated in FIG. 21 and designated by 2100, a material flow q5 is formed using sump liquid from the fourth rectification column 14, is conducted by means of a pump 7e through the modified heat exchanger 2, which is designated here by 2a, and is thereby cooled, and subsequently returned into the third rectification column 13. This makes it possible, in particular, to improve the extraction of nitrogen in the third rectification column 13, as a result of which higher constructions of all products are possible.

[0187] In another variant according to the invention, which is illustrated in FIG. 22 and designated by 2200, a material flow k5 formed by sump liquid from the fifth rectification column 15 is correspondingly treated and returned to the fifth rectification column 15.

[0188] FIG. 23 illustrates an air separation unit according to another embodiment of the invention and is designated by 2300. This air separation unit differs from the previously shown embodiments in particular by a condenser evaporator 131 arranged in the sump of the third rectification column 13. This can be considered functionally as a division of the condenser evaporator in the second rectification column 12, which is designated here by 121a. In this way, the extraction of nitrogen in the second rectification column 12 or the third rectification column 13 can be improved.

[0189] As shown here, fluid in the form of a material flow i2 can be drawn from the second rectification column 2 via a side offtake, conducted through the condenser evaporator 141, thereby at least partially liquefied, and fed into the third rectification column 13. At the same height, liquid can be drawn from the third rectification column 13 and returned into the second rectification column 12 by means of a pump 7r.

[0190] A non-inventive variant is shown in FIG. 24 on the basis of the unit designated by 2400, which lacks the third rectification column 13 or in which the function thereof is integrated into the first rectification column 11. The material flow i2 is partially heated here in the main heat exchanger 1, expanded in an expansion machine 201a, cooled again in the main heat exchanger 1, and a fraction thereof is conducted through the condenser evaporator 121 of the second rectification column, thereby at least partially liquefied, and fractions thereof are in turn supplied to the first and second rectification columns 11, 12. The expansion machine 201a is coupled to a generator, for example.

[0191] In FIG. 25, an air separation unit again according to the invention in accordance with another embodiment of the present invention is illustrated and designated by 2500 as a whole. This air separation unit differs from the previous units, in which a material flow a1 is formed and expanded, by the further treatment of this material flow a1.

[0192] In the air separation unit 2500, the partial flow a1 is divided into partial flows a4 and a5, the fractions of which can each be adjusted via valves not designated separately. The partial flow a4 is expanded instead of the partial flow e, as was previously the case, in the expansion machine 3 and optionally the parallel expansion valve and is thus partially used for driving the compressor 5. As the entire partial flow a1 before, the partial flow a5 is fed, for example, into the third rectification column 13. The material flow e is nevertheless formed and partially treated as before, but not expanded by means of the expansion machine 3 and the expansion valve 4. It is fed into the third rectification column 13 below the material flow a5. In this case, the third rectification column 13 can be provided with an additional separating section 13a.

[0193] Rectification columns 11 to 15 can be thermally coupled by the measures illustrated in FIG. 25. Residual gas from the first rectification column 11 can be used for argon, oxygen, and nitrogen extraction. The flow e can be conducted entirely or partially to the second rectification column 12. The remainder can be discharged via the expansion machine 3 as a residual gas for use in the warm part 110.

[0194] In FIG. 26, an air separation unit according to another embodiment of the present invention is illustrated and designated overall by 2600. This air separation unit represents in particular a variant of the air separation unit 2500. The partial flow a1 is also divided here into partial flows a4 and a5, wherein, however, the material flow a4 is fed here to the material flow l before the latter is heated and discharged or supplied to the warm part 110. The partial flow a5 is fed into the second rectification column 12. The function of the expansion turbine 201 therefore corresponds here to that of a Lachmann turbine. Rectification columns 11 to 15 can be thermally coupled by the measures illustrated.

