Process and plant for providing a nitrogen product, an oxygen product and a hydrogen product

Abstract

A method for providing a nitrogen product, an oxygen product and a hydrogen product, wherein an air separation installation is used which is designed for the low-temperature separation of feed air and which has a rectification column system, the rectification column system comprising an air-fed rectification column and a main heat exchanger. The provision of the nitrogen product comprises, in particular, subjecting feed air to low-temperature rectification using the air-fed rectification column such that a tops gas is obtained, and using part of the tops gas as the nitrogen product. The provision of the oxygen product and the hydrogen product comprises subjecting water to water electrolysis in an electrolyzer, such that a water-containing oxygen stream and a hydrogen stream are obtained, the water-containing oxygen stream or part thereof being subjected, at least in one operating phase, to drying and, in an unmixed state, to liquefaction in the air separation installation.

Description

[0001] The invention relates to a method for providing a nitrogen product, an oxygen product and a hydrogen product, and to a corresponding installation in accordance with the preambles of the independent patent claims.PRIOR ART

[0002] The production of air products in the liquid or gaseous state by cryogenic fractionation of air in air fractionation installations is known and described, for example, in H.-W. Häring (editor), Industrial Gases Processing, Wiley-VCH, 2006, in particular Section 2.2.5, “Cryogenic Rectification.”

[0003] Air fractionation installations have rectification column systems which, for example, can conventionally be designed as two-column systems, in particular as classical Linde double-column systems, but also as triple-column or multi-column systems. In addition to the rectification columns for extracting nitrogen and / or oxygen in the liquid and / or gaseous state, i.e., rectification columns for nitrogen-oxygen separation, rectification columns for extracting further air components, in particular the noble gases krypton, xenon, and / or argon, can be provided. Frequently, the terms “rectification” and “distillation” as well as “column [Saule]” and “column [Kolonne]” or terms composed therefrom are used synonymously.

[0004] The rectification columns of the mentioned rectification column systems are operated at different pressure levels. Known double-column systems have what is known as a high-pressure column (also referred to as a pressure column, medium-pressure column, or lower column) and what is known as a low-pressure column (also referred to as an upper column). The high-pressure column is typically operated at a pressure level of 4 to 7 bar, in particular approximately 5.3 bar. The low-pressure column is operated at a pressure level of typically 1 to 2 bar, in particular approximately 1.4 bar. In certain cases, even higher pressure levels may be used in either rectification column. The pressures cited here and below are absolute pressures at the top of the respective columns indicated.

[0005] In particular, oxygen and hydrogen are required in addition to gaseous, high-purity nitrogen to supply semiconductor plants (so-called fabs). The nitrogen should typically only have approx. 1 ppb, maximum 1000 ppb, oxygen, be substantially particle-free and be able to be delivered at a significantly superatmospheric pressure level. Information in ppb or ppm here refers to the mole fraction. The oxygen should have a comparable purity. Specific requirement profiles are explained below.

[0006] So-called SPECTRA methods are known from the prior art for providing pressurized nitrogen as the main product. They are explained in more detail below. In a SPECTRA method, a so-called oxygen column, which can be operated at or above the pressure level of a typical low-pressure column, can be used in particular to obtain pure or high-purity oxygen in addition to a nitrogen product. This low-pressure column is present in an appropriately modified SPECTRA method in addition to the rectification column used for nitrogen extraction and is fed therefrom.

[0007] Thus, while SPECTRA methods are generally suitable for providing nitrogen and oxygen for corresponding applications, the provision of oxygen is typically associated with an extremely high energy requirement. Often, no rotating machines may be used for the production of high-purity oxygen so as not to compromise the purity of the oxygen. However, it may not be possible to dispense with corresponding pumps in conventional SPECTRA methods. The provision of hydrogen is also not directly possible using such installations.

[0008] The object of the present invention is to improve the provision of a nitrogen product, an oxygen product and a hydrogen product, in particular with the aforementioned purities and for the aforementioned applications, compared to the prior art.DISCLOSURE OF THE INVENTION

[0009] this background, the present invention proposes a method for providing a nitrogen product, an oxygen product and a hydrogen product, and a corresponding installation having the features of the independent claims. Preferred embodiments form the subject-matter of the dependent claims and of the following description.

