EP3343158A1 - Method for producing one or more air products, and air separation system - Google Patents

Abstract

The invention relates to a process for producing one or more air products by cryogenic separation of air in an air separation plant (100) with a distillation column system (10) comprising a high pressure column (111) and a low pressure column (112), wherein an amount of feed air in a main air compressor (101 ) is compressed to a first pressure level, of which a first portion and a second portion are recompressed in a post-compressor 105, the post-compressed first portion of the feed air quantity is further compressed using a first booster (108) and a second booster (109) and then cooled, is depressurized to the first pressure level and fed to the high pressure column (111), and the post-compressed second portion of the feed air quantity is cooled and then to a first pressure level using a first turboexpander (110) mechanically coupled to the second booster (109) relaxed and in the high pressure column (111) is fed. It is provided that the first portion and the second portion of the amount of feed air in the secondary compressor (105) are recompressed from the first pressure level to a second pressure level and taken to the secondary compressor (105) together at the second pressure level, the high-pressure column (111) impure nitrogen at the first pressure level and depressurized using a second turboexpander (115) mechanically coupled to the first booster (108) and the low pressure column (112) withdrawn an argon enriched fluid, depleted in argon and into the low pressure column (112) is returned. A corresponding air separation plant (100) is also an object of the invention.

Description

The invention relates to a method for the cryogenic separation of air 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 and, for example at H.-W. Haring (ed.), Industrial Gases Processing, Wiley-VCH, 2006, especially Section 2.2.5, "Cryogenic Rectification ", described.

Air separation plants have distillation column systems which can 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. In addition to the distillation columns for the production of nitrogen and / or oxygen in the liquid and / or gaseous state, ie the distillation columns for nitrogen-oxygen separation, distillation columns can be provided for obtaining further air components, in particular the noble gases krypton, xenon and / or argon.

The distillation columns of said distillation column systems are operated at different pressure levels. Known double column systems have a so-called high-pressure column (also referred to as a pressure column, medium-pressure column or lower column) and a so-called low-pressure column (also referred to as the upper column). The pressure level of the high-pressure column is for example 4 to 6 bar, in particular about 5.3 bar. The low-pressure column is operated at a pressure level of, for example, 1.3 to 1.7 bar, in particular about 1.4 bar. In certain cases, such as Integrated Gasification Combined Cycle (IGCC) combined gasification processes, pressures of 3 to 4 bar can also be used in the low pressure column. The pressures given here and below are absolute pressures at the top of said columns.

The object of the present invention is to make the low-temperature decomposition of air more energy-efficient and cost-effective.

Disclosure of the invention

Against this background, the present invention proposes a method for the cryogenic separation of air and an air separation plant with the features of the respective independent claims. Embodiments are each the subject of the dependent claims and the following description.

Before explaining the features and advantages of the present invention, some principles of the present invention will be further understood and terms used below defined.

The devices used in an air separation plant are described in the cited literature, for example in Haring in Section 2.2.5.6, "Apparatus". Insofar as the following definitions do not deviate from this, reference is expressly made to the cited technical literature for language use, which is used in the context of the present application.

Fluids and gases may be rich or poor in one or more components as used herein, with "rich" being for a content of at least 50%, 75%, 90%, 95%, 99%, 99.5%, 99, 9% or 99.99% and "poor" for a content of at most 50%, 25%, 10%, 5%, 1%, 0.1% or 0.01% on a molar, weight or volume basis , The term "predominantly" can correspond to the definition of "rich". Liquids and gases may also be enriched or depleted in one or more components, which terms refer to a content in a source liquid or gas from which the liquid or gas was recovered. The liquid or gas is "enriched" if it or this is at least 1.1 times, 1.5 times, 2 times, 5 times, 10 times 100 times or 1000 times, and depleted ", if this or this 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 liquid or the starting gas. If, for example, "oxygen" or "nitrogen" is mentioned here, one of them is one below Liquid or a gas that is rich in oxygen or nitrogen, but need not necessarily consist exclusively of it.

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. The same applies to temperature levels. The pressure levels indicated here in bar are absolute pressures.

