DE102013019147A1 - Process for obtaining at least one oxygen product in an air separation plant and air separation plant - Google Patents

Abstract

The invention relates to a method for obtaining at least one oxygen product in an air separation plant (100) with a destination column system having a low pressure column (32, 33) operating at at least a first pressure level and a high pressure column (31) operating at a second pressure level above first pressure levels is proposed. The high-pressure column (31) has a bottom evaporator. The method comprises providing at least a first compressed air flow (a) at the first pressure level, a second compressed air flow (b) at the second pressure level, and a third compressed air flow (c) at a third pressure level above the second pressure level. Furthermore, the method comprises feeding air of the first compressed air flow (a) into the low pressure column (32, 33), feeding air of the second compressed air flow (a) into the high pressure column (31) and air of the third compressed air flow (c) through the bottom evaporator (35). the high-pressure column (31) to lead. In the high-pressure column (31), an oxygen-enriched condensate and a nitrogen-enriched evaporate are recovered, at least from the air fed into the second compressed air stream (b), and in each case partially transferred to the low-pressure column (32, 33). In the low-pressure column (32, 33) at least one oxygen-rich stream (o) is obtained with a content of 60 to 99% oxygen and discharged as the oxygen product from the air separation plant (100). At least the first compressed air flow (a) is provided using a first compressor (11) with which the first compressed air flow (a) is compressed from an initial pressure level below the first pressure level only to the first pressure level.

Description

The invention relates to a method for obtaining at least one oxygen product in an air separation plant and an air separation plant according to the preambles of the independent claims.

State of the art

The production of air products in the liquid or gaseous state by cryogenic separation of air in air separation plants is known. Such air separation plants have distillation column systems, which may be designed, for example, as two-column systems, in particular as classic Linde double column systems, but also as three-column or multi-column systems. Furthermore, devices for obtaining further air components, in particular the noble gases krypton, xenon and / or argon, may be provided (see, for example, in this regard FG Kerry, Industrial Gas Handbook: Gas Separation and Purification, Boca Raton: CRC Press, 2006; Chapter 3: Air Separation Technology ).

The distillation column systems are operated at different operating pressures in their respective separation columns. Known double column systems have, for example, a so-called high-pressure column and a so-called low-pressure column. The operating pressure of the high-pressure column is, for example, 4.3 to 6.9 bar, preferably about 5.0 bar. The low-pressure column is operated at an operating pressure of, for example, 1.3 to 1.7 bar, preferably about 1.5 bar. The pressures given here and below are absolute pressures.

Air separation plants can be operated with so-called internal compression. In the internal compression, a liquid stream is taken from the distillation column system and at least partially brought to liquid pressure. The liquid brought to pressure is heated in a main heat exchanger of the air separation plant against a heat transfer medium and evaporated. The liquid stream may in particular be liquid oxygen, but also nitrogen or argon. The internal compression is thus used to obtain appropriate gaseous printed products. Among other things, the advantage of internal compression processes is that corresponding fluids do not have to be compressed outside the air separation plant in a gaseous state, which often proves to be very complicated and / or requires expensive safety measures.

The term "evaporation" includes, as also explained below, in the internal compression cases in which there is a supercritical pressure and therefore no phase transition takes place in the true sense. The liquid pressurized stream is then "pseudo-evaporated". A heat transfer medium is liquefied (or pseudo-liquefied if it is under supercritical pressure) against a (pseudo) vaporising stream. The heat carrier is usually formed by a part of the air separation plant supplied air.

In order to heat and vaporize the stream which has been brought to liquid pressure, this heat transfer medium must have a higher pressure than the liquid which has been pressurized due to thermodynamic conditions. Therefore, a correspondingly high-density power must be provided.

According to the product to be mainly produced in an air separation plant, its desired state of aggregation and / or its required purity, air separation plants can be structurally and / or operationally optimized in order, for example, to allow particularly low production and operating costs.

In particular, methods for obtaining so-called impure low-pressure oxygen, ie oxygen with a purity of, for example, less than 98%, which is additionally provided at a pressure of less than 2 bar, open up optimization possibilities. In such processes, other typical air products in the form of internally compressed, liquid or gaseous streams can be obtained. Typically, such methods are used to supply power plant processes with oxygen-assisted combustion, so-called oxyfuel processes.

The efficiency requirements of the air separation plants used here are becoming increasingly higher. In particular, for example, a specific energy consumption of less than 0.3 kWh per standard cubic meter air is required.

Compliance with such requirements, however, proves difficult with conventional air separation processes. There is therefore a need for more energy-efficient methods for providing corresponding products.

Disclosure of the invention

Against this background, the present invention proposes a method for obtaining at least one oxygen product in an air separation plant and an air separation plant with the features of the independent claims. Preferred embodiments are the subject of Subclaims and the following description.

Before explaining the features and advantages of the present invention, its principles and the terms used will be explained.

An "air separation plant" is charged with optionally dried and purified air, which is conventionally provided at least by means of a "main compressor" in the form of at least one compressed air flow. As mentioned, an air separation plant has a distillation column system for separating the air, in particular into nitrogen and oxygen, in a "separation unit". For this purpose, the air is cooled to near its dew point and introduced into the distillation column system, as explained above. In contrast to this, a pure "air liquefaction plant" does not comprise a distillation column system, ie no decomposition unit, but only a cryogenic liquefaction unit. Incidentally, their construction can correspond to that of an air separation plant.

