Method for producing air product at low temperature and air separation system

Abstract

The invention relates to a method for the low-temperature production of an air product, in which an air separation system (100) is used, which has a first rectification device (110), a second rectification device (120) and a compressor device (130), the first rectification device (110) and the second rectification device (120) each having a rectification column operating at a pressure level above 2 bar, the method comprises a combined operating mode in which raw material air is subjected to raw material air compression by using the compressor device (130) and then fed into the first rectification device (110) and the second rectification device (120) in proportion, in which high-purity nitrogen is provided by using the first rectification device (110) and the second rectification device (120), and in which the high-purity nitrogen is fed into the first rectification device (110) and the second rectification device (120). And wherein the high-purity nitrogen or part thereof provided by using the first rectification device (110) is subjected to high-purity nitrogen compression by means of the compressor device (130). The compressor arrangement (130) is provided with several first compressor units (131) and a second compressor unit (132), each of the first compressor units (131) having a first compressor stage (131a) and a second compressor stage (131b), in each of the first compressor units (131), the first compressor stage (131a) and the second compressor stage (131b) are mechanically coupled to each other, and in the combined operating mode the first compressor stages (131a) of the first compressor units (131) and the second compressor unit (132) are used for the raw material air compression and the second compressor stages (131b) of the first compressor units (131) are used for the high-purity nitrogen compression. The invention also relates to a corresponding air separation system (100).

Description

[0001] This invention relates to a method for producing air products at low temperatures and an air separation system. Background Technology

[0002] The preparation of liquid or gaseous air products by cryogenic separation of air in an air separation device is known, for example, as described in H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH, 2006, particularly in Section 2.2.5, “Cryogenic Rectification”. For the technical background of the present invention, refer to the corresponding literature.

[0003] A method for producing nitrogen by cryogenic decomposition of air is known from US 5,582,034 A, which uses a single distillation column. Liquids with varying nitrogen and oxygen contents are extracted from the bottom region of this distillation column. These liquids are used in a condenser evaporator to condense the nitrogen-rich top gas of the distillation column, thus providing reflux to the column. After the nitrogen-rich and oxygen-lean liquids evaporate, the resulting gas, or a portion thereof, is recompressed, cooled, and fed back into the distillation column. This gas is also referred to as the "residual gas recirculation stream." Similarly, after the corresponding evaporation, the nitrogen-lean and oxygen-rich liquids can be depressurized in a vacuum turbine, which drives a booster to recompress the residual gas recirculation stream. The remaining top gas from the distillation column is discharged as nitrogen product from an air separation unit.

[0004] Different methods of this kind are also described in WO 2021 / 180362 A1, and the applicant also refers to this type of method as the SPECTRA method. In this document, the explanation on page 2 of that document is explicitly cited, and the explanation there is further elaborated. Figure 1 The description is as follows. WO 2020 / 083528 A1 describes several design schemes in which, in addition to the initial single distillation column, a pure oxygen column and / or an argon column are additionally used to obtain nitrogen. Furthermore, a two-column method for simultaneously obtaining pressurized nitrogen and argon is known, for example, from WO 2023 / 030679A1.

[0005] The demand for air products from users such as chip manufacturers can fluctuate, specifically in terms of both quantity and type. For example, argon may be required only at specific times, or the required amount of pure nitrogen may vary. The required ratio of, for example, argon and / or oxygen to nitrogen in each case can lead to situations where, in terms of construction costs, it is advantageous to employ different types of equipment as described above. For this purpose, an air separation system with several distillation units can also be used, which operate together only at specific times and individually at other times, providing the corresponding air products.

[0006] However, there is still a need to improve such methods and air separation systems. Summary of the Invention

[0007] Against this backdrop, a method for producing air products at low temperatures and an air separation system, featuring the characteristics of corresponding independent patent claims, are proposed. The design schemes are the subject of the dependent claims and the following description.

[0008] The apparatus used in the air separation device is described in the cited technical documents, such as in Section 2.2.5.6 “Apparatus” of the Häring. Therefore, unless the definitions below deviate from those, the terminology used in the context of this application explicitly refers to the cited technical documents.

