Process for cryogenic separation of air, air separation plant and complex of at least two air separation plants

Abstract

This invention relates to a method for cryogenic separation of air using an air separation apparatus (100-400) with a distillation column system (10), the distillation column system having a pressure column (11) operating at a pressure level of 9 bar to 14.5 bar, a low-pressure column (12) operating at a pressure level of 2 bar to 5 bar, and an argon column (13). According to the invention, a second top gas or a portion thereof is used to form a circulating flow, the top gas or circulating flow being heated, compressed, recooled, and fed, either partially or completely, or proportionally, into the first distillation column (11) and / or the second distillation column (12) after partial or complete liquefaction or in a non-liquefied state. The subject matter of the invention also relates to a corresponding apparatus (100-400).

Description

[0001] The present invention relates to a method for separating air at low temperature, an air separation device, and a composite consisting of at least two air separation devices. Background of the Invention

[0003] The preparation of liquid or gaseous air products by separating air at low temperatures in an air separation device is known and, for example, by H.-W., Wiley-VCH Publishing Company, 2006. The book "Industrial Gases Processing" specifically describes this in Chapter 2.2.5, "Cryogenic Rectification".

[0004] Traditional air separation equipment includes distillation column systems, which can be designed as two-column systems, particularly twin-column systems, but also as three-column or multi-column systems. In addition to distillation columns for extracting liquid and / or gaseous nitrogen and / or oxygen, i.e., distillation columns for nitrogen-oxygen separation, distillation columns can also be installed for extracting other air components, especially rare gases.

[0005] This allows the distillation columns in the distillation column system to operate at different pressure levels. A known two-column system has a so-called pressure column (also known as a high-pressure column, intermediate-pressure column, or lower column) and a so-called low-pressure column (upper column). The high-pressure column typically operates at a pressure level of 4 to 7 bar, particularly about 5.3 bar, while the low-pressure column typically operates at a pressure level of 1 to 2 bar, particularly about 1.4 bar. In some cases, even higher pressure levels may be used in both distillation columns. The pressures described here and below are absolute pressures at the top of the respective given column.

[0006] Air separation equipment can be designed in various ways depending on the required air products and their desired aggregation state and pressure. For example, so-called internal compression has been disclosed for providing gaseous pressure products. In internal compression, a chilled liquid is extracted from a distillation column system, pressurized in its liquid state, and then heated to convert it into a gaseous or supercritical state. In this way, for example, internally compressed gaseous oxygen, internally compressed gaseous nitrogen, or internally compressed gaseous argon can be produced. Compared to the equally possible alternative, external compression, internal compression offers a number of technical advantages and, for example, in… This has been explained in Chapter 2.2.5.2 "Internal Compression" of the book (see above).

[0007] However, internal compression is not always advantageous or desirable. Therefore, especially at pressure levels of 9 to 14.5 bar where argon needs to be supplied in addition to compressed nitrogen, alternative equipment configurations are recommended. Generally, in such alternative configurations, a distillation column already operating at the desired product pressure is used to supply gaseous nitrogen. Therefore, there is no need to compress the nitrogen extracted from the corresponding distillation column. In this case, a distillation column used for argon extraction can also be used.

[0008] The object of this invention is to take measures to further improve the preparation of air products, particularly according to the stated requirements, and to make it more efficient and simple. Summary of the Invention

[0009] Against this backdrop, the present invention proposes a method for low-temperature air separation, an air separation device, and a composite consisting of at least two air separation devices. The embodiments are respectively the technical solution of the present invention and the subject matter described below.

[0010] The following will first provide a further explanation of some of the terminology used in describing the present invention and its advantages, as well as the basic technical background.

[0011] The apparatus used in air separation equipment is described in the cited technical documents, for example... See Section 2.2.5.6, “Apparatus”. Therefore, unless the definitions below deviate from this, the terminology used in the context of this application explicitly refers to the cited technical literature.