In air separation processes, turboexpanders can be used for cooling and liquefaction at different locations, as is generally known to those skilled in the art. In the following, we talk about "Claude turbines", "Lachmann turbines" and "pressurized nitrogen turbines". The function and purpose of such turboexpander is on specialist literature, for example FG Kerry, Industrial Gas Handbook: Gas Separation and Purification, CRC Press, 2006 , especially the Sections 2.4, "Contemporary Liquefaction Cycles", 2.6 , "Theoretical Analysis of the Claude Cycle" and 3.8.1, "The Lachman Principle ", directed.

By means of a Claude turbine cooled in the case of a double column system cooled compressed air from a higher pressure level to the pressure level of the high pressure column and fed into this. By means of a Lachmann turbine, however, cooled compressed air is expanded to the pressure level of the low-pressure column and fed into it. Nitrogen is finally released from the high-pressure column by means of a pressurized nitrogen turbine. This relaxation can take place before this nitrogen is completely heated in the main heat exchanger (so-called cold pressurized nitrogen turbine) or afterwards (so-called warm pressurized nitrogen turbine). The expanded nitrogen can then be used in particular for the regeneration of adsorbers. Also by the use of a pressurized nitrogen turbine, the Energy consumption of an air separation plant are lowered. If a pressure nitrogen turbine nitrogen supplied from the head of the high-pressure column, this is correspondingly pure. However, impure nitrogen from the high-pressure column can also be fed to a pressurized nitrogen turbine, as is the case within the scope of the present invention. In the latter case, a corresponding pressure nitrogen turbine is also referred to as "impure-pressure nitrogen turbine". An impure-pressure nitrogen turbine is characterized in that it is fed to a nitrogen-rich fluid from the high-pressure column whose nitrogen content is below the nitrogen of the top product of the high-pressure column, ie below the maximum nitrogen content that can be generated in the high-pressure column.

A turboexpander can be coupled via a common shaft with other expansion machines or energy converters such as oil brakes, generators or compressor stages. If one or more turbo expanders are coupled with one or more compressor stages (see below) and if necessary additionally mechanically braked, so that the compressor stage (s) are operated without external energy, for example by means of an electric motor, the term is also generally used for this arrangement "Boosterturbine" used. The compressor stage (s) of a corresponding booster turbine is or are generally referred to as a "booster". Such a booster turbine compresses at least one current by the relaxation of at least one other current, but without external, for example by means of an electric motor, supplied energy.

By contrast, a compressor is understood here to mean an externally, typically electrically, driven device which is set up for compressing 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 is. The compressor forms a structural unit, which, however, several single compressor units or "compressor stages" in the form of known piston, screw and / or Schaufelrad- or turbine assemblies (ie radial or axial compressor stages) may have. In particular, these compressor stages are driven by means of a common drive, for example via a common shaft or a common electric motor. Several compressor stages can thus together form one or more compressors.

Rotating units, for example expansion machines or expansion turbines, compressors or compressor stages, booster turbines or booster, rotors of electric motors and the like, can be mechanically coupled to one another, wherein a "mechanical coupling" in the parlance of this application is understood that via mechanical elements such Gears, belts, gears and the like, a fixed or mechanically adjustable speed relationship between such rotating units can be produced. A mechanical coupling can generally be made by two or more elements, each engaging, such as in form-engagement or frictional engagement, such as gears or traction sheaves with belts, or a non-rotatable connection. A mechanical coupling can in particular be effected via a common shaft, on which the rotating units are each secured in a rotationally fixed manner. The rotational speed of the rotating units is the same in this case.

The present invention is used in particular in connection with so-called MAC-BAC (Main Air Compressor / Booster Air Compressor) methods. A MAC-BAC process is characterized in that only a portion of the total amount of feed air supplied to the distillation column system is compressed to a pressure level which is substantially, i. is at least 3, 4 or 5 bar above the pressure level of the high pressure column. Another part of the distillation column system total supplied amount of feed air is only compressed to the pressure level of the high pressure column or a typically not more than 1 to 2 bar deviating from this pressure level and fed to this in the high pressure column. The compressed to the higher pressure level of the distillation column system total supplied compressed air can be relaxed in a MAC-BAC process after cooling partly in a Claude turbine, as illustrated in the accompanying drawings.