[0009] A method for producing air products at low temperatures is proposed, wherein an air separation system is used, the air separation system comprising: a first distillation unit having a dual-tower unit (111); a second distillation unit having a nitrogen tower (121); and a compressor unit, wherein the first and second distillation units each have a distillation tower operating at pressure levels above 2 bar, particularly above 3 bar, 4 bar, or 5 bar, particularly up to 10 bar, 12 bar, or 15 bar. The first and second distillation units are particularly decoupled to such an extent that there is no fluid exchange between them, i.e., no fluid is transferred from the first distillation unit to the second distillation unit or vice versa, or at most transferred to a very low extent, for example, less than 10% of the total amount of fluid processed in each of the first and second distillation units.

[0010] Two “distillation units” represent separate trains, meaning they can operate independently of each other in principle in their cold sections, and specifically each has its own cold box or set of cold boxes, which are separate from the other distillation unit. The air inlets of the cold boxes of the two distillation units are, in particular, separate. For example, a nitrogen column used in a second distillation unit consists of a single column with a top condenser. The second distillation unit may (but not necessarily) have one or more other columns, such as a pure oxygen column. The dual-column unit consists of a high-pressure column, a low-pressure column, and a condenser-evaporator (main condenser), with the two columns exchanging heat via the condenser-evaporator. The first distillation unit may (but not necessarily) have one or more other columns, particularly for obtaining one or more rare gases, such as argon.

[0011] The provided method includes a combined operating mode in which feed air is compressed using a compressor and then proportionally fed into a first distillation unit and a second distillation unit. The first distillation unit may be specifically equipped with a first main heat exchanger, and the second distillation unit may be specifically equipped with a second main heat exchanger, wherein the air supplied to the first distillation unit is proportionally directed through the first main heat exchanger, and the air supplied to the second distillation unit is proportionally directed separately through the second main heat exchanger; that is, the air supplied to the first distillation unit is not directed through the second main heat exchanger, and vice versa. Here, a small amount, for example less than 10%, of feed air can also be treated differently.

[0012] Furthermore, it is configured to provide high-purity nitrogen in combined operation mode using a first distillation unit and a second distillation unit, and to subject the first high-purity nitrogen product provided by the first distillation unit to high-purity nitrogen compression using a compressor unit in combined operation mode. The second high-purity nitrogen product from the second distillation unit is not introduced into the compressor unit.

[0013] Of course, in addition to the first high-purity nitrogen product, a further high-purity nitrogen stream can be obtained from the first distillation unit, for example, extracted from the twin towers together with the first high-pressure nitrogen product, but not fed into the compressor unit.

[0014] Furthermore, in this invention, at least a portion of the high-purity nitrogen compressed in the second compressor stage of the first compressor unit is returned to the first distillation unit as a circulating nitrogen stream. The remainder is typically obtained as the final product.

[0015] In this document, "high-purity nitrogen" is specifically understood as gaseous nitrogen with an extremely low oxygen content, which can be in the single-digit, double-digit, or triple-digit ppb (parts per billion), i.e., particularly below 100, 50, 10, 5, 1, 0.5, or 0.1 ppb. Argon content can generally be higher, specifically, for example, in the single-digit, double-digit, or triple-digit ppm range or lower, i.e., particularly below 100, 50, 10, 5, 1, 0.5, or 0.1 ppb. High-purity nitrogen compression specifically compresses pressures in the range of 2 to 5 bar to pressures in the range of 8 to 15 bar. Feed air compression specifically compresses atmospheric pressure to pressures in the range of 8 to 15 bar. High-purity nitrogen from the secondary distillation unit can be supplied as a high-purity nitrogen product, particularly uncompressed.

[0016] The compressor unit provided in this case has several first compressor units and one second compressor unit, wherein each of the first compressor units has a first compressor stage and a second compressor stage, wherein the first compressor stage and the second compressor stage are mechanically coupled to each other in each of the first compressor units, and in a combined operation mode the first compressor stage and the second compressor unit of the first compressor unit are used for raw material air compression and the second compressor stage of the first compressor unit is used for high-purity nitrogen compression.

