Method and apparatus for cryogenic separation of air

Abstract

The invention provides a method for cryogenic separation of air using an air separation plant (100, 200, 300) configured as a high pressure air separation plant, wherein several partial air streams are formed from initially compressed air (A), which are at least partially further compressed, cooled in a main heat exchanger (3) and expanded before being introduced into a column system (10). The partial air streams include a first partial air stream (C) and a second partial air stream (E), the air of which is compressed in parallel in a first warm booster (5) and a second warm booster (7) and thereafter expanded in a first expander (4) and a second expander (6) which are mechanically connected to the first booster (5) and to the second booster (7), respectively. Gaseous oxygen is produced and withdrawn at an internal pressure of between 3 bar and 9 bar absolute, without using recirculation or excess air and without using a Lashmet turbine. A corresponding air separation plant (100) is also part of the invention.

Description

[0001] The present invention relates to a method and corresponding apparatus for cryogenic air separation according to the preamble of the independent claim. Background Technology

[0002] It is known to prepare air products in liquid or gaseous form by performing cryogenic separation of air in an air separation device (air separation unit), and for example in H.-W. In (Ed.), Industrial Gases Processing, Wiley-VCH, 2006, it is described in particular in Section 2.2.5, “Cryogenic Distillation”.

[0003] Classic types of air separation equipment have a tower system, which can be designed as a two-tower system, especially a twin-tower system, but can also be designed as a three-tower or multi-tower system. In addition to distillation towers for recovering liquid and / or gaseous nitrogen and / or oxygen, i.e., distillation towers for separating nitrogen and oxygen, distillation towers for recovering other air components, especially inert gases, can also be provided.

[0004] The distillation columns in the aforementioned column system operate within different pressure ranges. Known two-column systems include a so-called pressure column (also known as a high-pressure column, medium-pressure column, or lower-pressure column) and a so-called low-pressure column (also known as an upper column). The high-pressure column typically operates between 4 and 7 bar, particularly in the pressure range of approximately 5.3 bar, while the low-pressure column typically operates between 1 and 2 bar, particularly in the pressure range of approximately 1.4 bar. In some cases, higher pressures may also be used in both distillation columns. The pressures indicated here and below are the absolute pressures at the top of the respective columns.

[0005] For air separation, the so-called Main Air Compressor / Booster Air Compressor (MAC-BAC) method or the so-called High Pressure (HAP) method can be used. The MAC-BAC method is more conventional, while the HAP method has been increasingly used as an alternative in recent times. The HAP method is used in the context of this invention.

[0006] The main air compressor / boost air compressor method is characterized in that only a portion of the total supply air volume to the tower system is compressed to a pressure within a pressure range significantly higher than the pressure range where the pressure tower typically operates (see above). Another portion of the supply air volume is compressed only to a pressure within this pressure range, or at most to a maximum pressure 1 to 2 bar higher than this, and is supplied to the pressure tower without further expansion. For example, in... of Figure 2 An example of this method is shown in .3A (see above).

[0007] However, in the high-pressure method, the total amount of air supplied to the pressure tower, especially the total amount of air supplied to the tower system as a whole, is compressed to a pressure range significantly higher than the operating pressure range of the pressure tower. The corresponding pressure range is, for example, between 10 bar and 100 bar. Therefore, the air supplied to the pressure tower is expanded in the high-pressure method before being supplied to the tower. The high-pressure method has been described many times and is known, for example, from EP 2980514 A1 and EP 2963367 A1.

[0008] In the apparatus disclosed in US 6257020 B1 for separating air by cryogenic distillation, all air is compressed to a medium pressure. A portion of the air is compressed to an intermediate pressure, and another portion of that air is compressed to a high pressure. The high-pressure air is split into at least two portions and expanded in two turbine expanders, with the cooling flow from the warm turbine expander being at least partially recirculated to the warm end of an exchanger at a higher pressure. Liquid from the air separation unit evaporates in the exchanger.

[0009] According to US 5,400,600 A, the supply air, fully compressed to the first high pressure P1, is partially further compressed to pressure P2. At an intermediate temperature, a portion of each air stream expands in a turbine. One of the turbines may have an output at a pressure P3 between P1 and the intermediate pressure. The majority of the separated oxygen is taken as a liquid from the low-pressure tower, pumped to the production pressure, and evaporates in the heat exchange line through condensation or pseudo-condensation of the air at one of pressures P1, P2, and P3, depending on whether the condensation occurs at subcritical or supercritical pressure.

[0010] Air separation equipment can be designed differently depending on the air product to be supplied and the required aggregation and pressure conditions. For example, so-called internal compression is known to provide gaseous pressure products. In this method, a cryogenic liquid is taken from the tower system, pressurized in its liquid state, and converted into a gaseous or supercritical state by heating in the main heat exchanger. In this way, for example, internally compressed gaseous oxygen, internally compressed gaseous nitrogen, or internally compressed gaseous argon can be produced. Internal compression offers several advantages over external compression, which is also possible, for example in... (See above), Section 2.2.5.2, “Internal Compression”, for an explanation. The present invention also relates to an air separation method including internal compression.

[0011] Classical air separation methods and equipment are sometimes not optimal when more unusual product profiles are required (i.e., the amount or proportion of liquid or gaseous air products at a given pressure).

[0012] For example, a low-pressure oxygen product (at about 3 to 9 bar) combined with a large amount of liquid products is a slightly unusual product profile, especially if the ratio of the total value characterizing all liquid products (referred to herein as "liquid nitrogen equivalent") to the low-pressure gaseous oxygen product is about 0.93. For the definitions of the terms "liquid product" and "gaseous product" and the liquid nitrogen equivalent, refer to the following explanation. For such a product profile, a high-pressure air separation method or apparatus including a so-called excess air turbine is considered. In the excess air turbine, compressed and cooled air is re-expanded without being separated, heated, or discharged from the air separation device or returned to the inlet of the main air compressor. In this way, additional cooling capacity is obtained. An air separation apparatus with an excess air turbine is shown, for example, in US 3,905,201 A. In the high-pressure method, the air supplied to the excess air turbine is typically formed from air that has already been expanded to a pressure within the corresponding pressure range along with the air supplied to the pressure tower. This air is heated before and after expansion in the excess air turbine. In excess air turbines, pressurized nitrogen, typically from a pressure tower, is also expanded and then treated accordingly along with excess air.