[0195] The partial flow d is formed and compressed as before, wherein a compressor used for this purpose, which is therefore designated differently by 5a, is however driven here purely by motor. The partial flow e is fed into the fourth rectification column 14, as previously explained with reference to FIG. 25.

[0196] In the air separation units 2700 and 2800 according to embodiments of the invention illustrated in FIGS. 27 and 28 in a partial representation, the material flow l1 mentioned for the first time with reference to FIG. 14 is formed. Reference is explicitly made to the explanations in that regard. As illustrated in FIG. 28 on the basis of the air separation unit 2800, the material flow l1 can first be partially heated in the main heat exchanger 1, compressed in a compressor 201b which is coupled to the expansion machine 201, subsequently supplied again to the main heat exchanger 1 at an intermediate temperature level, further heated, and subsequently supplied to the compressor 1401.

[0197] As illustrated in a partial representation in FIG. 29, in an air separation unit 2900, according to an embodiment of the invention, the nitrogen of the material flow h, as previously illustrated with respect to FIGS. 28 and 29, may also be correspondingly compressed. The use of the compressor designated by 1401′ here is optional.

[0198] FIG. 30 illustrates an air separation unit 3000 in accordance with a non-inventive embodiment in the form of a schematic unit diagram.

[0199] The air separation unit 3000 according to FIG. 30 has major commonalities with the air separation unit 100 which is likewise not-inventive and is illustrated in FIG. 1. Only the differences are explained below.

[0200] Here, after being conducted through the condenser evaporator 121 of the second rectification column 12, the partial flow c is not combined with additional material flows before it is fed into the first rectification column 11. Furthermore, no portion of the material flow e is branched off here, as the material flow e1 in FIG. 1 or the air separation unit 100, so that the entire material flow e is supplied here to the heat exchanger 2. The material flow e is expanded here in the form of two partial flows in two expansion machines 3 and 4. The expansion machine 4 is coupled to a generator.

[0201] As illustrated here, above the material flow i, the material flow j here designated differently is discharged from the second rectification column and, in particular, added to the second rectification column 2 at the head. In the the material flow l is withdrawn from the head of the second rectification column 12 and can be heated without being combined with an additional material flow and, in particular after compression in a compressor 3001, can be discharged as an additional gaseous nitrogen product H from the air separation unit 100. The gaseous nitrogen product C represents the “additional nitrogen-rich air product” previously explained with reference to different embodiments of the invention.

[0202] As indicated here in a highly simplified manner, in the air separation unit 3000, the main heat exchanger 1 may be arranged in a first prefabricated cold box 3010. The first rectification column 11 with the heat exchanger 2 used to cool its head gas may be arranged in a second prefabricated cold box 3020. The second rectification column may be arranged in a third prefabricated cold box 3030. Unlike in the highly simplified representation of FIG. 1, these cold boxes completely each of the respectively mentioned elements.

[0203] FIG. 31 shows a variant of the air separation unit 3000 according to FIG. 31, which however represents an embodiment of the present invention and is designated overall by 3100. In contrast to the unit 3000 illustrated in FIG. 30, a partial flow a1 of the feed air flow is provided here in addition to the third rectification column 13 mentioned several times, and furthermore an argon extraction is provided in a fourth rectification column 14. Furthermore, a fifth rectification column 15 is provided in the air separation unit 3100. The terms “first,” “second,” “third,” “fourth,” and “fifth” rectification column are used consistently with the specifications given above, so that reference may be made thereto.

[0204] The formation and treatment of the material flows d, e, f, g, h, i, k, and l takes place substantially as already explained with respect to the unit 100 or 3000 according to FIG. 1 or 30, wherein again only one expansion machine 4 is illustrated in the unit 3100 instead of the expansion machines 3 and 4, and the material flow i is not fed directly into the second rectification column 12 but is conducted beforehand through the condenser evaporator 121 and a supercooling heat exchanger 202. Furthermore, the material flow k can be temporarily stored in a tank system 203 in the example illustrated here. The material flow l is also conducted through the supercooling heat exchanger 202.

