METHOD AND APPARATUS FOR PROVIDING ONE OR MORE OXYGEN-RICH, GAS-FORMED AIR PRODUCTS

Description

[0001] The invention relates to a method for providing one or more oxygen-rich, gaseous air products and a corresponding system according to the preambles of the independent claims. 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 is described, for example, in H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH, 2006, in particular section 2.2.5, "Cryogenic Rectification".

[0003] The term "air product" here refers to a fluid that is at least partially produced by the low-temperature decomposition of atmospheric air. An air product contains one or more atmospheric gases in a different composition than those found in atmospheric air. An air product can exist in a gaseous, liquid, or supercritical state and can be converted from one of these states to another. In particular, a liquid air product can be converted to the gaseous state ("evaporated") or to the supercritical state ("pseudo-evaporated") by heating it to a specific pressure, depending on whether the pressure during heating is below or above the critical pressure.

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

[0005] The rectification columns of the aforementioned rectification column systems operate at different pressures. Common double-column systems feature a high-pressure column (also known as a pressure column, medium-pressure column, or bottom column) and a low-pressure column (also known as the top column). The high-pressure column is typically operated at a pressure of 4 to 7 bar, particularly around 5.3 bar. The low-pressure column is typically operated at a pressure of 1 to 2 bar, particularly around 1.4 bar. In certain cases, higher pressures can be used in both rectification columns. The pressures specified here are absolute pressures at the top of the respective columns.

[0006] Air separation can be achieved using so-called main air compressor / booster air compressor (MAC-BAC) processes or so-called high air pressure (HAP) processes. Main air compressor / booster air compressor processes are the more conventional methods, while high air pressure processes have increasingly been used as alternatives in recent years. The present invention is used in conjunction with HAP processes, so the following explanations regarding this apply generally and also to the present invention. Due to significantly lower costs—the main and booster compressors are, in a sense, integrated into one machine—and 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 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 operates. Another portion of the feed air is compressed only to this pressure, or to a pressure differing from it by no more than 1 to 2 bar, and fed into the high-pressure column at this pressure. A main compressor / post-compressor process is used, for example, at Häring (so) in Figure 2 .3A shown.

[0008] In contrast, in a high-pressure air process, the entire quantity of feed air supplied to the rectification column system is compressed to a pressure that is significantly higher, i.e., by at least 3, 4, 5, 6, 7, 8, 9, or 10 bar, and for example up to 14, 16, 18, or 20 bar, than the pressure at which the high-pressure column is operated. 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 typically employ internal compression (IV). In internal compression, at least one gaseous, pressurized air product, supplied by the air separation unit, is generated by extracting a cryogenic, liquid air product from the rectification column system, subjecting it to a pressure increase to a product pressure, and then heating it at that pressure to convert it into the gaseous or supercritical state. 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 the alternative external compression method and is explained, for example, in Häring (so) in section 2.2.5.2, "Internal Compression".Air separation systems for low-temperature separation using internal compression are also shown in US 2007 / 0209389 A1 and WO 2015 / 127648 A1.

[0010] D1 discloses a method and a corresponding apparatus having the features of the preambles of claims 1 and 14 respectively.

[0011] The present invention aims to provide a cost-effective and efficient high-pressure process, with the goal of advantageous use under certain boundary conditions specified below. Disclosure of the invention

[0012] Against this background, the present invention proposes a method for providing one or more oxygen-rich, gaseous air products and a corresponding system with the respective features of the independent claims. Embodiments of the invention are the subject of the respective dependent claims and the following description.

[0013] First, further fundamentals of the invention are explained in more detail and terms used to describe the invention are defined.

[0014] The term "feed air volume" or simply "feed air" refers here to the total amount of air supplied to the rectification column system of an air separation plant. As previously explained, in a main compressor / recompressor process, only a portion of this feed air volume is compressed to a pressure level significantly above the (operating) pressure level of the high-pressure column. In contrast, in a high-pressure process, such as the one described in the present invention, the entire feed air volume is compressed to such a high pressure level. For the meaning of the term "significantly" in connection with main compressor / recompressor and high-pressure processes, please refer to the explanations above.

[0015] In this context, a "cryogenic" liquid is understood to be a liquid medium whose boiling point is significantly below ambient temperature, e.g., -50 °C or less, and especially -100 °C or less. Examples of cryogenic liquids include liquid air, liquid oxygen, liquid nitrogen, liquid argon, or liquids rich in these compounds.

[0016] For information on the devices and apparatus used in air separation plants, please refer to technical literature such as Häring (so), in particular section 2.2.5.6, "Apparatus". To clarify and distinguish these devices more precisely, some aspects of such devices are explained below.