[0017] As understood herein, a "compressor" or "compressor unit" is a device adapted to compress at least one gaseous flow from at least one inlet pressure when fed into the compressor to a final pressure when extracted from the compressor. The compressor is typically formed as a structural unit; however, this structural unit may have several "compressor stages" (i.e., axial or radial compressor stages) in the form of pistons, screws, and / or impellers or turbines. This also applies particularly to the "main (air) compressor" of an air separation device, characterized in that it compresses all or most of the air supplied to the air separation device, i.e., the entire feed air flow. In particular, the corresponding compressor stages are driven by means of a common drive, for example, via a common shaft. The term "compressor unit" will be used hereinafter, where some compressor units may have compressor stages for different compression purposes, and these compressor stages are mechanically coupled to each other, for example, via a common shaft.

[0018] This invention, in its various design embodiments, particularly relates to the possibility of improving construction costs for supplying feed air to different distillation units while simultaneously compressing high-purity nitrogen products. The following explanation is based on a system with two distillation units, one designed with a twin-tower configuration and an argon extraction system, and the other designed as a SPECTRA unit without an argon extraction system. The method or corresponding system presented herein is extensible, particularly extended to further SPECTRA units for nitrogen extraction.

[0019] SPECTRA units with argon acquisition are conventionally equipped with a four-stage main air compressor and a two-stage nitrogen compressor in a combined configuration (to reduce construction costs). SPECTRA units without argon acquisition are conventionally equipped with a three- or four-stage main air compressor.

[0020] This invention was specifically developed for a configuration requiring N+2 air compressor units. Specifically, this configuration should enable a 50% reduction in the total gas supply, resulting in 50% operation of each unit. Furthermore, it should be feasible for each of these units to operate while other units are under maintenance / shutdown. Therefore, conventional solutions might result in the use of N+2 machines, i.e., 2+2 SPECTRA units with argon acquisition and 2+2 SPECTRA units without argon acquisition, thus a total of eight machines. The design of this invention provides a solution that minimizes the number of installed machines while still ensuring overall high efficiency and flexible operation.

[0021] To obtain argon, an air separation unit with so-called primary argon towers and pure argon towers can be used. (See Häring's book above.) Figure 2 .3A shows an example and is described from page 26 in the section “Rectification in the Low-pressure, Crude and Pure Argon Column” and from page 29 in the section “Cryogenic Production of Pure Argon”. In a conventional primary argon column, primary argon is obtained and processed into pure argon in a downstream pure argon column. In principle, the pure argon column can be omitted for argon acquisition if the distillation column involved is adjusted accordingly. Pure argon can be extracted, for example, from the primary argon column or a similar distillation column at a lower position than the fluid conventionally transferred to the pure argon column, where the portion arranged above the extraction point is used for nitrogen separation. The terms “argon acquisition column” and “argon acquisition system” are also used above and below.

[0022] This invention, through the ingenious interconnection of air compression and high-purity nitrogen compression, and the intelligent definition of compression requirements, enables the reduction of construction and operating costs while adhering to flexibility and product requirements. At least one compressor in the compressor, i.e., the second compressor unit, is not a combined compressor and is therefore adapted for use only in compressed air.

[0023] Specifically, one, several, or all of the first compressor units may have two to four first compressor stages and / or two to four second compressor stages. In this case, in one, several, or all of the first compressor stages, one, several, or all of the first compressor stages may be mechanically coupled to one, several, or all of the second compressor stages. Paired coupling of one first compressor stage and one second compressor stage may also be provided. Therefore, the above explanation regarding "first compressor stage" and "second compressor stage" also applies to this type of design.

[0024] Similarly, in the design of the present invention, the compressor device may have two or more second compressor units, one, several or all of which may operate as described above.

[0025] The first compressor stages of different first compressor units can be decoupled from each other, and the second compressor stages of different first compressor units can also be decoupled from each other.

[0026] Specifically, the first distillation unit has a dual-tower unit comprising a pressure tower, a low-pressure tower, and an argon extraction tower, wherein high-purity nitrogen supplied by the first distillation unit is extracted from the dual-tower unit, particularly at the top of the pressure tower and / or the low-pressure tower, and wherein argon product is extracted from the argon extraction tower. The pressure tower and the low-pressure tower can be housed in a common enclosure, or they can be provided separately. The low-pressure tower can be designed as a single-piece or two-piece unit. The operating pressure of the pressure tower can be, in particular, from 9 bar to 14.5 bar.