[0013] However, as discovered according to the invention, the high-pressure method with excess air turbines has several disadvantages. First, the relatively high volumetric airflow rate (approximately 150,000 standard cubic meters per hour at approximately 15.8 bar in one illustrative example) in the “warm” components of the equipment represents a disadvantage, considering the capital expenditure required for the piping and molecular sieve slides / containers needed to regulate the supply air. Second, the need for relatively large excess air turbines (for expanding the mixed flow comprising excess air and pressurized nitrogen from the pressure tower) also increases capital expenditure. Third, a product compressor for the low-pressure nitrogen from the low-pressure tower must be provided, which must handle a volume of approximately 19,000 standard cubic meters per hour. This also leads to high capital expenditure, as a four-stage compressor is typically required. Low-pressure recirculation is also generally not very efficient for high liquid yields and requires a relatively high heat exchanger surface area.

[0014] One object of the present invention is to provide a method and an apparatus by which the above-mentioned product requirements can be met more efficiently and, in particular, with lower operating and capital expenditures. Summary of the Invention

[0015] Against this backdrop, the present invention proposes a method and corresponding apparatus for cryogenic air separation, having the features of the independent claims. Preferred embodiments of the invention are the subject of the dependent claims and the following description.

[0016] In the following text, before proceeding to the specific features and advantages of the invention, some basic principles of the invention are explained and the terminology used to describe the invention is defined.

[0017] For more information on the equipment and apparatus used in air separation equipment, please refer to technical documents such as (See above), especially section 2.2.5.6, “Apparatus”. In the following text, some aspects of this apparatus will be explained in more detail for clarification and clearer distinction.

[0018] In air separation methods and apparatus, multi-stage turbo compressors are used to compress all the air to be separated; such compressors are referred to as "main air compressors" or simply "main compressors." The mechanical design of turbo compressors is essentially known to those skilled in the art. In a turbo compressor, the medium to be compressed is compressed by means of turbine blades or impellers arranged on a turbine impeller or directly on a shaft. A turbo compressor forms a single structural unit, but in a multi-stage turbo compressor, it may comprise multiple compressor stages. A compressor stage typically includes a corresponding arrangement of turbine impellers or turbine blades. All these compressor stages may be driven by a common shaft. However, it is also conceivable that compressor stages are driven in groups on different shafts, where these shafts may also be interconnected via gears at different speeds.

[0019] The main air compressor is characterized in that it compresses the entire volume of air supplied to the tower system for the production of air products, i.e., the entire supply air. Correspondingly, a "boost air compressor" or "post-compressor" may also be provided, where only a portion of the air volume compressed in the main air compressor is brought to even higher pressures. This can also be a turbo compressor. To compress a portion of the air volume, a separate turbo compressor, also called a booster, is typically provided, but compared to the main air compressor or boost air compressor, such a separate turbo compressor only compresses the air to a relatively small extent. Booster air compressors can also be present in high-pressure methods, where they begin compressing a portion of the air volume from a correspondingly higher pressure. If the feed to the booster is supplied at a temperature above 0°C, particularly above 10°C or above 20°C and at most 50°C, the booster is called a "warm booster."

[0020] Air can also expand at several points in the air separation device; for this purpose, an expander in the form of a turbo expander can be used. The turbo expander can also be coupled to and drive a turbo compressor. A turbo expander is also referred to as an "expansion turbine," or simply "turbo" or "expander" below; these terms are used synonymously. The terms "turbocharger" or "boost turbine" are also used for such arrangements if one or more turbo compressors are driven without an external power supply (i.e., via one or more turbo expanders). In a turbocharger, the turbo expander or expansion turbine and the turbo compressor or booster are mechanically coupled, where this coupling can result in the same speed (e.g., via a common shaft) or different speeds (e.g., via a plug-in gearbox).

[0021] In typical air separation equipment, appropriate expansion turbines at different locations can be used for cooling and liquefaction of fluid flows. These turbines are in particular the so-called Joule-Thomson turbines, Claude turbines, Lachmann turbines, and the excess air turbines already mentioned above. For the function and purpose of some of these turbines, see also technical literature such as F.G. Kerry, Industrial Gas Handbook: Gas Separation and Purification, CRC Press, 2006, especially Section 2.4, “Contemporary Liquefaction Cycles”, Section 2.6, “Theoretical Analysis of the Claude Cycle”, and Section 3.8.1, “The Lachmann Principle”.

[0022] Generally, the term "air product" as used herein refers to a liquid or gaseous fluid in which at least one air component (nitrogen, oxygen, inert gas) is present in greater quantities than in atmospheric air. Air products can be substantially pure air components, meaning at least 90%, 95%, or 99% purity. Such air products may be referred to herein solely by the name of the primary component ("oxygen," "nitrogen," etc.), even if small amounts of one or more other components are present in the air product. "Liquid product" refers to air product that is removed from the air separation unit in a liquid state and does not evaporate therein, rather than internally compressed air product that was initially generated in a liquid state and subsequently evaporated, or internally compressed air product that has been removed from the tower system in a gaseous state ("gaseous product").

[0023] The liquid nitrogen equivalent LIN-E mentioned above corresponds to the sum of all liquid nitrogen products LIN, all liquid oxygen products LOX multiplied by a factor of 1.07, and all liquid argon products LAR multiplied by a factor of 0.9, where all stated values ​​are normalized to cubic meters per hour (Nm³).3 / h) represents. In other words, LIN-E[Nm 3 / h]=LIN[Nm 3 / h]+1.07 x LOX[Nm 3 / h]+0.9 x LAR[Nm 3 / h).

[0024] Different air products such as liquid oxygen, liquid nitrogen, or liquid argon can be discharged from the air separation device in a liquid state without evaporation, wherein the corresponding amounts formed and discharged are referred to herein by terms such as “liquid quantity,” “liquid discharge quantity,” or “liquid production,” which is different from air products that evaporate through internal compression, the quantity of which is hereinafter referred to as “internal compression quantity,” etc.

[0025] In the following text, pressure and temperature ranges are given to characterize pressure and temperature. This is to indicate that pressure and temperature do not need to be in the form of precise pressure or temperature values. For example, in the distillation column of an air separation unit, different pressures exist, but all these pressures fall within the overall pressure range. Different pressure and temperature ranges can be separate or overlapping ranges. The pressure expressed in bar here is always absolute pressure.

[0026] Features and advantages of the present invention

[0027] According to one embodiment of the invention, neither the recirculated flow drawn from and subsequently introduced into the same tower nor the excess air expanded in the excess air turbine is used. To provide the gaseous supply air to be introduced into the pressure tower (hereinafter referred to as the "first portion air flow"), according to one embodiment of the invention, a (main) expander is provided. As a result, the air to be separated in the tower system is provided at a relatively low quantity, for example, about 140,000 standard cubic meters per hour, at a pressure level of, for example, about 21.5 bar, resulting in a relatively compact "warm" component of the equipment (including the aforementioned parts) in one embodiment of the invention.