[0012] A "condenser-evaporator" refers to a heat exchanger in which a first condensing fluid flow and a second evaporating fluid flow exchange heat indirectly. Each condenser-evaporator has a liquefaction chamber and an evaporation chamber. The liquefaction chamber and the evaporation chamber have liquefaction channels and evaporation channels. The first fluid flow is condensed (liquefied) in the liquefaction chamber, and the second fluid flow is evaporated in the evaporation chamber. The evaporation chamber and the liquefaction chamber are formed by a group of channels that have mutual heat exchange relationships. A condenser-evaporator is also referred to as a "top condenser" and a "bottom evaporator" in terms of its function, where a top condenser is a condenser-evaporator that condenses the top gas of a distillation column, and a bottom evaporator is a condenser-evaporator that evaporates the bottom liquid of a distillation column. However, the bottom liquid can also be evaporated in the top condenser, as in the top condenser of this invention.

[0013] An expansion turbine or expander, which can be connected via the same shaft to other expansion turbines or energy converters (e.g., hydraulic brakes, generators, or compressors), is adapted to expand a gaseous flow or a medium flow that is at least partially liquid. In this invention, in particular, the expansion turbine may be designed as a turbine expander. The term "turbine-driven" compressor or alternatively "turbocharger" is used if the compressor is driven by one or more expansion turbines and does not have an externally fed energy source (e.g., from an electric motor). The configuration of a turbine-driven compressor with an expansion turbine is also referred to as a "turbocharger turbine" or "turbocharger." The following reference to expansion in a turbocharger turbine refers to the turbine section. The same applies to compression, where compression occurs in the compressor section of the turbocharger turbine or turbocharger.

[0014] In air separation equipment, a multi-stage turbo compressor is used to compress the added air to be separated; this turbo compressor is referred to herein as the "main air compressor." The mechanical structure of the turbo compressor is generally a well-known technical field for those skilled in the art. In a turbo compressor, the medium to be compressed is compressed by means of turbine blades arranged on a turbine or impeller or directly on a shaft. Here, the turbo compressor forms a structural unit, although this structural unit may have multiple compression stages in a multi-stage turbo compressor. The compression stages here typically involve corresponding arrangements of turbine blades. All these compression stages may be driven by the same shaft. However, they can also be configured to be driven in groups by different shafts, wherein the shafts may also be connected to each other via a reduction gear.

[0015] Furthermore, the main air compressor is characterized in that all the air supplied to the distillation column system and used to prepare air products is compressed by the main air compressor; that is, all the added air is compressed. Correspondingly, a "secondary compressor" can also be provided, but in this secondary compressor, only a portion of the air compressed in the main air compressor is increased to a higher pressure. This compressor can also be designed as a turbo compressor. The same compressor or a compression stage of such a compressor can also be used as both the main air compressor and the secondary compressor. To achieve the purpose of compressing a portion of the air, other turbo compressors in the form of boosters are generally also provided in the air separation equipment; the compression range of these other turbo compressors is usually relatively smaller compared to the main air compressor or the secondary compressor.

[0016] In the language used herein, fluids and gases may be rich in or poor in one or more components, where “rich in” can mean a content of at least 50%, 75%, 90%, 95%, 99%, 99.5%, 99.9%, or 99.99% on a molar, weight, or volume basis, and “poor in” can mean a content of at most 50%, 25%, 10%, 5%, 1%, 0.1%, or 0.01%. The term “major” can be used to correspond to the definition of “rich in”. Furthermore, liquids and gases may be enriched in or depleted in one or more components, where these terms refer to the content in the initial liquid or gas, i.e., the liquid or gas from which it was extracted. A liquid or gas is considered "enriched" if it contains at least 1.1, 1.5, 2, 5, 10, 100, or 1,000 times the content of the corresponding component relative to the initial liquid or gas; and "depleted" if it contains at most 0.9, 0.5, 0.1, 0.01, or 0.001 times the content of the corresponding component. The term "oxygen" or "nitrogen" as used herein may also be understood as a liquid or gas rich in oxygen or nitrogen, but its composition is not limited to these definitions.

[0017] This disclosure uses the terms "pressure level" and "temperature level" to characterize pressure and temperature, thereby indicating that it is not necessary to use corresponding pressure and temperature in the form of precise pressure or temperature values ​​in the corresponding equipment to achieve the concept of the invention. However, such pressure and temperature typically fluctuate within a certain range, such as 1%, 5%, 10%, 20%, or even 50% above or below the average value. Here, the corresponding pressure level and temperature level may be within non-overlapping ranges or within overlapping ranges. In particular, for example, the pressure level includes unavoidable or expected pressure loss. The corresponding content applies to the temperature level.