An "air product" is any product that can be produced, at least by compressing and cooling air, and in particular, but not necessarily, by subsequent cryogenic rectification. In particular, these may be liquid or gaseous oxygen (LOX, GOX), liquid or gaseous nitrogen (LIN, GAN), liquid or gaseous argon (LAR, GAR), liquid or gaseous xenon, liquid or gaseous krypton, liquid or gaseous neon , liquid or gaseous helium, etc. but also, for example, liquid air (LAIR). The terms "oxygen", "nitrogen", etc., in each case also designate "impure" cryogenic liquids or gases which have the respective air component in an amount which is above that of atmospheric air. It does not have to be pure liquids or gases with high contents. In particular, in the context of this application the term "impure oxygen" denotes a mixture of air components which contains at least 80, 85, 90, 95 or 98 and at most 99% oxygen.

Liquid and gaseous streams may be rich or poor in one or more components as used herein, with "rich" for a content of at least 90%, 95%, 99%, 99.5%, 99.9%, 99.99 % or 99.999% and "poor" for a content of at most 10%, 5%, 1%, 0.1%, 0.01% or 0.001% on a molar, weight or volume basis. Liquid and gaseous streams may also be enriched or depleted in one or more components as used herein, which terms refer to a corresponding level in a starting mixture from which the liquid or gaseous stream was obtained. The liquid or gaseous stream is "enriched" if it is at least 1.1 times, 1.5 times, 2 times, 5 times, 10 times 100 times or 1000 times, "depleted", if it contains at most 0.9 times, 0.5 times, 0.1 times, 0.01 times or 0.001 times the content of a corresponding component, based on the starting mixture.

A corresponding fluid, which is at a temperature above the critical temperature and a pressure above the critical pressure, is in the supercritical state. If the temperature is lowered to a value below the critical temperature, the fluid previously present in the supercritical state changes to a liquid state. However, since it is not possible to distinguish between liquid and gaseous phases in the supercritical state, this is not a matter of "liquefaction" in the strict sense, the fluid is "pseudo-liquefied". Nevertheless, such a "pseudo-liquefaction" in the context of this application should also fall under the term "liquefaction". A liquefaction is therefore always present when a fluid, starting from a not or not clearly liquid state in the liquid state passes. The same applies to the term "evaporation", which also includes a "pseudo-vaporization", ie the transition from the liquid to the supercritical state.

A "compressor" is a device designed to compress at least one gaseous stream from at least one inlet pressure at which it is fed to the compressor to at least one final pressure at which it is taken from the compressor. A compressor forms a structural unit, which, however, can have a plurality of "compressor stages" in the form of piston, screw and / or Schaufelrad- or turbine assemblies (ie axial or radial compressor stages). This also applies in particular to the "main (air) compressor" of an air treatment plant, which is characterized in that the total or the majority of the amount of air fed into the air treatment plant, ie the feed air flow, is compressed by this. A "secondary compressor", in which typically a part of the air quantity compressed in the main compressor is brought to an even higher pressure, is often likewise of multi-stage design. In particular, corresponding compressor stages are driven by means of a common drive, for example via a common shaft.

A "relaxation turbine" or "relaxation machine", which has a common shaft with other expansion turbines or energy converters such as oil brakes, generators or Compressors can be coupled, is set up to relax a gaseous or at least partially liquid stream. In particular, expansion turbines may be designed for use in the present invention as a turboexpander. If a compressor is driven by one or more expansion turbines, but without externally, for example by means of an electric motor, supplied energy, the term "turbine-driven" compressor or alternatively "booster" is used. Arrangements of turbine-driven compressors and expansion turbines are also referred to as "booster turbines".

A "heat exchanger" is used for the indirect transfer of heat between at least two z. B. countercurrently guided to each other streams, such as a warm compressed air stream and one or more cold streams or a cryogenic liquid air product and one or more hot streams. A heat exchanger may be formed of a single or multiple heat exchanger sections connected in parallel and / or in series, e.g. B. from one or more plate heat exchanger blocks. A heat exchanger, for example, the "main heat exchanger" used in an air treatment plant, which is characterized in that it is cooled or heated by the majority of the streams to be cooled or heated, has "passages" as separate fluid channels with heat exchange surfaces are formed.

The distillation columns of distillation column systems in air separation plants are at least partially equipped with a "top condenser". This applies at least to the high-pressure column of classic double-column systems. The top condenser, which is designed, for example, as a condenser evaporator, is usually also referred to here as a "main condenser". In a condenser evaporator, a liquid to be evaporated ("cooling medium") in an evaporation space is at least partially vaporized against a gaseous fluid in a liquefaction space. The gaseous fluid liquefies thereby at least partially. In conventional air separation plants, a gaseous top product (so-called head nitrogen) of the high-pressure column is liquefied in the main condenser and a bottom product of the low-pressure column, which is arranged above the high-pressure column, evaporates. Such a main capacitor is often arranged within the low pressure column (internal main condenser), alternatively it can be housed in a separate container outside the low pressure column and connected via lines to the low pressure column (external main capacitor).

A "condenser evaporator" has a liquefaction space and an evaporation space. Evaporation and liquefaction space are each formed by groups of passages (liquefaction or evaporation passages), which are in fluid communication with each other. In the liquefaction space, the condensation of a first fluid flow is performed, in the evaporation space, the evaporation of a second fluid flow. The two fluid streams are in indirect heat exchange. Corresponding evaporators are also referred to as bath evaporators or bath condensers.