[0010] Prior to explaining the features and advantages of the present invention, some of the principles of the present invention will be explained in greater detail, and terms used below will be defined.

[0011] The devices used in an air fractionation installation are described in the cited technical literature, for example in Häring (see above) in Section 2.2.5.6, “Apparatus.” Unless the following definitions differ, reference is therefore explicitly made to the cited technical literature with respect to terminology used within the framework of the present application.

[0012] A “heat exchanger” for use in the context of the present invention can be designed in a manner customary in the art. It serves for the indirect transfer of heat between at least two fluid streams which are, for example, conducted in counterflow to one another, for example, a warm compressed air stream and one or more cold fluid streams or a cryogenic liquid air product and one or more warm or warmer but possibly also even cryogenic fluid streams. A heat exchanger can be formed from one or more heat exchanger sections connected in parallel and / or serially, e.g., from one or more plate heat exchanger blocks. It is, for example, a plate fin heat exchanger. Such a heat exchanger has “passages” which take the form of fluid channels separated from one another and having heat exchange surfaces, and which are connected together in parallel and separated by other passages to form “passage groups.” The characteristic of a heat exchanger is that at one time heat is exchanged therein between two mobile media, namely at least one fluid stream to be cooled and at least one fluid stream to be heated.

[0013] A “condenser evaporator” refers to a heat exchanger in which a condensing fluid stream enters into indirect heat exchange with an evaporating fluid stream. Each condenser evaporator has a liquefaction chamber and an evaporation chamber. The liquefaction and evaporation chambers have liquefaction or evaporation passages. Condensation (liquefaction) of the condensing fluid stream is carried out in the liquefaction chamber, and evaporation of the evaporating fluid stream is carried out in the evaporation chamber. The evaporation and liquefaction chambers are formed by groups of passages, which are in a heat-exchanging relationship with one another.

[0014] The present invention may in particular comprise the low-temperature separation of air according to the SPECTRA method mentioned at the outset, as described, for example, in EP 2 789 958 A1 and the further patent literature cited therein. In its simplest form, this method is a single-column method. However, the present invention can also be used with any other methods for low-temperature separation of air. The description of a SPECTRA method serves here only as an example.

[0015] As mentioned, in a SPECTRA method, in addition to an air-fed rectification column, a rectification column fed in turn from the air-fed rectification column and used for oxygen recovery can be employed. This is also the case in embodiments of the present invention, whereas other embodiments of the invention do not provide for the use of such a rectification column.

[0016] Thus, while the SPECTRA method was originally, and also in corresponding embodiments of the invention, only intended to provide gaseous nitrogen at the pressure level of the air-fed rectification column, the use of a further rectification column of the type explained, as is the case in other corresponding embodiments of the invention, also enables the additional recovery of pure oxygen.

[0017] As in other methods for the low-temperature fractionation of air, compressed and pre-purified air is also cooled in the SPECTRA method to a temperature suitable for rectification. This means that it can be partially liquefied in conventional methods. The air is rectified at the typical pressure of a high-pressure column, as explained at the outset, yielding the tops gas enriched in nitrogen in comparison to atmospheric air and a liquid bottoms liquid enriched in oxygen in comparison to atmospheric air.

[0018] A return flow of the air-fed rectification column used for this purpose is provided in a heat exchanger by condensing tops gas of the air-fed rectification column, more precisely part of this tops gas. In this heat exchanger, a condenser evaporator, fluid, which is also taken from the air-fed rectification column, is used for cooling and thereby evaporated or partially evaporated. Further tops gas may be provided as a nitrogen-rich product.

[0019] In a SPECTRA method, as can also be used within the scope of the present invention, two material streams (hereinafter referred to as the “first” and “second” material streams) with different oxygen contents are formed by evaporating liquid from the air-fed rectification column in the aforementioned condenser evaporator, the first material stream being formed with a first, lower oxygen content and the second material stream being formed with a second, higher oxygen content.

[0020] In one embodiment of the invention, the first material stream can be formed using liquid which is taken from the air-fed rectification column with the first oxygen content, and the second material stream can be formed using liquid which is already taken from the air-fed rectification column with the second, higher oxygen content. In this embodiment, the liquid used to form the first material stream can be taken from the air-fed rectification column from an intermediate tray or from a liquid retention device. In this embodiment, the liquid used to form the second material stream can in particular be at least part of the liquid bottoms product of the air-fed rectification column.

