Method and system for providing a pressurized, oxygen-rich, gaseous air product

Description

[0001] The invention relates to a method for providing a pressurized, oxygen-rich, gaseous air product and a corresponding system according to the preambles of the independent patent claims. Such a method and system are known from EP-A-3 696 486. State of the art

[0002] The production of air products in liquid or gaseous state by cryogenic separation of air in air separation plants is known and described, for example, in H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH, 2006, especially Section 2.2.5, "Cryogenic Rectification."

[0003] The term "air product" here refers to a fluid that is at least partially produced by cryogenic decomposition of atmospheric air. An air product, as understood here, comprises one or more air gases contained in atmospheric air with a different composition than that of atmospheric air. An air product can, in principle, be present or provided in a gaseous, liquid, or supercritical state and can be converted from one of these states of matter to another. In particular, a liquid air product can be converted into a gaseous state ("evaporated") or into a supercritical state ("pseudo-evaporated") by heating to a certain pressure, depending on whether the pressure during heating is below or above the critical pressure. Reference to "evaporation" in the following shall also include corresponding pseudo-evaporation.

[0004] Air separation plants have rectification column systems, which are traditionally designed as two-column systems, particularly classic Linde double-column systems, but can also be designed as three- or multi-column systems. In addition to the rectification columns for the recovery of nitrogen and / or oxygen in the liquid and / or gaseous state, i.e., the rectification columns for nitrogen-oxygen separation, rectification columns can be provided for the recovery of other air components, particularly the noble gases krypton, xenon, and / or argon. The terms "rectification" and "distillation," as well as "column" and "column," or combinations thereof, are often used synonymously.

[0005] The rectification columns of the aforementioned rectification column systems are operated at different pressures. Known double-column systems comprise a so-called high-pressure column (also referred to as a pressure column, medium-pressure column, or lower column) and a so-called low-pressure column (also referred to as the upper column). The high-pressure column is typically operated at a pressure of 4 to 7 bar, in particular approximately 5.3 bar. The low-pressure column is typically operated at a pressure of 1 to 2 bar, in particular approximately 1.4 bar. In certain cases, higher pressures can also be used in both rectification columns. The pressures specified here are absolute pressures at the top of the respective columns.

[0006] For air separation, so-called main air compressor / booster air compressor (MAC-BAC) processes or so-called high air pressure (HAP) processes can be used. Main air compressor / booster air compressor processes are the more conventional processes, and high air pressure processes have recently been increasingly used as alternatives to main air compressor / booster air compressor processes. The present invention is used in conjunction with high air pressure processes, so the following explanations in this regard apply generally and also to the present invention. Due to significantly lower costs—the main air compressor and booster air compressor are, in a sense, integrated into one machine—and fundamentally comparable efficiency, high air pressure processes can represent an advantageous alternative to main air compressor / booster air compressor processes.

[0007] Main compressor / post-compressor processes are characterized by the fact that only a portion of the total feed air quantity supplied to the rectification column system is compressed to a pressure that is significantly higher, i.e., at least 3, 4, 5, 6, 7, 8, 9, or 10 bar, than the pressure at which the high-pressure column is operated. A further portion of the feed air quantity is compressed only to this pressure or to a pressure that differs from it by no more than 1 to 2 bar, and is fed into the high-pressure column at this lower pressure, in particular without additional expansion. A main compressor / post-compressor process is shown, for example, in Häring (see above) in Figure 2.3A.

[0008] In a high-pressure air process, however, the entire amount of feed air supplied to the rectification column system is compressed to a pressure that is significantly higher than the pressure at which the high-pressure column is operated, i.e., at least 3, 4, 5, 6, 7, 8, 9, or 10 bar, and, for example, up to 14, 16, 18, or 20 bar. High-pressure air processes are known, for example, from EP 2 980 514 A1 and EP 2 963 367 A1.

[0009] High-pressure air processes are typically used with so-called internal compression (IV, IC). In internal compression, at least one gaseous, pressurized air product, which is provided by the air separation plant, is formed by withdrawing a cryogenic, liquid air product from the rectification column system, subjecting it to a pressure increase to a product pressure, and then heating it to the gaseous or supercritical state at the product pressure. For example, gaseous, pressurized oxygen (GOX IV, GOX IC), gaseous, pressurized nitrogen (GAN IV, GAN IC), and / or gaseous, pressurized argon (GAR IV, GAR IC) can be produced by internal compression. Internal compression offers several advantages over external compression, which is also an alternative and is explained, for example, in Häring (see above) in Section 2.2.5.2, "Internal Compression."