[0018] Advantages of the present invention

[0019] This invention discovers that the requirements described at the outset of this document can be particularly advantageously achieved when extracting gaseous compressed nitrogen at pressure levels of 9 to 14.5 bar and additionally performing argon extraction: operating a dual-tower system at a higher pressure level, while simultaneously venting nitrogen from the top of the low-pressure tower and partially or entirely heating, compressing, reheating, and subsequently feeding it into the pressure tower and / or the low-pressure tower in a refluxed state after liquefaction. Within the scope of this invention, the low-pressure tower is configured to provide a nitrogen-rich top gas with specifications as described below by using a suitable nitrogen section in the upper region, which is used to form the reflux stream. This invention also utilizes one or more additional distillation towers, such as crude argon towers and pure argon towers of known types, for argon extraction.

[0020] This invention proposes a method for cryogenic air separation using an air separation device with a distillation column system, wherein the distillation column system has a first distillation column, a second distillation column, and a third distillation column. The first and second distillation columns specifically refer to distillation columns that can be constructed according to known dual-column systems (pressure column and low-pressure column) and, in principle, employ similar connection schemes. However, they operate at higher pressure levels. The third distillation column is particularly a crude argon column or a single column for extracting argon products, which partially combines the functions of a pure oxygen column and a pure argon column by having an additional section for nitrogen separation.

[0021] The first distillation column of the present invention operates at a first pressure level, and a first feed stream is fed into the first distillation column. The feed stream is formed by using cooled compressed air, and a first bottom liquid rich in oxygen and argon and a first top gas rich in nitrogen are formed in the first distillation column compared with the first feed stream.

[0022] The first bottom liquid may in particular have an oxygen content of 28 to 38%, as well as argon and nitrogen. The first top gas may in particular have an oxygen content of 0.1 to 100 ppb, for example about 10 ppb, an argon content of 1 to 100 ppm, for example about 30 ppm, and the remainder is essentially nitrogen and, where appropriate, trace components.

[0023] The second distillation column operates at a second pressure level in this invention, and at least one second addendum stream is fed into the second distillation column, which is formed by using a first bottom liquid or a portion thereof. As will be explained below, the first bottom liquid or a corresponding portion thereof can also be used, in particular, to cool the top condensate of the argon extraction column, thereby producing evaporated and unevaporated components fed into the second distillation column as an addendum stream. An oxygen-rich second bottom liquid and a nitrogen-rich second top gas are formed in the second distillation column.

[0024] In particular, a second top gas can be formed with an oxygen content of 1 to 1000 ppb, for example, about 100 ppb, and an argon content of 3 to 300 ppm, for example, about 90 ppm. In certain cases, such as in... Figure 2 In the illustrated embodiment, the first and second top gases may also have substantially the same composition.

[0025] A third additive stream, formed by using a fluid having an argon content higher than that of the second bottom liquid and the second top gas, is fed into the third distillation column. This fluid is extracted from the second distillation column, typically above or below the so-called argon bulge, forming a third top gas rich in argon compared to the third additive stream. The third additive stream does not necessarily have to be formed directly from a fluid with an argon content higher than that of the second bottom liquid and the second top gas, extracted from the second distillation column. Instead, it can also be formed by using a fluid extracted from another distillation column or another separation apparatus, which is fed with the fluid extracted from the second distillation column. Accordingly, the following description is in conjunction with a fourth distillation column used for extracting high-purity oxygen.

[0026] In this invention, the first distillation column may be equipped with 80 to 110, for example 90, theoretical plates; the second distillation column may be equipped with 90 to 150, for example 110, theoretical plates; and the third distillation column may be equipped with 210 to 280, for example 250, theoretical plates.

[0027] In this invention, the first pressure level at the top of the first distillation column is 9 to 14.5 bar, for example, about 11.6 bar, and the second pressure level at the top of the second distillation column is 2 to 5 bar, for example, about 3.5 bar.

[0028] According to the present invention, a second top gas or a portion thereof is used to form a circulating flow, which is then heated, compressed, recooled, and partially or completely liquefied, or fed partially or completely, or proportionally, into the first and / or second distillation columns in a non-liquefied state. This significantly improves the efficiency of the air separation apparatus proposed herein. In other words, in one embodiment of the invention, at least a portion of the second top gas can be sequentially heated, compressed, recooled, and subsequently fed into the first distillation column as a circulating gas.