[0017] In air separation plants, multi-stage turbo compressors, referred to here as "main air compressors," are used to compress the input air. The mechanical design of turbo compressors is generally well-known to those skilled in the art. In a turbo compressor, the medium to be compressed is compressed by turbine blades arranged on a turbine wheel or directly on a shaft. A turbo compressor thus forms a single structural unit, which, in the case of a multi-stage turbo compressor, can comprise several compressor stages. A compressor stage typically includes 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, which can also be connected to each other via gearboxes.

[0018] The main air compressor is further characterized by the fact that it compresses the entire volume of air fed into the distillation column system and used for the production of air products—that is, the entire input air volume. A secondary compressor may also be provided, but in this secondary compressor, only a portion of the input air compressed in the main compressor is increased to an even higher pressure. This secondary compressor may also be a turbo compressor. Additional turbo compressors, also known as boosters, are typically used to compress partial volumes of air. However, compared to the main air compressor or the secondary compressor, these perform only a relatively small amount of compression. A secondary compressor may also be present in a high-pressure process; however, in this case, it compresses a portion of the input air volume from a higher pressure level.

[0019] 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 be at the same speed (for example, via a common shaft) or at different speeds (for example, via an intermediate gearbox).

[0020] In this context, a "cold compressor" or "cold booster" is understood to be a compressor or booster to which fluid is supplied at a temperature level below the ambient temperature, in particular at less than 0 °C, -50 °C or -100 °C and possibly more than -150 °C or -200 °C.

[0021] In the terminology used here, liquid, gaseous, or supercritical fluids can be described as rich or poor in one or more components, where "rich" refers to a content of at least 75%, 90%, 95%, 99%, 99.5%, 99.9%, or 99.99%, and "poor" to 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 denotes a content of more than 90%. For example, if "nitrogen" is mentioned here, it could refer to a pure gas or a nitrogen-rich gas.

[0022] The terms "pressure level" and "temperature level" are used below to characterize pressures and temperatures, indicating that pressures and temperatures do not need to be expressed as exact pressure or temperature values ​​to realize an inventive concept. However, such pressures and temperatures typically fall within certain ranges, for example, ±1%, 5%, or 10% around a mean value. Different pressure and temperature levels may lie in disjoint ranges or in ranges that overlap. In particular, pressure levels include unavoidable or expected pressure losses, such as those resulting from cooling effects. The same applies to temperature levels. Pressure levels given here in bar are absolute pressures. Advantages of the invention

[0023] Well-known high-pressure air cooling 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 exit the system or corresponding process in liquid form, meaning that no evaporation or pseudo-evaporation occurs. Such products cannot be used to cool input streams into the system or process. Therefore, when fewer air products exit the system or corresponding process in liquid form, and instead they evaporate or pseudo-evaporate, there is, in effect, an excess of cooling capacity.

[0024] For low liquid output, a so-called cold booster can be used, for example, to increase process efficiency by converting excess cold into higher air pressure: The heat input from the cold booster partially dissipates the excess cold; however, the cold booster also compresses a portion of the intake air, allowing, for example, a corresponding reduction in the power required by the main air compressor. As mentioned above, the intake temperature of a cold booster is below the ambient temperature, thus reducing power consumption, assuming ideal gas behavior for the sake of simplicity.

[0025] The invention is used in a high-pressure air process in which gaseous oxygen is to be produced without (significant) liquid production.

[0026] The special feature lies particularly in the division of gaseous oxygen into two fractions at different pressures (almost pressureless and pressurized, for example at approximately 31 bar) in a ratio of approximately 1 to 2. An exemplary range of air products (all gaseous) for which the invention is said to be suitable is given in Table 1 below. However, the invention is not limited to this specific example or even to the orders of magnitude given here. Table 1 product Quantity (Nm³ / h) Pressure (bar) oxygen 18.700 1,3 oxygen 44.750 31 argon 1.865 17 Nitrogen 75.000 1,3

[0027] The method proposed according to the invention is also particularly suitable for use with process air supplied at a pressure level of approximately 6 bar (for example, from an existing supply network at the site, a so-called "air rail"). For this reason, an air separation plant as proposed in one embodiment of the invention, or a corresponding method, comprises a configuration typical of a main compressor / secondary compressor process, but in which the entire quantity of process air is nevertheless brought to a pressure level typical for a high-pressure process, and in which an injection turbine (Lachmann turbine) is also provided. As explained below, however, a second turbine can also be used within the scope of the present invention instead of an injection or Lachmann turbine, which expands air into the high-pressure column in the manner of a Claude turbine.For the terms "Claude turbine" and "Lachmann turbine", reference is made to specialist literature, for example FG Kerry, Industrial Gas Handbook: Gas Separation and Purification, CRC Press, 2006, in particular sections 2.4, "Contemporary Liquefaction Cycles", 2.6, "Theoretical Analysis of the Claude Cycle" and 3.8.1, "The Lachmann Principle".