In HAP process, which are also used in the air separation, however, the total, the distillation column system total supplied amount of feed air is compressed to a pressure level that is substantially, ie at least 3 bar, above the pressure level of the high pressure column. The pressure difference is at least 3 bar, but can also be significantly higher, for example at 4, 5, 6, 7, 8, 9 or 10 bar and up to 14, 16, 18 or 20 bar. HAP methods are for example from EP 2 980 514 A1 and the EP 2 963 367 A1 known.

All nitrogen taken from the high-pressure column and neither condensed nor recycled as reflux into it nor used as a liquid reflux to the low-pressure column, basically affects the separation in the low-pressure column because it is no longer available there as reflux. Such nitrogen is nitrogen taken from the air separation plant in the form of a liquid or gaseous nitrogen product, and the nitrogen which, as explained, is expanded and otherwise utilized in the pressurized nitrogen turbine. This also includes internally compressed nitrogen, ie liquid nitrogen, which is taken from the high-pressure column, pressurized in a pump and evaporated in the main heat exchanger. The internal compression is also included, for example Haring, Section 2.2.5.2, "Internal Compression "explains.

An "argon discharge" is here generally understood as a measure in which a fluid is withdrawn from the low-pressure column which is enriched in argon with respect to an oxygen-rich liquid fed from the low-pressure column, in particular the low-pressure column bottoms product, i. For example, has at least twice, five times or ten times the argon content. Argon ejection further includes not returning at least a portion of the argon contained in a corresponding withdrawn fluid to the low pressure column. The fluid is in particular subjected to an argon removal and only then returned to the low-pressure column. Classical types of argon discharge are a transfer of a corresponding fluid into a crude argon column or argon discharge column, from which only an argon-poor, oxygen-rich fluid is returned to the low-pressure column.

The advantageous effect of the argon discharge is due to the fact that the oxygen-argon separation for the discharged argon in the low-pressure column is no longer required. The separation of the argon from the oxygen in the low pressure column itself is basically expensive and requires a corresponding "heating" performance of the main capacitor. Argon is discharged and thus omits the oxygen-argon separation or is this For example, in a crude argon column or Argonausschleussäule relocated, the corresponding amount of argon no longer has to be separated in the oxygen section of the low pressure column and the heating power of the main capacitor can be reduced. Therefore, with the same yield of oxygen, either more air can be blown into the low-pressure column or more pressure nitrogen can be removed from the high-pressure column, which in turn offers energetic advantages.

In a conventional crude argon column crude argon can be recovered and processed in a downstream pure argon column to an argon product. An Argonausschleussäule, however, serves primarily for Argonausschleusung for the purpose explained above. In principle, an "argon discharge column" can be understood to mean a separation column for the argon-oxygen separation, which does not serve to obtain a pure argon product but to remove argon from the air to be separated in the high-pressure column and low-pressure column. Their circuit differs only slightly from that of a conventional crude argon column, but it contains significantly less theoretical plates, namely less than 40, especially between 15 and 30. Like a crude argon column, the bottom region of an argon discharge column is connected to an intermediate point of the low pressure column and the argon discharge column is passed through cooled a top condenser, on its evaporation side typically relaxed bottoms liquid from the high pressure column is introduced. An argon discharge column typically does not have a bottom evaporator.

Advantages of the invention

A significant advantage of the present invention is that, as also explained below, a known double column system with high and low pressure column used more efficiently, i. better "exhausted" than with the use of conventional methods.

For this purpose, the use of a MAC / BAC method and a double Nachboostern in a Joule-Thomson turbine (also referred to as liquid turbine or Dense Fluid Expander) relaxed air (so-called throttle or Joule-Thomson current). This two-time boosting takes place first using an impure-pressure nitrogen turbine and then using a so-called medium-pressure turbine, so a turbine that relaxes the air, which is then fed into the high pressure column, which is cooled in contrast to the relaxed in the Joule-Thomson turbine air only to a much lesser extent. The medium-pressure turbine is fed directly from the outlet of the booster (and not by an intermediate withdrawal). The advantages of the present invention unfold, for example, in combination with an argon discharge column (dummy argon column), as already explained.