[0029] In the case of partial or complete liquefaction, in this invention, in particular, the liquefaction can be carried out using a condenser-evaporator arranged in the bottom region of another distillation column, which will be described below, and / or a main condenser that heat-exchangeably connects the first and second distillation columns together.

[0030] In this invention, in particular, well more than 85%, for example, about 90%, of the argon can be transferred from the second distillation column to the argon extraction system, i.e., the third distillation column, to extract the argon product. A yield of more than 85%, for example, about 90%, of the argon can also be obtained during the argon extraction process. A yield of more than 90% is also possible.

[0031] In this invention, particularly in certain embodiments, the pressure tower can be operated at a first pressure level without compressing the nitrogen products. For the compressor that compresses the second top gas or a corresponding portion thereof to form a circulating flow, a relatively simple implementation can be used, for example, employing only two compression stages. Such a compressor can also be constructed, in particular, as a so-called combined compressor, which, for example, also includes four stages that function as a main air compressor. In other words, a single, commonly driven compressor configuration can be used to compress both the compressed air and the second top gas or a corresponding portion thereof used to form the circulating flow.

[0032] Unlike the method described at the beginning of this paper for extracting nitrogen from uncompressed product, this invention eliminates the need for a separate distillation column and corresponding equipment, thus requiring significantly lower investment costs. Consequently, it achieves much higher argon production with comparable energy requirements compared to known methods.

[0033] As previously stated, in this invention, at least a portion of the first top gas is discharged from the air separation device as compressed nitrogen product at a first pressure level, i.e., without further compression.

[0034] In principle, to form a circulating flow, only the first portion of the second top gas can be heated, compressed, recooled, and fed partially or completely, or non-liquefied, into the first and / or second distillation columns, while only the second portion of the second top gas is heated and compressed to provide the compressed nitrogen product discharged from the air separation unit. This heating and compression of the second portion can, in particular, be carried out concurrently with the first portion. The main advantage of this alternative, compared to using the first top gas as the product, is that the heat exchanger used to cool the compressed stream is much smaller and requires less energy. The disadvantage is the need to compress a high-purity nitrogen product, as the purity of the second top gas in this case is very similar to that of the first top gas. Compressing a high-purity nitrogen product is often undesirable or unacceptable due to the potential presence of impurities.

[0035] In one embodiment of the invention, the circulating stream may be fed into the first distillation column, partially or entirely, in a non-liquefied state within an intermediate region. The "intermediate region" refers to the area above and below which baffles are provided. Specifically, a partition section is provided above the intermediate region, which further purifies the fed circulating stream or a corresponding portion thereof, thereby contributing to the formation of a first top gas of higher purity, i.e., a more pure compressed nitrogen product.

[0036] In another embodiment of the invention, a condenser-evaporator that heat-exchangeably connects the first distillation column and the second distillation column is used to condense the circulating stream or a portion thereof and feed it into the first distillation column.

[0037] In another embodiment of the invention, the circulating stream, or part or all of it, is condensed and fed into a second distillation column. This involves a shift in the feed point, particularly compared to the previously described variants. The liquefaction is particularly achieved using a condenser-evaporator arranged in the bottom region of the other distillation column, as described below.

[0038] In a particularly preferred embodiment of the invention, another air separation unit is used to provide a nitrogen-rich gas with an oxygen content of 0.1 to 100 ppm at an ambient pressure level of up to 1.5 bar, which is at least partially collected with a circulating stream having a very similar oxygen content. This has a particular advantage over separate purification units for the corresponding gas, as the invention allows for further purification of this gas to a certain extent in the first distillation column. This process optimization ensures that the purity of the second top gas discharged from the other air separation unit is similar to that of the nitrogen-rich gas. The implementation of this feed also increases overall throughput and reduces energy requirements. Equipment costs are also reduced because the amount of separated gas requiring compression is much smaller.

[0039] In this embodiment of the invention, the nitrogen-rich gas provided by the other air separation device can be compressed at least partially to a second pressure level first, and then combined with the circulating flow.

[0040] In a particularly preferred embodiment of the invention, as previously described, a fluid with an argon content higher than that of the second bottom liquid and the second top gas, and extracted from the second distillation column, can be fed into another, namely a fourth, distillation column. The third additive stream can be formed using the fluid extracted from this other distillation column. This other distillation column is specifically configured to produce high-purity oxygen products and operates as described above.

