EP3864357A1

EP3864357A1 - Method for obtaining one or more air products and air separation system

Info

Publication number: EP3864357A1
Application number: EP19797562.6A
Authority: EP
Inventors: Dirk Schwenk; Dimitri GOLUBEV
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2018-10-09
Filing date: 2019-10-08
Publication date: 2021-08-18
Also published as: WO2020074120A1; KR20210070988A; CN112654827A; US20220026145A1; CN112654827B

Abstract

The invention relates to a method for obtaining one or more air products, wherein an air separation system (100) having a rectification column system (10) is used, in which pressurised air is processed in an adjustable total air volume, wherein the total air volume is set to a first value during a first operating period (T1) and set to a second value that is different from the first value during a second operating period (T2), and wherein the setting of the total air volume is changed from the first value to the second value in a third operating period (T3) from a first time (X1) to a second time (X2). The second operating period (T2) is after the first operating period (T1), the third operating period (T3) is between the first operating period (T1) and the second operating period (T2). According to the invention, in the third operating period (T3), a setting of a volume of a fluid, which is formed via rectification using the pressurised air and transported in or out of the rectification column system (10), is changed from a third time (X3) up to a fourth time (X4), wherein the third time (X3) is before or after the first time (X1) and before the second time (X2), and the fourth time (X4) is after the first time (X1) and the third time (X3) and before or after the second time (X2). A time period between the first time (X1) and the second time (X2) is set to be substantially the same as a time period between the third time (X3) and the fourth time (X4). The invention also relates to a corresponding air separation system (100).

Description

description

Process for obtaining one or more air products and air cereal plants

The invention relates to a method for obtaining one or more air products and a corresponding air separation plant according to the respective preambles of the independent claims.

State of the art

The production of air products in liquid or gaseous state by low-temperature separation of air in air separation plants is known and

for example at H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH,

2006, in particular Section 2.2.5, "Cryogenic Rectification".

Air separation plants have rectification column systems which can be designed, for example, as two-column systems, in particular as classic Linde double-column systems, but also as three- or multi-column systems. In addition to the

Rectification columns for the production of nitrogen and / or oxygen in a liquid and / or gaseous state, ie the rectification columns for nitrogen-oxygen separation, rectification columns for the production of further air components, in particular the noble gases krypton, xenon and / or argon, can be provided. Even if rectification columns for obtaining further air components are not specifically discussed below, air separation plants with corresponding rectification columns can also be the subject of the present invention at any time.

The rectification columns of the rectification column systems mentioned are operated at different pressure levels. 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 an upper column). The pressure level of the high pressure column is, for example, 4.7 to 6.7 bar, preferably about 5.5 bar. The low pressure column is operated at a pressure level of, for example, 1.3 to 1.8 bar, preferably approximately 1.4 bar. The pressure levels given here and below are absolute pressures that at the top of each of the columns mentioned. The values mentioned are only examples that can be changed if necessary.

US 4,251,248 A discloses a method and apparatus for automatically changing operations in an air separation plant to increase or decrease product quantities. Intended change values, among other things for feed air, are calculated from the values of the correspondingly increased or decreased product quantities.

In US 5 901 580 A, purities of air products are kept substantially constant with fluctuations in the demand for one of the products or the amount or pressure of the feed air by introducing an excess of nitrogen-rich liquid into the rectification column system when the demand for the product or the amount of feed air increases and by withdrawing and storing an excess of nitrogen-rich liquid from the distillation apparatus as the demand for the product or the amount of feed air decreases.

A cryogenic air separation plant, which is subject to periods with considerable changes in product demand, is the subject of US 6 006 546 A. The plant is specifically controlled during these periods in order to minimize the effects of transient operation on the product purity.

According to US Pat. No. 5,224,336 A, rapid changes in the oxygen demand and the feed air pressure are compensated for by a net transfer of the cold in the form of liquid nitrogen into and out of the distillation system. This cold transfer is carried out using a liquid nitrogen reservoir connected to the reflux path of the distillation system.