[0027] The argon column can also be designed as a one-piece or two-piece unit. The first distillation unit may include one or more distillation columns for the preparation of ultra-high purity oxygen and / or for the preparation of krypton / xenon feedstock mixtures and / or for the preparation of helium / neon feedstock mixtures.

[0028] The second distillation unit specifically features a nitrogen column from which high-purity nitrogen, supplied by the second distillation unit, is extracted, and it does not have an argon extraction column. It can specifically be a distillation column, as known in the SPECTRA system. In particular, the second distillation unit can have exactly one nitrogen column, specifically as a single column, or there can be one or more nitrogen columns together with one or more further columns, particularly for the production of ultra-high purity oxygen, as explained at the beginning.

[0029] The first distillation unit or its twin-tower unit operates specifically as known counterparts. Liquid is specifically extracted from the nitrogen column of the second distillation unit, depressurized, evaporated relative to the condensate top gas of the second nitrogen column, and at least partially recompressed and fed back into the nitrogen column. The second nitrogen column here is specifically those types of distillation columns described in references to US 5,582,034 A, WO2021 / 180362 A1, and WO 2020 / 083528 A1, or the SPECTRA method, etc. The aforementioned recompression can be specifically carried out here by using a turbocharger coupled to a depressurization turbine.

[0030] A "pressure reducing turbine" or "pressure reducer" can be connected via a common shaft to other pressure reducing turbines or energy converters, such as hydraulic brakes, generators, or compressors, for reducing the pressure of a gas flow or at least a portion of a liquid flow. In this invention, in particular, the pressure reducing turbine can be designed as a turbine expander. If the compressor is driven by one or more pressure reducing turbines but without externally supplied energy, such as energy supplied by an electric motor, the term "turbine-driven compressor" or alternatively "turbocharger" is used.

[0031] Liquids with varying nitrogen and oxygen contents can be specifically extracted from the bottom region of the nitrogen column (in the second distillation unit), with the liquid having a higher nitrogen content being specifically the liquid already mentioned. These liquids can be used in a condenser evaporator to condense the nitrogen-rich top gas of the distillation column, thus providing reflux to the nitrogen column. After the nitrogen-rich and oxygen-lean liquids evaporate, the resulting gas, or a portion thereof, can be recompressed, cooled, and fed back into the nitrogen column. This gas is also referred to as the "residual gas recirculation stream." Similarly, after the corresponding evaporation, the nitrogen-lean and oxygen-rich liquids can be depressurized in a vacuum turbine, which drives a booster to recompress the residual gas recirculation stream. Other top gases from the nitrogen column can be exported as nitrogen products from an air separation unit.

[0032] In one embodiment of the invention, as previously described, each first compressor unit may have up to four first compressor stages and up to two second compressor stages. The corresponding distribution of the compressor stages or their intended use for a specific purpose can be achieved, in particular, by adjusting the proportions of nitrogen and other air components in the atmosphere.

[0033] The method specifically includes a first standalone operating mode in which the feed air is compressed and fed only into the first distillation unit, and in which at least a portion of the first compressor unit operates while the second compressor unit does not operate. In the corresponding design, the SPECTRA unit, which does not yield argon, can therefore be shut down, for example, to allow for maintenance or to reduce the total amount of nitrogen supplied.

[0034] Specifically, the design also includes a second, separate operating mode in which the feed air is compressed and fed only into the second distillation unit, and in which the second compressor unit operates while the first compressor unit does not. In this way, it is possible to specifically switch from combined nitrogen and argon production to pure nitrogen production with a reduced nitrogen content.

[0035] Combined operating modes and / or first individual operating modes may specifically include a design operating mode in which all first compressor units operate, and one or more special operating modes in which at least one of the first compressor units does not operate. The corresponding design schemes make it possible to adjust to accommodate different product and operating requirements.

[0036] A special operating mode, or at least one of several special operating modes, can be specifically designated as a maintenance operating mode, in which the amount of compressed feed air is the same as in the design operating mode. In this design, the throughput of the compressor unit that continues to operate actively can be increased.