[0028] In this context, the present invention proposes a process for producing one or more oxygen-rich, gaseous air products using an air separation plant comprising a rectification column system with a high-pressure column. A total quantity of feed air supplied to the rectification column system is compressed to a first pressure level that is at least 3 bar (further values ​​have already been mentioned in the introduction and are also suitable for the present invention) above the operating pressure level at which the high-pressure column is operated.A first process stream, consisting predominantly or exclusively of pressurized non-liquefied air, and a second process stream, consisting predominantly or exclusively of pressurized liquefied air, are generated. The first and second process streams are then separately subjected to expansion to the operating pressure level of the high-pressure column and partially or completely fed into the high-pressure column. It is understood that, after expansion, additional material streams can be added to the first and second process streams and fed into the high-pressure column together with them. Furthermore, it is understood that not the entire first or second process stream needs to be fed into the high-pressure column after expansion.

[0029] The first process stream, which comprises predominantly or exclusively pressurized non-liquefied air, is expanded, in particular, in an expansion turbine, as will be explained in detail below. This is a so-called turbine stream, as is also generated in known air separation processes. The expansion turbine used to expand such a turbine stream is a typical Claude turbine. The second process stream, generated within the scope of the present invention and comprising predominantly or exclusively pressurized liquefied air, corresponds to a known throttled stream, as is also generated in the prior art. For expanding the second process stream, i.e., the throttled stream, an expansion valve can be used, for example, within the scope of the present invention; however, a so-called liquid turbine can also be used, for example.A so-called dense liquid expander (DLE), as known from the prior art, is used. The advantages of liquid turbines are extensively described in the prior art, for example in Häring (so), section 2.2.5.6, "Apparatus", pages 48 and 49.

[0030] It is understood that, within the scope of the present invention, the first and second process streams are generated at a pressure level above the operating pressure level of the high-pressure column. Within the scope of the present invention, the operating pressure level of the high-pressure column is understood to be, in particular, the pressure level present at an inlet point of the first or second process stream into the high-pressure column, or a pressure range encompassing the pressures at these inlets. It is known that rectification columns can exhibit pressure gradients during operation. Therefore, as mentioned, the term "operating pressure level" refers to the pressure at the respective inlet point or a corresponding pressure range. Specific values, which also apply to the present invention, have been mentioned in the introduction.

[0031] According to the invention, a portion of the input air is used to form the first and second process streams. This portion is supplied at the first pressure and temperature level and is successively subjected to cooling to a second temperature level, compression to a second pressure level, cooling to a third temperature level, and, while maintaining a liquid phase and a gas phase, phase separation. Within the scope of the present invention, the first temperature level is particularly above 0 °C, for example, at ambient temperature, typically in a range of 10 to 50 °C. Within the scope of the present invention, the second temperature level is particularly between -120 and -150 °C; thus, compression to the second pressure level is carried out starting from a correspondingly low temperature level. A compressor used for compression to the second pressure level is...A booster, which is advantageously driven by means of an expansion turbine that expands the first process stream to the operating pressure level of the high-pressure column, is therefore a so-called cold booster, as already explained in the introduction.

[0032] Within the scope of the present invention, the first pressure level (upstream of the cold booster) is particularly between 7 and 13 bar, and the second pressure level (downstream of the cold booster), to which the air used to form the first and second process streams is compressed after cooling to the second temperature level, is particularly between 11 and 17 bar. The third temperature level, to which the air used to form the first and second process streams is cooled after compression to the second pressure level (after having been heated by the compression), is particularly between -140 and -170 °C.

[0033] Within the scope of the present invention, it is provided that the first process stream is formed using at least a portion of the gas phase from the aforementioned phase separation, and that the second process stream is formed using at least a portion of the liquid phase formed in the phase separation. In particular, the first process stream can comprise the entire gas phase and / or the second process stream the entire liquid phase, each formed in the phase separation.

[0034] The first process stream is subjected to pressure reduction to the high-pressure column pressure level at the second pressure level and the third temperature level. Within the scope of the present invention, the second pressure level and the third temperature level are selected such that, upon reduction of the first process stream to the operating pressure level of the high-pressure column, a liquid fraction of 5% to 15%, based on the total first process stream, is formed. For example, the liquid fraction within the scope of the present invention is approximately 10%.

[0035] In other words, the expansion turbine used for the expansion of the first process stream, according to the present invention, is operated with a defined (dew) state at the turbine inlet, resulting in a corresponding liquid fraction at the turbine outlet. Such measures allow the process potential to be optimally exploited and ensure reliable operation. The aforementioned liquid fraction refers in particular to a fraction calculated from the respective standard volumes of the fractions formed.

