METHOD AND INSTALLATION FOR LOW TEMPERATURE SEPARATION OF AIR

Abstract

A method for low temperature separation of air using an air separating installation having a distillation column system which has a first, a second, a third and a fourth separating unit. Compressed and cooled air is fed into the first separating unit. An oxygen-enriched, nitrogen-depleted, argon-containing first sump liquid and a nitrogen-enriched, oxygen-depleted first head gas are formed by means of the first separating unit. An oxygen-rich second sump liquid and an argon-enriched second head gas are formed by means of the second separating unit. A liquid return to the second separating unit is provided by means of the third separating unit. A fourth sump liquid and a fourth head gas are formed by means of the fourth separating unit, and the fourth sump liquid is at least partially returned to the second separating unit.

Claims

1: Method for low temperature separation of air using an air separating installation with a distillation column system (100) that has a first separating unit (110), a second separating unit (120), a third separating unit (130), and a fourth separating unit (140), wherein compressed and cooled air is fed into the first separating unit (110), the first separating unit (110) is operated at a first pressure level of 4 to 9 bar of absolute pressure, the second separating unit (120), the third separating unit (130), and the fourth separating unit (140) are operated at a second pressure level of 1 to 3 bar of absolute pressure, an oxygen-enriched, nitrogen-depleted, argon-containing first sump liquid and a nitrogen-enriched, oxygen-depleted first head gas are formed by means of the first separating unit (110), the first sump liquid is partially or completely transferred into the fourth separating unit (130), the first head gas is partially or completely liquefied and returned to the first separating unit (110), an oxygen-rich second sump liquid and an argon-enriched second head gas are formed by means of the second separating unit (120), a first fraction of the second head gas is transferred into the third separating unit (130) and a second fraction of the second head gas is transferred into the fourth separating unit (140), the argon which is contained in a quantity of air supplied overall to the distillation column system (100) is partially or completely separated off by means of the third separating unit (130), a liquid return flow is provided to the second separating unit (120) by means of the third separating unit (130), a fourth sump liquid and a fourth head gas are formed by means of the fourth separating unit (140), and the fourth sump liquid is partially or completely returned to the second separating unit (120), wherein the second separating unit (120) has 10 to 50 theoretical plates, that the third separating unit (130) has 10 to 60 theoretical plates, that the third separating unit (130) is arranged above the second separating unit (120), that the fourth separating unit (140) is arranged adjacent to the first separating unit (110), and that the third separating unit (130) opens in a lower region with respect to an upper region of the second separating unit (120) or the third separating unit (130) is connected to the second separating unit (120) via pipelines which run between an upper region of the second separating unit (120) and a lower region of the third separating unit (130).

2: The method according to claim 1, in which a lower termination of the fourth separating unit (140) is arranged no more than eight meters above a lower termination of the first separating unit (110).

3: The method according to claim 1, in which compressed and cooled air which is fed into the first separating unit comprises a gaseous and a liquefied feed air stream (1, 2).

4: The method according to claim 1, in which the first separating unit (110) and the second separating unit (120) are arranged within a common column jacket or in two column jackets that are structurally connected to one another, wherein the common column jacket or the column jacket of the second separating unit (120) is structurally connected to the third separating unit (130).

5: The method according to claim 1, in which the fourth separating unit has 18 to 55 theoretical plates.

6: The method according to claim 1, in which the first fraction of the second head gas comprises 20 to 60 volume percent and the second fraction of the second head gas comprises 40 to 80 volume percent of the second head gas.

7: The method according to claim 1, in which the fourth sump liquid is returned to the second separating unit (120) using a transfer pump (170) or using two or more transfer pumps arranged in parallel.

8: The method according to claim 1, in which the first separating unit (110), the second separating unit (120), and the third separating unit (130) are arranged in a common cold box (A).

9: The method according to claim 8, in which the fourth separating unit (140) is arranged in the common cold box (A) or a further cold box (B).

10; The method according to claim 9, in which the first separating unit (110), the second separating unit (120), and the third separating unit (130) on the one hand and the fourth separating unit (140) on the other hand are connected to one another and/or to one another to further apparatuses by means of piping (20) which runs vertically in sections, wherein at least a part of the piping (20) is arranged in a separate piping cold box (C).

11: The method according to claim 10, in which a supercooler (120) is also arranged in the piping cold box (C).

12: The method according to claim 1, in which a liquid air product is removed from the distillation column system (100), pressure-increased in the liquid state, converted into the gaseous or supercritical state by heating, and discharged from the air separating installation.