In a method proposed in US Pat. No. 6,185,960 B1 for producing a pressurized gaseous product by low-temperature separation of air, this takes place at times in a gas operation and at times in a combined operation using the internal compression and corresponding cooling.

Irrespective of the specific design of an air separation plant, flexible operation is often desired, ie an appropriate air separation plant should be closed certain times can provide significantly larger or smaller quantities of certain air products with a correspondingly higher or lower use of air. In this context, rapid switching between such operating states with different production quantities is often desired.

Corresponding switching processes are also referred to below as "load changes". It can be assumed that rapid load changes lead to an overall higher efficiency of an air separation plant. In addition, in the event that rapid load changes are implemented, backup memories with less

Capacity required because less or no liquid from such

Backup storage is taken to support load changes. It can therefore be assumed that the production costs of corresponding air separation plants will decrease.

The object of the present invention is to make the extraction of air products more flexible using air separation plants and to enable faster load changes overall.

Disclosure of the invention

This task is accomplished by a method of obtaining one or more

Air products and a corresponding air separation plant with the respective

Features of the independent claims solved. Advantageous embodiments are the subject of the respective dependent claims and the

following description.

Some terms used in the description of the present invention and its advantages and the underlying technical background are first explained in more detail below.

So-called main compressors / post-compressors (Main Air Compressor / Booster Air Compressor, MAC-BAC) processes or so-called

High air pressure (HAP) processes can be used. The main compressor / post-compressor process is the rather

more conventional processes, high air pressure processes are increasingly coming in younger Time as an alternative to use. The present invention is suitable for both applications.

The main compressor / post-compressor process is characterized in that only a part of the total amount of feed air supplied to the rectification column system is compressed to a pressure level that is significant, i.e. is at least 3, 4, 5, 6, 7, 8, 9 or 10 bar, above the pressure level of the high pressure column. Another part of the amount of air used is only the pressure level of the high pressure column or a pressure level that is not more than 1 to 2 bar from the pressure level of the

High-pressure column differentiates, compresses, and is fed into the high-pressure column at this lower pressure level. An example of a main compressor / post-compressor process is shown by Häring (see above) in Figure 2.3A.

With a high-air pressure process, however, the entire is

Rectification column system total amount of feed air supplied

Compressed pressure level, that is, i.e. is at least 3, 4, 5, 6, 7, 8, 9 or 10 bar above the pressure level of the high pressure column. The pressure difference can be up to 14, 16, 18 or 20 bar, for example. High air pressure processes are known for example from EP 2 980 514 A1 and EP 2 963 367 A1.

The present invention can be used in air separation plants with so-called

Internal compression (IV, Internal Compression, IC) are used, but also in air separation plants with external compression. In the case of internal compression, at least one product which is provided by means of the air separation plant is formed by removing a cryogenic liquid from the rectification column system, subjecting it to a pressure increase in the liquid state, and, depending on the pressure present, by heating either in the gaseous or in the supercritical state is transferred. For example, internally compressed gaseous oxygen (GOX IV, GOX IC), internally compressed gaseous nitrogen (GAN IV, GAN IC) or internally compressed gaseous argon (GAR IV, GAR IC) can be generated by means of internal compression. Internal compression offers a number of technical advantages compared to an external compression of corresponding products, which is also possible in principle, and is explained in the specialist literature, for example by Häring (see above), Section 2.2.5.2, "Internal Compression". Liquids and gases can be rich or poor in one or more components in the language used here, "rich" for a content of at least 90%, 95%, 99%, 99.5%, 99.9% or 99.99 % and "poor" for a content of at most 10%, 5%, 1%, 0.1% or 0.01% on mole, weight or

Volume basis can stand.

Liquids and gases can, in the language used here, be enriched or depleted in one or more components, these terms relating to a content in a starting liquid or gas from which the liquid or gas under consideration was obtained. The liquid or gas is "enriched" if it contains at least 1.1 times, 1.5 times, 2 times, 5 times, 10 times 100 times or 1,000 times the content, and " depleted "if this or this contains at most 0.9 times, 0.5, 0.1 times, 0.01 times or 0.001 times the content of a corresponding component, based on the starting liquid or gas. If, for example, "oxygen" is used here, this also means a liquid or a gas that is rich in

Is oxygen, but need not consist exclusively of it.