[0028] Further according to the invention, a Joule-Thomson flow (hereinafter referred to as the "secondary air" flow) required for internal vapor compression of oxygen at a pressure ranging from 3 to 9 bar, for example, about 5 bar, is supplied from another expander operating at an outlet pressure of, for example, about 13 bar, which also makes the unit quite compact. According to one embodiment of the invention, improved cooling distribution is achieved by using a so-called self-reinforcing warmer on this other expander, as described below; however, this other expander can also be coupled to a brake and / or a generator, for example, as provided in another embodiment of the invention.

[0029] To evaporate the internal compressed oxygen products in the main heat exchanger, ideally, a countercurrent airflow is required. This countercurrent airflow is condensed under pressure, and its quantity allows the evaporation process to proceed with the minimum possible temperature difference. On the other hand, to obtain the liquid products, a certain total cooling power is required (in this case, the sum of the powers of the two turbines). The efficiency of the equipment depends not on the magnitude of this cooling power, but on how it is distributed between the two turbines, as this affects the QT distribution in the main heat exchanger.

[0030] The amount of air provided in the form of a Joule-Thomson flow (i.e., the second-part airflow) expanding in another expander is primarily defined by the evaporation of oxygen products. If a warm-charger is not used to increase the pressure of this flow, as can be done in one embodiment of the invention, where the additional expander is coupled to a brake and / or a generator, the turbine power can be affected only by its inlet temperature. Conversely, if a warm-charger is used, there are effectively further degrees of freedom to optimize the turbine power, since not only the inlet temperature but also the inlet pressure can be varied. With the warm-charger according to an embodiment of the invention, it has been found that significantly higher power can be achieved for the turbine expanding the second-part airflow, and significantly lower power for the (main) turbine, thus significantly improving the efficiency of the method. The QT plot (heat function / temperature curve in the main heat exchanger) reveals the described differences: however, if the expander for the second-part airflow is coupled to a braking device such as a generator, as in the embodiment of the invention, the turbine power can be, for example, approximately 452 kW, resulting in a temperature decrease from, for example, approximately 279 K to 238 K, a reduction of 41 K. Conversely, in different embodiments of the invention using a warm-up compressor, the turbine power can be, for example, about 743 kW and the temperature reduction can be, for example, from about 277 K to 209 K, i.e., a reduction of 68 K. Overall, there is a lower average temperature difference in the main heat exchanger, corresponding to lower thermodynamic losses.

[0031] Using a cold compressor or cold booster as a braking device for the turbine used to expand the second-stage airflow has proven to be less advantageous because the cooling required to produce the liquid product (which is expensive in terms of the energy required for its production) is lost through cold compression. (No excessive cooling capacity is produced in this method because a large amount of liquid product is required, for example, a ratio of liquid nitrogen equivalent to internally compressed gaseous oxygen greater than 0.6).

[0032] Therefore, according to the present invention, the imbalance of Ns number (i.e., specific velocity) between the expander and the booster is not a problem, since the flow rates of the expander and the booster are the same. In a single-stage compressor that compresses the entire amount of pressurized nitrogen taken from the pressure tower, for example, about 19,000 standard cubic meters per hour, the nitrogen is compressed downstream of the heating in the main heat exchanger.

[0033] In a particularly preferred embodiment, a second operating mode is provided, wherein instead of the large amount of liquid oxygen provided in the first operating mode, a much smaller amount of oxygen is provided, and the amount of internally compressed oxygen is significantly increased compared to the first operating mode. Further explanation is given below.

[0034] According to the present invention, a method for cryogenic air separation using an air separation device comprising a tower system having a pressure tower operating at pressures within a first pressure range and a low-pressure tower operating at pressures within a second pressure range below the first pressure range. Therefore, the present invention particularly relates to an air separation device or unit comprising at least the known dual-tower system as explained at the outset, but which may also be configured differently.

[0035] According to the invention, compressed air is supplied to the tower system and at least the pressure tower thereon. All air supplied to the tower system is compressed to a pressure within a third pressure range, which is at least 5 bar higher than the first pressure range. In other words, as previously described, this corresponds to a high-pressure configuration. The air compressed to the first pressure range forms several partial airflows, which are at least partially further compressed, cooled, and expanded in the main heat exchanger before being introduced into the tower system.

[0036] According to the invention, the partial airflow includes a first partial airflow in which air is at least partially compressed in the order shown and in a single pass in a first booster to a pressure within a fourth pressure range higher than a third pressure range, cooled in a main heat exchanger, expanded in a first expander mechanically connected to the first booster to a pressure within a first pressure range, i.e., it is self-pressurized, and introduced into a pressure tower. According to the invention, the first booster operates as a warm booster, i.e., operates at an inlet temperature greater than 0°C.

[0037] As described above, in order to provide gaseous supply air to be introduced into the pressure tower, a (primary) expander is provided, which is the first expander just mentioned. Regarding the advantages of this feature, including the option of providing a relatively compact "temperature" component of the equipment, refer to the explanation above.

[0038] According to the invention, the partial airflow includes a second partial airflow in which air is supplied at least partially, in the order shown, and in a single pass, to a second expander at a pressure higher than or corresponding to a fifth pressure range of the third pressure range, in which it is expanded to a pressure higher than the first pressure range and lower than the fifth pressure range of the sixth pressure range, further expanded to a pressure within the first or second pressure range, and introduced into the tower system, particularly in a liquid or two-phase state, after being expanded in a Joule-Thomson valve.

[0039] In this document, the expression "in a single pass" is intended to refer to an arrangement in which no air in the referred portion of the airflow (i.e., the first or second portion of the airflow) is heated in the main heat exchanger or recirculated to any upstream location compressed to a third, fourth, or fifth pressure level, recompressed, and only subsequently introduced into the tower system. Preferably, the main portion of the first and second portion of the airflow, i.e., at least 75%, 80%, or 90%, or all or substantially all of the air in the first and second portion of the airflow, is introduced into the tower system, and in particular, is not recompressed.

[0040] Furthermore, the air separation device operates without expanding the air from the first and / or second portion of the flow into the turbine in the low-pressure tower. That is, in this invention, "Rahiman" or "turbine" air is not used to "blow" into the tower system, and as mentioned, no recirculated flow of the supplied air is formed.