[0036] The operation of the expansion turbine according to the invention for expanding the first process stream is to be considered in particular in connection with a used injection turbine or an expansion turbine that expands a further turbine stream, as explained below.

[0037] According to the invention, to form at least a third process stream, which is subjected to expansion using an expansion turbine and fed into the rectification column system, a further portion of the feed air is used. This feed air is supplied at the first pressure and temperature levels and is cooled without further compression. Additional process streams can also be supplied that are not subjected to further compression but are used elsewhere, for example, fed into the rectification column system. These are partially explained below.

[0038] If the process proposed according to the invention were considered conventionally, i.e., with usual optimization of the turbine inlet temperatures, it would be found that the outlet state of a corresponding injection turbine is strongly pre-liquefied, and the inlet state of the turbine used for the expansion of the first process stream exhibits only a relatively small superheat of approximately 2 to 2.5 K above the dew point. Such operating conditions are unfavorable from an operational engineering perspective, since, firstly, additional measures would be required to reliably convey the liquid accumulating at the outlet of the injection turbine into the low-pressure column, and secondly, pre-liquefaction could occur upstream of the expansion turbine used for the expansion of the first process stream. With such pre-liquefaction, [further complications may arise].Damage to the inlet nozzles in a corresponding expansion turbine and to the impeller surface is to be feared.

[0039] Therefore, in an advantageous embodiment of the present invention, it is further proposed to raise the inlet temperature of a corresponding third process stream into the injection turbine (i.e., a Lachmann turbine) or the turbine that expands the corresponding air into the high-pressure column (i.e., a Claude turbine), or to select a higher temperature such that no liquid is produced at its outlet. Conversely, the inlet temperature of the turbine used to expand the first process stream is set lower, so that the liquid that would be "missing" from a balance perspective is practically produced by said turbine during the expansion of the first process stream.

[0040] A key feature of the present invention is that the turbine flow, i.e., the first process flow and the second process flow (a throttled flow), are cooled together and pre-liquefied before entering the turbine, as previously explained. The resulting liquid is separated in a separator and, in particular, returned to the heat exchanger for subcooling in the form of the second process flow. The gas from a corresponding separator is fed directly into the turbine in the form of the first process flow, as previously described in other words.

[0041] In all cases, within the scope of the present invention, in addition to the second process stream, a further process stream can also be liquefied in a main heat exchanger of the air separation plant and partially or completely expanded into the high-pressure column, in particular together with the second process stream, wherein expansion can take place separately from the second process stream or together with it.

[0042] As already explained, in the context of the present invention an injection turbine or Lachmann turbine is advantageously used or a corresponding material flow is formed.

[0043] However, a second turbine stream can also be provided, or air can be expanded in a Claude turbine. In other words, according to particularly preferred embodiments of the present invention, the third process stream, which comprises predominantly or exclusively pressurized unliquefied air, is subjected to (turbine) expansion to an operating pressure level of a low-pressure column of the rectification column system and is partially or completely fed into the low-pressure column, or is subjected to expansion to the operating pressure level of the high-pressure column and is partially or completely fed into the high-pressure column. The third process stream is subjected to expansion, in particular, at a temperature level that is more than 10 K above the third temperature level and differs from the second temperature level by less than 10 K.

[0044] As already mentioned, the expansion of such a third process stream is carried out in the context of the present invention in such a way that no, or no significant, liquid fraction forms at the outlet of an expansion turbine used for this expansion. This liquid fraction, which is required for balance reasons, is instead formed in the expansion turbine used for the expansion of the first process stream, as already mentioned.

[0045] Within the scope of the present invention, air supplied at the first pressure and temperature levels is also used to form the third process stream. This air is then cooled to a fourth temperature level. The fourth temperature level can be, in particular, between -120 and -150 °C. It is selected, in combination with the pressure used (i.e., the first pressure level, since no further compression takes place), such that the described outlet conditions are established at a turbine used for the expansion of the third process stream.

[0046] Within the scope of the present invention, the total air volume is advantageously brought to the first pressure level using an air compressor and a booster arranged in parallel to the air compressor. The air used to form the third process stream is also part of this total air volume. The booster is coupled to and driven by an expansion machine used in the expansion of the third process stream. The booster can be driven exclusively or partially by this expansion machine; in other words, an additional motor drive can also be used, for example. The coupling can also be achieved with the interposition of a brake, so that not all of the drive power released during the expansion of the third process stream is used to drive the booster.