The present application uses to characterize pressures and

Temperatures the terms "pressure level" and "temperature level", which is intended to express that pressures and temperatures in one

corresponding system do not have to be used in the form of exact pressure or temperature values in order to implement the inventive concept. However, such pressures and temperatures are typically in certain ranges, for example ± 1%, 5%, 10% or 20% around an average. Corresponding pressure levels and temperature levels can lie in disjoint areas or in areas that overlap one another. In particular, pressure levels include, for example, unavoidable or expected pressure drops. The same applies to temperature levels. The pressure levels given here in bar are absolute pressures.

Advantages of the invention Depending on the "direction" of the load changes explained above (from high to low production volume or vice versa) occurs in conventional

Air separation plants - based on the load condition to be set subsequently - either an excess or a deficit of cryogenic liquids in the rectification section, i.e. the rectification column system. The reason for this is the amount of cryogenic liquids stored on the dividing plates or in liquid distributors and packs of the rectification columns, in particular the high and low pressure columns. This amount of liquid depends on the load: the lower the load, the less liquid is distributed on the partitions. When the load is reduced, excess liquid is released. This excess liquid should be stored in the system so that it can be used to compensate for the deficit if the load increases.

In conventional air separation plants without argon production, only the sump of the high pressure column is the storage for the liquid. Additional liquid containers present in corresponding air separation plants, for example for the heat-exchanging connecting the high and low pressure columns

Main capacitor, or a so-called secondary capacitor, should be off

For safety reasons, they are typically operated with the liquid level unchanged and are therefore ruled out as storage containers for load changes. Further is illustrated below with reference to Figure 1, which is a corresponding

Air separation plant shows. It goes without saying that "fast" controllers are also required for fast load changes, which only lead to small deviations between setpoint and actual values.

Rapid load changes can lead to changed product compositions. If, for example, the air separation plant illustrated in FIG. 1 is operated with an otherwise unchanged operation at an increased load change speed (75% load to 100% load at 4% per minute), an increase in

Observe oxygen content in the gaseous top product of the high pressure column, as also illustrated in Figure 2 (see lane 103 there). This increase is to be assessed negatively, since it means the purity of at least two air products, namely a liquid pressure nitrogen product (LIN) formed by liquefaction from the top product of the high pressure column and one in the form of a gaseous pressurized nitrogen product (PGAN) liquefied from the air separation plant portion of this overhead product.

An obvious solution to avoid a corresponding deterioration of the product cleanliness would be to operate the plant with a product cleanliness that includes a certain buffer for such operating conditions, so that the required purity can always be maintained. The disadvantage of this, however, is that a product purity that is greater than is actually required must be provided for most operating states. This would therefore either lead to higher ones

Investment costs (more separation stages in the high pressure column) or higher operating costs (due to an excess of feed air).

In the context of the present invention, it was recognized that the problems explained can be solved by a delayed or leading

Setpoint adjustment of regulators which influence the amount of a material flow led into or out of the rectification column system in an air separation plant in response to a change in the air separation plant or its

Rectification column system processed amount of air is made. This can take place in the form of a delayed setpoint adjustment, in particular, as described in the following, in particular with regard to the amount of a nitrogen-rich liquid which is produced from a top product of the

High pressure column is formed. However, the present invention is not limited to this specific case. Rather, the basic finding of the invention consists in the fact that a leading or trailing adjustment of corresponding fluid flows or their amounts in corresponding

Deployment scenarios can be particularly advantageous.