13: Air separating installation with a distillation column system (100) that has a first separating unit (110), a second separating unit (120), a third separating unit (130), and a fourth separating unit (140), wherein the air separating installation is set up to feed compressed and cooled air into the first separating unit (110), to operate the first separating unit (110) at a first pressure level of 4 to 9 bar of absolute pressure, to operate the second separating unit (120), the third separating unit (130), and the fourth separating unit (140) at a second pressure level of 1 to 3 bar of absolute pressure, to form an oxygen-enriched, nitrogen-depleted, argon-containing first sump liquid and a nitrogen-enriched, oxygen-depleted first head gas by means of the first separating unit (110), to transfer the first sump liquid partially or completely into the fourth separating unit (130), to partially or completely liquefy the first head gas and to return it to the first separating unit (110), to form an oxygen-rich second sump liquid and an argon-enriched second head gas by means of the second separating unit (120), to transfer a first fraction of the second head gas into the third separating unit (130) and a second fraction of the second head gas into the fourth separating unit (140), to partially or completely separate off the argon which is contained in a quantity of air supplied overall to the distillation column system (100) by means of the third separating unit (130), to provide a liquid return flow to the second separating unit (120) by means of the third separating unit (130), to form a fourth sump liquid and a fourth head gas by means of the fourth separating unit (140), and to return the fourth sump liquid at least partially to the second separating unit (120), wherein the second separating unit (120) has 10 to 50 theoretical plates, the third separating unit (130) has 10 to 60 theoretical plates, that the third separating unit (130) is arranged above the second separating unit (120), that the fourth separating unit (140) is arranged adjacent to the first separating unit (110), and that the third separating unit (130) opens in a lower region with respect to an upper region of the second separating unit (120), or the third separating unit (130) is connected to the second separating unit (120) via pipelines which run between an upper region of the second separating unit (120) and a lower region of the third separating unit (130).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] FIG. 1 illustrates a distillation column system of an air separating installation in accordance with an embodiment of the present invention in a partial representation.

DETAILED DESCRIPTION OF THE DRAWINGS

[0062] FIG. 1 shows a distillation column system of an air separating installation set up for operation according to one embodiment of the present invention in a greatly simplified partial representation. The distillation column system illustrated in FIG. 1 is designated as a whole with 100. It is provided in an air separating installation 200 which is only indicated here.

[0063] The components of the distillation column system 100 illustrated in FIG. 1 comprise a first separating unit 110, a second separating unit 120, a third separating unit 130, and a fourth separating unit 140, a main condenser 150, a supercooling counter-flow heat exchanger 160, a transfer pump 170, an internal compression pump 180, and a head condenser 190.

[0064] The first separating unit 110 corresponds to a high-pressure column of a conventional air separating installation. The first separating unit is operated at a corresponding pressure level, referred to herein as the “first pressure level.” The second separating unit 120 and the fourth separating unit 140 correspond to a first section and a second section of a low-pressure column of a conventional air separating installation. They are operated at a corresponding common pressure level, referred to herein as the “second pressure level.” The third separating unit 130 represents an argon discharge column. It is also operated at the second pressure level.

[0065] In the distillation column system 100 illustrated in FIG. 1, the first separating unit 110 and the second separating unit 120 are in heat-exchanging connection via the main condenser 150, as also explained below. Furthermore, the first separating unit 110 and the second separating unit 120 are arranged in particular within a common column jacket and, in the sense explained above, one above the other, in particular one directly above the other. The head condenser 190 is arranged at the upper end of the third separating unit 130. In the alternative illustrated here, the third separating unit (130) opens in a lower region with respect to an upper region of the second separating unit (120). However, it is alternatively also possible for the third separating unit (130) to be connected to the second separating unit (120) via pipelines which run between an upper region of the second separating unit (120) and a lower region of the third separating unit (130). This is not illustrated separately.

[0066] With regard to further explanations regarding an air separating installation, of which the distillation column system 110 may be a part, reference is made to relevant technical literature, e.g., Haring (see above), in particular chapter 2.2.5 and FIG. 2.3A. In such an air separating installation, in particular a gaseous feed air stream 1 and a liquefied feed air stream 2 can be provided. In this connection, in particular a main air compressor, cleaning and preparation devices, turbines, expansion valves, and a main heat exchanger of a known type can be used.

