METHOD AND PLANT FOR PROVIDING A PRESSURIZED OXYGEN-RICH, GASEOUS AIR PRODUCT

Abstract

The invention relates to a high-atmospheric-pressure method for producing a pressurized oxygen-rich, gaseous air product. A first partial quantity of the feed air quantity is supplied at a temperature in a first temperature range to a first turbine unit (5), decompressed using same, and fed into a high-pressure column (111). A second partial quantity of the feed air quantity is supplied at a temperature in a second temperature range to a second turbine unit (6), decompressed using same, and fed into a low-pressure column (12). The pressurized, oxygen-rich air product is provided as an internal compression product at 16 to 50 bar, wherein evaporation is effected proceeding from a temperature in a third temperature range. The third temperature range lies above the first and second temperature range, the second temperature range is selected such that a two-phase mixture with a liquid proportion of 5 to 15% forms at the outlet of the second turbine unit (6), the temperature in the first temperature range and the temperature in the second differ from each other by not more than 10 K, and a portion of less than 5% of all air products removed from the air separation plant (100) is removed from the air separation plant in an unevaporated and liquid state. The first turbine unit is braked by a cold compressor (4), the second by a generator (G) or a warm booster. The invention also relates to an air separation plant (100).

Description

The invention relates to a method for providing a pressurized, oxygen-rich, gaseous air product and to a corresponding plant in accordance with the generic terms of the independent claims.

PRIOR ART

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

The term “air product” is to relate here to a fluid which is provided at least partially by the low-temperature separation of atmospheric air. An air product according to the underlying understanding comprises one or more air gases contained in atmospheric air in a different composition than in atmospheric air. An air product can in principle be present or provided in a gaseous, liquid or supercritical state and can be converted from one of these aggregate states to another. In particular, a liquid air product can, by heating at a certain pressure, be converted to a gaseous state (“evaporated”) or converted to a supercritical state (“pseudo-evaporated”), depending on whether the pressure is below or above critical pressure during heating. Where “evaporation” is referred to below, it should also include a corresponding pseudo-evaporation.

Air separation plants comprise rectification column systems which are conventionally designed as two-column systems, in particular as classic Linde double-column systems, but also as triple-column or multi-column systems. In addition to the rectification columns for extracting nitrogen and/or oxygen in the liquid and/or gaseous state, i.e., rectification columns for nitrogen-oxygen separation, rectification columns for extracting further air components, in particular the noble gases krypton, xenon, and/or argon, can be provided. Frequently, and here too, the terms “rectification” and “distillation” or terms composed therefrom are used synonymously.

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

For air separation, so-called main air compressor/booster compressor (MAC-BAC) methods or so-called high air pressure (HAP) methods can be used. The main compressor/booster compressor methods are the more conventional methods; high-atmospheric-pressure methods have been increasingly used as alternatives to main compressor/booster compressor methods in recent times. The present invention is used in conjunction with high-atmospheric-pressure methods, so that the following explanations relating thereto apply in general and also to the present invention. Significantly lower costs (main compressor and booster compressor are integrated in a machine to a certain extent) and comparable efficiency in principle mean that high-atmospheric-pressure methods can represent an advantageous alternative to main compressor/booster compressor methods.

Main air compressors/booster compressors are characterized in that only a portion of the total feed air quantity that is supplied to the rectification column system is compressed to a pressure which is substantially above the pressure at which the high-pressure column is operated, i.e., by at least 3, 4, 5, 6, 7, 8, 9, or 10 bar. A further portion of the feed air quantity is compressed only to this pressure or to a pressure which differs by no more than 1 to 2 bar therefrom, and is fed into the high-pressure column at this lower pressure, in particular without additional decompression. A main compressor/booster compressor method is shown, for example, in Häring (see above) in FIG. 2.3A.

In a high-atmospheric-pressure method, on the other hand, the entire feed air quantity that is supplied in total to the rectification column system is compressed to a pressure which is substantially above the pressure at which the high-pressure column is operated, 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. High air pressure methods are known, for example, from EP 2 980 514 A1 and EP 2 963 367 A1.