Against this background, the present invention proposes a method for

Obtaining one or more air products, in which an air separation plant with a rectification column system is used, in which compressed air is processed in an adjustable total air quantity. If the term “total air volume” is used here, it should always be understood that the total air volume processed in a corresponding system at a particular point in time, ie treated by rectification. Any air other than the total air volume is not processed in the air separation plant or in its rectification column system. Within the scope of the present invention, the total air volume is set to a first value during a first operating period and to a second value that differs from the first value during a second operating period. There are therefore different total air volumes in these two operating periods, the first total air volume being larger or smaller than the second

Total air volume can be. A corresponding air separation plant is therefore operated in the first and the second operating period in different load conditions, in particular in one of the two operating periods

Full load operation is present or can take place. In other words, the present invention relates to cases of load increase and load reduction.

In the context of the present invention, as is known in principle, the setting of the total air quantity is changed from the first value to the second value in a third operating period from a first point in time and up to a second point in time, that is to say a load change is carried out. It goes without saying that the second operating period lies after the first operating period and the third operating period lies between the first operating period and the second operating period. Without further measures, as mentioned, this can lead to the disadvantageous effects explained. A load change can represent a load increase or load reduction, depending on whether the first total air volume is less or higher than the second total air volume. The first, second and third operating periods represent operating periods that do not overlap one another and the third

The operating period is always between the first and the second or the second and the first operating period. This does not exclude the existence of other operating periods.

According to the invention, in the third operating period, a setting of an amount of a liquid which is formed by rectification using the compressed air and transported in or out of the rectification column system is changed from a third point in time and up to a fourth point in time, the third point in time before or after the first time and before the second time and the fourth

Time after the first time and the third time and before or after the second time. The first, the second, the third and the fourth point in time each lie within the third operating period, but for example the third may be before the first or the fourth after the second point in time, that is to say the third operating period does not have to begin with the first point in time and end at the second point in time. The third operating period can lie between the earliest time and the latest time of these times, but can also extend over a longer period. According to the invention, a period between the first point in time and the second point in time is set such that it differs by no more than 20%, 10%, 5% or 1% from a period between the third point in time and the fourth point in time. The above

Periods can also be set the same or essentially the same. The setting can be made in particular by using appropriate setpoints or default values in a regulation or control.

Within the scope of the present invention, therefore, a change in the amount of the fluid, which is generated by rectification using the compressed air and transported in or out of the rectification column system, is not synchronized with the change in the total amount of air. This change is made in particular by a corresponding setpoint specification of a control or regulating system of an air separation plant and is carried out by suitable actuators, in particular valves, slides and the like. A corresponding control or regulation can take place in particular on the basis of recorded actual values and thereby include all measures known from the field of control or regulation technology, insofar as they are suitable and expedient for use in the present invention.

The change in the amount of fluid generated using the compressed air by rectification and in or out of the rectification column system

transported, can be done in particular using a corresponding setpoint. In certain cases, for example in the air separation plants shown in the attached FIGS. 1 to 4, it can also be provided that a corresponding controller output is additionally readjusted (typically in a range of not more than ± 5%) by a trim controller. In extreme cases, this can mean that an actual value at the end of the adjustment differs slightly (but at most by 5%) from an opposite setpoint. The present invention can be used in particular in air separation plants whose rectification column system has a high-pressure column operated at a first pressure level and a low-pressure column operated at a second pressure level below the first pressure level, the liquid, the amount of which is changed in the third operating period, as mentioned Part of a gaseous nitrogen-rich top product of the high pressure column, which is liquefied and fed as a return to the low pressure column. The

The present invention can be used in particular in an air separation plant with a secondary condenser for heating an internally compressed oxygen product. In an appropriate air separation plant, internal or external compression of air products can and can

procedural interconnections with nitrogen and air circuits are used. Air separation plants with several high pressure columns can also be used.

Regardless of the number of high and low pressure columns, the first pressure level in the context of the present invention can in particular be 5 or 7 to 12 bar

Absolute pressure and the second pressure level are in particular 1, 3 or 1, 8 to 3.5 bar absolute pressure. The present invention can thus be used in particular in so-called "elevated pressure" air separation plants in which the operating pressures of the distillation column systems are above the conventional values mentioned at the outset. Nevertheless, the invention can also be used in connection with conventional pressure levels in the distillation column system.