Through the use of the impure-pressure nitrogen turbine, the rectification system can be operated with an optimal so-called Einblaseäquivalent, which energy can be saved. The EinblaseEquivalent is usually defined as the sum of the amount of nitrogen taken from the high pressure column and returned neither as a return in this nor used as a liquid reflux to the low pressure column, and the amount of relaxed in the low pressure column compressed air in proportion to the total in the Distillation column system fed compressed air. For example, if an impure-pressure nitrogen turbine used and relaxed in this a lot of impure nitrogen M1 from the high-pressure column, a quantity M2 of nitrogen, which is taken from the high-pressure column, taken as a liquid and / or gaseous nitrogen product of the air separation plant (ie not as reflux on the high pressure column and / or the low pressure column used), and a total amount of compressed air M3 supplied to the distillation column system, the Einblaseäquivalent E results $$\mathrm{e}=\left(\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">M</figure-callout>}\mathrm{1}+\mathrm{M}\mathrm{2}\right)/\mathrm{M}\mathrm{3}$$

Basically, the increase in the Einblaseäquivalents allows a reduction in energy requirements.

The oxygen content in the turbine stream supplied to the impure nitrogen turbine advantageously corresponds approximately to the oxygen content of a so-called impure nitrogen stream (also referred to as waste gas) from the low-pressure column. In this case, the stated material flows are in equilibrium with each other and no additional separation work (for cleaning the turbine stream to the purity of "pure" compressed nitrogen with an oxygen content in the ppm range) can be used.

The Nachboostern of the throttle current leads in the context of the present invention also to a cost reduction, since in this case the booster can be reduced by one or two stages and therefore can be created and operated cost-effective.

The use of two turbines operated at different temperature levels also allows for better optimization of the Q-T profile in the main heat exchanger and possibly a more efficient mid-pressure turbine design, since the liquid fraction at the turbine outlet is lower. Also in this way energy is saved

The use of a medium pressure turbine finally allows a relatively large removal of the pure nitrogen product from the head of the high pressure column, since the impure nitrogen turbine is thereby relieved, and / or a relatively large liquid production of liquid nitrogen, liquid oxygen and / or, if a complete argon system is present , Liquid argon.

The present invention proposes a method for producing one or more air products by cryogenic separation of air in an air separation plant having a distillation column system comprising a high pressure column and a low pressure column, wherein an amount of feed air in a main air compressor is compressed to a first pressure level, of which a first fraction and a second portion be post-compacted in a reboiler. This corresponds to performing a MAC-BAC process as previously explained.

The post-compressed first portion of the amount of feed air is further compressed in the context of the inventive method successively using a first booster and a second booster and then cooled, relaxed to the first pressure level and fed into the high-pressure column. This proportion is the already mentioned Joule-Thomson flow, with the previously described Joule-Thomson turbine or a combination of turbine and throttle valves being used for the expansion of the after-compressed and twice-boosted first portion of the feed air quantity ,

The post-compressed second portion of the feed air quantity is cooled in the context of the present invention and then using a first Turboexpanders, which is mechanically coupled to the second booster, relaxed to the first pressure level and fed into the high-pressure column. The first turboexpander is a so-called medium-pressure turbine, which was also mentioned earlier.

According to the invention, it is now provided that the first portion and the second portion of the amount of feed air in the secondary compressor are recompressed from the first pressure level to a second pressure level and removed together from the after-compressor at the second pressure level. In other words, the Joule-Thomson stream and the medium pressure turbine supplied compressed air stream are taken together from the booster, there is no intermediate removal of at least these shares from the booster.

In the context of the present invention, high-pressure column is further removed from impure nitrogen at the first pressure level and expanded using a second turboexpander, which is mechanically coupled to the first booster, that is to say the already mentioned impure-pressure nitrogen turbine. For the composition of the "impure" nitrogen, reference is made in particular to the explanations below.