High-atmospheric-pressure methods are typically used with so-called internal compression (IV, IC). In internal compression, at least one gaseous, pressurized air product provided by means of the air separation plant is formed by taking a cryogenic liquid air product from the rectification column system, subjecting it to an increase in pressure, and at the product pressure converting it to the gaseous or supercritical state by heating. 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 means of internal compression. The internal compression offers a range of advantages over an alternative, likewise possible external compression and is explained, for example, in Häring (see above), in section 2.2.5.2, “Internal Compression.”

High-atmospheric-pressure methods can be used in different embodiments. These are often classified and differentiated according to the liquid capacity of the plant, i.e., according to the quantity of air products provided in liquid form and removed from the plant in liquid form, or according to the ratio of internally compressed air products to liquid products. In high-atmospheric-pressure methods, if the liquid capacity is not too high, a cold booster or cold compressor of the type explained below, for example, is used in order to, in this way, increase the efficiency of the method by converting the then excess cooling capacity to higher air pressure.

Also known are high-atmospheric-pressure methods having a so-called Lachmann turbine or injection turbine (also upper column expander) of the type also explained below. The air expanded in the Lachmann turbine is fed into the low-pressure column. The Lachmann turbine can be provided as a further turbine unit in addition to a turbine unit by means of which gaseous compressed air is expanded into the high-pressure column, i.e., a so-called Claude turbine.

There is a need to improve process control, particularly in cases in which, by means of a high-atmospheric-pressure method, predominantly or exclusively internally compressed gaseous oxygen is to be provided at a pressure in a range of from 16 to 50 bar (abs.). The object of the invention is to increase the efficiency and competitiveness of high-atmospheric-pressure methods in particular for typical gas plants of this kind.

DISCLOSURE OF THE INVENTION

Against this background, the present invention proposes a method for preparing one or more oxygen-rich gaseous air products and a corresponding plant having the respective features of the independent claims. Embodiments of the invention are the subject matter of the respective dependent claims and of the description below.

Some basic principles of the present invention are first explained in more detail and terms used to describe the invention are defined.

A “feed air quantity,” or “feed air” for short, is understood here to mean the entire (“used”) air supplied to the rectification column system of an air separation plant. As already explained above, said feed air quantity is only partially compressed in a main compressor/booster compressor method to a pressure in a range significantly above a pressure range in which the high-pressure column is operated. In contrast, in a high-atmospheric-pressure method, as is the subject matter of the present invention, the entire feed air quantity is compressed to a pressure in such a high pressure range. For the meaning of the term “significant” in connection with main compressor/secondary compressor and high air pressure methods, please refer to the explanations above.

A “cryogenic” liquid is understood here to mean a liquid medium whose boiling point is markedly below the ambient temperature, for example at −50° C. or below, in particular at −100° C. or below. Examples of cryogenic fluids include liquid air, liquid oxygen, liquid nitrogen, liquid argon or fluids rich in the specified compounds.

Regarding the devices or apparatuses used in air separation units, reference is made to specialist literature, such as Häring (see above), in particular section 2.2.5.6, “Apparatus.” In the following, some aspects of corresponding devices are explained in more detail for clarification and clearer delimitation.

Multi-stage turbocompressors, referred to herein as “main air compressors,” are used in air separation plants to compress the feed air quantity. In principle, mechanical structure of turbocompressors is known to the skilled person. In a turbocompressor, the medium to be compressed is compressed by means of turbine blades arranged on a turbine wheel or directly on a shaft. A turbocompressor forms a structural unit, but in the case of a multistage turbocompressor it can have a plurality of compressor stages. A compressor stage usually comprises a turbine wheel or a corresponding arrangement of turbine blades. All of such compressor stages may be driven by a common shaft. However, it is also possible to drive the compressor stages in groups with different shafts, wherein the shafts can also be connected to each other via gears.