[0010] High-pressure air processes can be used in various configurations. These are often classified and differentiated according to the system's liquid output, i.e., the amount of liquid air products supplied and removed from the system, or the ratio of internally compressed air products to liquid products. If the liquid output is not too high, a cold booster or cold compressor of the type described below is used in high-pressure processes, for example, to increase the efficiency of the process by converting the excess cooling capacity into higher air pressure.

[0011] High-pressure processes using a so-called Lachmann or upper column expander, also described below, are also known. The air expanded in the Lachmann turbine is fed into the low-pressure column. The Lachmann turbine can be provided as an additional turbine unit alongside a turbine unit used to expand gaseous compressed air into the high-pressure column, i.e., a so-called Claude turbine.

[0012] Particularly in cases where a high-pressure process is intended to provide predominantly or exclusively internally compressed gaseous oxygen at a pressure in the range of 16 to 50 bar (absolute), there is a need for improvement in process control. The invention aims to increase the efficiency and competitiveness of high-pressure processes, particularly for such typical gas plants. Disclosure of the invention

[0013] Against this background, the present invention proposes a method for providing one or more oxygen-rich, gaseous air products and a corresponding system having the respective features of the independent patent claims. Embodiments of the invention are the subject of the respective dependent patent claims and the following description.

[0014] First, further principles of the invention are explained in more detail and terms used to describe the invention are defined.

[0015] The term "feed air quantity" or "feed air" for short is understood here to mean the total air supplied ("used") to the rectification column system of an air separation plant. As already explained above, in a main compressor / post-compressor process, only a portion of this feed air quantity is compressed to a pressure in a range significantly above the pressure range in which the high-pressure column is operated. In contrast, in a high-air pressure process, as is the subject of the present invention, the entire feed air quantity is compressed to a pressure in such a high pressure range. For the meaning of the term "significantly" in connection with main compressor / post-compressor and high-air pressure processes, reference is made to the above explanations.

[0016] A "cryogenic" liquid is defined here as a liquid medium whose boiling point is significantly below the ambient temperature, e.g., -50 °C or below, especially -100 °C or below. Examples of cryogenic liquids include liquid air, liquid oxygen, liquid nitrogen, liquid argon, or liquids rich in these compounds.

[0017] For information on the devices and apparatus used in air separation plants, please refer to specialist literature such as Häring (see above), particularly Section 2.2.5.6, "Apparatus." For clarification and clarity, some aspects of such devices are explained in more detail below.

[0018] In air separation plants, multi-stage turbocompressors, referred to here as "main air compressors," are used to compress the feed air. The mechanical design of turbocompressors is generally familiar to those skilled in the art. In a turbocompressor, the medium to be compressed is compressed by means of turbine blades arranged on a turbine wheel or directly on a shaft. A turbocompressor forms a structural unit, which, however, in a multi-stage turbocompressor, can have several compressor stages. A compressor stage usually comprises a turbine wheel or a corresponding arrangement of turbine blades. All of these compressor stages can be driven by a common shaft. However, it is also possible to drive the compressor stages in groups with different shafts, whereby the shafts can also be connected to each other via gears.

[0019] The main air compressor is further characterized by the fact that it compresses the entire air volume fed into the distillation column system and used to produce air products, i.e., the entire feed air volume. Accordingly, a "post-compressor" can also be provided, in which only a portion of the feed air volume compressed in the main air compressor is brought to an even higher pressure. This can also be designed as a turbo compressor. To compress partial air volumes, additional turbo compressors, also referred to as boosters, are typically provided. Compared to the main air compressor or the post-compressor, however, they typically only perform a relatively small amount of compression, especially in relation to the compressed air volume. A post-compressor can also be present in a high-air-pressure process, but this compresses a portion of the feed air volume starting from a higher pressure.

[0020] A "cold compressor" or "cold booster" is understood here to mean a compressor or booster to which fluid is supplied at a temperature in a temperature range significantly below the ambient temperature of the air separation plant, in particular at a temperature of less than 0 °C, -50 °C or -100 °C and in particular more than -150 °C or -200 °C.

[0021] Air can also be expanded at several points in air separation plants, for which expansion machines in the form of turboexpanders, also referred to here as "expansion turbines," can be used. Turboexpanders can also be coupled to and drive turbocompressors. If one or more turbocompressors are driven without externally supplied energy, i.e., only via one or more turboexpanders, the term "turbine booster" is also used for such an arrangement. In a turbine booster, the turboexpander (the expansion turbine) and the turbocompressor (the booster) are mechanically coupled, whereby the coupling can occur at the same speed (for example, via a common shaft) or at different speeds (for example, via an intermediate gear). Reference to a "turbine unit" here refers in particular to an arrangement with at least one expansion turbine.