[0041] In one embodiment of the invention, at least a portion of the air in the second portion of the airflow is compressed to a pressure within a fifth pressure range in a second supercharger mechanically connected to the second expander before being expanded in the second expander. That is, in this case, the fifth pressure range is higher than the third pressure range. According to this embodiment of the invention, the second supercharger also operates as a warm supercharger, i.e., operates at an inlet temperature greater than 0°C. For the advantages of "self-propelled" operation using such a turbine, refer to the description already given above for such embodiments.

[0042] In an alternative embodiment of the invention, the fifth pressure range corresponds to the third pressure range, and therefore the air in the second portion of the airflow is not compressed in the supercharger before being expanded in the second expander, which can be coupled to a braking device, particularly selected from hydraulic brakes and generators or combinations thereof. In yet another embodiment, a combination of the second supercharger and the braking device can be used to brake the second expander.

[0043] Therefore, according to the present invention and its embodiments, essentially two partial flows are ultimately supplied to the tower system, which is contrary to arrangements such as those disclosed, for example, in US 5,400,600 A, in which a Rashiman flow is also formed, blown into the low-pressure tower. The arrangement disclosed in US 5,400,600 A is incompatible with the arrangement provided according to the embodiments of the present invention because the specific speeds of the turbine and the supercharger are technically impractical due to the large difference in quantity (the amount of turbine air, i.e., the amount of the first partial flow, will be too large, and the amount of Joule-Thomson air, i.e., the amount of the second partial flow, will be relatively small). That is, an expert would not consider modifying the arrangement proposed in US 5,400,600 A to obtain the arrangement proposed according to the embodiments of the present invention.

[0044] In this regard, the air in the second part of the airflow is at least partially cooled in the first cooling step before being expanded to a pressure within the sixth pressure range, and at least partially cooled (and liquefied) in the second cooling step after being expanded to a pressure within the sixth pressure range, wherein the first and second cooling steps are performed using the main heat exchanger.

[0045] Furthermore, according to the invention, internally compressed gaseous oxygen is produced and removed from the method or apparatus at an absolute pressure between 3 bar and 9 bar, preferably between 4 bar and 6 bar. Therefore, the invention is particularly suitable for providing the product profile described at the beginning.

[0046] The second portion of the airflow corresponds to the Joule-Thomson flow described above, which is required for the evaporation of the internally compressed oxygen. Regarding the advantages of processing this portion of the airflow according to the invention, refer to the explanation already given above.

[0047] According to one embodiment of the invention, since the air in the second portion of the airflow is at least partially compressed to the pressure within the fifth pressure range before the first cooling step, and particularly since the second expander is mechanically coupled to the second supercharger in this case, the improved refrigeration distribution mentioned above is provided. According to a corresponding embodiment of the invention, there is no problem with the imbalance Ns number between the expander and the supercharger.

[0048] However, according to an alternative embodiment of the invention, the air in the second portion of the airflow can also undergo the first cooling step without being pressurized in a warm-up compressor beforehand.

[0049] In an embodiment of the invention, the partial airflow includes a third partial airflow, wherein the air is at least partially liquefied in the main heat exchanger, expanded to a pressure within the first or second pressure range, and introduced into the tower system. This third partial airflow is specifically liquefied in the main heat exchanger to provide another Joule-Thomson flow.

[0050] When such a third airflow is formed, in a preferred embodiment of the invention and at least in the first operating mode, the air in the third airflow is at least partially compressed in the first booster to a pressure within a fourth pressure range and liquefied in the main heat exchanger at that pressure.

[0051] However, in such an implementation, in the second operating mode, the air in the third airflow can also be at least partially liquefied in the main heat exchanger at a pressure within the third pressure range. In this case, the air in the third airflow is not compressed to a pressure within the fourth pressure range in the first booster, but is bypassed by the first booster through a suitable valve arrangement.

[0052] The second operating mode specifically corresponds to an increase in the formation of internally compressed oxygen at the expense of liquid oxygen formation. In other words, in the second operating mode, at least 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, and up to 2.5 times or 3.0 times the amount of internally compressed gaseous oxygen can be removed from the air separation device compared to the first operating mode, and in the second operating mode, at most 0.0 times, 0.1 times, 0.2 times, 0.3 times, 0.4 times, or 0.5 times the amount of liquid oxygen can be removed from the air separation device compared to the first operating mode.

[0053] According to the invention, the first and second turbochargers are preferably operated at an inlet temperature in a temperature range above 0°C, particularly above 10 or 20°C and up to about 50°C.

[0054] According to the present invention, as described above, internally compressed gaseous oxygen at a pressure range of 3 to 9 bar is removed from the method or apparatus. Furthermore, in connection with this, it is preferable to also remove liquid products from the air separation method or apparatus, wherein, at least in the first operating mode, the ratio of the total amount of all liquid products (expressed as the aforementioned liquid nitrogen equivalent) to the total amount of all gaseous oxygen products or internally compressed gaseous oxygen is in the range of 0.6 to 1.6.

[0055] According to the invention, the first pressure range is particularly from 4 bar to 7 bar, the second pressure range is from 1 bar to 2 bar, the third pressure range is from 15 bar to 28 bar, the fourth pressure range is from 25 bar to 38 bar, the fifth pressure range, when not corresponding to the third pressure range, is from 20 bar to 45 bar, and the sixth pressure range is from 9 bar to 21 bar absolute pressure.

[0056] Furthermore, in the method according to the invention, from the air compressed to a first pressure range, a relative proportion of 0.6 to 0.8 is provided as a first portion of the airflow, and a relative proportion of 0.15 to 0.3 is provided as a second portion of the airflow. A relative proportion of 0.05 to 0.15 may be provided as a third portion of the airflow.

[0057] As described above, the air in the second airflow is preferably at least partially liquefied in the main heat exchanger before being expanded to a pressure within the first or second pressure range, and is subsequently introduced into the tower system.

[0058] In this regard, the air in the first portion of the airflow is preferably at least partially cooled in the main heat exchanger to a temperature range between -132°C and -92°C before being expanded in the first expander, and the air in the second portion of the airflow is preferably at least partially cooled in the first cooling step to a temperature range between -30°C and 30°C, and at least partially cooled in the second cooling step to a temperature range between -87°C and -47°C.

[0059] In the method according to the invention, the gaseous nitrogen removed from the pressure tower can be heated, in particular, in the main heat exchanger and subsequently compressed to a product pressure of, for example, 7 to 12 bar.