[0021] In another embodiment, however, the same liquid can initially be used to form the first and second material streams, for example bottoms liquid from the air-fed rectification column or another liquid taken from the air-fed rectification column. This can be conducted through the first condenser evaporator, where it is partially evaporated and subjected to phase separation to obtain a gas fraction and a liquid fraction. In this embodiment, the first material stream can be formed with the first oxygen content using the gas fraction or a portion thereof. In this embodiment, the second material stream can be formed by evaporation of the liquid fraction or part thereof in the first condenser evaporator.

[0022] In both embodiments, however, the first and second material streams are each fluid which is used beforehand in the aforementioned condenser evaporator for cooling and for condensing the corresponding portion of tops gas from the air-fed rectification column.

[0023] In general, in a SPECTRA method, after being used in the aforementioned condenser evaporator for cooling, the first material stream can be at least partially compressed by means of a cold compressor and returned to the air-fed rectification column. This is also the case in the context of the present invention. In a SPECTRA method, after being used in the aforementioned condenser evaporator for cooling, the second material stream may be at least partially expanded and discharged from the air separation installation as a so-called residual gas mixture. This can also be provided within the scope of the present invention.

[0024] For the compression of the first material stream (or a corresponding portion), one or more compressors can be used which are coupled to one or more expansion machines in which the expansion of the second material stream (or a corresponding portion) is carried out. It is understood that only portions of the first or second material stream may also in each case be compressed or expanded in the correspondingly coupled units. An expansion machine that is not coupled to a corresponding compressor can, if present, be braked in particular mechanically and / or by generator. Braking is also possible in the case of an expansion machine that is coupled to a compressor. Any variants of the expansion and recompression can be provided without departing from the scope of the invention.

[0025] In the SPECTRA methods used according to a variant of the invention with oxygen recovery in a further rectification column fed from the air-fed rectification column, a further condenser evaporator is typically present in the lower region of the second rectification column, and is used for boiling bottoms liquid from the further rectification column. This condenser evaporator is conventionally operated with air (feed air) that is compressed (at least) in the main air compressor and cooled in the main heat exchanger, and which is supplied to the first rectification column. In particular, this feed air can also be air that is initially present in gaseous form and is liquefied in the further condenser evaporator before it is fed into the air-fed rectification column. It is a portion of the feed air supplied overall to the first rectification column. Further (gaseous) feed air can be fed into the air-fed rectification column without any corresponding liquefaction. Variants can also be used with regard to feeding the air-fed rectification column and operating the further condenser evaporator without departing from the scope of the invention in each case.ADVANTAGES OF THE INVENTION

[0026] The present invention proposes to allow the production of hydrogen to take place at the same location as the production of nitrogen by means of cryogenic air separation in order to supply corresponding consumers. The oxygen obtained during the production of hydrogen is freed from water and, optionally, from other components such as hydrogen and then, as explained in detail below, liquefied in the air separation installation located at the same location and, optionally, supercooled in a supercooling counterflow unit present in the air separation installation. The liquid oxygen obtained in this way can be stored in liquid form. An increase in pressure by means of pressure build-up evaporation, a cryogenic pump and the like as well as subsequent evaporation in the main heat exchanger of the air separation installation (in particular in the manner of a known internal compression) can also be provided. The oxygen stream from the electrolysis is not mixed with a process stream of the air separation before it is liquefied and usually not even after it has been liquefied. A “process stream of the air separation” is a stream derived from the feed air, for example a nitrogen or non-pure oxygen product. The oxygen stream from the electrolysis is therefore not a process stream of the air separation. The liquefaction of the electrolysis oxygen according to the invention does not interfere with the low-temperature separation process of the air separation; rather, there is preferably no mixing of the oxygen stream from the electrolysis with any process stream of the air separation. The air separation installation only delivers the liquefaction cooling, but does not contribute to purifying the oxygen from the electrolysis.

[0027] The present invention makes use of the fact that during the production of hydrogen by means of water electrolysis, high-purity oxygen can be obtained which is mainly only contaminated with water and which, in particular, is not contaminated by mixing with an impure oxygen product.