The main air compressor is further characterized by the fact that the entire quantity of air fed into the distillation column system and used for the production of air products, i.e., the entire feed air quantity, is compressed by said main air compressor. Accordingly, a “booster compressor” can also be provided, in which, however, only part of the quantity of feed air compressed in the main air compressor is brought to an even higher pressure. This can also be designed as a turbocompressor. To compress partial quantities of air, additional turbocompressors are typically provided, which are also designated as boosters, but typically only perform compression on a relatively small scale compared to the main air compressor or the booster compressor, in particular based on the quantity of air compressed. A secondary compressor can also be present in a high air pressure method, but this compresses a portion of the quantity of feed air then starting from a higher pressure.

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

Air can also be decompressed at a plurality of locations in air separation units, for which purpose decompression machines in the form of turboexpanders, also referred to herein as “decompression turbines,” may also be used, among other things. Turboexpanders can also be coupled with and drive turbocompressors. If one or more turbocompressors are driven without externally fed 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, wherein the coupling can be at the same speed (for example, via a common shaft) or at different speeds (for example, via an intermediate gearbox). Any reference made here to a “turbine unit” should in particular be understood to mean an arrangement having at least one expansion turbine.

In typical air separation plants, corresponding expansion turbines are present at various points for the generation of cold and liquefaction of mass flows. These are in particular the Claude turbines mentioned and the Lachmann turbines likewise mentioned, and optionally so-called Joule-Thomson turbines. Regarding the function and purpose of corresponding turbines, reference is made to the technical literature, for example F. G. 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.”

A “throttle stream” or “Joule-Thomson stream” is understood to mean a quantity of air which, in the main heat exchanger of an air separation plant, liquefies at least predominantly under pressure and is then fed, in particular via a throttle valve, in particular into the high-pressure column. Instead of a throttle valve, a Joule-Thomson turbine can also be used.

In the language as used herein, liquid fluids, gaseous fluids, or also fluids present in a supercritical state may be rich or poor in one or more components, wherein “rich” may refer to a content of at least 75%, 90%, 95%, 99%, 99.5%, 99.9%, or 99.99%, and “poor” may refer 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” may correspond to the definition of “rich” as was just given, but in particular denotes a content of more than 90%. If, for example, “nitrogen” or “oxygen” are mentioned here, it can be a pure gas, but also a gas rich in nitrogen or oxygen.

In the following, reference is made to the characterization of pressures and temperatures of pressures or temperatures in certain pressure or temperature ranges. This is to express that pressures and temperatures do not have to be used in the form of exact pressure or temperature values in order to realize an inventive concept. However, such pressures and temperatures typically fall within corresponding ranges that are, for example, ±1%, 5%, or 10% around an average. Different pressure or temperature ranges can thereby represent disjunct regions or regions which overlap. In particular, for example, the specification of pressure ranges includes unavoidable or expected pressure losses, for example due to line resistances and the like. The same applies to temperature ranges. Pressures or pressure range limits specified here in bar, unless otherwise stated, are absolute pressures.

Advantages of the Invention

Known high-atmospheric-pressure methods are, as mentioned, often classified and differentiated according to the so-called liquid capacity or according to the ratio of internally compressed products to liquid products. The liquid capacity in this case denotes the quantity of air products which are discharged from the plant in liquid form or a corresponding method in which no evaporation or pseudo-evaporation thus takes place. Therefore, no feed streams into the plant or the method can be cooled by a corresponding evaporation by means of such products. For this reason, to some extent cooling is present in excess if smaller amounts of air products are discharged from the plant or a corresponding process in liquid form, but are instead evaporated or pseudo-evaporated.

In the case of low liquid capacity, a so-called cold booster can thus be used, for example, in order to increase process efficiency by converting such excess cold to higher air pressure. The heat input by the cold booster “destroys” the cold present in excess in part, but, in contrast to this, the cold booster compresses a portion of the feed air, so that, for example, the power of the main air compressor can be reduced accordingly. As already mentioned above, the suction temperature of a cold booster is below the ambient temperature, so that power consumption is reduced in the case of ideal gas behavior assumed for simplification.