[0060] Air separation equipment including a tower system is also part of the present invention, the tower system having a pressure tower adapted to operate at a pressure within a first pressure range, a low-pressure tower adapted to operate at a pressure within a second pressure range below the first pressure range, a first booster adapted to operate at an inlet temperature greater than 0°C, a first expander mechanically connected to the first booster, and a main heat exchanger.

[0061] According to the invention, the air separation device includes means adapted to supply compressed air to a tower system and at least to a pressure tower to compress all the air supplied to the tower system to a pressure in a third pressure range of at least 5 bar above a first pressure range to form a plurality of partial airflows from the air compressed to the first pressure range, and to further compress, cool and expand the partial airflows at least partially before being introduced into the tower system.

[0062] According to the invention, the partial airflow includes a first partial airflow, and the air separation device includes means adapted to cause the air of the first partial airflow to be compressed in the first booster to a pressure in a fourth pressure range above the third pressure range in the order shown and in a single pass, to be expanded in the first expander to a pressure in the first pressure range, to be cooled in the main heat exchanger before being expanded to the pressure in the first pressure range, and to be introduced into the pressure tower after being expanded to the pressure in the first pressure range.

[0063] In the device according to the invention, the partial airflow includes a second partial airflow, and the air separation device includes a means adapted to subject the air of the second partial airflow to, at least partially, in the order shown and in a single pass, an expansion from a pressure in the second expander that is above or corresponds to the third pressure range to a pressure in a sixth pressure range between the first pressure range and the fifth pressure range, a further expansion to a pressure in the first pressure range or the second pressure range, and to being introduced into the pressure tower.

[0064] The air separation device according to the invention is adapted to at least partially cool the air of the second portion of the airflow in a first cooling step before it is expanded to a pressure within a sixth pressure range, and is adapted to at least partially cool the air of the second portion of the airflow after it is expanded to a pressure within a sixth pressure range in a second cooling step, and is adapted to perform the first and second cooling steps using a main heat exchanger.

[0065] Furthermore, according to the invention, an apparatus including an internal compression pump is provided, which is adapted to generate and remove internally compressed gaseous oxygen in a method or apparatus at an absolute pressure between 3 bar and 9 bar, preferably between 4 bar and 6 bar, and the air separation device is adapted to operate without expanding the first and / or second portion of the air flow into a turbine in a low-pressure tower.

[0066] According to one embodiment of the invention, a second booster can be provided, which is adapted to operate at an inlet temperature greater than 0°C and is mechanically coupled to the second expander. The second booster is particularly adapted to compress at least a portion of the air in the second partial airflow to a pressure within a fifth pressure range, in which case the fifth pressure range is higher than the third pressure range.

[0067] For further features and specific advantages of the device according to the invention, refer to the foregoing description of the method and embodiments thereof. This also applies to the device according to a particularly preferred embodiment of the invention, which includes means adapted to perform the corresponding method.

[0068] The invention will be further described with reference to the accompanying drawings, which illustrate embodiments of the invention. Attached Figure Description

[0069] Figure 1 An air separation device according to a particularly preferred embodiment of the invention is shown.

[0070] Figure 2 An air separation device according to another particularly preferred embodiment of the invention is shown.

[0071] Figure 3An air separation device according to another particularly preferred embodiment of the invention is shown.

[0072] Figure 4 An air separation device according to another particularly preferred embodiment of the invention is shown.

[0073] In the following explanation of the method and its steps, the same applies to the apparatus suitable for performing such a method.

[0074] Embodiments of the present invention

[0075] Figure 1 An air separation device 100 according to a particularly preferred embodiment of the present invention is shown.

[0076] As mentioned, air separation devices of the type shown are described elsewhere, such as in H.-W. Industrial Gases Processing, Wiley-VCH, 2006, specifically Section 2.2.5, “Cryogenic Rectification”. For a detailed explanation of the structure and function, please also refer to relevant technical documents. Air separation equipment used in the application of this invention can be designed in various ways, as long as it includes the claimed features.

[0077] Figure 1 The air separation device 100 shown includes a main air compressor 1, an absorber slide 2, a main heat exchanger 3, an expansion turbine 4 connected to a booster 5 (i.e., a booster turbine), an expansion turbine 6 connected to a booster 7 (i.e., another expansion turbine), internal compression pumps 8.1 and 8.2, a reverse flow recooler 9, and a tower system 10.

[0078] In the example shown, the distillation tower system 10 includes a conventional dual-tower arrangement consisting of a high-pressure tower 11 and a low-pressure tower 12, as well as a crude argon tower 13 and a pure argon tower 14.

[0079] In the air separation device 100, the supply air stream formed by atmospheric air A is drawn in and compressed via a filter (not separately labeled) by means of the main air compressor 1. The air separation device operates on a high-pressure basis, and thus the air is compressed to a pressure within a corresponding high-pressure range previously referred to as the "third pressure range". The compressed supply air stream, still denoted as A, is optionally pre-cooled in a pre-cooling unit (not shown in detail) and then purified in the absorber slide 2 in a manner known per se.

[0080] A portion of the compressed and purified airflow A, flow B, is further compressed in the supercharger 5 connected to the expansion turbine 4 to a pressure range higher than the initial pressure range previously referred to as the "fourth pressure range". Previously, the supercharger 5 and the expansion turbine 4 were referred to as the "first supercharger" and the "first expansion turbine", respectively. The supercharger 5 operates as a warm supercharger as defined above.

[0081] Partial flow C (formerly referred to as the "first partial airflow") of partial flow B is at a pressure within the fourth pressure range in this specific example, is partially cooled in the main heat exchanger 3, then expanded in the first expansion turbine 4 and introduced into the pressure tower 11. The expansion in the first expansion turbine 4 is performed to a pressure within the pressure range in which the pressure tower 11 operates, and this pressure range is formerly referred to as the "first pressure range".

[0082] Another portion of flow B, flow D (formerly referred to as the "third portion air flow"), is fully cooled and liquefied in the main heat exchanger 3 at a fourth pressure range, and then expanded to a pressure within the first pressure range using a valve not separately marked, and introduced into the pressure tower 11. Alternatively, the aforementioned final expansion step can also be performed to a pressure within the pressure range in which the low-pressure tower 12 operates, formerly referred to as the "second pressure range," in which case the third portion air flow can be introduced into the low-pressure tower 12.