Within the scope of the present invention, in particular flexible

Load change speeds can be realized. In other words, a

Period between the first point in time and the second point in time can be set by changing the first point in time and / or the second point in time. In this context, it proves to be particularly advantageous if, for example, a delay time provided within the scope of the present invention is applied to it

Change is adjusted, i.e. if a period between the first point in time and the third point in time depends on the setting of the period between the first point in time and the second point in time by changing the third

Time is set. In this way you can also change Load change speeds achieve the advantages of the invention. In this case, it can in particular be provided that if the third point in time lies after the first point in time and the fourth point in time after the second point in time, the period between the first point in time and the third point in time is extended if the point in time between the first point in time and the second point in time is shortened. In other words, when the load change speed increases

for example, a longer delay time can be selected.

In the context of the present invention, a change in load can in particular also include changing the quantities of the air products formed in each case. One or more air products can therefore be formed in an adjustable product quantity, the product quantity being set to a first value during the first operating period and to a second value different from the first value during the second operating period, and wherein the setting the amount of product is changed in the third operating period from the first point in time and up to the second point in time from the first value to the second value. A corresponding air product can in particular be such an air product that is at least partially formed from the gaseous nitrogen-rich top product of the high-pressure column. This can be provided in liquefied or non-liquefied form.

The present invention can be related to various

Load change scopes are used. For example, it can be provided that the first total air volume differs from the second total air volume by more than 5 and up to 30, 40 or 50 percentage points.

In particular, the change in the total air volume can take place gradually or continuously in the third operating period, and preferably with an average rate of change (based on the gradual change) or a rate of change (in the case of continuous change) of the total air volume of 0.1 (in the case of extraction) of argon) or 1 to 10 percentage points per minute.

In general, argon extraction can be provided in the context of the present invention, ie in the method the rectification column system can in particular one or more for the extraction of an argon-rich air product have rectification columns set up and the argon-rich air product can be formed in the process. An "argon-rich" air product has at least 50, 60, 70, 80 or 90 mole percent argon.

The present invention also extends to an air separation plant which is set up to obtain one or more air products and a

Rectification column system, wherein the air separation plant is set up to supply compressed air in an adjustable total amount of air

To process rectification column system and thereby set the total air volume during a first operating period to a first value and during a second operating period to a second value that differs from the first value, and the setting of the total air volume in a third

Change operating period from a first point in time and up to a second point in time from the first value to the second value. As mentioned, the second operating period lies after the first operating period and the third operating period lies between the first operating period and the second operating period.

According to the invention, the air separation plant is equipped with a control unit, which is set up for programming purposes in the third operating period

Adjust an amount of a liquid that is formed by rectification using the compressed air and transported into or out of the rectification column system from a third point in time and up to a fourth point in time, the third point in time before or after the first point in time and before the second Time and the fourth time after the first time and the third time and before or after the second time. It is also set up to cover a period between the first point in time and the second point in time

Set it to differ by no more than 20% or any of the aforementioned difference values from a period between the third point in time and the fourth point in time.

The control unit is set up, in particular, in terms of program technology

Carrying out methods as previously explained in different configurations. For further advantages of corresponding air separation plants and configurations according to the invention, reference is expressly made to the above explanations regarding the method according to the invention and its different advantageous configurations. An air separation plant provided according to the invention is

especially set up for carrying out corresponding methods and has specifically designed means for this purpose.

The invention is explained in more detail below with reference to the accompanying drawings, which show, among other things, an air separation plant that can be operated according to an embodiment of the invention.

Brief description of the drawings

FIG. 1 shows an air separation plant that can be operated in accordance with an embodiment of the invention in the form of a simplified process flow diagram.

Figure 2 shows changes in material flows and their compositions in a method not according to the invention in the form of a diagram.

Figure 3 shows changes in material flows and their compositions in a method according to an embodiment of the invention in the form of a diagram.

Figure 4 shows changes in material flows and their compositions in a method according to an embodiment of the invention in the form of a diagram.