[0022] In typical air separation plants, expansion turbines are installed at various locations for the refrigeration and liquefaction of material streams. These include, in particular, the aforementioned Claude turbines and the also mentioned Lachmann turbines, as well as, in some cases, so-called Joule-Thomson turbines. For the function and purpose of such turbines, please refer to the specialist literature, for example, FG Kerry, Industrial Gas Handbook: Gas Separation and Purification, CRC Press, 2006, especially sections 2.4, "Contemporary Liquefaction Cycles," 2.6, "Theoretical Analysis of the Claude Cycle," and 3.8.1, "The Lachmann Principle."

[0023] A "throttle flow" or "Joule-Thomson flow" refers to a quantity of air that is at least predominantly liquefied under pressure in the main heat exchanger of an air separation plant and then fed, particularly via a throttle valve, into the high-pressure column. A Joule-Thomson turbine can also be used instead of a throttle valve.

[0024] As used herein, fluids, whether liquid, gaseous, or in a supercritical state, can be rich or poor in one or more components, where "rich" can mean a content of at least 75%, 90%, 95%, 99%, 99.5%, 99.9%, or 99.99%, and "poor" can mean a content of at most 25%, 10%, 5%, 1%, 0.1%, or 0.01% on a molar, weight, or volume basis. The term "predominantly" can correspond to the definition of "rich" just given, but specifically refers to a content of more than 90%. For example, if "nitrogen" or "oxygen" is mentioned here, it can refer to a pure gas, but also to a gas rich in nitrogen or oxygen.

[0025] To characterize pressures and temperatures, reference is made below to pressures or temperatures in specific pressure or temperature ranges. This is intended to express that pressures and temperatures do not have to be used in the form of exact pressure or temperature values in order to implement an inventive concept. However, such pressures and temperatures typically lie in corresponding ranges which, for example, lie within ± 1%, 5% or 10% of a mean value. Different pressure or temperature ranges can represent disjoint ranges or ranges which overlap one another. In particular, the specification of pressure ranges includes unavoidable or expected pressure losses, for example due to line resistances and the like. The same applies to pressure ranges. Pressures or pressure range limits specified here in bar are absolute pressures unless otherwise stated. Advantages of the invention

[0026] As mentioned, known high-pressure air processes are often classified and differentiated according to their so-called liquid output, or the ratio of internally compressed products to liquid products. Liquid output refers to the quantity of air products that are discharged from the plant or a corresponding process in liquid form, i.e., for which no evaporation or pseudo-evaporation occurs. Using such products, feed streams into the plant or process cannot be cooled by evaporation. Therefore, when smaller quantities of air products are discharged from the plant or a corresponding process in liquid form, but instead are evaporated or pseudo-evaporated, a certain excess of cold is available.

[0027] For low liquid flow rates, a so-called cold booster can be used, for example, to increase process efficiency by converting this excess cold into higher air pressure. The heat input from the cold booster partially "destroys" the excess cold, but in return, the cold booster compresses part of the feed air, so that, for example, the output of the main air compressor can be reduced accordingly. As already mentioned above, the intake temperature of a cold booster is below the ambient temperature, so that the power consumption is reduced, assuming ideal gas behavior for simplification.

[0028] The invention is used in a high-pressure air process in which, as mentioned, gaseous oxygen is to be produced without (significant) liquid production, and in which an injection turbine (Lachmann turbine) is provided as a second turbine unit next to a first turbine unit which expands air into the high-pressure column in the manner of a Claude turbine.

[0029] The present invention achieves the above-mentioned object in particular by supplying air to the Lachmann turbine at a significantly lower air inlet temperature than in known processes. This results in strong pre-liquefaction at the turbine outlet of the Lachmann turbine. Accordingly, the air volumes to be liquefied in the main heat exchanger as throttle flow or throttle flows are significantly reduced, resulting in a noticeable increase in efficiency. The amount of heat to be transferred in the lower area of the main heat exchanger, i.e., at the location where the condensation of air flows occurs, is thus lower, and the performance of the cold compressor is reduced.

[0030] Overall, against this background, the present invention proposes a process for producing a pressurized, oxygen-rich, gaseous air product using an air separation plant which has a rectification column system with a high-pressure column and a low-pressure column as well as a main heat exchanger, a first turbine unit and a second turbine unit.