The present application uses the terms "pressure level" and "temperature level" to characterize pressures and temperatures, thereby indicating that corresponding pressures and temperatures in a given plant need not be used in the form of exact pressure or temperature values to realize the innovative concept. However, such pressures and temperatures typically range in certain ranges that are, for example, ± 1%, 5%, 10%, 20% or even 50% about an average. Corresponding pressure levels and temperature levels can be in disjoint areas or in areas that overlap one another. In particular, for example, pressure levels include unavoidable or expected pressure drops, for example, due to cooling effects. The same applies to temperature levels. The pressure levels indicated here in bar are absolute pressures.

Advantages of the invention

The present invention is based on a known per se method for obtaining at least one oxygen product in an air separation plant. The oxygen product is in particular the mentioned "impure low-pressure oxygen", ie oxygen whose purity is, for example, 60 to 99% and whose pressure is, for example, 1 to 2 bar. Impure low-pressure oxygen is, as mentioned, particularly suitable for use in processes for oxygen-enriched combustion (so-called oxyfuel process) and in metallurgy. The comparatively low oxygen contents required in these applications make it possible to produce very efficient air separation plants in accordance with the requirements mentioned above.

The present invention, as will also be explained below, is based in particular on known "dual reboiler" methods, as described for example in the DE 1 259 363 B are described.

In this case, an air separation plant is used with a distillation column system, which has a low-pressure column, which is operated at least a first pressure level, and a high-pressure column, which is operated at a second pressure level above the first pressure level. The high-pressure column has a bottom evaporator. Such a bottom evaporator is provided for heating a condensate deposited in the high-pressure column. The low-pressure column also has at least one bottom evaporator; this is the main condenser explained at the beginning, which heats the condensate obtained in the low-pressure column. In particular, the high-pressure column and the low-pressure column or a part of such a low-pressure column are in heat-exchanging connection, wherein the main capacitor produces this heat-exchanging compound.

Furthermore, at least one first compressed air flow at the first pressure level, a second compressed air flow at the second pressure level, and a third compressed air flow at a third pressure level above the second pressure level are provided within the scope of the method according to the invention. In the context of the present application, the first pressure level may in particular comprise a range of 1.4 to 1.7 bar, the second pressure level a range of 4 to 6 bar and the third pressure level a range of 7 to 10 bar.

Air of the first compressed air flow, d. H. all or part of the air provided in the form of the first compressed air flow is fed into the low-pressure column. Air of the second compressed air stream, d. H. all or part of the air from the second compressed air stream is fed into the high-pressure column. Air of the third compressed air stream, d. H. All or part of the air of the third compressed air stream is passed through the sump evaporator to the high pressure column. The air of the third compressed air flow is thus used to heat the condensate of the high pressure column.

In the high-pressure column, an oxygen-enriched condensate and a nitrogen-enriched evaporate are obtained at least from the air fed into this second compressed air stream. The recovery is carried out in a manner known per se by the action of the internals provided in the high-pressure column, soils, etc. A condensate is also referred to as bottoms fraction or bottoms liquid, an evaporate also as top fraction or top gas. The oxygen-enriched condensate and the nitrogen-enriched evaporate are each partially transferred to the low-pressure column.

In the low pressure column at least one oxygen-rich stream is obtained with a content of 60 to 99% oxygen and discharged as the mentioned oxygen product from the air separation plant. The plant according to the invention can also comprise the recovery of different oxygen-rich streams, as explained in detail with reference to the accompanying figures. For example, a first part can be taken off in gaseous form above a sump of the low-pressure column and a second part in the form of a partial stream of the condensate can be removed from the low-pressure column. The present invention can also be used in particular in connection with internal compression methods, as explained above.

According to the invention it is provided to provide at least the first compressed air flow using a first compressor. With the first compressor, the first compressed air flow is compressed from an initial pressure level below the first pressure level, for example, starting from atmospheric pressure, only to the first pressure level. The fact that the first compressor compresses the first compressed air flow starting from the initial pressure level "only to the first pressure level" means that in such a compressor the maximum pressure of the compressed stream in this compressor corresponds to the first pressure level. It is therefore in particular not a multi-stage compressor, the first compressed air flow at about an intermediate pressure corresponding to the first pressure level would be removed. The output pressure level may in particular correspond to atmospheric pressure or be slightly below atmospheric pressure. The latter pressure arises in particular when an air feed stream is sucked by means of the first compressor via a filter. The first compressor can be provided in particular as a blower (so-called blower), which enables a particularly simple and cost-effective production and low maintenance susceptibility.

In other words, the present invention proposes to use at least in part only air at the pressure of the low pressure column, that is, air used in the air separation plant. H. the "first" pressure level to condense. This saves a considerable amount of compressor power. The fed into the low pressure column air is therefore not previously to a higher pressure level, z. B. the second or third pressure level, compressed and then relaxed to the first pressure level, rather, the compression takes place from the beginning only to the first pressure level. As mentioned, this allows the use of low cost compressors (blowers).

Such a method is particularly advantageous because, as mentioned, a bottom evaporator is provided in the bottom of the high-pressure column. The efficiency of the decomposition of the air in the high-pressure column, ie the respective Enrichment levels in the oxygen-enriched condensate and the nitrogen-enriched evaporate are thereby enhanced. As a result, a significantly higher amount of air from the first pressure level can be fed into the low-pressure column. Corresponding air fed into the low-pressure column is basically detrimental to the purity of the products obtained in the low-pressure column, but increases the overall efficiency. As a result of the improved separation in the high-pressure column, the negative effects on the purity of the products obtained in the low-pressure column can be compensated, especially since "impure" oxygen should be obtained in any case in this case.