[0028] The product spectrum that can be provided within the scope of the present invention makes it possible to provide the required proportions of nitrogen, oxygen and hydrogen for the aforementioned fabs in a particularly advantageous manner. Typically, such fabs require approx. 0.75% of the nitrogen quantity in high-purity oxygen and 1.50% in hydrogen, i.e., the requirement for oxygen and water is approx. in a ratio of 1 to 2. This corresponds exactly to the proportions obtained in water electrolysis. Any additional high-purity oxygen provided within the scope of the present invention can, for example, be sold on the market.

[0029] Overall, the present invention makes it possible to reduce the total energy requirement and the capital expenditure for the production of nitrogen, oxygen and hydrogen products of the type explained. In particular, the air separation installation can also be operated in a load-flexible manner. For example, if oxygen is not liquefied but only taken from a tank, liquid nitrogen can also be produced, or it is possible to feed liquid nitrogen into the installation in order to liquefy gaseous oxygen.

[0030] Overall, the present invention proposes, in the language of the claims, a method for providing a nitrogen product, an oxygen product and a hydrogen product, wherein a installation is used which is designed for the low-temperature separation of air and which has a rectification column system comprising an air-fed rectification column, a main heat exchanger and optionally a supercooling counterflow unit. The main heat exchanger and supercooling counterflow unit can be combined in one apparatus as a combined main heat exchanger-supercooler. As mentioned, the installation may in particular be designed to perform a SPECTRA method, but this is not a mandatory requirement.

[0031] The term “main heat exchanger” is used here to mean an apparatus in which feed air is cooled to approximately the dew point. The main heat exchanger can consist of a plurality of blocks connected in parallel and / or in series.

[0032] The provision of the nitrogen product comprises subjecting feed air to low-temperature rectification using the rectification column system and taking the nitrogen product or a precursor product from the rectification column system.

[0033] The term “precursor product” is intended here in particular to designate a mixture of substances or a pure substance, using which the actual product is formed, wherein the formation may comprise, for example, further purification, pressurization, heating, cooling, rectification, mixing or separation of fractions or portions.

[0034] When a SPECTRA method is used within the scope of the present invention, which may optionally be the case, feed air is subjected to low-temperature rectification using the air-fed rectification column so as to obtain a tops gas, and part of the tops gas is used as the nitrogen product or a precursor product of the nitrogen product.

[0035] On the other hand, the provision of the oxygen product and the hydrogen product comprises, according to the invention, subjecting water to water electrolysis in an electrolyzer so as to obtain a water-containing oxygen stream and a hydrogen stream, the water-containing oxygen stream or part thereof being subjected, at least in an operating phase, to drying and thereafter to liquefaction in the main heat exchanger so as to obtain a liquid oxygen stream, and the liquid oxygen stream or part thereof being used to provide the oxygen product. Details and embodiments according to the invention are explained below. Advantages of the measures proposed according to the invention have already been explained above.

[0036] Within the scope of the invention, the following configurations of the oxygen liquefaction are possible:

[0037] Configuration 1 (main heat exchanger only)

[0038] cooling in the warm part of the main heat exchanger

[0039] complete liquefaction in the cold part of the main heat exchanger

[0040] Configuration 2 (supercooling counterflow unit only)

[0041] cooling and complete liquefaction supercooling counterflow unit

[0042] Configuration 3 (main heat exchanger and supercooling counterflow unit)

[0043] 3a: cooling and complete liquefaction in the main heat exchanger-followed by supercooling in the supercooling counterflow unit

[0044] 3b: cooling and partial liquefaction in the main heat exchanger-followed by further liquefaction and then supercooling in the supercooling counterflow unit

[0045] 3c: cooling only in the main heat exchanger-followed by liquefaction and then supercooling in the supercooling counterflow unit

[0046] In configurations 1 to 3c, the main heat exchanger and supercooling counterflow unit can be implemented as separate apparatuses or alternatively as a combined main heat exchanger / supercooler.

[0047] In addition to the oxygen flow from the electrolysis, for example, a liquid

[0048] which is taken from the distillation system, cooled in the supercooling counterflow unit and reintroduced into the distillation system, and gas which is taken from the rectification column system and heated in the supercooling counterflow unit, also flow through the supercooling counterflow unit.