[0031] The high-pressure column is operated in a first pressure range of 4 to 7 bar, in particular approximately 5.3 bar, the low-pressure column is operated in a second pressure range of 1 to 2 bar, in particular approximately 1.4 bar, and at least a predominant portion of the total feed air quantity supplied to the rectification column system, in particular the entire feed air quantity as is customary in a high-air pressure process, is compressed to a pressure in a third pressure range that is more than 3 bar above the first pressure range. For further possible pressure differences, explicit reference is again made to the above explanations regarding high-air pressure processes.

[0032] A first portion of the feed air quantity compressed to the pressure in the third pressure range is fed to the first turbine unit at the pressure in the third pressure range or at a pressure in a fourth pressure range above the third pressure range and at a temperature in a first temperature range, expanded to a pressure in the first pressure range using the first turbine unit, and fed into the high-pressure column. As explained further below, to provide the first portion at the temperature in the first temperature range, the main heat exchanger of the air separation plant is used in particular in the manner explained below, and the pressure in the fourth pressure range is optionally achieved using a corresponding booster unit in the manner explained below.In the context of the invention, the first turbine unit is in particular a typical Claude turbine as explained above, or the first turbine unit comprises such a turbine.

[0033] A second portion of the feed air quantity compressed to the pressure in the third pressure range is fed to the second turbine unit at the pressure in the third pressure range or at a pressure in a fifth pressure range above the third pressure range and at a temperature in a second temperature range, expanded to a pressure in the second pressure range using the second turbine unit, and fed into the low-pressure column. As explained further below, to provide the second portion at the temperature in the second temperature range, in particular the main heat exchanger of the air separation plant is used in the manner explained below, and the pressure in the fifth pressure range is optionally achieved using a corresponding booster unit in the manner explained below.In the context of the invention, the second turbine unit is in particular a typical Lachmann turbine as explained above, or the second turbine unit comprises such a turbine.

[0034] The invention comprises withdrawing oxygen-rich liquid from the rectification column system to provide the gaseous, pressurized, oxygen-rich air product, bringing it in the liquid state to a pressure in a sixth pressure range of 16 to 50 bar or 25 to 50 bar, in particular 40 to 50 bar, for example approximately 43 bar, while heating it to a temperature in a third temperature range, feeding it to the main heat exchanger, evaporating it therein at the temperature in the third temperature range, and discharging it from the air separation plant. The pressurized, oxygen-rich air product is thus provided as an internal compression product.

[0035] The third temperature range, i.e. the temperature range in which the temperature lies at which the oxygen-rich liquid is evaporated in the liquid state in the main heat exchanger after pressurization, lies according to the invention both above the first temperature range and above the second temperature range.

[0036] In the context of the present invention, the second temperature range is selected such that a two-phase mixture with a liquid fraction of 5 to 15%, in particular of 8 to 13%, is formed at the outlet of the second turbine unit, these percentages expressing in particular a molar fraction of the liquid fraction, based on a molar fraction of the total two-phase mixture.

[0037] Furthermore, within the scope of the present invention, the temperature in the first temperature range and the temperature in the second temperature range differ from each other by no more than 10 K.

[0038] According to the invention, the air separation plant is operated such that a proportion of less than 5%, in particular less than 2%, of all air products removed from the air separation plant are removed unevaporated and in the liquid state. Regarding the term "air product," which includes not only essentially pure products such as oxygen or nitrogen, but also impure streams (so-called waste gas), reference is made to the above explanations. With respect to essentially pure products, the proportion is less than 10%, in particular less than 5% or less than 2%. The "essentially pure" products include, in particular, nitrogen, oxygen, and argon, or fluids rich in each of the components mentioned.

[0039] The combination of the measures proposed according to the invention achieves, in particular, the advantages already mentioned. Reference is made to the above explanations.

[0040] In particular, the first and second temperature ranges are each 110 to 140 K, in particular 120 to 135 K.

[0041] The third temperature range is above the first temperature range and the second temperature range, and in particular by more than 10 K and up to 40 K above the first temperature range and the second temperature range.

[0042] In the method according to the invention, the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range is advantageously provided at the pressure in the fourth pressure range and is brought to the pressure in the fourth pressure range using a booster unit.

[0043] The booster unit used here will be used to drive the first turbine unit.