At least the second compressed air stream is advantageously provided by using a second compressor, with which the second compressed air stream is compressed from the mentioned initial pressure level, or else, starting from the first pressure level, only to the second pressure level. In other words, a portion of the first compressed air flow may be used to form the second compressed air flow, or the second compressor may compress "fresh" feed air from the output pressure level.

At least the third compressed air stream is advantageously provided by using a secondary compressor with which the third compressed air stream is recompressed from the second pressure level to the third pressure level. For the formation of the third compressed air flow so advantageously a part of the second compressed air stream is recompressed at the second pressure level.

An essential feature of the present invention is that an air quantity of the air fed into the low-pressure column of the first compressed air flow at least 25 to 50%, in particular 35 to 45% of a total amount of air fed into the distillation column system. In other words, only a part, for example, half or a little more than half of the total amount of air to the usual pressures of 5 bar and more (here the second and the third pressure level) is compressed. By contrast, a relatively large amount of air is only compressed to the first pressure level below 2 bar, so that the energy consumption of the overall process is thereby significantly reduced.

In the context of the present invention, the air of the third compressed air stream guided through the bottom evaporator is advantageously then at least partially fed into the low pressure column.

Air of the third compressed air stream is advantageously passed to a first part through the bottom evaporator and expanded to a second part by means of an expansion turbine and fed into the low pressure column. The relaxation by means of the expansion turbine, which may be coupled to a generator and / or generator-driven compressor, allows additional recovery of cold.

Advantageously, further air of the second compressed air stream is fed to a first part in the high pressure column and expanded to a second part by means of an expansion turbine and fed into the low pressure column. This can be done alternatively to the relaxation of the air of the third compressed air flow or in addition thereto. This also allows a flexible extraction of cold.

In the method according to the invention, the oxygen-enriched condensate and the nitrogen-enriched evaporate from the high-pressure column are further at least partially cooled and / or liquefied and transferred to the low-pressure column, as far as known.

In the low-pressure column, at least one oxygen-enriched condensate and at least one nitrogen-enriched evaporate are also recovered from the streams or fractions fed into these.

Particular advantages are achieved when a two-part low-pressure column is used which comprises a first column part and a second column part, wherein in the first column part and the second column part in each case a liquid, oxygen-enriched condensate and a nitrogen-enriched evaporate is obtained. This arrangement allows, as explained, a particularly efficient and demand-driven operation of a corresponding system.

The column parts of a corresponding two-part low-pressure column are in particular coupled to one another in that at least part of the condensate obtained in the second column part is transferred into the first column part.

The explained advantages result in particular in that the first column part and the second column part of a two-part low-pressure column are operated at different pressure levels. At least one of these pressure levels corresponds to the first-mentioned pressure level mentioned several times. In particular, this makes it possible to provide products from corresponding column parts, as required, for example, to provide gas for the regeneration of molecular sieve absorbers in cleaning devices of corresponding air separation plants and of residual nitrogen which is used in an evaporative cooler. Appropriate fractions can with the in each case the required pressure levels are provided in the said devices (corresponding to the operating pressures of the respective column parts of the two-part low-pressure column) and therefore no longer have to be subjected to energy-intensive, pressure-influencing measures.

In a corresponding two-part low-pressure column, the oxygen-rich stream, which is discharged as the oxygen product from the air separation plant, is advantageously taken from the first column part. The first column part is the column part into which the oxygen-enriched condensate is transferred from the other (second) column part, and in which there is a bottom evaporator, through which an evaporate of the high-pressure column is led to liquefaction.

As mentioned, for example for supplying cleaning devices and / or evaporative coolers, parts of the nitrogen-enriched evaporate are taken from the first column part and the second column part of the two-part low-pressure column and discharged from the distillation column system.

An air separation plant also provided according to the invention benefits from the advantages explained above. In particular, such an air separation plant comprises all means which enable it to carry out the method explained above. In particular, such an air separation plant is equipped with means which are adapted to provide at least the first compressed air flow using a first compressor which is adapted to compress the first compressed air flow from an initial pressure level below the first pressure level only to the first pressure level.

The invention and embodiments of the invention will be explained in more detail with reference to the accompanying drawings.

Brief description of the drawings

1 shows an air separation plant according to an embodiment of the invention in a schematic representation.

2 shows an air separation plant according to an embodiment of the invention in a schematic partial representation.

3 shows an air separation plant according to an embodiment of the invention in a schematic partial representation.

4 shows an air separation plant according to an embodiment of the invention in a schematic partial representation.

5 shows an air separation plant according to an embodiment of the invention in a schematic partial representation.

6 shows an air separation plant according to an embodiment of the invention in a schematic partial representation.

7 shows an air separation plant according to an embodiment of the invention in a schematic partial representation.

8th illustrates a method for providing compressed air streams according to an embodiment of the invention

9 illustrates a method for providing compressed air streams according to an embodiment of the invention

10 illustrates a method for providing compressed air streams according to an embodiment of the invention

In the figures, corresponding elements carry identical reference numerals and will not be explained repeatedly for the sake of clarity.

Detailed description of the drawings

In 1 is an air separation plant according to an embodiment of the invention shown schematically and in total with 100 designated. The air separation plant 100 includes a first part of the plant 10 , which pretreatment of the air separation plant 100 air is used, a second part of the installation 20 which is used to cool the air separation plant 100 used air, and a third part of the plant 30 (Disassembly), which is used to disassemble the in the air separation plant 100 used air is set up.