[0041] This other distillation column specifically has a first (upper) section and a second (lower) section, wherein a "baffle" distillation section is arranged between the first and second sections, which is specifically used to trap hydrocarbons. The first section of this other distillation column can functionally be constructed as the lowermost part of a crude argon column and correspondingly coupled to a true crude argon column, i.e., a third column. This implementation is adopted particularly for structural space reasons to reduce the overall structural height of the air separation unit. The fluid extracted from the second distillation column and used to form the third additive stream is fed into the lower region of the first section. Gas is extracted from the upper region of the first section and used to form the third additive stream. The bottom liquid formed in the third column is at least partially transferred to the upper region of the first section.

[0042] Liquid is extracted from the middle region of the first section and fed into the upper region of the second section for true pure oxygen extraction. Gas is extracted from the upper region of the second section and fed into the middle region of the first section, where pure oxygen is formed in the lower region of the second section and discharged from the air separation device. In particular, pure oxygen with an argon residual content of 5 to 500 ppb can be formed, for example, about 10 ppb.

[0043] If no other two-part column is provided, the fluid originating from the second column can be directly fed into the third column, i.e., the crude argon column.

[0044] In this invention, a condenser-evaporator is specifically used to heat the lower region of the second section of another distillation column, in which a portion of the first top gas and / or circulating stream is used as the heating fluid. Subsequently, this portion of the first top gas and / or circulating stream used as the heating fluid can be fed into the first or second distillation column, particularly in a liquefied state.

[0045] According to a particularly preferred embodiment of the invention, gas, particularly so-called impure nitrogen, can be extracted from the second distillation column below the nitrogen section, heated, turbine-expanded, and discharged from the air separator. A key advantage of the invention is that only a single cryogenic expander is required, while simultaneously enabling relatively high liquid production.

[0046] As mentioned several times, the first bottom liquid, or at least the portion thereof used to form the second additive stream, can be fed in to condense the top gas of at least the third distillation column. The third top gas can, in particular, be purified to pure argon in a pure argon column in the manner of the prior art.

[0047] The features of the air separation device also proposed according to the invention should be clearly referred to in the corresponding technical solutions. This air separation device is particularly adapted for performing the methods as previously described in the embodiments. Therefore, reference should be made explicitly to the foregoing description of the method according to the invention and its advantageous embodiments.

[0048] The invention will now be described in more detail with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. Attached Figure Description

[0049] Figures 1 to 5 Air separation devices are shown in different embodiments of the present invention.

[0050] In the figures, structurally or functionally corresponding elements are given with the same reference numerals and will not be explained again for clarity. The descriptions of devices and device components also apply to the corresponding methods and method steps.

[0051] exist Figure 1The air separation device according to an embodiment of the present invention is shown in the form of a simplified flowchart and is generally marked with 100.

[0052] In the air separation device 100, air is drawn in through a filter 2 by a main air compressor 1 and compressed to a pressure level of, for example, approximately 12.5 bar. After cooling and water deposition in an adsorption station 3 employing a known structure, residual water and carbon dioxide are removed from the compressed air. The structure of the relevant components is described in the technical reference at the beginning of this document.

[0053] The resulting compressed gas flow a passes through the main heat exchanger 4 from the hot end to the cold end and is fed as an additive flow (also referred to as the "first additive flow" above and below) into the pressure column 11 ("first distillation column") of the distillation column system 10. In the example shown, the distillation column system 10, in addition to the pressure column 11, also includes a low-pressure column 12 ("second distillation column"), a crude argon column 13 ("third distillation column"), and a pure oxygen column 14 ("fourth distillation column") and a pure argon column 15 ("fifth distillation column") with an upper section 14a ("first section") and a lower section 14b ("second section"). The pressure column 11 is heat-exchangeably connected to the low-pressure column 12 via a main condenser 16, which can be constructed in particular as a multi-layer bath evaporator, and a bottom evaporator 17 is arranged in the bottom layer of the lower section 14b of the pure oxygen column 14. In the example shown, the distillation column system 10 is also equipped with a subcooled countercurrent heat exchanger 18.