[0044] In one embodiment of the invention, the first subset of the feed air quantity compressed to the pressure in the third pressure range can be cooled in a first cooling step in the main heat exchanger before it is brought to the pressure in the fourth pressure range using the booster unit, and the first subset of the feed air quantity compressed to the pressure in the third pressure range can be cooled in a second cooling step in the main heat exchanger after it has been brought to the pressure in the fourth pressure range using the booster unit, wherein the second cooling step comprises cooling to the aforementioned temperature in the first temperature range.

[0045] A third portion of the feed air compressed to the pressure in the third pressure range can be subjected to the first cooling step, in particular together with the first portion of the feed air compressed to the pressure in the third pressure range, and brought to the pressure in the fourth pressure range using the booster unit. The third portion of the feed air compressed to the pressure in the third pressure range and then further compressed to the pressure in the fourth pressure range is liquefied at the pressure in the fourth pressure range in the main heat exchanger, subsequently expanded, and fed into the high-pressure column. The first portion is withdrawn from the main heat exchanger, in particular, at a withdrawal point corresponding to the temperature in the first temperature range, whereas the third portion is passed through the main heat exchanger to the cold end. The third portion thus forms a throttle flow.

[0046] In the method according to the invention, the second subset of the feed air quantity compressed to the pressure in the third pressure range can be provided, in particular, at the pressure in the fifth pressure range and, in the process, brought to the pressure in the fourth pressure range using an additional booster unit. In this case, the additional booster unit can, in particular, drive the second turbine unit, thus being designed to be "self-boosted."

[0047] In all cases, a fourth portion of the feed air compressed to the pressure in the third pressure range can be cooled in the main heat exchanger together with the second portion of the feed air compressed to the pressure in the third pressure range. The second portion can be discharged from the main heat exchanger at a point corresponding to the temperature in the second temperature range, while the fourth portion can be further cooled and liquefied. The fourth portion can be withdrawn from the cold side of the main heat exchanger and fed into the high-pressure column as an additional throttle stream.

[0048] In the process according to the invention, the two-phase mixture forming at the outlet of the second turbine unit is advantageously subjected to phase separation in a suitable phase separator and then fed into the low-pressure column in separate phases, ie in the form of a gas stream and a liquid stream.

[0049] In another embodiment of the present invention, the two-phase mixture forming at the outlet of the second turbine unit is fed into the low-pressure column in two phases. By selecting a suitable two-phase line, a pump can be dispensed with, since liquid droplets are entrained due to the relatively high flow velocity.

[0050] The present invention further relates to an air separation plant for providing a pressurized, oxygen-rich, gaseous air product. Regarding the features of the air separation plant proposed according to the invention, reference is expressly made to the corresponding independent patent claim. A corresponding air separation plant benefits from the advantages previously explained with regard to the process according to the invention and its preferred embodiments, to which reference is therefore expressly made. In particular, such an air separation plant is configured to carry out a process according to one of the previously explained embodiments and has means configured for this purpose.

[0051] The invention is explained in more detail below with reference to the accompanying drawings, which illustrate preferred embodiments of the present invention. Short description of the drawings

[0052] The Figures 1 to 5 illustrate air separation plants according to preferred embodiments of the invention.

[0053] The Figures 6 and 7 show temperature-enthalpy diagrams. Detailed description of the drawings

[0054] In Figure 1 An air separation plant, designated 100, according to a preferred embodiment of the invention is illustrated. The air separation plant 100 comprises a rectification column system 10 with a high-pressure column 11 and a low-pressure column 12, which are interconnected in a known manner.

[0055] Air separation plants of the type shown have been described in many other places, for example, by Häring (see above), particularly in Section 2.2.5, "Cryogenic Rectification." For detailed explanations of their design and operation, please refer to the relevant specialist literature. An air separation plant for use with the present invention can be designed in a variety of ways.

[0056] In the embodiment illustrated here, the high-pressure column 11 is operated in a first pressure range, the low-pressure column 12 is operated in a second pressure range, and at least a predominant portion of a total feed air quantity supplied to the rectification column system 10, here in the form of a compressed air stream a, is compressed to a pressure in a third pressure range which is significantly above the first pressure range.

[0057] In the Figure 1In the air separation plant 100 illustrated, feed air is sucked in by means of a main air compressor 1, compressed to the pressure in the third pressure range, cooled in a direct contact cooler (also not separately designated) and freed in particular from water and carbon dioxide in a pre-cleaning unit 2.

[0058] The feed air thus provided as the aforementioned compressed air stream a at the pressure in the third pressure range is then divided into two substreams b and c, both of which are fed to a main heat exchanger 3 on the hot side and cooled therein. Further substreams are formed by extraction at intermediate temperature levels and on the cold side of the main heat exchanger 3, which represent substreams of the feed air of the compressed air stream a, referred to here as "first" to "fourth" substreams and are indicated by a1 to a4.