[0083] In the example shown here, another portion of the compressed and purified airflow A, flow E (formerly referred to as the "second portion airflow"), is further compressed in the supercharger 7 connected to the expansion turbine 6 to a pressure range also higher than the initial pressure range (formerly referred to as the "fifth pressure range"). It is then cooled and liquefied in the main heat exchanger 3 before being expanded in the expansion turbine 6, and is reintroduced into the main heat exchanger 3 for further cooling before being introduced into the pressure tower 11. The supercharger 7 and the expansion turbine 6 are formerly referred to as the "second supercharger" and the "second expansion turbine," respectively, and the cooling steps in the main heat exchanger 3 before and after the expansion of the expansion turbine 6 are referred to as the "first cooling step" and the "second cooling step," respectively. Like the supercharger 5, the supercharger 7 operates as a warm supercharger as defined above. It should be noted that in alternative embodiments outside the present invention, the supercharger 7 may also be omitted, in which case the expansion turbine 6 may alternatively be connected to a generator or brake. Furthermore, in this case, the second portion airflow is supplied to the first cooling step at a pressure within a third pressure range.

[0084] In the second expansion turbine 6, expansion is performed to a pressure range higher than the first pressure range and lower than the third and fifth pressure ranges (hereinafter referred to as the "sixth pressure range"). Thereafter, using a valve not separately labeled, the second partial flow E is expanded to a pressure within the first pressure range. Partial flows D and E, i.e., the previously mentioned third and second partial air flows, are combined in the illustrated example and then introduced into pressure tower 11. Similar to partial air flow D, partial air flow E can also optionally be expanded to a pressure within the second pressure range instead of the first pressure range; in this case, partial air flow E can also be introduced into low-pressure tower 12.

[0085] In high-pressure column 11, an oxygen-enriched liquid bottom fraction and a nitrogen-enriched gas top fraction are formed. The oxygen-enriched liquid bottom fraction taken from high-pressure column 11 is known to be used in part as a heating medium in the oil sump evaporator of pure argon column 14, and is supplied in a defined proportion to the top condenser of pure argon column 14 and the top condenser of crude argon column 13. The fluids evaporated in the evaporation chambers of the head condensers of crude argon column 13 and pure argon column 14 are combined and transferred to low-pressure column 12, such as the remaining purified liquid in these evaporation chambers.

[0086] On one hand, the gaseous nitrogen-rich head product is taken from the head of the high-pressure column 11, liquefied in the main condenser of the heat exchange connection between the high-pressure column 11 and the low-pressure column 12, and then fed back to the high-pressure column 11 as reflux. Another portion is internally compressed in pump 8.1, heated in the main heat exchanger, and provided as internally compressed gaseous nitrogen product GANIC. Yet another portion is subcooled in subcooler 9 and expanded into the low-pressure column 12. In addition, a portion of the gaseous nitrogen-rich head product (in the form of a stream denoted as F) is heated in gaseous form in the main heat exchanger 3 and partially provided as a sealing gas SG, and compressed in compressor 20 for gaseous nitrogen, which is arranged downstream of the warm side of the main heat exchanger.

[0087] In low-pressure column 12, an oxygen-rich liquid bottom fraction and a nitrogen-rich gas top fraction are formed. The former is partially pressurized in liquid form in pump 8.2, heated in main heat exchanger 3, and used as the internally compressed gaseous oxygen product ICGOX 1. The other fraction is at least partially subcooled in subcooler 9 and provided as liquid oxygen product LOX. The liquid nitrogen-rich stream is taken from the liquid retention device at the head of low-pressure column 12 and discharged from air separation unit 100 as liquid nitrogen product LIN. The gaseous nitrogen-rich stream taken from the head of low-pressure column 12 passes through subcooler 9 and main heat exchanger 5 and is provided as nitrogen product LPGAN at the pressure of low-pressure column 12. In addition, the stream taken from the upper section of low-pressure column 12, after being heated in main heat exchanger 3, is used as so-called impure nitrogen in a pre-cooling unit (not shown), or after being heated by means of an electric heater, is used as a regeneration stream in absorber slide 2. It is then discharged into atmospheric ATM.

[0088] The operation of the argon system, including crude argon column 13 and pure argon column 14, is generally known and will not be explained in more detail. Using the argon system, liquid argon product LAR is provided, while primarily, nitrogen from the top of the pure argon column can be released into the atmosphere.

[0089] In a specific example, airflow A can be provided at a rate of approximately 139,700 standard cubic meters per hour and a pressure of approximately 21.50 bar (third pressure range), while being further compressed in supercharger 5 to a pressure of approximately 31.6 bar (fourth pressure range). A portion of the airflow D, i.e., the first portion of the airflow, is formed in this example at a rate of approximately 11,000 standard cubic meters per hour. In the first turbine 4, a power output corresponding to approximately 1,688 kilowatts is provided. In this example, a portion of the airflow E, i.e., the second portion of the airflow, can be compressed in the second supercharger 7 to a pressure of approximately 37.5 bar (fifth pressure range). In this example, a portion of the airflow E is formed at a rate of approximately 31,750 standard cubic meters per hour. In the second turbine 6, a power output corresponding to approximately 742 kilowatts is provided. The outlet pressure of the second turbine 6 (fifth pressure range) is approximately 13 bar in this example.

[0090] Regarding the supplied air products, in the example just mentioned, pressurized gaseous nitrogen (PGAN) can be supplied at a rate of approximately 19,200 standard cubic meters per hour, wherein the pressurized gaseous nitrogen (PGAN) is supplied to compressor 20 at a pressure of approximately 5.1 bar. Internally compressed nitrogen (GAN) is supplied at a rate of approximately 1,160 standard cubic meters per hour and a pressure of approximately 61 bar. In this example, internally compressed oxygen (ICGOX 1) is supplied at a rate of approximately 18,500 standard cubic meters per hour and a pressure of approximately 4.8 bar. Liquid oxygen (LOX) is supplied at a rate of approximately 7,600 standard cubic meters per hour, while liquid argon (LAR) is supplied at a rate of approximately 992 standard cubic meters per hour. Liquid nitrogen (LIN) is supplied at a rate of approximately 8,200 standard cubic meters per hour.

[0091] Additional fluid flows can be provided and processed as needed; a non-limiting example is shown in the form of flow X.

[0092] Figure 2 An air separation device 200 according to another particularly preferred embodiment of the invention is shown.

[0093] and Figure 1 The air separation device 100 shown is different; the first booster 5 can be configured according to... Figure 2 The air separation device 200 is bypassed, as shown by the flow D.1 provided instead of flow D.2, so that a portion of the air in flow D can be directly drawn from air flow A, i.e., at the first pressure level. This bypass is achieved by closing valve 202 while opening valve 201, and is preferably achieved in the operating mode previously referred to as the "second operating mode". Closing valve 201 by opening valve 202 is essentially achieved by providing flow D.2 instead of flow D.1. Figure 1 The operation of the air separation device 100 shown is previously referred to as the "first operating mode".