[0054] A top gas (“first top gas”) is formed at the top of pressure tower 11. In the illustrated example, a portion of this top gas is guided as mass stream b through the main condenser 16, and another portion is guided as mass stream c through the bottom evaporator 17. A portion of the resulting condensate is fed back to pressure tower 11 as reflux. Other condensate may be guided as a liquid nitrogen stream through subcooled countercurrent heat exchanger 18 and provided, for example, as a corresponding product. Unlike the illustrated configuration, mass stream c may also be fed into pressure tower 11 independently of mass stream b, or subcooled independently in subcooled countercurrent heat exchanger 18 and fed into low-pressure tower 12. Another portion of the top gas from pressure tower 11 is used to form mass stream d, which is heated in the main heat exchanger 4 and discharged as a product from air separation unit 100 with, for example, an oxygen content of about 10 ppc and a pressure of, for example, about 11.8 bar.

[0055] A bottom liquid (“first bottom liquid”) is formed in the bottom layer of pressure column 11 and discharged therefrom as mass stream e. Mass stream e is first directed through subcooled countercurrent heat exchanger 18 and then used in a known manner to cool the unmarked top condensers of crude argon column 13 and pure argon column 15. Evaporated and unevaporated components are fed into low-pressure column 12 as mass stream f (including the “second additive stream”). Starting from the middle region of pressure column 11, a fluid with a lower nitrogen content is extracted from pressure column 11 as top gas, directed through subcooled countercurrent heat exchanger 18, and subsequently fed into low-pressure column 12.

[0056] A bottom liquid (“second bottom liquid”) is formed in the low-pressure tower 12, which is discharged from it in the form of material stream h, pressurized in pump 5, heated in the main heat exchanger 4, and discharged as an internally compressed oxygen product. Above the bottom, gas is discharged from the low-pressure tower 12 in the form of material stream i, which is combined with material stream k, which will be described below, to form a combined stream i with an oxygen content of, for example, about 90%. This combined stream is partially heated in the main heat exchanger 4, expanded in the generator turbine 6, reheated in the main heat exchanger 4, and used, for example, as a regeneration gas in the adsorption station 3.

[0057] A gaseous compressed nitrogen stream (“second top gas”) is discharged from the top of the low-pressure tower 12 as a mass stream n. This compressed nitrogen stream is present, for example, at a pressure level of about 3.7 bar and has an oxygen content of, for example, about 100 ppb. This compressed nitrogen stream (minus the aforementioned mass stream k) is used to form a circulating stream, which is first guided through a subcooled countercurrent heat exchanger 18, then heated in the main heat exchanger 4, compressed in the compressor 7, cooled again in the main heat exchanger 4, and fed into the pressure tower 11 within the aforementioned intermediate region.

[0058] Argon-rich gas in the form of mass stream o is extracted from low-pressure tower 11 and fed into the upper part 14a of pure oxygen tower 14. As previously mentioned, this upper part 14a in the illustrated example is functionally part of crude argon tower 13. Therefore, refer to the foregoing explanation. In another construction scheme with a corresponding modification to the crude argon tower, mass stream o can also be fed directly into the crude argon tower. The bottom liquid from the lower region of upper part 14a is returned to low-pressure tower 11 in the form of mass stream p. The top gas from upper part 14a of pure oxygen tower 14 is used to feed to crude argon tower 13, and the bottom liquid of crude argon tower is pumped back to upper part 14a of pure oxygen tower 14 by means of pump 8. Upper part 14a and lower part 14b of pure oxygen tower 14 are connected by mass streams s and t. Mass stream s is discharged in liquid form from the middle region of upper part 14a and applied to lower part 14b. Mass stream t is discharged in gaseous form at the top of lower part 14b and fed into the middle region of upper part 14a. A high-purity oxygen stream with a residual argon content of, for example, approximately 10 ppb, is discharged from the bottom layer of the lower part 14b of the pure oxygen tower. Here, pressurized evaporation can also be used, for example, and internally compressed products can be provided accordingly.

[0059] The operation of the crude argon column 13 and the pure argon column 15 is largely the same as in the prior art, and therefore will not be described in detail. Pure argon is discharged from the pure argon column 15, which can be partially stored or temporarily stored in the storage tank T, and partially provided as an internally compressed product with an oxygen content of, for example, about 1 ppm, by means of the pump 8.