The first part of the plant 10 is designed to provide compressed air streams at different pressure levels, here designated a and b and LP-AIR (Low Pressure Air) and MP-AIR (Medium Pressure Air). The first compressed air flow a is provided at a pressure level of, for example, 1.4 to 1.7 bar, the second compressed air flow b at a pressure level of, for example, 4 to 6 bar. A part of the second compressed air flow b is brought by re-compression to an even higher pressure level of for example 7 to 10 bar. Such a third compressed air flow is denoted by c or HP-AIR (High Pressure Air). To its provision is a post-compressor 23 provided. The after-compressor 23 is an unspecified aftercooler downstream.

To generate the first compressed air flow a ambient air (AIR) via a first filter 11 sucked in and in a first compressor 12 , which is in particular designed in one stage (so-called blower) to the aforementioned pressure level of, for example, 1.4 to 1.7 bar compressed. The air is then by means of cooling water H2O in a first direct contact cooler 13 cooled to about ambient temperature (for example 20 ° C) and in a first cleaning device 14 cleaned. The first cleaning device 14 For example, a pair of adsorbent containers filled with molecular sieve comprises the adsorber containers of the first purification device 14 are used in alternating operation and by means of a Regeneriergasstroms d, the third part of the plant 30 For example, can be removed as impure nitrogen flow (WHOLE), regenerated. Optionally, the regeneration gas stream d may also be partly blown off to the atmosphere ATM, for example after the respective regeneration has been carried out. For heating at least a part of the Regeneriergasstroms d can be a heater 15 be provided, which can be operated for example electrically and / or by means of a steam system (not shown). Even after use for regeneration of the adsorber of the first cleaning device 14 For example, the regeneration gas stream d can be blown off to the atmosphere ATM. Downstream of the first cleaning device 14 is the first compressed air flow a at the said pressure level of, for example, 1.4 to 1.7 bar in purified form.

The second compressed air flow b is in the first part of the plant 10 provided in a comparable manner. Ambient air (AIR) is via a second filter 16 aspirated and by means of a particular multi-stage and with intermediate cooling formed second compressor 17 compressed to the also mentioned pressure level of for example 4 to 6 bar. After passing through a second direct contact cooler 18 , which is also operated with water H2O, the air in a substantially the first cleaning device 14 corresponding second cleaning device 19 cleaned. The second compressed air flow b is thus at the mentioned pressure level of for example 4 to 6 bar in purified form.

The second part of the plant 20 comprises as a central components a first heat exchanger 21 and a second heat exchanger 22 , wherein the first heat exchanger 21 also as "main heat exchanger" and the second heat exchanger 22 also referred to as "nitrogen heat exchanger". It is understood that the first heat exchanger 21 and the second heat exchanger 22 , as also shown below, can be provided in the form of a plurality of heat exchanger blocks and / or in a correspondingly summarized form as a single heat exchanger block. Furthermore, the second part of the installation comprises 20 a generator turbine 24 (so-called Lachmann turbine), in which a part of the third compressed air flow c can be relaxed. To pressurize a liquid air product is a pump 25 intended.

The third part of the plant 30 comprises as distillation column system a high pressure column 31 as well as a two-part low-pressure column 32 . 33 with a first pillar part 32 and a second column part 33 , The high pressure column 31 and the first column part 32 the low pressure column 32 . 33 are via a condenser evaporator (also called main condenser) 34 together in heat exchanging connection. An operation of the main capacitor 34 is not illustrated, however, as far as known from conventional air separation plants. In particular, in a condensation space of the main capacitor 34 a gaseous, nitrogen-enriched stream (evaporate) from the top of the high-pressure column 31 liquefied and, for example, partly as reflux to the high pressure column 31 given. Another part can, as illustrated here with stream k and as explained below on the low pressure column 32 or their first column part 32 and / or second column part 33 be abandoned. The flow k is previously through a subcooling countercurrent 36 guided. In the bottom area of the high-pressure column 31 is a condenser evaporator 35 provided in the context of the present invention, the third compressed air flow c is charged and in which this third compressed air flow c is at least partially liquefied.

The third compressed air flow c is initially at the warm end in the first heat exchanger 21 fed and passes through this part (stream e) to the cold end. The current e is then in the mentioned condenser evaporator 35 this liquefies and heats up a liquid oxygen-enriched bottom product (condensate) accumulating in the bottom of the high-pressure column. A second partial stream of the third compressed air stream c (stream f) is the first heat exchanger 21 taken at an intermediate temperature and in the generator turbine 24 relaxed. The relaxation takes place at a pressure level, on which also the second column part 33 the low pressure column 32 . 33 is operated, for example, the mentioned 1.4 to 1.7 bar.

The liquefied stream e is passed through the subcooling countercurrent 36 guided and via corresponding expansion valves (without designation) partly in the first column part 32 of the Low-pressure column 32 . 33 and partly in the second column part 33 the low pressure column 32 . 33 relaxed.

Not used to form the third compressed air flow c shares of the second compressed air flow b are separated in the example shown by the first heat exchanger 21 and the second heat exchanger 22 guided (currents g and h). The flows g and h are downstream of the first heat exchanger 21 and the second heat exchanger 22 united and fed into the high-pressure column, which is operated at a pressure level corresponding to the pressure level of the second compressed air flow, and thus the pressure level of the currents g and h. This is, as mentioned, for example, a pressure level of 4 to 6 bar.

From the air of streams g and h is in the high pressure column 31 a gaseous, nitrogen-enriched overhead product (evaporate) and a liquid, oxygen-enriched bottom product (condensate) produced. A portion of the gaseous, nitrogen-enriched overhead product may also be referred to as stream gaseous pressure nitrogen (PGAN) from the air separation plant 100 discharged and provided as an air product. Another portion of the gaseous, nitrogen-enriched overhead product may, as explained, be in the main condenser 34 be liquefied (not shown). A correspondingly obtained current k is, as mentioned, at least in part by the supercooling countercurrent 36 guided and, similar to the current e, but in each case higher position, in the second column part 32 and the third pillar part 33 the low pressure column 32 . 33 fed.