[0037] However, special operating modes, or at least one of several special operating modes, can also be used to specifically reduce the load, where the amount of compressed feed air is lower than in the design operating mode. In such a design, the overall throughput is reduced.

[0038] In addition, one of the special operating modes, or one of the multiple special operating modes, can be a cyclic reduction mode.

[0039] -In the designed operating mode, the first amount of nitrogen is returned to the first distillation unit (110) as a circulating nitrogen stream, and

[0040] - In the cyclic reduction mode, a second nitrogen amount less than the first nitrogen amount is returned to the first distillation unit (110) as a cyclic nitrogen stream.

[0041] Within the framework of this invention, various special operating modes can be combined.

[0042] Other operating modes can be configured, such as a maintenance mode, in which the first and second distillation units are operating and two or three compressor stages of the first or second compressor stage are operating. Here, the second compressor stage can operate in an internal loop. Furthermore, it is possible for only the second distillation unit to be operating and only a combined compressor with the first and second compressor stages to be operating, wherein the second compressor stage operates in an internal loop (i.e., in "idle" mode). The corresponding provisions also apply to several first and second compressor stages, provided they are included in the first compressor unit in one design.

[0043] In the method of the present invention, it is advantageous that the first distillation apparatus is provided with a first pre-purification unit and a first main heat exchanger unit, and the second distillation apparatus is provided with a second pre-purification unit and a second main heat exchanger unit.

[0044] Two pre-purification units and two main heat exchanger units of known types can be used. The first distillation unit can be allocated one of the two pre-purification units and one of the two main heat exchanger units, and the second distillation unit can be allocated the other of the two pre-purification units and the other of the two main heat exchanger units. Therefore, the term "distillation unit" as used herein should be understood as a corresponding combination of units.

[0045] The air separation system proposed in this paper for the production of air products at low temperatures includes a first distillation unit, a second distillation unit, and a compressor unit. Each of the first and second distillation units has a distillation column adapted for operation at temperatures above 2 bar. The air separation system is adapted to perform a combined operation mode in which the feed air is compressed by the compressor unit and then fed into the first and second distillation units in proportion. High-purity nitrogen is provided by the first and second distillation units, and the high-purity nitrogen or a portion thereof provided by the first distillation unit is compressed by the compressor unit.

[0046] The proposed compressor unit includes several first compressor units and one second compressor unit, wherein each of the first compressor units has a first compressor stage and a second compressor stage, and in each of the first compressor units, the first compressor stage and the second compressor stage are mechanically coupled to each other. The air separation system is adapted to use the first compressor stage and the second compressor unit of the first compressor unit for feed air compression and the second compressor stage of the first compressor unit for high-purity nitrogen compression in a combined operation mode.

[0047] For further features and advantages of the corresponding air separation system and its design, please refer specifically to the above description of the method and its design proposed according to the present invention, as these descriptions are equally applicable here.

[0048] The corresponding content also applies to air separation systems, which are adapted according to one design of the present invention to perform the methods described according to any design of the present invention. Attached Figure Description

[0049] Embodiments of the present invention will be described below by way of example only, in conjunction with the accompanying drawings and an explanation of the technical background.

[0050] Figure 1 A simplified schematic diagram illustrates an air separation system according to one embodiment of the present invention.

[0051] Figure 2The operating mode of an air separation system according to one embodiment of the present invention is shown. Detailed Implementation

[0052] The following embodiments are provided only to help the reader understand the claimed and foregoing features. They are merely representative examples and should not be considered as an exhaustive representation and / or limitation of the features of the invention. It should be understood that the advantages, embodiments, examples, functions, features, structures and / or other aspects described above and below should not be considered as limitations on the scope of the invention as defined in the claims or on the equivalents of the claims, and other embodiments and modifications may be used as long as they do not depart from the scope of the claimed invention.

[0053] Different embodiments of the invention may include, or consist of, other suitable combinations of the said elements, components, features, parts, steps, devices, etc., even if such combinations are not specifically described herein. Furthermore, this disclosure may also include other inventions that are not currently claimed but may be claimed in the future, particularly if such inventions are included within the scope of the independent claims.