[0049] Configuration 4 (separate heat exchanger only)

[0050] cooling in the warm part of the separate heat exchanger

[0051] complete liquefaction in the cold part of the main heat exchanger

[0052] Configuration 5 (separate heat exchanger and supercooling counterflow unit)

[0053] 3a: cooling and complete liquefaction in the separate heat exchanger-followed by supercooling in the supercooling counterflow unit

[0054] 3b: cooling and partial liquefaction in the separate heat exchanger-followed by further liquefaction and then supercooling in the supercooling counterflow unit

[0055] 3c: cooling only in the separate heat exchanger-followed by liquefaction and then supercooling in the supercooling counterflow unit

[0056] One or more process streams of the air separation, for example air, nitrogen or oxygen, are preferably used as refrigerants in the separate heat exchanger. They extract heat from the oxygen flow from the electrolysis through indirect heat exchange. The separate heat exchanger can, for example, be connected in parallel on the air side to the main heat exchanger

[0057] In the separate heat exchanger, the oxygen from the electrolysis is preferably liquefied by indirect heat exchange with a liquid cold stream that has a nitrogen content of more than 30 mol %, wherein the cold stream is evaporated. A third process stream preferably does not flow through the separate heat exchanger.

[0058] The present invention may comprise forming the liquid oxygen stream formed to provide the oxygen product as a supercooled liquid oxygen stream by supercooling in the supercooling counterflow unit. In this case, the oxygen stream from the electrolysis is cooled in the main heat exchanger and completely or partially liquefied; in the case of partial liquefaction, the liquefaction is first completed in the supercooling counterflow unit and then the liquid is supercooled. Alternatively, it is also possible to cool or supercool the liquid oxygen stream only by conducting it through the main heat exchanger, in particular if it is at a superatmospheric pressure level.

[0059] Within the scope of the present invention, the water-containing oxygen stream can be provided using a low-pressure electrolysis. Alternatively, provision using high-pressure electrolysis is also possible. Within the scope of the present invention, water electrolysis can be performed, for example, in the form of alkaline electrolysis (AEL) or electrolysis on a proton exchange membrane (PEM) or anion exchange membrane (AEM). Both methods are low-temperature electrolyses which can typically be used at operating temperatures of below 60° C. High-temperature electrolysis methods, for example using solid oxide electrolysis cells (SOEC), are also used for electrolysis, for example of water and / or carbon dioxide, and can be used in connection with the present invention. Reference is made to the relevant technical literature for all methods.

[0060] Depending on the pressure level at which the liquefaction is to take place in the main heat exchanger and the pressure level of the water electrolysis, the water-containing oxygen stream or part thereof can be subjected to compression after drying and before liquefaction in the main heat exchanger.

[0061] The provision of the oxygen product can in particular comprise (further) purification, in particular rectification for depletion of argon, to which in particular the evaporated liquid oxygen may be subjected.

[0062] As mentioned, the present invention can in particular enable load-flexible operation. In other words, in one embodiment of the invention, it is possible for the liquid oxygen stream to be formed only in a first operating phase, wherein the liquid oxygen stream can be temporarily stored in the first operating phase for later provision of the oxygen product, and wherein in a second operating phase the oxygen product can be obtained as a gaseous pressurized oxygen product using the temporarily stored liquid oxygen stream or part thereof with heating in the main heat exchanger. In particular, in the second operating phase, a gaseous nitrogen stream can be subjected to liquefaction in the main heat exchanger so as to obtain a liquid nitrogen stream, and the liquid nitrogen stream or a part thereof can be used as the or a further nitrogen product or can be temporarily stored for later provision of the or a further nitrogen product. It is also possible to subject the liquid nitrogen stream to internal compression of a known type, without or with intermediate storage. This can take place in the first and second operating modes. Any measures mentioned for one of the operating modes can also be carried out in other operating modes.

[0063] The present invention may also comprise, in particular, the use of further cooling media, so that in a method according to one embodiment of the invention, the liquefaction is performed using liquid air.

[0064] In one embodiment of the invention in which a SPECTRA method is used, the air-fed rectification column can be operated using a condenser evaporator, in which a first and a second material stream are formed below an operating pressure level of the air-fed rectification column by evaporating liquid from the air-fed rectification column, further tops gas of the air-fed rectification column being condensed in the condenser evaporator and returned to the air-fed rectification column as a return flow.