[0059] In the embodiment illustrated here, the first subset of the total feed air quantity of the compressed air stream a compressed to the pressure in the third pressure range is fed to a first turbine unit 5 in the form of the subset a1 at a pressure in a fourth pressure range above the third pressure range and at a temperature in a first temperature range, expanded to a pressure in the first pressure range using the first turbine unit 5, and fed into the high-pressure column 11.

[0060] The first subset, i.e. substream a1, is brought to the pressure in the fourth pressure range as part of substream b using a booster unit 4, wherein the booster unit 4 is driven by the first turbine unit 5. The first subset, i.e. substream a1, is cooled in a first cooling step in the main heat exchanger 3 before it is brought to the pressure in the fourth pressure range using the booster unit 4, and the first subset, i.e. stream a1, is cooled in a second cooling step in the main heat exchanger 3 after it has been brought to the pressure in the fourth pressure range using the booster unit 4. The second cooling step comprises cooling to the temperature in the aforementioned first temperature range.

[0061] In the embodiment illustrated here, however, the second subset of the feed air quantity of the compressed air stream a compressed to the pressure in the third pressure range is fed as part of the subset c at the pressure in the third pressure range and at a temperature in a second temperature range in the form of the subset a2 to a second turbine unit 6, which in the embodiment illustrated here is coupled to a generator G, expanded to a pressure in the second pressure range using the second turbine unit 6, and then fed into the low-pressure column 12.

[0062] The second temperature range is selected such that a two-phase mixture with the previously specified liquid fraction forms at the outlet of the second turbine unit 6. In the embodiment illustrated here, the two-phase mixture forming at the outlet of the second turbine unit 6 is subjected to phase separation in a phase separator 7 and then fed into the low-pressure column 12 in separate phases in the form of a liquid stream a2I and a gas stream a2g.

[0063] The third subset of the feed air quantity of the compressed air stream a, compressed to the pressure in the third pressure range, is subjected to the first cooling step in the form of the aforementioned subset a3 together with the first subset, i.e. subset a1, and thus as part of subset b, and is also brought to the pressure in the fourth pressure range using the booster unit 4, wherein the third subset, i.e. subset a3, is liquefied, expanded, but at the pressure in the fourth pressure range in the main heat exchanger 3 and fed into the high-pressure column 11.

[0064] The fourth subset of the feed air quantity of the compressed air stream a, compressed to the pressure in the third pressure range, is fed in the form of the aforementioned subset a4 together with the second subset, i.e. subset a2, and thus as part of subset c, to the main heat exchanger 3, but is not removed therefrom at the temperature in the second temperature range, but is also liquefied in the main heat exchanger, then expanded, and fed into the high-pressure column 11.

[0065] In the embodiment illustrated here, the partial streams a3 and a4 used as throttle streams are combined to form a total stream k before being fed into the high-pressure column 11.

[0066] To provide the gaseous, pressurized, oxygen-rich air product, oxygen-rich liquid is withdrawn in the form of a stream I from the rectification column system 10, more precisely from a bottom of the low-pressure column 11, brought to a pressure in a sixth pressure range in the liquid state by heating to a temperature in a third temperature range by means of an internal compression pump 8, evaporated at the temperature in the third temperature range in the main heat exchanger 3 and discharged from the air separation plant 100.

[0067] For further interconnection of the components of the air separation plant 100, which may in particular also include a subcooling counterflow 9, reference is made to the cited specialist literature. In particular, only a small portion of air products is removed from the air separation plant 100 unevaporated and in a liquid state, for example in the form of a liquid oxygen stream m.

[0068] The air separation unit 200 according to Figure 2 differs from the air separation plant 100 according to Figure 1 essentially due to the absence of the phase separator 7, whereby the two-phase stream a2 is fed into the low-pressure column 12 in two phases.

[0069] The air separation unit 300 according to Figure 3 differs from the air separation units 100 and 200 according to Figures 1 and 2 essentially by providing the pressurized, oxygen-rich air product in the form of two fractions or partial streams I1 and I2, which are formed from the partial stream I and evaporated in the main heat exchanger 3 at different pressures.