[0060] exist Figure 2 An air separation device according to another embodiment of the invention is shown in simplified flowchart form and is generally labeled with 200.

[0061] and Figure 1 Unlike the air separation device 100 shown, here no mass stream d is formed; instead, the top gas from the low-pressure tower 12 is used to provide the nitrogen product. The mass stream, denoted by w, is discharged from the low-pressure tower 12. After the mass stream k is branched as previously described, heated in the main heat exchanger 4, and compressed in the compressor 7, a portion is provided as a product in the form of mass stream x, while the other portion is recooled in the form of mass stream n and merged with the top gas discharged from the pressure tower 11, and processed in the same manner as the latter. See previously discussed... Figure 1 The relevant explanation of "first top gas".

[0062] In other words, a corresponding portion of the material stream n, such as the top gas discharged from the first distillation column, is fed into the pressure column 11 and the low-pressure column 12. In the embodiment of the invention shown here, the material stream n is fed to the top gas of the pressure column 11 before condensation, thereby using the material stream n to form material streams b and c. As from the intermediate region (e.g. Figure 1An alternative starting from the intermediate region of the air separation device 100 shown is to form a material flow g, denoted by g for simplicity, from the corresponding condensate.

[0063] exist Figure 3 An air separation device according to another embodiment of the invention is shown in simplified flowchart form and is generally labeled with 300.

[0064] Figure 3 The air separation device 300 shown is Figure 2 The variant of the air separation device 200 shown, wherein the material flow n is similar to Figure 1 The air separation device 100 shown is fed into the intermediate region of the pressure tower 11. However, in this embodiment, it is used in conjunction with... Figure 2 The air separation device 200 shown forms a material flow g in the same manner.

[0065] exist Figure 4 An air separation device according to another embodiment of the invention is shown in simplified flowchart form and is generally labeled with 400.

[0066] In the example shown here, Figure 4 The air separation device 400 shown is Figure 1 Variations of the air separation device 100 shown; will be described below and in Figure 4 The measures shown can also be applied to all other embodiments of the present invention.

[0067] Figure 4 The air separation device 400 shown corresponds to another air separation device 1000 used to provide a substance stream z, which, for example, exists at a pressure level of about 1.1 bar and has an oxygen content of about 1 ppm, with the remainder being nitrogen. Substance stream z can be extracted, for example, from a low-pressure column (not shown) of the other air separation device 1000. This substance stream can be brought to the pressure level of substance stream n in a corresponding compressor 1001. By feeding substance stream z to substance stream n, it is unnecessary to purify substance stream z, for example, to an oxygen content of about 1 ppb, because substance stream z can be used to provide a substance stream d with a correspondingly lower oxygen content.

[0068] exist Figure 5 An air separation device according to another embodiment of the invention is shown in simplified flowchart form and is generally labeled with 500.

[0069] Figure 5The air separation device 500 shown is a variant of the air separation device previously shown, wherein the material flow n is cooled in the main heat exchanger 4 and then merges with the material flow c to form the material flow y here. This material flow is first guided through the condenser evaporator 17, then through the subcooled countercurrent heat exchanger 18, and fed in a liquefied state at the top of the second distillation column 12.

Claims

1. A method for cryogenic separation of air using an air separation apparatus (100-400) with a distillation column system (10), said distillation column system having a first distillation column (11), a second distillation column (12) and a third distillation column (13), wherein - The first distillation column (11) is operated at a first pressure level, a first additive stream formed using cooled compressed air is fed into the first distillation column (11), and a first bottom liquid rich in oxygen and argon and a first top gas rich in nitrogen are formed in the first distillation column (11) compared to the first additive stream. - The second distillation column (12) is operated at a second pressure level, and a second additive stream formed using at least a portion of the first bottom liquid is fed into the second distillation column (12), and an oxygen-rich second bottom liquid and a nitrogen-rich second top gas are formed in the second distillation column (12). - A third additive stream, formed using a certain fluid, is fed into the third distillation column (13), the fluid having a higher argon content than the second bottom liquid and the second top gas and being extracted from the second distillation column (12), and forming a third top gas in the third distillation column (13) that is richer in argon than the third additive stream. - The first pressure level at the top of the first distillation column (11) is 9 to 14.5 bar, and the second pressure level at the top of the second distillation column (12) is 2 to 5 bar. - Using the second top gas or a portion thereof to form a circulating flow, the top gas or the circulating flow is heated, compressed, recooled, and fed entirely into the second distillation column (12) after partial or complete liquefaction, wherein the circulating flow is partially or completely liquefied by using a condenser evaporator (17) located in the bottom region of another distillation column after cooling, and then fed entirely into the second distillation column (12).