In the example shown, the first column part 32 and the second column part 33 the low pressure column 32 . 33 be operated at slightly different pressure levels or at equal pressure levels. Operation at slightly different pressure levels makes it possible, for example, to provide a regeneration gas flow d at optimized pressure, so that no energy-consuming further pressure-influencing measures are required.

In the second column part 33 the low pressure column 32 . 33 is in addition to the already mentioned power f after the relaxation in the generator turbine 24 and the respective proportions of the currents e and k, the first compressed air flow a fed. From air of these streams is in the second column part 33 the low pressure column 32 . 33 also produces a liquid, oxygen-enriched bottoms product and a nitrogen-enriched gaseous overhead product. From the head of the second column part 33 the low pressure column 32 . 33 a gaseous nitrogen stream I (GAN2) is withdrawn at a corresponding pressure level of, for example, 1.4 to 1.7 bar, in the second heat exchanger 32 heated and from the air separation plant 100 discharged and / or in the direct contact cooler 13 used to condition a water flow H2O. From the bottom of the second column part 33 the low pressure column 32 . 33 a liquid stream m is withdrawn and into the first column part 32 the low pressure column 32 . 33 transferred.

In the first column part 32 the low pressure column 32 . 33 the already mentioned components of the currents e and k are fed in. In addition, from the bottom of the high pressure column 31 a portion of the resulting liquid, oxygen-enriched bottom product (condensate) as stream p through the subcooling countercurrent 36 and then into the first column section 32 the low pressure column 32 . 33 transferred. From the first column part 32 the low pressure column 32 . 33 For example, a gaseous, oxygen-enriched stream n may be withdrawn immediately above the sump in the first heat exchanger 21 heated and as gaseous oxygen product (GOX) at the pressure level of the first column part 32 the low pressure column 32 . 33 , For example, 1.4 to 1.7 bar are provided. Another oxygen stream o becomes liquid from the bottom of the first column part 32 the low pressure column 32 . 33 withdrawn, by means of the pump 25 brought to liquid pressure and in the first heat exchanger 20 evaporated to a gaseous oxygen product (PGOX). This is the repeatedly mentioned internal compression.

One recognizes 1 in that here two gaseous nitrogen streams, namely in the form of the regeneration gas stream d (FULL) from the head of the first column part 32 the low pressure column 32 . 33 and in the form of the current I (GAN2) from the head of the second column part 33 the low pressure column 32 . 33 can be obtained. Because the first pillar part 32 and the second column part 33 the low pressure column 32 . 33 can be operated at different pressures, allows in the 1 shown air separation plant optimized provision of appropriate currents. This allows, as mentioned, a waiver of further pressure-influencing measures and corresponding devices.

In 2 an air separation plant according to an embodiment of the invention is illustrated in the form of a schematic partial representation. It is only the plant parts 20 and 30 shown on a representation of the first part of the plant 10 for pretreatment of the air used was omitted. Again, however, corresponding compressed air streams (first compressed air flow a, second compressed air flow b and third compressed air flow c) are provided at the pressure levels mentioned several times.

In the in 2 embodiment shown is only a single (main) heat exchanger 21 . 22 provided, a separate second (nitrogen) heat exchanger 22 is not trained. Furthermore, the low pressure column 32 . 33 in the in 2 illustrated embodiment integrally formed. Nevertheless, the feeding of the streams a, e, f, p and k essentially corresponds to the feeding into the two-part low-pressure column 32 . 33 the air separation plant 100 of the 1 , with the difference that the mentioned currents are not divided into sub-streams before the feed. The feeding of the second compressed air flow b in the high-pressure column is carried out according to the air separation plant 100 of the 1 , The removal of the currents i, n and o is essentially also as previously explained. Because the low pressure column 32 . 33 is formed in one piece, only one stream q from the head of the low pressure column 32 . 33 taken in the subcooling countercurrent 36 and the main heat exchanger 21 . 22 heated and discharged as a nitrogen product (GAN). The in the 2 illustrated embodiment thus allows no immediate provision of different nitrogen flows at different pressure levels, as with respect to the nitrogen flows d and l (GANZ and GAN2) in the air separation plant 100 of the 1 the case is.

3 illustrates an air separation plant according to another embodiment of the invention in a schematic partial representation. Here, too, was on the presentation of the first part of the plant 10 waived.

Like the in 1 shown air separation plant 100 includes the in 3 in partial representation shown air separation plant a two-part low-pressure column 32 . 33 however, the second column part 33 the low pressure column 32 . 33 next to the first pillar part 32 the low pressure column 32 . 33 is shown. In particular, in the in 3 illustrated embodiment of the second column part 33 the low pressure column 32 . 33 at a lower pressure level than the first column part 32 the two-part low-pressure column 32 . 33 operated.

To be with it again - from the head of the first pillar part 32 and from the head of the second column part 33 the low pressure column 32 . 33 - Two nitrogen streams d and l obtained. According to 3 however, both streams d and l will be in the subcooler countercurrent 36 heated. As in 2 is a one-piece main heat exchanger 21 . 22 intended. The others in 3 have already been explained and / or arise directly from the synopsis with the preceding figures.