[0047] It should be clarified once again that, within the scope of the present invention and according to the embodiment just described, a first portion of the total air volume is passed through the air compressor and not through the booster, and a second portion of the total air volume is passed through the booster and not through the air compressor. Using the total air volume, the first, second, and third process streams are formed; however, a further process stream can also be formed in the form of an additional throttled stream, the air from which can be cooled and liquefied in a main heat exchanger of the air separation plant and fed into the high-pressure column. For further details, reference is made to the technical literature cited at the outset.

[0048] Advantageously, the second portion of the total air volume comprises 5% to 25% of the total air volume, and the first portion comprises, in particular, the remainder. These proportions are also based on standard volume flows. Within the scope of the present invention, the first portion can, in the evaluated case, comprise, in particular, 13% to 17% of the total air volume. By compressing this portion of the total air volume in a booster, a cost reduction for the air compressor can be achieved within the scope of the present invention. The air compressor can thus be designed, in particular, as a single-stage unit. It can, in particular, be supplied with air originating from an air supply network, which is already compressed to a specific pressure level within this network. However, the air compressor can also be connected downstream of further compressor stages, for example, as a compressor stage.

[0049] It should be emphasized in particular that, within the scope of the present invention, the booster is not used to compress an air volume that has already undergone purification. Rather, within the scope of the present invention, the booster is used, in particular, upstream of a corresponding purification system. In other words, according to a particularly preferred embodiment, the total air volume is compressed in a water-containing state using the air compressor and the booster, and then, i.e., after compression, pre-cooled and dried. As already mentioned, the total air volume can be supplied to the air compressor and the booster at a super-atmospheric pressure level. The total air volume can be supplied externally to this super-atmospheric output pressure level or compressed to this output pressure level within the air separation unit.

[0050] As explained several times, the present invention is used in air separation processes in which no or only extremely small quantities of liquid air products are formed. In other words, the present invention comprises the discharge, at any given time, of a quantity of one or more air products corresponding to a maximum of 2% of the total air volume from the air separation plant in liquid form. This discharge can be continuous or intermittent. The maximum quantity can, in particular, also be 1.5%, 1%, or 0.5%.

[0051] Within the scope of the present invention, two or more than two oxygen-rich, gaseous air products are provided. A first of these oxygen-rich, gaseous air products can be provided by internal compression, as explained several times above. For this purpose, oxygen-rich liquid is typically withdrawn from the low-pressure column, pressurized using an internal compression pump, and, at the pressure to which it was pressurized by the internal compression pump, converted into the gaseous or supercritical state in a main heat exchanger of the air separation plant. A second of these oxygen-rich, gaseous air products is, within the scope of the present invention, in particular withdrawn in gaseous form from the low-pressure column without pressure increase.

[0052] Just to clarify, it should be summarized again that the air used to provide the first and second process streams is subjected to cooling to the second temperature level at the first pressure level and the first temperature level, compression to the second pressure level at the second temperature level and the first pressure level, cooling to the third temperature level at the second pressure level and a temperature level above the second temperature level, and phase separation at the second pressure level and the third temperature level.

[0053] The present invention further relates to an air separation plant for providing one or more oxygen-rich, gaseous air products. For the features of the air separation plant proposed according to the invention, express reference is made to the corresponding independent claim. Such an air separation plant benefits from the advantages previously explained with regard to the process according to the invention and its preferred embodiments, to which express reference is therefore made. In particular, such an air separation plant is configured to carry out a process according to one of the previously explained embodiments and includes means provided for this purpose.

[0054] The invention is explained in more detail below with reference to the accompanying drawings, which illustrate preferred embodiments of the present invention.

[0055] Brief description of the drawings Figure 1 illustrates an air separation plant according to a particularly preferred embodiment of the invention. Figure 2 illustrates an air separation plant according to a particularly preferred embodiment of the invention. Figure 3 illustrates an air separation plant according to a particularly preferred embodiment of the invention.

[0056] The figures illustrate structurally or functionally corresponding elements with identical reference symbols, which are not explained again for the sake of clarity. Detailed description of the drawings

[0057] In the Figures 1 to 3Air separation plants designated 100, 200, and 300, respectively, according to preferred embodiments of the invention, are illustrated. Air separation plants 100, 200, and 300 have a number of identically designed components, but in practice, their construction may differ. Air separation plant 100 is described first. Figure 1 explained; regarding the in the Figures 2 and 3 The following discussion focuses only on the differentiating features of the illustrated air separation plants 200 and 300.

[0058] In the Figure 1 In the illustrated air separation plant 100, air A, which has already been pressurized outside the plant 100, is supplied in the form of a feed air stream a. This air can, for example, originate from a supply network and be at a pressure of approximately 6 bar. This differs from the illustration according to... Figure 1However, the air A can also be pressurized within the air separation plant 100.