Detailed description of the drawings

In FIG. 1, an air separation plant that can be operated in accordance with an embodiment of the invention is illustrated in the form of a simplified process flow diagram and is designated overall by 100. Regarding the components of the air separation plant 100 not explained below, reference is made to relevant specialist literature, in particular the chapter cited above by Häring. The air separation plant 100 has a distillation column system 10, the one

High pressure column 11 and a low pressure column 12 includes. In the air separation plant 200, feed air (A) is drawn in and compressed by means of a main air compressor 1 via a filter 2. An appropriately educated

Compressed air stream a is precooled and cleaned in a generally known manner in a pre-cooling device 3 operated with cooling water (B) and a cleaning device 4. Air of the pre-cooled and cleaned compressed air stream a is fed to a main heat exchanger 5 on the warm side in the form of two partial streams b and c.

The partial flow b is the main heat exchanger 5 on one

The intermediate temperature level is removed and expanded (blown) into the low-pressure column 12 by means of a blowing-in turbine 6, which can be coupled to an oil brake or a generator that is not specifically designated. The partial flow c, however, is taken from the main heat exchanger 5 on the cold side, by a

Auxiliary condenser 7 out and fed into the high pressure column 1 1 via a valve not specifically designated.

In the high pressure column 1 1 an oxygen-enriched liquid

Bottom product and a nitrogen-enriched or nitrogen-rich gaseous top product are formed. The bottom product of the high-pressure column 11 is passed in the form of a stream d through a countercooling countercurrent 8 and into the

Low pressure column 12 fed. The top product of the high-pressure column 11 is liquefied partly in the form of a stream e in a main condenser 13 which connects the high-pressure column 11 and the low-pressure column 12 in a heat-exchanging manner, and partly in the form of a stream f in the main heat exchanger 5 and is heated as a gaseous one

Pressure nitrogen product exported from the plant. The liquefied fraction is partly returned in the form of a stream g to the high-pressure column 11 as a return line, and in particular in further adjustable proportions it is fed in the form of a stream h into a tank 20 and in the form of a stream i through the supercooling counterflow 8 and onto it Low pressure column 12 abandoned.

An oxygen-rich liquid sump product is formed in the low-pressure column 12 and pressure-increased in the form of a material flow k in an internal compression pump 9 in the liquid state. At least a part of this can be fed to the secondary condenser 7 in the form of a stream I and heated there. If required, a further portion in the form of a material flow m can be fed back into the low-pressure column 12 via a valve, which is not specifically designated. In the secondary condenser 7, the material flow I is evaporated, at least for the most part. A correspondingly evaporated stream n is in

Main heat exchanger 5 is heated, in the process converted from the liquid to the gaseous or supercritical state and designed as a gaseous pressurized oxygen product (C) from the air separation plant 100. A fill level in a liquid container of the secondary condenser 7 is regulated by the inlet flow I. If necessary, liquid can be released into the atmosphere (D) in the form of a stream o. A liquid level in the liquid container of the secondary condenser 7, but also a liquid level in the low pressure column 12 and thus in a liquid container of the main condenser 13 should, as mentioned, be kept constant for safety reasons. This essentially leaves the sump of the high-pressure column 11 in the air separation plant 100 illustrated here as a possible one

Liquid storage for load changes.

From the head of the low pressure column 12 is illustrated in the here

Air separation plant head gas is drawn off in the form of a material flow p and partly in the form of a material flow q through the supercooling counterflow 8 and the

Main heat exchanger 5 out and heated in this way. The same applies to so-called impure nitrogen, which in the form of a stream r from the

Low pressure column 12 is withdrawn. The last-mentioned material flows can be used in various ways in the air separation plant 100, provided as a product, and / or released into the atmosphere (D).

The tank 20 can in particular be used to buffer a return flow to the low pressure column 12. In other words, in particular if, in certain operating states, the i can be provided in the form of the material flow

nitrogen-rich liquid for the operation of the low-pressure column 12 is not sufficient, a corresponding addition can be made by means of a stream of material s from the tank 20, and if the amount of such a nitrogen-rich

Liquid exceeds the demand for product or the need in the air separation plant 100, a feed into the tank 20 can be made.