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

The present invention achieves the object mentioned above in particular in that air of the Lachmann turbine is supplied with a significantly lower air inlet temperature than in known methods. This results in a strong preliquefaction at the turbine outlet of the Lachmann turbine. Accordingly, this leads to a clear reduction in the quantities of air to be liquefied in the main heat exchanger as throttle stream or throttle streams, which results in a noticeable increase in efficiency. The amount of heat to be transmitted in the lower region of the main heat exchanger, i.e., at the point at which the condensation of air flows takes place, is thereby lower and the power of the cold compressor is reduced.

Overall, against this background, the present invention proposes a method for producing a pressurized, oxygen-rich, gaseous air product using an air separation plant, which comprises a rectification column system having a high-pressure column and a low-pressure column and a main heat exchanger, a first turbine unit and a second turbine unit.

The high-pressure column is operated in a first pressure range of from 4 to 7 bar, in particular from about 5.3 bar, the low-pressure column is operated in a second pressure range of from 1 to 2 bar, in particular about 1.4 bar, and at least a predominant portion of a feed air quantity supplied overall to the rectification column system, in particular the entire feed air quantity as is typical in a high-atmospheric-pressure method, is compressed to a pressure in a third pressure range which is more than 3 bar above the first pressure range. For further possible pressure differences, reference is made again to the above explanations regarding high-atmospheric-pressure methods.

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

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

The invention comprises oxygen-rich liquid being removed from the rectification column system to provide the gaseous, pressurized, oxygen-rich air product, being brought to a pressure in a sixth pressure range of from 16 to 50 bar or 25 to 50 bar, in particular 40 to 50 bar, for example approximately 43 bar, in a liquid state under heating to a temperature in a third temperature range, being supplied to the main heat exchanger, evaporated therein at the temperature in the third temperature range and discharged from the air separation plant. The pressurized oxygen-rich air product is thus provided as an internal compression product.

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

In the context of the present invention, the second temperature range is selected such that a two-phase mixture having a liquid content of 5 to 15%, in particular of 8 to 13%, forms at the outlet of the second turbine unit, wherein these percentages in particular express a mole fraction of the liquid proportion, based on an amount of substance of the overall two-phase mixture.

In the context of the present invention, the temperature in the first temperature range and the temperature in the second furthermore do not differ by more than 10 K from each other.

According to the invention, the air separation plant is operated in such a way that a portion of less than 5%, in particular less than 2%, of all air products of the air separation plant that are removed from the air separation plant are removed in an unevaporated and liquid state. Reference is made to the above explanations for the term “air product,” which not only covers substantially pure products, such as oxygen or, but also impure streams (so-called waste gas). Based on substantially pure products, the portion is less than 10%, in particular less than 5% or less than 2%. The “substantially pure” products comprise in particular nitrogen, oxygen, and argon, or fluids which are in each case rich in the particular component mentioned.

By combining the measures proposed according to the invention, the advantages already mentioned above are in particular achieved. Reference is made in this context to the explanations above.

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

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

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

The booster unit used here can in particular be used to drive the first turbine unit.

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

A third partial quantity of the feed air quantity compressed to the pressure in the third pressure range can in particular be subjected to the first cooling step together with the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range and brought to the pressure in the fourth pressure range using the booster unit, wherein the third partial quantity of the feed air quantity further compressed to the pressure in the third pressure range and then to the pressure in the fourth pressure range is liquefied in the main heat exchanger, subsequently decompressed, and fed into the high-pressure column. The first partial quantity is removed from the main heat exchanger in particular at a removal point corresponding to the temperature in the first temperature range, whereas the third partial quantity is guided through the main heat exchanger up to the cold end. In this way, the third partial quantity forms a throttle stream.

In the method according to the invention, the second partial quantity of the feed air quantity compressed to the pressure in the third pressure range can, in particular, be provided at the pressure in the fifth pressure range and thereby be brought to the pressure in the fourth pressure range using a further booster unit. In this case, the further booster unit can in particular drive the second turbine unit, i.e., it is designed to be “self-boosted”.

If the second partial quantity of the feed air quantity compressed to the pressure in the third pressure range is not to be brought to the pressure in the fifth pressure range, the second turbine unit can in particular be designed to be oil or generator braked, as is known per se.