[0067] The feed air streams 1 and 2 are fed into the first separating unit 110 at feed positions 111 and 112, respectively. In the first separating unit 110, an oxygen-enriched, nitrogen-depleted, argon-containing sump liquid and a nitrogen-enriched, oxygen-depleted head gas are formed at the first pressure level. The sump liquid is withdrawn from the first separating unit 110 in the form of a stream of material 3. The head gas is withdrawn from the first separating unit 110 in the form of a stream of material 4. Directly below the feed position 112 for the feed air stream 2, liquid in the form of a stream of material 5 is conducted out of the first separating unit 110.

[0068] The stream of material 3 is passed through the supercooling counter-flow heat exchanger 160 and partially fed in the form of a stream of material 31 into the fourth separating unit 140 at a feed position 141. Another part is transferred in the form of a stream of material 32 into an evaporation chamber of the head condenser 190. A liquid stream of material 33 and a gaseous stream of material 34 are withdrawn from the evaporation chamber of the head condenser 190 and likewise fed into the fourth separating unit 140, in particular at different heights. The stream of material 4 is also divided into two substreams 41 and 42. The first substream 41 is partially or completely liquefied in the main condenser 150. A first fraction 411 of the first substream 41 is returned as a return flow to the first separating unit 110 at a feed position 113. A second fraction 412 of the first substream 41 is passed through the supercooling counter-flow heat exchanger 160 and guided as a return flow to the fourth separating unit 140. The substream 42 is conducted out of the distillation column system 100 as a gaseous pressurized nitrogen product. The stream of material 5 is passed through the supercooling counter-flow heat exchanger 160 and fed into the fourth separating unit 140 at a feed position 142.

[0069] An oxygen-rich sump liquid and an argon-enriched head gas are formed in the second separating unit 120. The sump liquid is withdrawn from the second separating unit 120 in the form of a stream of material 6. A first substream 61 of the stream of material 6 is pressure-increased in the internal compression pump 180 in the liquid state, converted into the gaseous or supercritical state by heating (not separately illustrated in FIG. 1), and conducted out as an internally compressed pressurized oxygen product. A second substream 62 of the stream of material 6 is provided as a liquid oxygen product after partially passing through the supercooling counter-flow heat exchanger 160 and corresponding tempering.

[0070] The head gas of the second separating unit 120 rises partly into the third separating unit 130, which is arranged above the second separating unit 120 and which opens in a lower region, in particular without a cross-sectional tapering toward the second separating unit 120. Another part of the head gas is withdrawn in the form of a stream of material 7. The stream of material 7 is fed a lower region of the fourth separating unit 140 at a feed position 143.

[0071] In the third separating unit 130, a head gas containing at least the predominant part of the argon previously contained in the feed air supplied to the distillation column system 100 is formed. This head gas from the third separating unit 130 is withdrawn in the form of a stream of material 8. Liquid which trickles down from the third separating unit 130 and is in this way depleted of argon or is (substantially) free of argon, directly reaches the second separating unit 120 again. An argon discharge therefore occurs in the third separating unit 130.

[0072] A sump liquid and a head gas are formed in the fourth separating unit 140. The sump liquid is withdrawn from the fourth separating unit 140 in the form of a stream of material 9 and is returned by means of the transfer pump 170 to the second separating unit 120 as a return flow and is in this case fed into the second separating unit 120 at a feed position 114. A stream of material 10, known as impure nitrogen, is removed from the fourth separating unit, passed through the supercooling counter-flow heat exchanger 160, and conducted out of the distillation column system 100. The same applies to a nitrogen-rich stream of material 11 which is provided as a gaseous low-pressure nitrogen product. Nitrogen-rich liquid in the form of a stream of material 12 is withdrawn from a liquid retention device at the head of the fourth separating unit (140) and provided as a liquid nitrogen product. If no gaseous low-pressure nitrogen product is required, a corresponding separating section in the fourth separating unit 14 can be omitted and all the head gas can be withdrawn as impure nitrogen corresponding to the stream of material 10.

[0073] As illustrated here but not mandatory for the present invention, the first separating unit 110, the second separating unit 120, and the third separating unit 130 on the one hand and the fourth separating unit 140 on the other hand are each provided in a cold box A and B, respectively, and are connected to one another and/or to one another to further apparatuses, such as the supercooling counter-flow heat exchanger 160 and the main heat exchanger not shown, by means of lines or piping, denoted together here by 20. The piping extends vertically at least in sections. At least a part of such piping 20 can be arranged separately from the two cold boxes A and B, in which the first separating unit 110, the second separating unit 120, and the third separating unit 130 on the one hand and the fourth separating unit 140 on the other hand are arranged, in an additional cold box C. This additional cold box C for the piping may also contain, in particular, the supercooler 160.