[0070] The air separation unit 400 according to Figure 4 differs from the air separation plants 100 to 300 according to Figures 1 to 4Essentially, the second subset a2 (and the fourth subset a4) of the feed air quantity compressed to the pressure in the third pressure range is provided at a pressure in a fifth pressure range and is thereby brought to the pressure in the fifth pressure range using a further booster unit 41, which is driven in particular by the turbine 6 (i.e., is "self-boosted"). The further booster unit 41 is formed by a warm booster for air, i.e., by a booster with an inlet temperature above 273 K.

[0071] The air separation unit 500 according to Figure 5 differs from the air separation plants 100 to 400 according to Figures 1 to 4Essentially by using an argon discharge column 51 of a known type, as described, for example, in EP 3 067 649 A1. A gaseous stream s enriched in argon is withdrawn from the argon discharge column 51 and heated in the main heat exchanger 3. The argon discharge column 51 is fed from the low-pressure column 12, and bottoms liquid (in each case without a separate designation) is returned to the low-pressure column 12 after being depleted of argon. Bottoms liquid from the high-pressure column 11 is used to cool a top condenser of the argon discharge column 51 and is fed into the low-pressure column 12 after partial evaporation.

[0072] An "argon discharge column" refers here to a separation column for argon-oxygen separation. Its design differs only slightly from that of a conventional crude argon column, although it contains significantly fewer theoretical plates, namely fewer than 40, and particularly between 35 and 15. Like a crude argon column, the bottom section of an argon discharge column is connected to an intermediate point in the low-pressure column, and the argon discharge column is cooled by a top condenser, on whose evaporation side expanded bottom liquid from the high-pressure column is introduced. An argon discharge column does not have a bottom evaporator.

[0073] In the Figures 6 and 7are temperature-enthalpy diagrams of the main heat exchanger 3 of an air separation plant according to an embodiment of the invention, for example an air separation plant 100 to 500 according to the Figures 1 to 5 , where a temperature on the vertical axis in K is plotted against an enthalpy sum in kW on the horizontal axis and the diagram is plotted according to Figure 7 an enlarged view of the diagram according to Figure 6 The temperature points Ta1 and Ta2 correspond to the extraction temperature levels of the partial streams a1 and a2, respectively.

[0074] The air separation plants according to Figures 1 to 5 can, of course, also be adapted to produce low-pressure nitrogen product (LPGAN) as a by-product of air separation. This can be achieved by using a corresponding separation section in the low-pressure column 12.

Claims

1. A method for producing a pressurized, oxygen-rich, gaseous air product using an air separation plant (100) comprising a rectification column system (10) having a high-pressure column (11) and a low-pressure column (12) and a main heat exchanger (3), a first turbine unit (4), and a second turbine unit (4), wherein - the high-pressure column (11) is operated in a first pressure range of 4 to 7 bar, the low-pressure column (12) is operated in a second pressure range of 1 to 2 bar, and at least a predominant proportion of a total feed air quantity supplied to the rectification column system (10) is compressed to a pressure in a third pressure range which is more than 3 bar above the first pressure range, - a first partial quantity of the feed air quantity compressed to the pressure in the third pressure range is supplied to the first turbine unit (5) at the pressure in the third pressure range or at a pressure in a fourth pressure range above the third pressure range and at a temperature in a first temperature range, decompressed to a pressure in the first pressure range using the first turbine unit (5), and fed into the high-pressure column (11), - a second partial quantity of the feed air quantity compressed to the pressure in the third pressure range is supplied to the second turbine unit (6) at the pressure in the third pressure range or at a pressure in a fifth pressure range above the third pressure range and at a temperature in a second temperature range, decompressed to a pressure in the second pressure range using the second turbine unit (6), and fed into the high-pressure column (12), - oxygen-rich liquid is withdrawn from the rectification column system (10) to provide the gaseous, pressurized, oxygen-rich air product, brought to a pressure in a sixth pressure range of 16 to 50 in a liquid state, supplied to the main heat exchanger (3), evaporated therein at the temperature in a third temperature range, and discharged from the air separation plant (100), wherein - the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range is provided at the pressure in the fourth pressure range and is thereby brought to the pressure in the fourth pressure range using a booster unit (4), - the first turbine unit (5) is used to drive the booster unit (4), - the second turbine unit (6) is coupled to a generator (G) or to a warm booster compressor (41) for air, and - a proportion of less than 5% of all air products withdrawn from the air separation plant (100) is withdrawn from the air separation plant (100) in an unevaporated and liquid state, characterized in that - the second temperature range is selected such that a two-phase mixture having a liquid proportion of 5 to 15% forms at the outlet of the second turbine unit (6), - the third temperature range is above the first temperature range and the second temperature range, and - the temperature in the first temperature range and the temperature in the second differ from each other by not more than 10 K.