[0065] Furthermore, in this embodiment, the first material stream can be formed with a first oxygen content and the second material stream with a second oxygen content above the first oxygen content, the first material stream or part thereof being subjected to recompression to the first pressure level and fed into the air-fed rectification column, and the second material stream or part thereof being subjected to work-performing expansion and discharged from the installation.

[0066] As mentioned, the invention can be used in a SPECTRA method without or with an additional oxygen column, wherein in the latter case this oxygen column is used as a further rectification column fed from the air-fed rectification column, and wherein bottoms liquid of the second rectification column is used to provide the oxygen product. The liquid oxygen stream can be fed into the further rectification column, thereby enabling further purification.

[0067] Within the scope of the present invention, evaporation losses from a tank can also be reduced, wherein in particular oxygen evaporated in a tank is fed into the main heat exchanger and / or the supercooling counterflow unit of the installation. In particular, it is heated in the supercooling counterflow unit or main heat exchanger.

[0068] The invention also extends to a installation for providing a nitrogen product, an oxygen product and a hydrogen product, the installation being designed for low-temperature separation of air and having a rectification column system comprising an air-fed rectification column, a main heat exchanger and a supercooling counterflow unit, the installation for providing the nitrogen product being designed to subject feed air to low-temperature rectification using the air-fed rectification column so as to obtain a tops gas and to use part of the tops gas as the nitrogen product.

[0069] According to the invention, the installation comprises an electrolyzer designed to subject, for the provision of the oxygen product and the hydrogen product so as to obtain a water-containing oxygen stream and a hydrogen stream, to a water electrolysis, the installation being designed to subject the water-containing oxygen stream or part thereof, at least in an operating phase, to drying and then to liquefaction in the main heat exchanger so as to obtain a liquid oxygen stream, and to use the liquid oxygen stream or part thereof to provide the oxygen product.

[0070] Reference is made to the above explanations of the method according to the invention and its embodiments for further features and advantages of the air fractionation installation according to the invention which is configured in particular for carrying out a method as explained above in different embodiments and has corresponding means realized in terms of devices.

[0071] The invention is described in more detail hereafter with reference to the accompanying drawings, which illustrate preferred embodiments of the present invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 shows a installation according to an embodiment of the invention.

[0073] FIG. 2 shows a installation according to a further embodiment of the invention.

[0074] FIG. 3 shows a system according to the invention incorporating a main heat exchanger and a supercooling counterflow unit.

[0075] In the figures, elements corresponding functionally or structurally to one another are indicated by identical reference signs and only for the sake of clarity are not repeatedly explained below.DETAILED DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 illustrates a installation 100 according to one embodiment of the invention in the form of a schematic installation diagram.

[0077] The installation 100 is designed for the low-temperature separation of air and for this purpose comprises a rectification column system 10 with an air-fed rectification column 11 which is designed for nitrogen recovery and is operated with a condenser evaporator 13. A further rectification column 12 fed from the air-fed rectification column 11 for the recovery of oxygen is not present, but is nevertheless shown (crossed out) to illustrate the modification of a installation according to the prior art carried out within the scope of the invention.

[0078] By means of a main air compressor 1 of the air fractionation installation 100, air is sucked in from the atmosphere via a filter (not separately designated) and compressed. After cooling in an aftercooler (likewise not designated separately) downstream of the main air compressor 1, the feed air stream a formed in this way is further cooled in a direct contact cooler 2 operated with water. The feed air stream a is then subjected to cleaning in an adsorber unit 3. For further explanations in this context, reference is made to the technical literature, for example in connection with FIG. 2.3A in Häring (see above).

[0079] After cooling in the main heat exchanger 4, the feed air stream a is fed into the air-fed rectification column 11, in which the correspondingly fed air is rectified. Tops gas of the air-fed rectification column 11 is partially discharged from the air separation installation 100 in the form of a material stream d as a nitrogen product or sealing gas.

[0080] In the condenser evaporator 13, in the specific embodiment illustrated here, a first material stream g and a second material stream h are subjected to evaporation below an operating pressure level of the air-fed rectification column 11 (for this purpose, in particular, a corresponding expansion takes place in valves not separately designated).

[0081] The first material stream g is formed using liquid taken from the air-fed rectification column 11 with a first oxygen content, and the second material stream h is formed using liquid (in particular bottoms liquid) taken from the air-fed rectification column 11 with a second oxygen content above the first oxygen content.