Finally, in the context of the present invention, he low-pressure column, an argon-enriched fluid removed, depleted of argon and returned to the low pressure column. This is done in particular using an argon discharge column, as already mentioned above. As a result of the measures mentioned, an argon discharge takes place from the low-pressure column. In this way, despite removal of liquid and / or pressurized nitrogen from the high-pressure column, which is carried out according to the invention, the oxygen yield in the low-pressure column can be maintained.

In the context of the present invention, the impure nitrogen removed from the high-pressure column has an oxygen content of from 0.1 to 5 mol%, in particular from 0.5 to 2 mol%.

The cooling of the first portion of the amount of feed air after its compression using the first booster and the second booster is carried out in the context of present invention, in particular in the main heat exchanger of the air separation plant, wherein the first portion of the amount of feed air in the main heat exchanger to a temperature level of 95 to 110 K, in particular from 97 to 105 K, is cooled.

The cooling of the second portion of the amount of feed air before its relaxation using the first turboexpander can also be carried out in the main heat exchanger of the air separation plant, wherein the second portion of the feed air amount to the main heat exchanger at a temperature level of 130 ... to 200 K, in particular from 150 to 180 K. , is taken.

The impure nitrogen can be heated to a temperature level of 110 to 160 K, in particular from 120 to 150 K, in the context of the present invention before its expansion in the second turboexpander in the main heat exchanger of the air separation plant. Alternatively, the impure nitrogen may be heated to a corresponding temperature level prior to its expansion in the second turboexpander in a secondary heat exchanger provided in addition to the main heat exchanger of the air separation plant.

Advantageously, the depletion of the argon-enriched fluid to argon is accomplished by means of a distillation column having less than 40 theoretical plates, in particular an argon discharge column having the characteristics given above. However, it is also possible to use a conventional crude argon column, in particular in combination with a pure argon column.

Advantageously, the further compression of the post-compressed first portion of the feed air quantity in the context of the present invention using the first booster and the second booster to a third pressure level of 50 to 95 bar, in particular from 60 to 90 bar.

In the context of the present invention, a third portion of the amount of feed air is advantageously cooled at the first pressure level and also fed to the high-pressure column. This is the regular feed air into the high pressure column. In the context of the present invention, the first portion of the feed air quantity of 15 to 40 percent, in particular from 20 to 30 percent of Feed air amount, the second portion of the feed air amount of 5 to 30 percent, in particular from 10 to 20 percent of the feed air and / or the third portion of the feed air amount of 40 to 70 percent, in particular from 45 to 60 percent of the amount of feed air.

The low-pressure column can also be taken from impure nitrogen and, in particular, heated together with the impure nitrogen removed from the high-pressure column and expanded using the second turboexpander. As mentioned, the impure nitrogen removed from the low pressure column and taken from the high pressure column and expanded using the second turboexpander advantageously have an identical or comparable oxygen content.

The invention also extends to an air separation plant having a distillation column system comprising a high pressure column and a low pressure column as set forth in the corresponding independent claim.

The air separation plant according to the invention, which is advantageously set up for carrying out a method, as explained above, benefits in the same way from the advantages of the method according to the invention in its explained embodiments. Reference is therefore expressly made to the above explanations.

Brief description of the drawings

• FIG. 1 illustrates an air separation plant according to an embodiment of the present invention.
• FIG. 2 illustrates an air separation plant according to an embodiment of the present invention.
• FIG. 3 illustrates an air separation plant according to an embodiment of the present invention.
• FIG. 4 illustrates an air separation plant according to an embodiment of the present invention.
• FIG. 5 illustrates an air separation plant according to an embodiment of the present invention.

Detailed description of the drawings

In the following figures, corresponding elements with identical reference numerals are given. These are not explained repeatedly for the sake of clarity. For further details regarding the function of air separation plants and their respective components, reference should be made to the cited technical literature (see, for example, Häring, FIG. 2 .3A and related explanations).

FIG. 1 shows an air separation plant, which is adapted for operation according to an embodiment of the present invention. The air separation plant is designated 100 in total.