In all cases, a fourth partial quantity of the feed air quantity compressed to the pressure in the third pressure range can be cooled together with the second partial quantity of the feed air quantity compressed to the pressure in the third pressure range in the main heat exchanger, wherein the second partial quantity can be discharged from the main heat exchanger at a point corresponding to the temperature in the second temperature range, but the fourth partial quantity can be further cooled and liquefied. The fourth partial quantity can thereby be withdrawn from the main heat exchanger on the cold side and fed into the high-pressure column as a further throttle stream.

In the method according to the invention, the two-phase mixture forming at the outlet of the second turbine unit is advantageously fed to a phase separation in a suitable phase separator and then fed into the low-pressure column in a separate phase, i.e., in the form of a gas stream and a liquid stream.

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

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

The invention is described in more detail hereafter with reference to the accompanying drawings, which illustrate preferred embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 5 illustrate air separation plants according to preferred embodiments of the invention.

FIGS. 6 and 7 show temperature enthalpy diagrams.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an air separation plant, denoted by 100, according to a preferred embodiment of the invention. The air separation plant 100 comprises a rectification column system 10 having a high-pressure column 11 and a low-pressure column 12, which are connected in a known manner.

Air separation plants of the type shown are often described elsewhere, for example in Häring (see above), in particular section 2.2.5 there, “Cryogenic Rectification”. For detailed explanations regarding structure and operating principle, reference is therefore made to corresponding technical literature. An air separation plant for use of the present invention can be designed in a wide variety of ways.

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

In the air separation plant 100 illustrated in FIG. 1, feed air is drawn in by means of a main air compressor 1, compressed to the pressure in the third pressure range, cooled in a direct contact cooler, likewise not denoted separately, and in particular freed of water and carbon dioxide in a pre-purification unit 2.

The feed air provided in this way as the mentioned compressed air stream a at the pressure in the third pressure range is then divided into two partial streams b and c, which both are supplied to a main heat exchanger 3 on the hot side and are cooled therein. In each case, further partial streams are formed by removal at intermediate temperature levels and on the cold side of the main heat exchanger 3, which partial streams here represent partial quantities of the feed air of the compressed air stream a, referred to as “first” to “fourth” partial quantities, and are indicated by a1 to a4.

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

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

In the embodiment illustrated here, on the other hand, the second partial quantity of the feed air quantity of the compressed air flow a compressed to the pressure in the third pressure range is supplied to a second turbine unit 6 as part of the partial stream c at the pressure in the third pressure range and at a temperature in a second temperature range in the form of the partial stream a2, which turbine unit 6, in the embodiment illustrated here, is coupled to a generator G, decompressed to a pressure in the second pressure range using the second turbine unit 6, and then fed into the low-pressure column 12.

The second temperature range is selected in such a way that a two-phase mixture with the liquid portion previously indicated several times forms at the outlet of the second turbine unit 6. In the embodiment illustrated here, the two-phase mixture forming at the outlet of the second turbine unit 6 is supplied in a phase separator 7 in the embodiment of a phase separation illustrated here and then fed into the low-pressure column 12 in a separate phase in the form of a liquid stream a2l and a gas stream a2g.

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

The fourth partial quantity of the feed air quantity of the compressed air stream a compressed to the pressure in the third pressure range is supplied to the main heat exchanger 3 in the form of the mentioned partial stream a4 together with the second partial quantity, i.e., the partial stream a2, and thus as part of the partial stream c, but is not removed from the second heat exchanger 3 at the temperature in the second temperature range, but is instead also liquefied in the main heat exchanger, then decompressed, and fed into the high-pressure column 11.

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

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

For further interconnection of the components of the air separation plant 100, which in particular can also comprise a subcooling counter-flow heat exchanger 9, reference is made to the cited technical literature. In particular, only a small portion of air products is removed from the air separation plant 100 in an unevaporated and liquid state, for example in the form of a liquid oxygen stream m.

The air separation plant 200 according to FIG. 2 differs from the air separation plant 100 according to FIG. 1 substantially by the absence of the phase separator 7, wherein the two-phase stream a2 is fed biphasically into the low-pressure column 12.