[0059] The intake air A of the intake air stream a is, after pre-cooling (which is required in certain cases) in a heat exchanger (not specifically designated), split into two partial streams b and c, wherein partial stream b is compressed in an air compressor 101 and partial stream c in a booster 102. In the terminology used here, a pressure level upstream of the air compressor 101 and the booster 102 is referred to as the "outlet pressure level," while a pressure level downstream of the air compressor 101 and the booster 102 is referred to as the "first pressure level." The air compressor 101 is preferably a single-stage design. As explained above, the majority of the intake air A is compressed in the form of mass stream b in the air compressor 101, while a smaller portion is compressed in parallel in the booster 102.

[0060] After compression, the partial flows b and c are combined in the illustrated example to form a collecting flow d, which is cooled in a generally known manner in a pre-cooling device 103 using cooling water (supply B, return C). The cooled feed air flow is further referred to as d and is then fed to a cleaning device 104, for example comprising a pair of adsorber tanks operated alternately.

[0061] The resulting mass flow, now free of water and carbon dioxide and referred to here as d, is divided into several partial flows. One partial flow e is fed (at the first pressure level and a temperature level referred to here as the "first temperature level") to a main heat exchanger 105 of the air separation plant 100. Partial flow e is withdrawn from the main heat exchanger 105 at a temperature level referred to here as the "second temperature level." Partial flow e is initially still at the first pressure level. At the first pressure level and the second temperature level, partial flow e is subjected to compression in a cold booster 106. This increases its pressure to a higher level, referred to here as the "second pressure level."

[0062] The temperature of the partial flow e increases due to the compression introduced by the heat of compression, so that the partial flow e is fed back into the main heat exchanger 105 at an intermediate temperature level above the second temperature level. The partial flow e is then further cooled in the main heat exchanger 105 to a temperature level referred to here as the "third temperature level". At the second pressure level and the third temperature level obtained through cooling, the partial flow e is then fed into a separator 107 and subjected to phase separation.

[0063] In the example shown here, a gas phase in the form of a mass flow f and a liquid phase in the form of a mass flow g are drawn off from separator 107. Mass flow f is referred to here as the "first process flow," and mass flow g as the "second process flow." Due to the previously described treatment, the first process flow comprises unliquefied, pressurized air, and the second process flow g comprises pressurized and liquefied air.

[0064] The first process stream f is expanded in an expansion turbine 108 and fed into a high-pressure column 111 of the air separation plant 100. As explained previously, the expansion turbine 108 is operated in such a way that a defined liquid fraction forms at its outlet. The expansion in the expansion turbine 108 is brought to the operating pressure level of the high-pressure column 111, or to the pressure level present at the feed point in the high-pressure column 111.

[0065] The second process stream g is in the Figure 1The illustrated example is fed back into the main heat exchanger 105 and extracted at the cold end. The second process stream g is combined with a partial stream h of the mass stream d, which was passed through the main heat exchanger 105 from the hot to the cold end and thereby liquefied, after the second process stream g and the partial stream h have each been expanded in appropriate expansion devices, for example, expansion valves, which are not specifically described here. The expansion also takes place to a pressure level of the high-pressure column 111 or a pressure level that is present at a feed point into the high-pressure column 111. A mass stream formed from the second process stream g and the partial stream h is designated as a combined stream with the reference symbol i.

[0066] In the air separation plant 100 according to Figure 1Furthermore, air is blown into a low-pressure column 112 of the air separation plant 100, for which a generally known Lachmann turbine 109 is used. The Lachmann turbine 109 is an expansion turbine, which is used in the Figure 1 The illustrated configuration of the air separation unit 100 is mechanically coupled to the previously described booster 102. The air expanded in the expansion turbine 109 is a partial stream k of the mass stream d, which was previously cooled to an intermediate temperature level in the main heat exchanger 105 (referred to here as the "fourth temperature level"). The air expanded in the expansion turbine 109 of partial stream k is fed (see connection 2) into the low-pressure column 112, as already mentioned.

[0067] In the illustrated example, the air separation plant 100 comprises, in addition to the high-pressure column 111 and the low-pressure column 112 in a rectification column system designated 110, a crude argon column 113 and a pure argon column 114. The operation of the rectification column system 110 is known from the prior art.

[0068] Air separation plants of the type shown are described in many other places, for example in Häring (so) zu Figure 2 .3A. For detailed explanations of the structure and function, reference is therefore made to relevant technical literature. An air separation plant for the use of the present invention can be designed in a variety of ways.