2. The method of claim 1, wherein the other distillation column does not have a top condenser.

3. The method of claim 1, wherein a first portion of the second top gas is used to form the circulating flow, and wherein only a second portion of the second top gas is heated, compressed, and used to provide compressed nitrogen products discharged from the air separation device (100-400).

4. The method according to any one of claims 1-3, wherein another air separation device (1000) is used, wherein the other air separation device is used to provide a nitrogen-rich gas with an oxygen content of 0.1 to 100 ppm at a pressure level of up to 1.5 bar ambient pressure and to collect it partially or entirely with the circulating flow.

5. The method of claim 4, wherein the nitrogen-rich gas provided by means of the other air separation device (1000) is first partially or entirely compressed to the second pressure level in a manner separate from the circulating flow, and then merged with the circulating flow.

6. The method according to any one of claims 1-3, wherein a portion of the first top gas is discharged from the air separation device (100-400) as compressed nitrogen product at the first pressure level.

7. The method according to any one of claims 1-3, wherein the other distillation column (14) has a first section (14a) and a second section (14b), wherein - The fluid extracted from the second distillation column (12) and used to form the third additive stream is fed into the lower region of the first section (14a). - Gas is extracted from the upper region of the first portion (14a) and used to form the third additive stream. - A bottom liquid is formed in the third distillation column (13) and at least partially moved to the upper region of the first section (14a). - The liquid is extracted from the middle region of the first part (14a) and fed into the upper region of the second part (14b). - Gas is extracted from the upper region of the second part (14b) and fed into the middle region of the first part (14a), and - Pure oxygen is formed in the lower region of the second part (14b) and discharged from the air separation device (100-400).

8. The method according to any one of claims 1-3, wherein a condenser evaporator (17) is used to heat the lower region of the second part (14b), wherein a portion of the circulating flow is used as a heating fluid in the condenser evaporator.

9. The method of claim 8, wherein the portion of the circulating flow used as a heating fluid is subsequently fed into the second distillation column (12).

10. The method according to any one of claims 1-3, wherein the gas is extracted from the second distillation column (12), heated, turbine-expanded, and discharged from the air separation device (100-400).

11. The method according to any one of claims 1-3, wherein the first bottom liquid or at least a portion thereof used to form the second additive stream is fed in to condense the top gas of at least the third distillation column (13).

12. The method according to any one of claims 1-3, wherein the third top gas is purified into pure oxygen in a pure argon tower (15).

13. An air separation device (100-400) having a distillation column system (10), said distillation column system having a first distillation column (11), a second distillation column (12) and a third distillation column (13), and said air separation device being configured such that, - The first distillation column (11) is operated at a first pressure level, a first additive stream formed using cooled compressed air is fed into the first distillation column (11), and a first bottom liquid rich in oxygen and argon and a first top gas rich in nitrogen are formed in the first distillation column (11) compared to the first additive stream. - The second distillation column (12) is operated at a second pressure level, and a second additive stream formed using at least a portion of the first bottom liquid is fed into the second distillation column (12), and an oxygen-rich second bottom liquid and a nitrogen-rich second top gas are formed in the second distillation column (12). - A third additive stream, formed using a certain fluid, is fed into the third distillation column (13), the fluid having a higher argon content than the second bottom liquid and the second top gas and being extracted from the second distillation column (12), and forming a third top gas in the third distillation column (13) that is richer in argon than the third additive stream. wherein The air separation equipment (100-400) is configured to operate in such a way that... - The first pressure level at the top of the first distillation column (11) is 9 to 14.5 bar, and the second pressure level at the top of the second distillation column (12) is 2 to 5 bar. - Using the second top gas or a portion thereof to form a circulating flow, the top gas or the circulating flow is heated, compressed, recooled, and partially or completely liquefied before being partially or completely fed into the second distillation column (12), wherein the circulating flow is partially or completely liquefied by using a condenser evaporator (17) located in the bottom region of another distillation column after cooling, and then completely fed into the second distillation column (12).

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