[0082] Further tops gas of the air-fed rectification column 11 is condensed in the form of a material stream i in the first condenser evaporator 13 and returned to the air-fed rectification column 11 as a return flow. As illustrated here in the form of a material stream k, a part can also be supercooled in a supercooling counterflow unit 5 and provided as liquid nitrogen F. It is also possible to feed in liquid nitrogen. A material stream I heated thereby is treated as explained in more detail below. A further discharge in the form of a purge stream m may also be provided. A possible (further) feeding of liquid nitrogen (LIN injection) is illustrated in the form of a material stream x.

[0083] After its evaporation or partial evaporation in the first condenser evaporator 13, gas of the first material stream g is subjected in a compressor 6 to recompression to the first pressure level and fed into the air-fed rectification column 11. A portion indicated by a dashed line can also be returned to compression in the compressor 6. Part of the material stream g can also be discharged into the atmosphere in the form of a material stream n.

[0084] After being evaporated or partially evaporated in the first condenser evaporator 13 in the example illustrated here, gas of the second material stream h is subjected to expansion in an expansion machine 7 coupled to the compressor 6 and, after heating in the main heat exchanger 4, is used as regeneration gas in the adsorber unit 3 or released into the atmosphere and thus discharged from the air separation installation 100.

[0085] In an electrolyzer 20, a hydrogen stream (not shown) and an oxygen stream o are formed by water electrolysis in a first operating phase. The former is provided as a hydrogen product. The latter is water-containing due to the type of production and is therefore freed of water and other components in a dryer 21. (The dryer consists, for example, of a conventional pair of adsorber containers that are operated alternately, as indicated in FIG. 3.) The dried oxygen stream, further designated as o, is conducted through the main heat exchanger 4, liquefied there, then supercooled in the supercooling counterflow unit 5 and fed into a tank unit 22 in a liquefied, supercooled state. In this way, an oxygen product is thus formed.

[0086] If required, in particular in a second operating phase, the oxygen stored in the tank unit, as further illustrated here with an oxygen flow o, can be pressurized, for example by means of a pressure build-up compression, heated in the main heat exchanger 4 and thereby evaporated and provided as a corresponding (further) oxygen product.

[0087] Alternatively, in FIG. 1, the supercooling counterflow unit 5 could be integrated into the main heat exchanger 4 in a manner known per se.

[0088] FIG. 2 illustrates a installation 200 according to one embodiment of the invention in the form of a schematic installation diagram.

[0089] In this installation, the already mentioned further rectification column 12 for oxygen recovery is present. This further rectification column 12 is fed with a side stream p of the air-fed rectification column 11, which is first conducted through a bottoms evaporator 14 of the further rectification column 12 and liquefied therein and then fed in an upper region to the further rectification column 12.

[0090] A portion of the air stream a, which is illustrated here in the form of a material stream b, is also conducted through the bottoms evaporator 14 and is then fed in a liquefied state into the air-fed rectification column 11.

[0091] Bottoms liquid of the further rectification column 12 is fed into the tank unit 23 in the form of a material stream q and can be used from this, as previously explained for the material stream o, to provide the oxygen product, as illustrated with a material stream q further designated by q. The oxygen stream o previously liquefied in the main heat exchanger 4 and then supercooled in the supercooling counterflow unit 5 is fed into the further rectification column 12 for further purification.

[0092] Alternatively, in FIG. 2, the supercooling counterflow unit 5 could be integrated into the main heat exchanger 4 in a manner known per se.

[0093] FIG. 3 shows an exemplary embodiment of the configuration 3 with cooling and liquefaction of the oxygen stream o in a separate heat exchanger 300. the liquefied oxygen is fed into the tank unit 22 via the outputs 201 and 302. All other features of FIG. 3 correspond to those of FIG. 2.