[0094] The second operating mode specifically corresponds to the increased formation of internally compressed oxygen ICGOX 1 at the expense of liquid oxygen (LOX). For example, in the second operating mode, the production of internally compressed oxygen ICGOX 1 can be increased to approximately 26,000 cubic meters per hour, while the production of liquid oxygen can be reduced to approximately 100 standard cubic meters per hour. (The production rate in the first operating mode can substantially correspond to the production rate previously discussed for the air separation unit 100.)

[0095] As a result of the reduced liquid production, the total amount of air supplied in the form of airflow A is not reduced, although flow A is supplied at a rate of approximately 141,500 standard cubic meters per hour, its pressure is reduced to, for example, approximately 17.4 bar absolute pressure. This means that the first booster 5 may not be able to cope with the significantly increased air volume supplied to it. Here, bypass D.1 via valve 201 begins to function, thereby reducing the load on the first booster 5.

[0096] In this second operating mode, and within the air separation device 200, airflow A can be provided at a rate of approximately 141,500 standard cubic meters per hour and a pressure of approximately 17.4 bar (third pressure range), while further compression is performed in the first booster 5 to a pressure of approximately 23.1 bar (fourth pressure range). In the first turbine 4, a power output corresponding to approximately 1331 kilowatts is provided. In this example, a portion of the airflow E, i.e., the second portion of the airflow, can be compressed to a pressure of approximately 24 bar (fifth pressure range) in the second booster 7. In this example, the portion of the airflow E is formed at a rate of approximately 24,000 standard cubic meters per hour. In the second turbine 6, a power output corresponding to approximately 344 kilowatts is provided. The outlet pressure of the second turbine (sixth pressure range) in this example is approximately 12.6 bar. A third portion of the airflow D is formed at a rate of approximately 22,500 standard cubic meters per hour.

[0097] Regarding the supplied air products, in this second operating mode, and in the air separation unit 200, pressurized gaseous nitrogen (PGAN) can be supplied at a rate of approximately 19,200 standard cubic meters per hour, wherein the pressurized gaseous nitrogen (PGAN) is supplied to compressor 20 at a pressure of approximately 5.3 bar. Internally compressed nitrogen (GAN) is supplied at a rate of approximately 1,160 standard cubic meters per hour and a pressure of approximately 61 bar. In this example, internally compressed oxygen (ICGOX 1) is supplied at a rate of approximately 2,600 standard cubic meters per hour, as already mentioned, and at a pressure of approximately 4.8 bar. Liquid oxygen (LOX) is supplied at a rate of approximately 100 standard cubic meters per hour, as also mentioned, while liquid argon (LAR) is supplied at a rate of approximately 992 standard cubic meters per hour, low-pressure gaseous nitrogen (LPGAN) is supplied at a rate of approximately 10,500 standard cubic meters per hour, and liquid nitrogen is supplied at a rate of 10,200 standard cubic meters per hour.

[0098] Therefore, the second operating mode can be used to provide other air separation products in substantially the same quantities as internally compressed oxygen ICGOX 1 and liquid oxygen LOX.

[0099] In other words, in the first operating mode of the air separation device 200 and in the air separation device 100, the air in the third portion of the airflow (D) is at least partially compressed to a pressure within the fourth pressure range in the first booster 5 and liquefied at a pressure within the fourth pressure range in the main heat exchanger 3. Conversely, in the second operating mode of the air separation device 200, but not in the air separation device 100, the air in the third portion of the airflow D is at least partially liquefied in the main heat exchanger 3 at a pressure within the third pressure range.

[0100] Figure 3 An air separation device 300 according to another particularly preferred embodiment of the invention is shown.

[0101] In the air separation device 300, liquid oxygen, which is internally compressed using pump 8.2, is split into two partial streams before being heated in the main heat exchanger 3, and is provided after passing through the main heat exchanger 3 in the form of two different fractions of internally compressed oxygen (ICGOX 1 and ICGOX 2).

[0102] Figure 4 An air separation device 400 according to another particularly preferred embodiment of the invention is shown.

[0103] like Figure 4 As shown, the portion E of the compressed and purified airflow A, referred to herein as the "second part airflow," is not further compressed in the supercharger (such as the supercharger 7 shown previously). That is, in this case, the "fifth" pressure range mentioned above corresponds to the "third" pressure range. Figure 4 In the example shown, the expansion turbine 6 is mechanically connected to the generator G.

Claims

1. A method for cryogenic air separation using an air separation device, the air separation device comprising a tower system (10), the tower system having a pressure tower (11) operating at pressures within a first pressure range and a low-pressure tower (12) operating at pressures within a second pressure range below the first pressure range, wherein - Compressed air (A) is supplied to the tower system (10) and at least the pressure tower (11), all the air supplied to the tower system (10) is compressed to a pressure in a third pressure range of at least 5 bar above the first pressure range, and the air (A) compressed to the third pressure range forms a plurality of partial airflows, which are at least partially further compressed, cooled and expanded in the main heat exchanger (3), and then introduced into the tower system (10). - The partial airflow includes a first partial airflow (C), in which the air is at least partially compressed in the order shown and in a single pass in a first intensifier (5) operating at an inlet temperature greater than 0°C to a pressure in a fourth pressure range above the third pressure range, cooled in the main heat exchanger (3), expanded in a first expander (4) mechanically connected to the first intensifier (5) to a pressure in the first pressure range, and introduced into the pressure tower (11). - The partial airflow includes a second partial airflow (E), in which air is supplied at least partially in the order shown and in a single pass at a pressure higher than or corresponding to a fifth pressure range of the third pressure range to a second expander, in which it is expanded to a pressure in a sixth pressure range between the first and fifth pressure ranges, further expanded to a pressure in the first or second pressure ranges, and introduced into the tower system (10). - The air in the second portion of the airflow is at least partially cooled before being expanded to the pressure within the sixth pressure range in the first cooling step, and at least partially cooled after being expanded to the pressure within the sixth pressure range in the second cooling step, the first cooling step and the second cooling step being performed using the main heat exchanger (3). - Internally compressed gaseous oxygen is generated in the method under an absolute pressure between 3 bar and 9 bar and is then removed by the method. - The air separation device is adapted to operate without expanding the air of the first portion of the airflow (C) and / or the air of the second portion of the airflow (E) into the turbine in the low-pressure tower (12). - The first pressure range is from 4 bar to 7 bar, the second pressure range is from 1 bar to 2 bar, and the third pressure range is from 15 bar to 28 bar. - When the fifth pressure range is higher than the third pressure range, at least a portion of the air in the second partial airflow (E) is compressed to the pressure in the second booster (7) mechanically connected to the second expander (6) before being expanded in the second expander (6), and when the fifth pressure range corresponds to the third pressure range, the second expander (6) is braked by a braking device selected from a hydraulic brake, a generator (G) or a combination thereof.