Figure 2 shows changes in material flows and their compositions in a method not according to the invention in the form of a diagram, with a time in Minutes is plotted on the abscissa compared to a normalized range of values from 0 to 100% on the ordinate. The representation of FIG. 1 corresponds to that of FIGS. 3 and 4, with the latter in each case corresponding changes in

Material flows and their compositions are illustrated in a method according to an embodiment of the invention.

As can be seen from FIG. 2, during a first operating period T1, one is fed into a distillation column system of an air separation plant, for example the air separation plant 100 according to FIG. 1, and processed there

Air quantity 101 is set to a first value and, during a second operating period T2, to a second value that differs from the first value. The corresponding guide vane position of the main air compressor is designated 101 ', the specification (ramp) for the guide vane position is designated 101 ". The same also applies to the amount of a gaseous nitrogen-rich top product of a high-pressure column of a corresponding system, which liquefies and returns to the

Low pressure column is abandoned. Such a material flow is designated by i in FIG. Its quantity is set via a specification (ramp) with regard to the position of a valve 11, which is arranged downstream of a subcooler 110 (see in each case FIG. 1). This specification is designated by 102 in FIG. There is no measurement. It goes without saying that the values used in each case differ from one another. Other material flows are also changed accordingly, but are not shown separately here.

As can be seen here, the change in the nitrogen-rich return quantity takes place in a ramp-like manner from the same point in time at the end of the first operating period T1 as the ramp-like change in the fed-in and processed air quantity 101. This disadvantageously leads to the fact that

Oxygen content 103 in a top product of the high pressure column is temporarily greatly increased here. This goes with a temporary increase in column temperature 104 of the high pressure column and with a decrease in column temperature 105 of

Low pressure column. A quantity of an oxygen product removed from the air separation plant is designated by 106.

In the operation illustrated in FIG. 3 according to an embodiment of the present invention, a third operating period T3 is therefore provided here. In This is, as is basically the case previously, in the

Distilled column system fed and processed there air quantity 101 changed from a first time X1 and up to a second time X2 from the first value to the second value.

In addition, it is provided here, however, that in the third operating period T3, a setting of an amount of a fluid, which is formed using the compressed air by rectification, and in or out of the rectification column system

is transported, namely here the gaseous nitrogen-rich top product of the high-pressure column, which is liquefied and fed as a return to the low-pressure column in accordance with the specification 102, is changed with a delay compared to the fed-in and processed air quantity 101, here here from a third point in time X3 and up to one fourth point in time X4. The third time X3 is after the first time X1 and before the second time X2 and the fourth time X4 is after the first time X1 and the third time X3 and after the second time X2.

The representation according to FIG. 4 corresponds to the representation according to FIG. 3 over an extended period of time. As further illustrated here, "purge" oxygen 107 is periodically blown off to the atmosphere (see stream o in FIG. 1) by one

Prevent accumulation of unwanted components. In principle, this can also be injected into the pressurized oxygen product (C).

As can be seen from FIGS. 3 and 4, when the present invention is used, there are in particular none in the embodiments shown

Deterioration of the purity of a nitrogen product (see the

Oxygen content 103 in the top product of the high pressure column).

Claims

1. A method for obtaining one or more air products, in which one

Air separation plant (100) with a rectification column system (10) is used, in which compressed air is processed in an adjustable total air volume, the total air volume during a first operating period (T1) to a first value and during a second operating period (T2) to a different value the first value differing second value is set, the setting of the total air quantity in a third operating period (T3) from a first point in time (X1) and up to a second point in time (X2) being changed from the first value to the second value, and wherein the second

Operating period (T2) after the first operating period (T1) and the third operating period (T3) between the first operating period (T1) and the second operating period (T2), characterized in that in the third operating period (T3) a setting of a quantity Liquid formed by rectification using the compressed air and transported in or out of the rectification column system (10) is changed from a third point in time (X3) and up to a fourth point in time (X4), the third point in time (X3) before or after the first time (X1) and before the second time (X2) and the fourth time (X4) after the first time (X1) and the third time (X3) and before or after the second time (X2), and a time period between the first time point (X1) and the second time point (X2) is set such that it does not differ by more than 20% from a time period between the third time point (X3) and the fourth time point eitpunkt (X4) differs.