[0054] Descriptions relating to apparatuses, devices, components, systems, etc., according to embodiments of the present invention are also applicable to processes, procedures, methods, etc., according to embodiments of the present invention, and vice versa. Components, method steps, etc., that are identical, have the same function, correspond in function, have the same structure, or are similar in construction, may be represented by the same reference numerals.

[0055] Figure 1 The first figure shows an air separation system according to an embodiment of the present invention.

[0056] The air separation system is designated as 100. It includes a first distillation unit 110, a second distillation unit 120, and a compressor unit 130. The first and second distillation units 110 and 120 are each shown in a cold box configuration, with the first distillation unit 110 showing a dual-tower system 111 and an argon tower 112, and the second distillation unit 120 showing a nitrogen tower 121. Additionally, main heat exchangers 116 and 126 are shown respectively for cooling the feed air. For the specific design of the aforementioned towers (systems), reference is made to the prior art mentioned at the beginning. By using the first and second distillation units 110 and 120, high-purity nitrogen is produced in each case, provided they are in operation. This high-purity nitrogen is specifically extracted from the top of the low-pressure tower (not shown separately) of the dual-tower system 111 and the nitrogen tower 121, respectively. The corresponding pure nitrogen streams are designated as 1 and 2, respectively. Similarly, the argon provided in the first distillation unit 110 is not shown separately, as are other air products, such as high-purity oxygen, where appropriate.

[0057] The compressor unit 130 here has three identically designated first compressor units 131, each shown with two compressor symbols, and a second compressor unit 132, which is also shown with compressor symbols. Each of the first compressor units 131 has several first compressor stages 131a and several second compressor stages 131b. Specific descriptions of the compressor stages are given above. In each of the first compressor units 131, the first compressor stages 131a and second compressor stages 131b are mechanically coupled, for example, via a common shaft, as shown by vertical lines in each case, or via a gear mechanism.

[0058] When in operation, the first compressor stage 131a draws in feed air in the form of feed air stream 3 via filter unit 133 in each case, as does the second compressor unit 132 or its compressor stage 132a. An aftercooler can be connected downstream of each of the compressor stages 131a and 132a. Depending on the operating mode, the corresponding compressed feed air can be combined in collection pipe 4 via valves also connected downstream (not shown separately), and then distributed via further valves (not shown separately) to the first pre-purification unit 115 and the second pre-purification unit 125, or only to one of them, and then similarly distributed to the first distillation unit 110 and the second distillation unit 120, or only to one of them. Here, water and carbon dioxide are removed from the feed air in pre-purification units 115 and 125, respectively, and the air is cooled in main heat exchangers 116 and 126, respectively. The residual gas 5 from distillation units 110 and 120, respectively, can be used for regeneration in pre-purification units 115 and 125, respectively.

[0059] A stream of high-purity nitrogen 1 from the first distillation unit 110 is fed into the distribution pipe 6, and from there via a valve (not shown separately) into the suction side of the second compressor stage 131b of the first compressor unit 131, and in each case, is in operation. A portion can be discharged from the air separation system 100 as product stream 7. After compression in the second compressor stage 131b, the high-purity nitrogen can be fed into the collection pipe 8, and from there it is guided back to the first distillation unit 110 as circulating nitrogen and discharged from the air separation system 100 as product stream 9, respectively.

[0060] As previously described, in a combined operating mode, at least one first compressor stage 131a and the second compressor unit 132 of the first compressor unit 131 can be used for feed air compression, and at least one second compressor stage 131b of the first compressor unit 131 can be used for high-purity nitrogen compression. In a first separate operating mode, the feed air is compressed and fed only into the first distillation unit 110, and in this first separate operating mode, at least a portion of the first compressor unit 131 operates while the second compressor unit 132 does not operate. In a second separate operating mode, the feed air is compressed and fed only into the second distillation unit 120, and in this second separate operating mode, the second compressor unit 132 operates while the first compressor unit 131 does not operate. The combined operating mode and / or the first separate operating mode may include a design operating mode in which all first compressor units operate, and one or more special operating modes in which at least one of the first compressor units does not operate.