Claims

1. A method for providing a nitrogen product, an oxygen product and a hydrogen product, wherein an air separation installation is used which is designed for the low-temperature separation of feed air and which has a rectification column system, the rectification column system comprising an air-fed rectification column and a main heat exchanger for cooling the feed air, the provision of the nitrogen product comprising subjecting feed air to low-temperature rectification using the rectification column system and taking the nitrogen product or a precursor thereof from the rectification column system, wherein the provision of the oxygen product and the hydrogen product comprises subjecting water to water electrolysis in an electrolyzer, such that a water-containing oxygen stream and a hydrogen stream are obtained, the water-containing oxygen stream or part thereof being subjected, at least in one operating phase, to drying and optionally to further purification steps such that a liquid oxygen stream is obtained, and the dried oxygen stream thereafter being introduced into the air separation installation without being mixed with a process stream of the air separation installation, and being subjected in an unmixed state to liquefaction in the air separation installation, and the liquid oxygen stream produced in the process or part thereof being used to provide the oxygen product.

2. The method according to claim 1, wherein the liquefaction of the dried oxygen stream is performed in the main heat exchanger, a supercooling counterflow unit of the air separation, in the supercooling part of a combined main heat exchanger-supercooler or in a separate heat exchanger of the air separation installation independent of the main heat exchanger and optionally the supercooling counterflow unit.

3. The method according to claim 1, wherein the feed air is subjected to the low-temperature rectification using the air-fed rectification column such that a tops gas is obtained, part of the tops gas being used as the nitrogen product or a precursor of the nitrogen product, two material streams with different oxygen contents being formed in a condenser evaporator by evaporating liquid from the air-fed rectification column, and a further part of the tops gas being condensed in the condenser evaporator and returned to the air-fed rectification column .

4. The method according to claim 1, wherein the water-containing oxygen stream is provided using electrolysis, in particular high-pressure electrolysis.

5. The method according to claim 1, wherein the water-containing oxygen stream or part thereof is subjected to compression after drying (21) and before liquefaction in the main heat exchanger.

6. The method according to claim 1, wherein the provision of the oxygen product comprises purification, in particular rectification for depletion of argon.

7. The method according to claim 1, wherein the liquid oxygen stream is formed only in a first operating phase, the liquid oxygen stream being temporarily stored in the first operating phase for later provision of the oxygen product, and the oxygen product being obtained in a second operating phase using the temporarily stored liquid oxygen stream or part thereof with heating in the main heat exchanger as a gaseous pressurized oxygen product.

8. The method according to claim 7, wherein, in the second operating phase, a gaseous nitrogen stream is subjected to liquefaction in the main heat exchanger so as to obtain a liquid nitrogen stream, the liquid nitrogen stream or part thereof being used as the or a further nitrogen product or being temporarily stored for later provision of the or a further nitrogen product.

9. The method according to claim 1, wherein the liquefaction is performed using liquid air.

10. The method according to claim 1, wherein the air-fed rectification column is operated using a condenser evaporator, in which a first and a second material stream are formed below an operating pressure level of the air-fed rectification column by evaporating liquid from the air-fed rectification column, further tops gas from the air-fed rectification column being condensed in the condenser evaporator and returned to the air-fed rectification column as a return flow.

11. The method according to claim 10, wherein the first material stream is formed with a first oxygen content and the second material stream is formed with a second oxygen content above the first oxygen content, the first material stream or part thereof being subjected to recompression to the first pressure level and being fed into the air-fed rectification column, and the second material stream or part thereof being subjected to a work-performing expansion and being discharged from the installation.

12. The method according to claim 10, wherein a further rectification column fed from the air-fed rectification column is used, wherein bottoms liquid from the second rectification column is used to provide the oxygen product.

13. The method according to claim 12, wherein the liquid oxygen stream is fed into the further rectification column.

14. An installation for providing a nitrogen product, an oxygen product and a hydrogen product, the installation comprising an air separation installation for low-temperature separation of feed air, which air separation installation in turn has a rectification column system comprising an air-fed rectification column, a main heat exchanger for cooling the feed air, the installation for providing the nitrogen product being designed to subject feed air to low-temperature rectification using the rectification column system and to take the nitrogen product or a precursor thereof from the rectification column system, wherein the installation comprises an electrolyzer designed to subject, for the provision of the oxygen product and the hydrogen product so as to obtain a water-containing oxygen stream and a hydrogen stream, to a water electrolysis, the installation being designed to subject the water-containing oxygen stream or part thereof, at least in an operating phase, to drying (21), so as to obtain a liquid oxygen stream and without mixing with a process stream of the air separation installation, and thereafter, in an unmixed state, to liquefaction in the air separation installation and to use the liquid oxygen stream produced in this process or part thereof to provide the oxygen product.

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