In the air separation plant 100, feed air in the form of a stream a (AIR) is sucked in by means of a main air compressor 101 in an amount of feed air via a filter 102 and compressed to a first pressure level. The feed air compressed to the first pressure level is branched off in part in the form of a stream b (Air1) and, moreover, in the form of a stream c subjected to a further processing known per se in a post-cooling unit 103 and an adsorber station 104.

At the first pressure level, the feed air of the material flow c compressed to the first pressure level and subjected to the treatment becomes a part in the form of a stream d of a recompression in a secondary compressor 105 and to a further part in the form of a stream e directly a cooling in a secondary heat exchanger 106 and a main heat exchanger 107 supplied.

In the example shown, the secondary compressor 105 comprises two compressor sections not designated separately and corresponding aftercoolers. A partial stream of the material stream d is taken in the illustrated example the post-compressor 105 in the form of a stream f at an intermediate pressure level (Air2), the rest is compressed in the secondary compressor 105 to a second pressure level and leaves the after-compressor in the form of a mass flow g.

The stream g is divided into a stream h and a stream i, the stream h at the second pressure level supplied to the main heat exchanger 107 and the flow i subjected to a further pressure increase to a third pressure level in a first booster 108 and a second booster 109 and on the third pressure level is supplied to the main heat exchanger 107.

The stream h is taken from the main heat exchanger 107 at an intermediate temperature level, in a first turboexpander 110, which is mechanically coupled to the second booster 109, relaxed again to the first pressure level and (see also linkage A) in a high pressure column 111 of a distillation column system 10, the Further, a low-pressure column 112 and an argon discharge column 113, fed.

The material flow i is taken from the main heat exchanger 107 cold side, using a generator turbine 114 or in a throttle valve (without designation) or both relaxed, thereby at least partially liquefied, and also fed into the high-pressure column 111. The relaxation of the material flow i prior to feeding into the high-pressure column 111 also takes place at the first pressure level.

The high-pressure column 111 is taken from impure nitrogen in the form of a stream k with the above-mentioned exemplary specifications at the first pressure level, the main heat exchanger 107 cold side supplied (see link B), this taken at an intermediate temperature and relaxed in a second turboexpander 115, which in turn is mechanically coupled to the first booster 108. The second turboexpander 115 is the repeatedly mentioned impure-pressure nitrogen turbine.

In the context of this application, the air of the material stream i is also referred to as the "first fraction" of the feed air quantity (of the material stream a), the air of the material stream h also as the "second fraction" of the feed air quantity and the air of the material stream e as the "third fraction" of the Used quantity of air. The amount of feed air is, as shown here, compressed in the main air compressor 101 to the first pressure level. The first portion and the second portion of the amount of feed air are in the secondary compressor 105 to the second Compressed pressure level and the re-compressor 105 taken together at the second pressure level.

The first portion of the feed air quantity is further compressed using the first booster 108 and the second booster 109 to a third pressure level, cooled in the main heat exchanger 107, then expanded to the first pressure level and fed into the high-pressure column 111.

After cooling down in the main heat exchanger 107, the second portion of the feed air quantity is expanded to the first pressure level in the first turboexpander 110, which is mechanically coupled to the second booster 109, and fed into the high-pressure column 111. The high-pressure column is taken from impure nitrogen at the first pressure level and expanded in the second turbo-expander 115 mechanically coupled to the first booster 108.

The third portion of the amount of feed air, ie the air of the stream e, is supplied to the secondary heat exchanger 106 in the form of two partial streams I and m, wherein the partial flow I the secondary heat exchanger 106 cold side and the partial flow m is taken from the secondary heat exchanger 106 at an intermediate temperature. The partial flow m is further cooled in the main heat exchanger 107 and removed from this cold side. Optionally, as illustrated in the form of a dashed material flow z, a subset of the third portion of the feed air quantity can also be cooled only in the main heat exchanger 107. The third portion of the amount of feed air is ultimately fed into the high-pressure column 111 as well.

From the bottom of the high-pressure column 111, an oxygen-enriched liquid in the form of a stream n is withdrawn, passed through a subcooler 116 and fed after use as a cooling medium in a top condenser of the argon discharge column 113 in the low pressure column 112.