[0061] The following reference Figure 2 The corresponding operating modes are explained in eleven views, showing a first compressor unit 131 with first and second compressor stages 131a, 131b and a second compressor unit 132 with compressor stage 132a. Compressor units 131 and 132 with compressor stages 131a, 131b and 132a are shown only in view A. Compressor units not in operation are indicated by an X. The numbers within the symbols representing compressor stages 131a, 131b and 132a indicate the corresponding throughput, for example, in thousands of standard cubic meters per hour. These are merely illustrative examples and do not limit the scope of the invention.

[0062] View A shows a combined and designed operating mode in which all first compressor units 131 and second compressor units 132 are in operation. In this configuration, theoretically, 240,000 standard cubic meters of feed air and 150,000 standard cubic meters of high-purity nitrogen per hour can be compressed.

[0063] View B shows the first standalone operating mode under the design operating conditions, in which the second compressor unit 132 is not in operation. Here, a total feed air volume of 120 standard cubic meters per hour is compressed equally by means of the three first compressor units 131 or their first compressor stages 131a. The same applies to a total of 99,000 (or 100,000) standard cubic meters per hour of high-purity nitrogen, which is compressed using the second compressor stage 131b.

[0064] View C also shows a first standalone operating mode where the second compressor unit 132 is not in operation. However, one of the first compressor units 131 is also not in operation here, thus creating a special operating mode. Here, the total feed air volume of 120,000 standard cubic meters per hour is compressed equally by means of both first compressor units 131 or their first compressor stages 131a. The same applies to a total of 100,000 standard cubic meters per hour of high-purity nitrogen, which is compressed using the second compressor stage 131b.

[0065] Views B and C here specifically correspond to the operating conditions designed to provide the maximum fluid volume.

[0066] The operating modes shown in views D and E are essentially the same as those shown in views B and C, but are set to cover the maximum liquid oxygen content.

[0067] The operating modes shown in views D and E are essentially the same as those shown in views B and C, except that the throughput is reduced. This first separate operation and special operating mode can, for example, be used to cover the maximum gas volume.

[0068] If there is a significant reduction in demand for the corresponding air product at certain times, a first standalone operation and a special operation mode can be set according to view H. In this first standalone operation and special operation mode, only the first compressor unit 131 is operating and provides a correspondingly low quantity.

[0069] Views I and K show the second operating mode, in which only the second compressor unit 132 is in operation, and here additionally has a different throughput. View L again shows the combined operating mode.

Claims

1. A method for cryogenic production of air products, in which an air separation system (100) is used, the air separation system having: - a first rectification device (110) having a double column unit (111), - a second rectification device (120) having a nitrogen column (121), and - a compressor device (130), wherein - the first rectification device (110) and the second rectification device (120) each have a rectification column operating at a pressure level above 2 bar, and - the method comprises a combined operating mode, in which - a feed air is subjected to a feed air compression by using the compressor device (130) and then proportionally fed into the first rectification device (110) and the second rectification device (120), in which - a first high-purity nitrogen product (1 specification) is provided by using the first rectification device (110), in particular by extracting the first high-purity nitrogen product from the double column unit (111), and a second high-purity nitrogen product (2 specification) is provided by using the second rectification device (120), in particular by extracting the second high-purity nitrogen product from the nitrogen column (121), and wherein - the first high-purity nitrogen product (1) is subjected to a high-purity nitrogen compression by using the compressor device (130), and - and the second high-purity nitrogen product (2) is not conducted into the compressor device (130), - the compressor device (130) has several first compressor units (131) and one second compressor unit (132), wherein - each of the first compressor units (131) has a first compressor stage (131a) and a second compressor stage (131b), - in the first compressor units (131) the first compressor stage (131a) and the second compressor stage (131b) are mechanically coupled to each other, and - in the combined operating mode - the first compressor stage (131a) of the first compressor units (131) and the second compressor unit (132) are used for the feed air compression and - the second compressor stage (131b) of the first compressor units (131) are used for the high-purity nitrogen compression - at least a part of the high-purity nitrogen compressed in the second compressor stage (131b) of the first compressor units (131) is conducted back to the first rectification device (110) as a recycle nitrogen stream.

2. The method according to claim 1, in which one, several or all of the first compressor units (131) have two to four of the first compressor stages (131a) and / or two to four of the second compressor stages (131b).