In 4 is an air separation plant according to another embodiment of the invention in partial representation (system parts 20 and 30 ). It is a one-piece main heat exchanger 21 . 22 and a two-part low pressure column 32 . 33 intended. The second column part 33 the two-part low-pressure column 32 . 33 will be at a lower pressure level than the first column part 32 the two-part low-pressure column 32 . 33 operated. The others in 4 illustrated features have already been explained and / or arise directly from the synopsis with the preceding figures.

In 5 is an air separation plant according to another embodiment of the invention in the form of a schematic partial representation (system parts 20 and 30 ). The main heat exchanger 21 . 22 is one-piece and the low-pressure column 32 . 33 formed in two parts, but here the first column part 32 and the second column part 33 the low pressure column 32 . 33 are structurally summarized. The low pressure column 32 . 33 for this purpose comprises a partition which defines an installation which serves as the second column part 32 the low pressure column 32 . 33 is operated. The pressure level on which the second column part 33 the low pressure column 32 . 33 is operated, is below the pressure level on which the first column part 32 the low pressure column 32 . 33 is operated. Further details also arise here directly from the synopsis with the previous figures.

Also the 6 and 7 illustrate air separation plants with two-part low-pressure column 32 . 33 in a schematic partial representation. While in the in 6 illustrated air separation plant, a first heat exchanger 21 and a second heat exchanger 22 are provided, these are in the in 7 illustrated air separation plant to a common (main) heat exchanger 21 . 22 summarized. Unlike in the 3 to 5 The air separation plants illustrated in FIG 6 that from the head of the second pillar part 33 the low pressure column 32 . 33 withdrawn nitrogen stream I not through the subcooling countercurrent 36 but instead in the second heat exchanger 22 heated. Furthermore, in the in 6 illustrated embodiment, a partial flow of the second compressed air flow b, here denoted by r, through the second heat exchanger 22 guided. In this way, an improved temperature compensation in the second heat exchanger 22 be effected. Instead of the partial flow r of the second compressed air flow b, for example, a corresponding partial flow of the third compressed air flow c can be used. In the in 6 illustrated embodiment is the pressure level on which the second column part 33 the low pressure column 32 . 33 is operated below the pressure level on which the first column part 32 the low pressure column 32 . 33 is operated.

In 7 is additionally a secondary capacitor 37 shown. In these, the flow o (oxygen-enriched stream from the bottom of the first column part 32 the low pressure column 32 . 33 ) by means of a pump 26 transferred. The secondary capacitor 37 is operated as a condenser evaporator, wherein, for example, the second compressed air flow b for heating the secondary condenser 37 is used. From the head of the evaporation chamber of the secondary condenser 37 For example, a gaseous oxygen stream s (alternatively or in addition to the multiply explained stream n) can be taken off in gaseous form and through the main heat exchanger 21 . 22 be guided. The stream s may be provided as a gaseous oxygen product GOX as previously explained. From the bottom of the secondary condenser 37 a liquid oxygen stream t can be withdrawn by means of the pump 25 pressure increased, liquid in the main heat exchanger 21 . 22 fed, evaporated in this, and discharged as a gaseous oxygen pressure product (PGOX). It is therefore a variant of an internal compression method.

In all in the 1 to 7 illustrated embodiments may also be provided, the generator turbine 24 to operate with a partial flow f corresponding partial flow of the second compressed air flow b. Instead of a generator turbine 24 As shown in the figures, an expansion turbine of a generator-driven compressor (booster) can also be used. The current i can also be used to drive a corresponding expansion machine, as an alternative or in addition to the generator turbine 24 Cold can be generated.

In the 8th to 10 Possibilities for providing the first compressed air flow a, the second compressed air flow b and the third compressed air flow c are illustrated schematically. The 8th to 10 correspond thus strongly schematized shown first plant parts 10 ,

According to the in 8th embodiment shown, which is essentially in the air separation plant 100 according to 1 According to the realized concept, air will be AIR in parallel via first and second filters 11 and 16 aspirated and then in separate first and second compressors 12 . 17 compacted. As already explained, the first compressor 12 , which is used to provide the first compressed air flow a, in particular a single-stage compressor (so-called blower), which can be created and operated particularly cost-effective. At the second compressor 17 On the other hand, it is in particular a multi-stage compressor with intercooling, as in 1 is illustrated in more detail. The simplified first and second pre-cooling devices shown here 13 and 18 as well as the first and second cleaning devices 14 and 19 were already referring to the 1 explained in detail. This also applies to the after-compressor 23 which is used to provide the third air pressure flow c.

An alternative to this, the in 9 is to use a common filter 11 . 16 for the entire air AIR. This is only downstream of the common filter 11 . 16 divided into sub-streams and the corresponding first and second compressors 12 . 17 fed. The further steps already with reference to the 8th have been explained remain unchanged.