[0069] In the example shown, two gaseous, oxygen-rich air products are provided at different pressure levels. To provide a gaseous, oxygen-rich air product at just above atmospheric pressure, i.e., the pressure level at which the low-pressure column 112 is operated, gaseous fluid is extracted from the low-pressure column 112 above its sump in the form of a mass flow I. This flow is heated in the main heat exchanger 105 without any further pressure-influencing measures and is provided as the corresponding air product, which is additionally designated here as D.

[0070] To provide the pressurized, oxygen-rich, gaseous air product, bottom liquid from the low-pressure column 112 is extracted in the form of a mass stream m, which, in the illustrated example, can also be partially supplied as liquid oxygen, here additionally designated K, in the form of a mass stream n from the air separation unit 100. This is preferably not the case, or only to a small extent, within the scope of the present invention. To provide the pressurized, oxygen-rich, gaseous air product, the remaining portion is brought to a higher pressure level, here designated as the "discharge pressure level," using an internal compression pump 115, converted into the gaseous or, depending on the pressure level, supercritical state in the main heat exchanger 105, and supplied in the form of a mass stream o as the corresponding air product, here additionally designated E.

[0071] In the Figure 1In the depicted air separation plant 100, pressurized, gaseous, argon-rich fluid is also provided as air product F. For this purpose, liquid is taken from the pure argon column 114 in the form of a mass flow p and, similar to the mass flow o, is brought to a higher pressure level in an internal compression pump 116, converted to a gaseous or supercritical state in the main heat exchanger 105 and provided in the form of the corresponding air product F.

[0072] As is known from the field of air separation, low-pressure nitrogen in the form of an air product G, nitrogen from the top of the high-pressure column 111 in the form of an air product H, and impure nitrogen from the top of the low-pressure column 112 in the form of an air product I can also be provided by means of the air separation plant 100. Further impure nitrogen can be withdrawn from the low-pressure column 112 in the form of a mass stream r and used, for example, as regeneration gas in the purification unit 104 or in the precooling unit 103 and subsequently vented to the atmosphere X. Theoretically, but preferably not within the scope of the present invention, a liquid nitrogen product L can be provided by removing liquid.

[0073] The air separation plant 200 according to Figure 2 differs from air separation plant 100 according to Figure 1in particular by the fact that the second process stream g is not further cooled in the main heat exchanger 105 before its expansion and feeding into the low-pressure column.

[0074] In the air separation plant 300, which is located in Figure 3 As illustrated, in contrast to the air separation plant 100 according to Figure 1 The partial flow k, which is expanded in the expansion turbine 109, is only provided for to be fed to the pressure level of the high-pressure column 111; the partial flow k is therefore not blown into the low-pressure column, but is supplied to the high-pressure column 111 as a further turbine flow.

Claims

1. A method for producing one or more oxygen-rich, gaseous air products using an air separation plant (100-300) that has a rectification column system (110) having a high-pressure column (111), wherein - a total feed air quantity that is supplied to the rectification column system (110) is compressed to a first pressure level that is at least 3 bar above an operating pressure level at which the high-pressure column (111) is operated, - in the air separation plant (100-300), a first process stream that predominantly or exclusively comprises pressurized non-liquefied air and a second process stream that predominantly or exclusively comprises pressurized liquefied air are formed, and - the first and second process streams, separately from one another, are subjected to a decompression to the operating pressure level of the high-pressure column (111) and are partially or completely fed into the high-pressure column (111), - to form the first and second process streams, a portion of the feed air quantity is used that is provided at the first pressure level and at a first temperature level and is successively subjected to cooling to a second temperature level of -120°C to -150°C, to compression to a second pressure level and to cooling to a third temperature level, - to form at least a third process stream that is subjected to a decompression using a decompression turbine (109) and fed into the rectification column system (110), a further portion of the feed air quantity is used that is provided at the first pressure level and at the first temperature level and is subjected to cooling without further compression, - the cooling of the first, the second and at least the third process streams is carried out exclusively using further process streams that are provided using the rectification column system (110), and - at any given time, a quantity of one or more air products in liquid state corresponding to a maximum of 2% of the total air quantity is discharged from the air separation plant (100-300), characterized in that - to form the first and second process streams, the portion of the feed air quantity, after being cooled to a third temperature level, is subjected to phase separation while maintaining a liquid phase and a gas phase, wherein the first process stream is formed using at least a portion of the gas phase and the second process stream is formed using at least a portion of the liquid phase, and - the first process stream is fed to a decompression at the second pressure level and at the third temperature level, wherein the second pressure level and the third temperature level are selected such that, when the first process stream is decompressed to the operating pressure level of the high-pressure column (111), a liquid fraction of 5% to 15% is formed, based on the total first process stream.