2. The method according to claim 1, wherein the first and second temperature ranges are 110 to 140 K.

3. The method according to claim 1 or 2, wherein the third temperature range is more than 10 K above the second temperature range.

4. The method according to any of the preceding claims, wherein the booster unit (4) is formed by a cold compressor.

5. The method according to any of the preceding claims, wherein the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range is cooled in a first cooling step in the main heat exchanger (3) before it is brought to the pressure in the fourth pressure range using the booster unit (4), and wherein the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range can be cooled in a second cooling step in the main heat exchanger (3) after it has been brought to the pressure in the fourth pressure range using the booster unit (4), wherein the second cooling step comprises cooling to the temperature in the first temperature range.

6. The method according to claim 5, wherein a third partial quantity of the feed air quantity compressed to the pressure in the third pressure range is subjected to the first cooling step together with the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range and brought to the pressure in the fourth pressure range using the booster unit (4), wherein the third partial quantity of the feed air quantity compressed to the pressure in the third pressure range is liquefied at the pressure in the fourth pressure range in the main heat exchanger, subsequently decompressed, and fed into the high-pressure column (11).

7. The method according to any of the preceding claims, wherein the second partial quantity of the feed air quantity compressed to the pressure in the third pressure range is provided at the pressure in the fifth pressure range and is thereby brought to the pressure in the fifth pressure range using a further booster unit (41).

8. The method according to any of the preceding claims, wherein the two-phase mixture forming at the outlet of the second turbine unit (6) is supplied to a phase separation and is then fed into the low-pressure column (12) in a separate phase.

9. The method according to any of claims 1 to 7, wherein the two-phase mixture forming at the outlet of the second turbine unit (6) is fed biphasically into the low-pressure column (12).

10. An air separation plant (100) which is configured for producing a pressurized, oxygen-rich, gaseous air product and has a rectification column system (10) having a high-pressure column (11) and a low-pressure column (12), as well as a main heat exchanger (3), a first turbine unit (4) and a second turbine unit (4), a booster unit (4) and a generator (G) or a warm booster compressor (41) for air, and wherein the air separation plant (100) is configured to - operate the high-pressure column (11) in a first pressure range of 4 to 7 bar, operate the low-pressure column (12) in a second pressure range of 1 to 2 bar, and compress at least a predominant proportion of a feed air quantity supplied overall to the rectification column system (10) to a pressure in a third pressure range which is more than 3 bar above the first pressure range, - supply a first partial quantity of the feed air quantity compressed to the pressure in the third pressure range to the first turbine unit (5) at the pressure in the third pressure range or at a pressure in a fourth pressure range above the third pressure range and at a temperature in a first temperature range, decompress it to a pressure in the first pressure range using the first turbine unit (5), and feed it into the high-pressure column (111), - supply a second partial quantity of the feed air quantity compressed to the pressure in the third pressure range to the second turbine unit (6) at the pressure in the third pressure range or at a pressure in a fifth pressure range above the third pressure range and at a temperature in a second temperature range, decompress it to a pressure in the second pressure range using the second turbine unit (6), and feed it into the high-pressure column (12), - remove oxygen-rich liquid from the rectification column system (10) to provide the gaseous, pressurized, oxygen-rich air product, bring it to a pressure in a sixth pressure range of 16 to 50 bar in the liquid state with heating to a temperature in a third temperature range, evaporate it in the main heat exchanger (3) at the temperature in the third temperature range, and discharge it from the air separation plant (100), and - remove a proportion of less than 5% of all air products of the air separation plant (100) removed from the air separation plant (100) in an unevaporated and liquid state, wherein the air separation plant (100) is configured such that - the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range is provided at the pressure in the fourth pressure range and is thereby brought to the pressure in the fourth pressure range using the booster unit (4), - the first turbine unit (5) is used to drive the booster unit (4), and - the second turbine unit (6) is coupled to the generator (G) or to the warm booster compressor (41) for air, characterized in that - the second temperature range can be adjusted such that a two-phase mixture having a liquid proportion of 5 to 15% forms at the outlet of the second turbine unit (6), - the air separation plant (100) is configured, by removal from the main heat exchanger (3) at suitable positions, so that the third temperature range is above the first temperature range and the second temperature range, and - the air separation plant (100) is configured such that the temperature in the first temperature range and the temperature in the second differ from each other by not more than 10 K.

11. The air separation plant (100) according to claim 10, wherein the booster unit (4) is formed by a cold compressor.