According to another alternative, the in 10 is illustrated, the division takes place only downstream of here the total air AIR compressing first compressor 12 , The compressed air there, which is present at the pressure level of the first compressed air flow a, by means of the second compressor 17 densified. Further recompression takes place in the already explained several times 23 ,

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 1259363 B [0024]

Cited non-patent literature

• FG Kerry, Industrial Gas Handbook: Gas Separation and Purification, Boca Raton: CRC Press, 2006; Chapter 3: Air Separation Technology [0002]

Claims (15)

Process for obtaining at least one oxygen product in an air separation plant ( 100 ) with a distillation column system ( 30 ) with a low-pressure column ( 32 . 33 ), which is operated on at least a first pressure level, and a high-pressure column ( 31 ), which is operated at a second pressure level above the first pressure level, wherein the high-pressure column ( 31 ) a sump evaporator ( 35 ) and the method comprises - providing at least a first compressed air flow (a) at the first pressure level, a second compressed air flow (b) at the second pressure level and a third compressed air flow (c) at a third pressure level above the second pressure level, - air of the first Compressed air flow (a) into the low-pressure column ( 32 . 33 ), air from the second compressed air stream (b) into the high-pressure column ( 31 ) and air of the third compressed air stream (c) through the bottom evaporator ( 35 ) of the high pressure column ( 31 ), - in the high-pressure column ( 31 ) at least from the fed into this air of the second compressed air stream (b) an oxygen-enriched condensate and a nitrogen-enriched evaporate and in each case partially in the low-pressure column ( 32 . 33 ), and - in the low-pressure column ( 32 . 33 ) at least one oxygen-rich stream ( 0 ) containing 60 to 99% oxygen and as the oxygen product from the air separation plant ( 100 ), characterized in that - at least the first compressed air flow (a) using a first compressor ( 11 ) is provided, with which the first compressed air flow (a) is compressed from an initial pressure level below the first pressure level only to the first pressure level. Method according to Claim 1, in which at least the second compressed air stream (b) is produced by using a second compressor ( 17 ) is provided, with which the second compressed air flow (b) is compressed from the initial pressure level or the first pressure level only to the second pressure level. Method according to one of the preceding claims, in which at least the third compressed air stream (c) is produced by using a secondary compressor ( 17 ) is provided, with which the third compressed air flow (c) is recompressed starting from the second pressure level to the third pressure level. Method according to one of the preceding claims, in which an amount of air flowing into the low-pressure column ( 32 . 33 ) fed air of the first compressed air stream (a), at least 25 to 50%, in particular 35 to 45% of a total in the distillation column system ( 30 ) supplied amount of air. Method according to one of the preceding claims, in which the by the bottom evaporator ( 35 ) guided air (s) of the third compressed air stream (c) then at least partially in the low pressure column ( 32 . 33 ) is fed. Method according to one of the preceding claims, wherein air of the third compressed air flow (c) to a first part by the bottom evaporator ( 35 ) and is expanded to a second part by means of an expansion turbine and into the low-pressure column ( 32 . 33 ) is fed. Method according to one of the preceding claims, wherein air of the second compressed air stream (b) to a first part in the high pressure column ( 31 ) and is expanded to a second part by means of an expansion turbine and into the low-pressure column ( 32 . 33 ) is fed. A process according to any one of the preceding claims, wherein the oxygen-enriched condensate and the nitrogen-enriched evaporate from the high-pressure column ( 31 ) each at least partially cooled and / or liquefied and in the low-pressure column ( 32 . 33 ) are transferred. Method according to one of the preceding claims, in which in the low-pressure column ( 32 . 33 ) At least one oxygen-enriched condensate and at least one nitrogen-enriched evaporate is obtained. Process according to Claim 9, in which a two-part low-pressure column ( 32 . 33 ) is used, which has a first column part ( 32 ) and a second column part ( 33 ), wherein in the first column part ( 32 ) and the second column part ( 33 ) Each of a liquid, oxygen-enriched condensate and a nitrogen-enriched evaporate is obtained. Method according to claim 10, in which in the first column part ( 32 ) and the second column part ( 33 ) Proportions of the oxygen-enriched condensate and the nitrogen-enriched evaporate from the high-pressure column ( 31 ), and in which at least a part of the in the second column part ( 33 ) condensate in the first column part ( 32 ) is transferred. Method according to Claim 10 or 11, in which the first column part ( 32 ) and the second column part ( 33 ) are operated at different pressure levels, one of which corresponds to the first pressure level. Method according to one of claims 10 to 12, wherein the oxygen-rich stream (o), which as the oxygen product from the air separation plant ( 100 ), the first column part ( 32 ) is taken. Method according to one of claims 10 to 13, wherein from the first column part ( 32 ) and from the second column part ( 33 ) are each taken from a part of the nitrogen-enriched evaporate and from the distillation column system ( 30 ) is discharged. Air separation plant ( 100 ), which is adapted to obtain at least one oxygen product, with a distillation column system ( 30 ) with a low-pressure column ( 32 . 33 ) and a high pressure column ( 31 ), which is a sump evaporator ( 35 ), as well as means, which are adapted to the low-pressure column ( 32 . 33 ) on at least a first pressure level and the high pressure column ( 31 ) to operate at a second pressure level above the first pressure level, further comprising means arranged therefor - at least a first compressed air flow (a) at the first pressure level, a second compressed air flow (b) at the second pressure level and a third compressed air flow ( c) provide at a third pressure level above the second pressure level, - air of the first compressed air flow (a) in the low-pressure column ( 32 . 33 ), air from the second compressed air stream (b) into the high-pressure column ( 31 ) and air of the third compressed air stream (c) through the bottom evaporator ( 35 ) of the high pressure column ( 31 ), - in the high-pressure column ( 31 ) at least from the fed into this air of the second compressed air stream (b) an oxygen-enriched condensate and a nitrogen-enriched evaporate and in each case partially in the low-pressure column ( 32 . 33 ), and - in the low-pressure column ( 32 . 33 ) to recover at least one oxygen-rich stream (o) with a content of 60 to 99% oxygen and as the oxygen product from the air separation plant ( 100 ), characterized in that - means are provided which are adapted to at least the first compressed air flow (a) using a first compressor ( 11 ), which is adapted to compress the first compressed air flow (a) from an initial pressure level below the first pressure level only to the first pressure level.

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