The air separation plant 300 according to FIG. 3 differs from the air separation plants 100 and 200 according to FIGS. 1 and 2 substantially by the provision of the pressurized, oxygen-rich air product in the form of two fractions or partial streams 11 and 12, which are formed from the partial stream I and are evaporated in the main heat exchanger 3 at different pressures.

The air separation plant 400 according to FIG. 4 differs from the air separation plants 100 to 300 according to FIGS. 1 to 4 substantially in that the second partial quantity a2 (and the fourth partial quantity a4) of the feed air quantity compressed to the pressure in the third pressure range is provided at a pressure in a fifth pressure range and thereby is brought to the pressure in the fifth pressure range using a further booster unit 41, which is driven in particular by the turbine 6 (i.e., “self-boosted”). The further booster unit 41 is formed by a warm booster, i.e., by a booster having an inlet temperature above 273 K.

The air separation plant 500 according to FIG. 5 differs from the air separation plants 100 to 400 according to FIGS. 1 to 4 substantially in that an argon discharge column 51 is used in a manner known per se, as described, for example, in EP 3 067 649 A1. A gaseous stream s enriched in argon is drawn off from the argon removal column 51 and heated in the main heat exchanger 3. The argon discharge column 51 is fed from the low-pressure column 12 and sump liquid (in each case without a separate designation) is returned to the low-pressure column 12 after being depleted of argon. To cool a top condenser of the argon discharge column 51, sump liquid from the high-pressure column 11 is used, which is fed into the low-pressure column 12 after partial evaporation

An “argon discharge column” in this case refers to a separating column for argon-oxygen separation which is not used to obtain a pure argon product, but rather to discharge argon from the air to be separated in the pressure column and low-pressure column. Its circuit differs only slightly from that of a conventional crude argon column, however it contains significantly fewer theoretical plates, namely less than 40, in particular between 35 and 15. Like a crude argon column, the sump region of an argon discharge column is connected to an intermediate point of the low-pressure column, and the argon discharge column is cooled by a top condenser, on the evaporation side of which expanded sump liquid from the high-pressure column is introduced; an argon discharge column does not have a sump evaporator.

FIGS. 6 and 7 show temperature enthalpy diagrams of the main heat exchanger 3 of an air separation plant according to an embodiment of the invention, for example an air separation plant 100 to 500 according to FIGS. 1 to 5, wherein in each case a temperature is plotted on the vertical axis in K relative to an enthalpy sum in kW plotted on the horizontal axis and the diagram according to FIG. 7 corresponds to an enlarged representation of the diagram according to FIG. 6. The temperature points Ta1 and Ta2 correspond in each case to the removal temperature level of the partial streams a1 and a2.

The air separation plants according to FIGS. 1 to 5 can of course also be adapted to yield a low-pressure nitrogen product (LPGAN) as a secondary product of the air separation. This can be done analogously by using a corresponding separation section in the low-pressure column 12.

Claims

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

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

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

4. The method according to claim 1, wherein the booster unit is formed by a cold compressor.

5. The method according to claim 1, wherein the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range is cooled in a first cooling step in the main heat exchanger before it is brought to the pressure in the fourth pressure range using the booster unit, and wherein the first partial quantity of the feed air quantity compressed to the pressure in the third pressure range can be cooled in a second cooling step in the main heat exchanger after it has been brought to the pressure in the fourth pressure range using the booster unit, wherein the second cooling step comprises cooling to the temperature in the first temperature range.

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

7. The method according to claim 1, wherein the second partial quantity of the feed air quantity compressed to the pressure in the third pressure range is provided at the pressure in the fifth pressure range and is thereby brought to the pressure in the fifth pressure range using a further booster unit.

8. The method according to claim 1, wherein the two-phase mixture forming at the outlet of the second turbine unit is supplied to a phase separation and is then fed into the low-pressure column in a separate phase.

9. The method according to claim 1, wherein the two-phase mixture forming at the outlet of the second turbine unit is fed biphasically into the low-pressure column.

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

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

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