2. The method according to claim 1, wherein the third process stream predominantly or exclusively comprises non-liquefied air, wherein the third process stream is subjected to a decompression to an operating pressure level of a low-pressure column (112) of the rectification column system (110) and is partially or completely fed into the low-pressure column (112), or is subjected to a decompression to the operating pressure level of the high-pressure column (111) and is partially or completely fed into the high-pressure column (111).

3. The method according to claim 2, wherein the third process stream is fed to a decompression at a temperature level that is more than 10 K above the third temperature level and differs from the second temperature level by less than 10 K.

4. The method according to claim 2 or 3, wherein the air used to form the third process stream is subjected to cooling to a fourth temperature level.

5. The method according to either of claims 3 to 4, wherein the total air quantity is brought to the first pressure level using an air compressor (101) and a booster (102) that is arranged parallel to the air compressor (101), wherein the booster (102) is coupled to and driven by a decompression turbine (109) that is used in the decompression of the third process stream.

6. The method according to claim 5, wherein a first portion of the total air quantity is passed through the air compressor (101) and not through the booster (102), and wherein a second portion of the total air quantity is passed through the booster (102) and not through the air compressor (101).

7. The method according to claim 6, wherein the second portion of the total air quantity comprises 5% to 25% of the total air quantity, and the first portion of the total air quantity comprises the remainder of the total air quantity.

8. The method according to any of claims 5 to 7, wherein the total air quantity is compressed in a water-containing state using the air compressor (101) and the booster (102) and thereafter is jointly pre-cooled and dried.

9. The method according to any of claims 5 to 8, wherein the air compressor (101) is a single-stage air compressor.

10. The method according to any of claims 5 to 9, wherein the total air quantity is supplied to the air compressor (101) and the booster (102) at a superatmospheric output pressure level.

11. The method according to claim 10, wherein the total air quantity is provided from outside the plant at the superatmospheric output pressure level or is compressed to the output pressure level in the air separation plant.

12. The method according to any of the preceding claims 2 to 11, wherein two or more than two oxygen-rich, gaseous air products are provided, wherein a first of the oxygen-rich, gaseous air products is provided by internal compression, and wherein a second of the oxygen-rich, gaseous air products is taken in gaseous form from the low-pressure column (112) without pressure increase.

13. The method according to one of the preceding claims, wherein the air used to provide the first and second process streams is subjected to cooling to the second temperature level at the first pressure level and the first temperature level, to compression to the second pressure level at the second temperature level and the first pressure level, to cooling to the third temperature level at the second pressure level and a temperature level above the second temperature level, and to phase separation at the second pressure level and the third temperature level.

14. An air separation plant (100-300) that has a rectification column system (110) having a high-pressure column (111) and is configured to provide one or more oxygen-rich, gaseous air products, wherein - means are provided that comprise a compressor (101) and are configured to compress a total feed air quantity that is supplied to the rectification column system (110) to a first pressure level that is at least 3 bar above an operating pressure level at which the high-pressure column (111) is operated, - means are provided that are configured to form a first process stream that predominantly or exclusively comprises pressurized non-liquefied air and a second process stream that predominantly or exclusively comprises pressurized liquefied air, and - means are provided that are configured to subject the first and second process streams, separately from one another, to a decompression to the operating pressure level of the high-pressure column (111) and to partially or completely feed them into the high-pressure column (111), - means are provided that are configured to use a portion of the feed air quantity that is provided at the first pressure level and at a first temperature level for the formation of the first and second process streams, and to subject this air successively to cooling to a second temperature level of -120°C to -150°C, to compression to a second pressure level and to cooling to a third temperature level, - means are provided that are configured to use a further portion of the feed air quantity that is provided at the first pressure level and at the first temperature level and is subjected to cooling without further compression for the formation of at least a third process stream, for the decompression of which a decompression turbine (109) is provided, and which is fed into the rectification column system (110), - means are provided that are configured to carry out the cooling of the first, the second and at least the third process streams exclusively using further process streams that are provided using the rectification column system (110), - means are provided that are configured to discharge from the air separation plant (100-300), at any given time, a quantity of one or more air products in liquid state corresponding to a maximum of 2% of the total air quantity, characterized in that - the means provided for the formation of the first and second process streams are configured to subject the portion of the feed air quantity, after cooling to the third temperature level, to phase separation while maintaining a liquid phase and a gas phase, - means are provided that are configured to form the first process stream using at least a portion of the gas phase and the second process stream using at least a portion of the liquid phase, and to feed the first process stream to a decompression at the second pressure level and at the third temperature level, and - means are provided that are configured to provide the second pressure level and the third temperature level in such a way that, when the first process stream is decompressed to the operating pressure level of the high-pressure column (111), a liquid fraction of 5% to 15% in relation to the total first process stream is formed.