Gaseous nitrogen is withdrawn from the top of the high-pressure column 111 in the form of a stream o, heated in the main heat exchanger 107 and provided in the form of one or more printed products (seal gas, PGAN). Further gaseous nitrogen is withdrawn from the top of the high-pressure column 111 in the form of a stream p and in a main condenser 117, the high-pressure column 111 and the Low pressure column 112 connects heat exchanging, at least partially liquefied. A partial flow q is returned to the high pressure column 111, a partial flow r is passed through the subcooler 116 and provided as a liquid nitrogen product (LIN). Impure nitrogen is drawn off liquid in addition to the mentioned stream k in the form of a stream s from the high pressure column 111, passed through the subcooler 116 and fed into the low pressure column 112.

From the bottom of the low-pressure column 112 oxygen in the form of a stream t is withdrawn, in a pump 118 liquid pressure increases (internal compression), heated in the main heat exchanger 107 at least partially in the form of streams u, v and transferred to the gaseous or supercritical state and as appropriate Printed products (IC GOX1, IC GOX2) delivered. Further oxygen is withdrawn in the form of a stream w from the low pressure column 112, passed in part through the subcooler 116 and discharged as a liquid product (LOX). If necessary, the stream w can also be branched off from the stream of material at the pump outlet or from the stream v, throttled to a lower pressure, fed to the subcooler 116 and then discharged as product.

From the top of the low pressure column 112 deducted impurity nitrogen is passed in the form of a stream x through the subcooler 116, then heated to parts in the secondary heat exchanger 106 and the main heat exchanger 107 and finally at will and as needed in the Nachkühleinheit 103 and / or in the adsorber 104th be used (see also link C).

Fluid withdrawn from the head of the argon discharge column 113 can be heated (see also linkage D) in the secondary heat exchanger 106 and released to the atmosphere (ATM). So it is not won argon product, but only discharged argon. However, as already mentioned above, a corresponding plant can also be equipped with a classical argon system, which may in particular comprise a crude and a pure argon column.

While in FIG. 1 an air separation plant 100 is illustrated, in which the stream k, ie the impure nitrogen from the high pressure column 111, is fed after its expansion in the turboexpander 115 to the guided through the main heat exchanger 107 portion of the stream x is in FIG. 2 a Air separation plant illustrated in which the feed to the guided through the secondary heat exchanger 106 portion illustrates.

In the in FIG. 3 illustrated air separation plant, the stream m is not performed by the secondary heat exchanger 106 but by the main heat exchanger 107 (corresponding to the flow z according to FIGS. 1 and 2 ). In the secondary heat exchanger 106, instead of the stream k (see links B and E) is heated.

In the in FIG. 4 the air separation plant illustrated, the secondary heat exchanger 106 is not present, the material flow e is therefore completely guided by the main heat exchanger 107. Accordingly, the stream x is completely heated in the main heat exchanger 107. The stream y is heated in the main heat exchanger 107.

In the in FIG. 4 In the case of the illustrated air separation plant, the low-pressure column 112 is extended by a section 112a for the production of low-pressure nitrogen. Therefore, a low-pressure nitrogen stream j can be withdrawn from the top of the low-pressure column 112. The low pressure nitrogen stream j is passed through the subcooler 116 and heated in a separate passage of the main heat exchanger 107. A partial stream of the stream r can be liquid at the top of the low pressure column 112 abandoned. In the FIG. 4 illustrated embodiment may be basically realized with all of the heat exchanger configurations shown in the previous figures, ie, the secondary heat exchanger 106 may or may not be present.