2. The method according to claim 1, wherein the second booster (7) operates at an inlet temperature greater than 0°C.

3. The method according to claim 1 or 2, wherein the partial airflow includes a third partial airflow (D), wherein the air in the third partial airflow (D) is at least partially liquefied in the main heat exchanger (3), expanded to a pressure within the first or second pressure range, and introduced into the tower system (10).

4. The method according to claim 3, wherein the air of the third portion of the airflow (D) is at least partially compressed to the pressure within the fourth pressure range in the first booster (5) at least in the first operating mode and is liquefied at the pressure within the fourth pressure range in the main heat exchanger (3).

5. The method according to claim 4, wherein in the second operating mode, the air of the third portion of the airflow (D) is at least partially liquefied in the main heat exchanger (3) at a pressure within the third pressure range.

6. The method of claim 5, wherein in the second operating mode, at least 1.1 times and at most 3.0 times the amount of internally compressed gaseous oxygen is removed from the air separation device compared to the first operating mode, and wherein in the second operating mode, at most 0.5 times the amount of liquid oxygen is removed from the air separation device compared to the first operating mode.

7. The method according to any one of claims 1-2 and 4-6, wherein liquid products are removed from the air separation device, wherein the ratio of the equivalent value characterizing the total amount of the liquid products to the total amount of the internally compressed gaseous oxygen is in the range of 0.6 to 1.6, the equivalent value corresponding to the sum of all liquid nitrogen products, all liquid oxygen products multiplied by a factor of 1.08, and all liquid argon products multiplied by a factor of 0.8, all values ​​expressed in normalized cubic meters per hour.

8. The method according to any one of claims 1-2 and 4-6, wherein the fourth pressure range is from 20 bar to 38 bar, the fifth pressure range is from 20 bar to 45 bar, and the sixth pressure range is from 9 bar to 21 bar absolute pressure.

9. The method according to any one of claims 1-2 and 4-6, wherein a relative proportion of 0.6 to 0.8 of the air (A) compressed to the third pressure range is provided as the first portion of the air flow (C) and a relative proportion of 0.15 to 0.30 is provided as the second portion of the air flow (E).

10. The method according to any one of claims 4-6, wherein a relative proportion of 0.05 to 0.15 of the air (A) compressed to the third pressure range is provided as the third portion of the air flow.

11. The method according to any one of claims 1-2 and 4-6, wherein the air in the second portion of the airflow (E) is at least partially liquefied in the main heat exchanger (3) before being expanded to a pressure within the first pressure range or the second pressure range and is thereafter introduced into the tower system (10).

12. The method according to any one of claims 1-2 and 4-6, wherein the air in the first partial airflow (C) is at least partially cooled in the main heat exchanger (3) to a temperature range between -132°C and -92°C before being expanded in the first expander (4), and wherein the air in the second partial airflow (E) is at least partially cooled in the first cooling step to a temperature range between -30°C and 30°C, and at least partially cooled in the second cooling step to a temperature range between -87°C and -47°C.

13. The method according to any one of claims 1-2 and 4-6, wherein the gaseous nitrogen taken from the pressure tower (11) is heated in the main heat exchanger (3) and subsequently compressed to the product pressure.

14. An air separation device comprising a tower system (10) having a pressure tower (11) adapted to operate at a pressure within a first pressure range, a low-pressure tower (12) adapted to operate at a pressure within a second pressure range below the first pressure range, a first booster (5) adapted to operate at an inlet temperature greater than 0°C, a first expander (4) mechanically connected to the first booster (7), a second expander (6), and a main heat exchanger (3), wherein - The air separation device includes means adapted to supply compressed air (A) to the tower system (10) and at least to the pressure tower (11) to compress all the air supplied to the tower system (10) to a pressure in a third pressure range at least 5 bar above the first pressure range, to form a plurality of partial airflows from the air (A) compressed to the pressure in the third pressure range, and to further compress, cool and expand, at least partially, the partial airflows before introducing them into the tower system (10). - The partial airflow includes a first partial airflow (C), and the air separation device includes a means adapted to compress the air of the first partial airflow (C) at least partially in the order shown and in a single pass in the first booster (5) to a pressure in a fourth pressure range higher than the third pressure range, in the first expander (4) to a pressure in the first pressure range, and to cool in the main heat exchanger (3) before expanding to the pressure in the first pressure range, and to introduce it into the pressure tower (11) after expanding to the pressure in the first pressure range. - The partial airflow includes a second partial airflow (E), and the air separation device includes a means adapted to subject the air of the second partial airflow (E) at least partially to expansion in the order shown and in a single pass from a pressure in the second expander (6) above or corresponding to the third pressure range to a pressure in a sixth pressure range between the first pressure range and the fifth pressure range, to further expansion to a pressure in the first pressure range or the second pressure range, and to introduction into the tower system (10). - The air separation device is adapted to at least partially cool the air of the second portion of the airflow in a first cooling step before it is expanded to a pressure within the sixth pressure range, and to at least partially cool the air of the second portion of the airflow after it is expanded to a pressure within the sixth pressure range in a second cooling step, and to perform the first cooling step and the second cooling step using the main heat exchanger (3). - The air separation device includes a means adapted to generate and extract internally compressed gaseous oxygen within the air separation device at an absolute pressure between 3 bar and 9 bar, and - The air separation device is adapted to operate without expanding the air of the first portion of the airflow (C) and / or the air of the second portion of the airflow (E) into the turbine in the low-pressure tower (12). - The first pressure range is from 4 bar to 7 bar, the second pressure range is from 1 bar to 2 bar, and the third pressure range is from 15 bar to 28 bar. - When the fifth pressure range is higher than the third pressure range, the second booster (7) is mechanically connected to the second expander (6), wherein the second booster (7) is adapted to compress at least a portion of the air in the second partial airflow to a pressure within the fifth pressure range, and when the fifth pressure range corresponds to the third pressure range, the second expander (6) is connected to a braking device selected from a hydraulic brake, a generator (G), or a combination thereof.

15. The air separation device according to claim 14, wherein the second booster is adapted to operate at an inlet temperature greater than 0°C.

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