[0205] A material flow corresponding to the material flow j according to unit 100 is not formed here. Instead, a liquid return flow n to the second rectification column 12 is formed by drawing head gas in the form of a material flow m from the fourth rectification column and liquefying it in the condenser evaporator 121. A portion of the liquefied head gas is conducted as through the supercooling heat exchanger 202 and is used in the form of the material flow n; another non-designated portion is returned as a return flow to the first rectification column 11. Additional liquid may be provided in the form of the liquid nitrogen X. In the unit 200, a material flow o is returned from the third rectification column 13 into the first rectification column 1 by means of a pump 204.

[0206] The fifth rectification column 15 here also represents a double column; with regard to its function, reference is made to the above explanations. The lower part 15b is operated with a condenser evaporator 151 which is heated by using a material flow p that is drawn from the third rectification column 13 and is subsequently, i.e., downstream of the condenser evaporator 151, returned into the third rectification column 13. Furthermore, ultrahigh-purity oxygen in the form of a material flow q is drawn in the lower part 15b. This material flow q is transferred to a tank system 205, temporarily stored there, evaporated in the main heat exchanger 1, and provided as an ultrahigh-purity oxygen product U.

[0207] A material flow r is drawn from the second rectification column 12 in the region of the argon transition or below a material flow r and fed into the upper part 15a of the fifth rectification column 15 which is separated from the lower part 15a by a barrier bottom 15c. Liquid depositing on the barrier bottom 15c is returned to the second rectification column 12 below the material flow r. The head gas of the upper part 15a and of the lower part 15b of the fifth rectification column 15 is transferred via a material flow s into the fourth rectification column 14. The sump liquid of the fourth rectification column 14 is conducted in the form of a material flow t to the head of the lower part 15a and of the upper part 15b of the fifth rectification column 15.

[0208] A head condenser 141 of the third rectification column 13 is cooled using sump liquid of the second rectification column 12 in the form of a material flow u which has previously been conducted through the supercooling heat exchanger 202. Liquid from an evaporation chamber of the head condenser 141 is returned into the second rectification column 12 in the form of a material flow v. Gas from an evaporation chamber of the head condenser 141 is withdrawn in the form of a material flow w and in part expanded into the second rectification column 12, and in part used to form a residual gas flow x which also comprises fluid which is drawn from the second and third rectification columns 12, 13.

[0209] Below the head, argon-rich liquid in the form of a material flow x is drawn from the fourth rectification column 14. This liquid can be stored in a tank system 206 before it can be subjected to internal compression by means of a pump 207, heated, and provided as an argon product V. Uncondensed head gas of the fourth rectification column 14 can be discharged to the atmosphere A in the form of a material flow y.

[0210] The main heat exchanger 1 in the air separation unit 3100 according to FIG. 31 may also be arranged in a first prefabricated cold box 3110. The first rectification column 11 with the heat exchanger 2 used for cooling its head gas may be arranged in a second prefabricated cold box 3120. The second rectification column 12 together with the third rectification column 13 may be arranged in a third prefabricated cold box 3130. In the shown example, the fifth rectification column 15 is also arranged in the third cold box 3130. In the shown example, the fourth rectification column 14 is arranged in an additional prefabricated cold box 3140 in which, for example, the fifth rectification column 15 may however also be arranged. However, the fourth rectification column 14 may also be arranged in the third cold box 3130. Any distribution is possible.

[0211] It should again be emphasized that although measures according to individual embodiments of the invention are each described in the preceding figures as part of corresponding units, they may also each be used alone or in other units without departing from the scope of the present invention. For example, in all cases, a motor and/or a turbine operation of a compressor may be provided, and/or expansion machines may be braked by means of a generator and/or by means of brakes and/or by coupling with a compressor.

[0212] Although certain air separation units are described above as variants of units explained above, it goes without saying that each of the measures or features proposed herein may also be used in units other than each of those described as the basis.