Claims (13)

A process for producing one or more air products by cryogenic separation of air in an air separation plant (100) with a distillation column system (10) comprising a high pressure column (111) and a low pressure column (112) an amount of feed air in a main air compressor (101) is compressed to a first pressure level, of which a first portion and a second portion are recompressed in a secondary compressor (105), - The recompressed first portion of the feed air quantity using a first booster (108) and a second booster (109) further compressed and then cooled, relaxed to the first pressure level and at least partially liquefied in the high-pressure column (111) is fed, and - the recompressed second portion of the amount of feed air cooled and then using a first turboexpander (110), which is mechanically coupled to the second booster (109), relaxed to the first pressure level and fed into the high-pressure column (111), characterized in that the first portion and the second portion of the amount of feed air in the post-compressor (105) are recompressed from the first pressure level to a second pressure level and taken together to the post-compressor (105) at the second pressure level, - the high-pressure column (111) taken out impure nitrogen at the first pressure level and using a second turboexpander (115), which is mechanically coupled to the first booster (108) is relaxed, and - The low-pressure column (112) removed an argon-enriched fluid, depleted of argon and returned to the low pressure column (112). The method of claim 1, wherein the impure nitrogen has an oxygen content of 0.5 to 2 mole percent. The method of claim 1 or 2, wherein the cooling of the first portion of the feed air quantity after its compression using the first booster (108) and the second booster (109) in the main heat exchanger (107) of the air separation plant (100) is performed, the first Proportion of the amount of feed air is taken from the main heat exchanger (107) at a temperature level of 95 to 110 K. Method according to one of the preceding claims, wherein the cooling of the second portion of the amount of feed air before its relaxation using the first turboexpander in the main heat exchanger (107) of the air separation plant (100) is performed, wherein the second portion of the amount of feed air to the main heat exchanger (107) on a Temperature level is taken from 150 to 180 K. Method according to one of the preceding claims, wherein the impure nitrogen before its expansion in the second turboexpander in the main heat exchanger (107) of the air separation plant (100) is heated to a temperature level of 120 to 150 K. Method according to one of claims 1 to 4, wherein the impure nitrogen is heated to a temperature level of 120 to 150 K before its expansion in the second turboexpander in a secondary heat exchanger provided in addition to the main heat exchanger (107) of the air separation plant (100). A process according to any one of the preceding claims, wherein the depletion of the argon-enriched fluid on argon is carried out by means of a distillation column (13) having less than 40 theoretical plates. Method according to one of the preceding claims, wherein the further compression of the post-compressed first portion of the feed air quantity using the first booster (108) and the second booster (109) to a third pressure level of 60 to 90 bar is performed. Method according to one of the preceding claims, in which a third portion of the amount of feed air is cooled at the first pressure level and also fed to the high-pressure column (111). The method of claim 9 wherein the first portion of the feed air amount comprises from 20 to 30 percent of the feed air amount, the second portion of the feed air amount comprises from 10 to 20 percent of the feed air amount, and / or the third portion of the feed air amount comprises from 45 to 60 percent of the feed air amount. A process according to any one of the preceding claims wherein the low pressure column (112) is taken from impure nitrogen and heated together with the impure nitrogen withdrawn from the high pressure column (111) and relieved using the second turboexpander (115). An air separation plant (100) comprising a distillation column system (10) comprising a high pressure column (111) and a low pressure column (112), the air separation unit comprising: a main air compressor (101) adapted to compress an amount of feed air to a first pressure level, and a reboiler adapted to re-compress a first portion and a second of the amount of feed air, a first booster (108) and a second booster (109) arranged to further compress the post-compressed first portion of the feed air quantity, means being arranged to subsequently cool the first portion to the first pressure level to relax and at least partially liquefied feed into the high-pressure column (111), and Means adapted to cool the post-compressed second portion of the feed air amount, and a first turboexpander (110) mechanically coupled to and arranged for the second booster (109); subsequently to relax the second portion of the amount of feed air to the first pressure level and to feed it into the high-pressure column (111), characterized by means adapted for - to recompress the first portion and the second portion of the feed air quantity in the secondary compressor (105) from the first pressure level to a second pressure level and to collect the secondary compressor (105) together at the second pressure level, to remove impure nitrogen from the high pressure column (111) at the first pressure level and to relax using a second turboexpander (115) mechanically coupled to the first booster (108), and - The low-pressure column (112) to remove an argon-enriched fluid, depleted of argon and in the low pressure column (112) due. Air separation plant (100) according to claim 12, which is adapted to carry out a method according to one of claims 1 to 11.

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