2. The method of claim 1, wherein the rectification column system (10) operated at a first pressure level high pressure column (1 1) and operated at a second pressure level below the first operating pressure

Low pressure column (12), wherein a gaseous nitrogen-rich

Top product is formed in the low pressure column (11).

3. The method of claim 2, wherein the liquid, the amount of which is changed in the third operating period (T3), is a portion of the gaseous nitrogen-rich top product of the high pressure column (11), which is liquefied and fed as a return to the low pressure column (12) .

4. The method according to claim 2 or claim 3, wherein the first pressure level at 5 to 12 bar absolute pressure and the second pressure level at 1.3 to 3.5 bar

Absolute pressure lies.

5. The method according to any one of claims 2, 3 or 4, in which a period between the first point in time (X1) and the second point in time (X2) is set by changing the first point in time (X1) and / or the second point in time (X2) .

6. The method of claim 5, wherein a period between the first

Time (X1) and the third time (X3) depending on the setting of the period between the first time (X1) and the second

Time (X2) is set by changing the third time (X3).

7. The method according to claim 6, wherein the third time (X3) after the first time (X1) and the fourth time (X4) after the second time (X2), the period between the first time (X1) and the third

Time (X3) is extended if the period between the first

Time (X1) and the second time (X2) is shortened.

8. The method according to any one of claims 2 to 7, in which one or more

Air products are formed in an adjustable product quantity, the product quantity being set to a first value during the first operating period (T1) and to a second value different from the first value during the second operating period (T2), and wherein the setting of the product quantity in the third operating period (T3) from the first

Time (X1) and up to the second time (X2) is changed from the first value to the second value.

9. The method of claim 8, wherein the one or more air products is or are at least partially formed from the gaseous nitrogen-rich top product of the high pressure column (11).

10. The method according to any one of the preceding claims, wherein the first

Total air volume differs from the second total air volume by more than 5 and up to 30 percentage points.

11. The method according to claim 10, wherein the change in the total amount of air in the third operating period (T3) takes place gradually or continuously.

12. The method according to claim 1 1, wherein an average rate of change in the gradual or a rate of change in the

continuous change in the total air volume in the third

Operating period (T3) is 0.1 to 10 percentage points per minute.

13. The method according to any one of the preceding claims, wherein the

Rectification column system (10) has one or more rectification columns set up to obtain an argon-rich air product and in which the argon-rich air product is formed in the process.

14. Air separation plant (100), which is set up to obtain one or more air products and has a rectification column system (10), the air separation plant (100) being set up to process compressed air in an adjustable total amount of air in the rectification column system (100) and thereby Set the total air volume during a first operating period (T1) to a first value and during a second operating period (T2) to a second value that differs from the first value, and adjust the total air volume in a third operating period (T3) from a first point in time (X1) and change up to a second point in time (X2) from the first value to the second value, the second operating period (T2) after the first operating period (T1) and the third operating period (T3) between the first operating period (T1) and the second operating period (T2), characterized in that the air separation plant (100) has a control unit (50), which is set up for programming purposes, in the third operating period (T3) a setting of an amount of a liquid which is formed by using the compressed air by rectification and transported in or out of the rectification column system (10) is to change from a third point in time (X3) and up to a fourth point in time (X4), the third Time (X3) before or after the first time (X1) and before the second time (X2) and the fourth time (X4) after the first time (X1) and the third time (X3) and before or after the second time ( X2), and a period between the first time (X1) and the second

Set the point in time (X2) in such a way that it is not more than 20% of one

Period between the third (X3) time and the fourth time (X4) differs.

15. Air separation plant (100) according to claim 14, wherein the control unit (50) is set up in terms of program technology to implement a method according to one of the

Perform claims 1 to 13.