3. The method according to claim 1 or 2, in which the compressor arrangement (130) comprises two or more second compressor units of the type in the second compressor unit (132) ​​ 4. The method according to any one of the preceding claims, wherein the first compressor stages (131a) of different first compressor units (131) are decoupled from each other and the second compressor stages (131b) of different first compressor units (131) are decoupled from each other.

5. The method according to one of the preceding claims, wherein - the first rectification device (110) has, in addition to the double column unit (111), an argon withdrawal column (112), wherein - argon product is withdrawn from the argon withdrawal column (112), and wherein - the second rectification device (120) has no argon withdrawal column.

6. The method according to claim 5, wherein liquid is withdrawn from the nitrogen column (121), is depressurized, evaporated against the condensed overhead gas of the second nitrogen column (121), and is at least partially subjected to re-compression and fed back into the second nitrogen column (121).

7. The method according to any one of the preceding claims, comprising a first individual operating mode, in which the raw material air is subjected to the compression and fed only into the first rectification device (110), and in which - at least a part of the first compressor units (131) is operated and - the second compressor units (132) are not operated.

8. The method according to claim 7, comprising a second individual operating mode, in which the raw material air is subjected to the compression and fed only into the second rectification device (120), and in which the second compressor units (132) are operated and the first compressor units (131) are not operated.

9. The method according to claim 7 or claim 8, wherein the combined operating mode and / or the first individual operating mode comprises a design operating mode in which all of the first compressor units (131) are operated, and one or more special operating modes in which at least one of the first compressor units (131) is not operated.

10. The method according to claim 9, wherein at least one of the special operating mode or the several special operating modes is a maintenance operating mode, in which the amount of raw material air subjected to the compression is the same as in the design operating mode.

11. The method according to claim 9 or claim 10, wherein at least one of the special operating mode or the several special operating modes is a reduced load operating mode, in which the amount of raw material air subjected to the compression is lower than in the design operating mode.

12. The method according to any one of claims 9 to 11, wherein at least one of the special operating mode or the several special operating modes is a reduced circulation mode, - a first amount of nitrogen is conducted back to the first rectification device (110) as a circulation nitrogen stream in the design operating mode and - a second amount of nitrogen, which is smaller than the first amount of nitrogen, is conducted back to the first rectification device (110) as a circulation nitrogen stream in the reduced circulation mode.

13. The method according to any one of the preceding claims, the method comprising - two or more first rectification devices (110) having double column units (111), and / or - two or more second rectification devices (120) having nitrogen columns (121), wherein - the first high-purity nitrogen product (1) from all second rectification devices is subjected to high-purity nitrogen compression by using the compressor device (130), and - the second high-purity nitrogen product (2) from one of the first rectification devices is not conducted into the compressor device (130).

14. Air separation system (100) for cryogenic production of air products, having a first rectifier device (110), a second rectifier device (120) and a compressor device (130), wherein the first rectifier device (110) and the second rectifier device (120) each have a rectification column which is adapted to be operated at more than 2 bar, and the air separation system (100) is adapted for performing a combined operating mode and in which combined operating mode a raw material air is subjected to raw material air compression by using the compressor device (130), is then proportionally fed into the first rectifier device (110) and the second rectifier device (110), and high-purity nitrogen is provided by using the first rectifier device (110) and the second rectifier device (110), and high-purity nitrogen provided by using the first rectifier device (110) or a part thereof is subjected to high-purity nitrogen compression by using the compressor device (130), characterized in that, The compressor device (130) has several first compressor units (131) and one second compressor unit (132), wherein each of the first compressor units (131) has a first compressor stage (131a) and a second compressor stage (131b), and in the first compressor units (131) the first compressor stage (131a) and the second compressor stage (131b) are mechanically coupled to each other, and wherein the air separation system (100) is adapted for using the first compressor stages (131a) of the first compressor units (131) and the second compressor unit (132) for the raw material air compression and the second compressor stages (131b) of the first compressor units (131) for the high-purity nitrogen compression in the combined operating mode.

15. The air separation system (100) according to claim 14, the air separation system being adapted for carrying out the method according to any one of claims 1 to 13.

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