EP3027988A2

EP3027988A2 - Method and device for producing compressed nitrogen

Info

Publication number: EP3027988A2
Application number: EP14744775.9A
Authority: EP
Inventors: Alexander Alekseev; Dimitri Goloubev; Thomas Eckert
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2013-08-02
Filing date: 2014-07-29
Publication date: 2016-06-08
Also published as: WO2015014485A2; US20160161181A1; MX2016001221A; WO2015014485A3

Abstract

The invention relates to a method and to a device that serve for producing compressed nitrogen by low-temperature decomposition of air in a distillation column system which has a high-pressure column (202), a low-pressure column (203), a high-pressure column head condenser (204) and a low-pressure column head condenser (205). A main air compressor (9) constitutes the only gas compressor powered by external energy. In the main air compressor (9) the feed air is compressed to a total air pressure which is at least 5 bars above the operating pressure of the high-pressure column (202). A first part-stream (56) of the high-pressure total air stream (11, 811) from the main air compressor (9) is expanded to perform work as operating pressure of the high-pressure column or a higher pressure (57) and is introduced into the distillation column system (201). A second part-stream (52, 55) of the high-pressure total air stream (11, 811) is cooled in a main heat exchanger (51) and is introduced at least partially in liquid form into the distillation column system (206, 210). An internally compressed nitrogen stream is formed by a part-stream (319) of the liquid nitrogen stream (215) from the high-pressure column head condenser (204) and/or a part-stream (234, 334) of the liquid nitrogen stream (232) from the low-pressure column head condenser (205); the internally compressed nitrogen stream is brought in the liquid state to a product pressure (235, 335a, 335b) which is between 15 and 100 bars; then the internally compressed nitrogen stream is heated in the main heat exchanger (51) and then extracted as a gaseous compressed nitrogen product (60) below the product pressure.

Description

description

Process and apparatus for producing pressurized nitrogen

The invention relates to a method for producing pressurized nitrogen according to the preamble of patent claim 1.

A method of the type mentioned is known from US 6141989. Here, in a distillation column system with three or even four condenser evaporators, pressurized nitrogen is produced under a product pressure of 12 bar by internal compression. In this case, nitrogen is brought to liquid product pressure and then evaporated in indirect heat exchange with air and warmed to about ambient temperature.

In the pressure data, the natural pressure losses are usually not included here. Here, pressures are considered "equal" if the pressure difference between the corresponding points is not greater than the natural conduction losses caused by pressure losses in piping, heat exchangers, coolers, adsorbers, etc. For example, the internal compression nitrogen flow experiences a pressure loss in the passages of the main heat exchanger; nevertheless, here the discharge pressure of the pressurized nitrogen product downstream of the

Main heat exchanger and the pressure upstream of the main heat exchanger equally referred to as "the product pressure".

The term "condenser-evaporator" refers to a heat exchanger in which a first condensing fluid stream undergoes indirect heat exchange with a second evaporating fluid stream. Each condenser evaporator has a

Liquefaction room and an evaporation room on that off

Condensing passages or evaporation passages exist. In the liquefaction space, the condensation (liquefaction) of a first fluid flow is performed, in the evaporation space the evaporation of a second fluid flow. Evaporation and liquefaction space are formed by groups of passages that are in heat exchange relationship with each other. The "main heat exchanger" is used for cooling of feed air in indirect

Heat exchange with recycle streams from the distillation column system. It can be composed of a single or several parallel and / or serially connected

Heat exchanger sections may be formed, for example, from one or more plate heat exchanger blocks. The main heat exchanger in this sense is formed, for example, in US Pat. No. 6,141,989 by the combination of a gas-gas exchanger with a condenser-evaporator, in which pumped high-pressure column nitrogen is vaporized in indirect heat exchange with a condensing substream of the feed air. In the main heat exchanger of the invention, the "internal condensing nitrogen stream" is vaporized (or, if its pressure is supercritically pseudo-vaporized) against a high pressure air stream and warmed. The high-pressure air is thereby cooled and liquefied or, if its pressure is supercritical, pseudo-liquefied. In the invention, preferably, no separate condenser-evaporator is used for nitrogen evaporation, but the (pseudo) evaporation and the

Heating takes place in an integrated main heat exchanger.

By an "oxygen-enriched product gas stream" is meant herein any gaseous product or residual stream that is discharged from the system and that has an oxygen content that is higher than that of air. It can be very pure oxygen or just a light one

oxygen-enriched residual gas. The process of the invention may comprise one or more such streams.

Since the pressurized nitrogen product of the above-mentioned US Pat. No. 6,141,989 is produced under a pressure of 12 bar, it has to be used outside the industry for many applications

Air separation plant using a gas compressor are further compressed, for example, to 100 bar.

The known method therefore requires two externally driven compressors 3 and 5, as shown schematically in FIG. 1, in order to deliver a pressurized nitrogen product below more than 12 bar. In particular, if at the site of the plant no efficient network for electrical power is available and a separate

Drive unit as a gas turbine unit 1 is available, this means several steps for transmitting the mechanical energy generated at the shaft of the gas turbine to the drive shafts of the compressor 3 and 5: First is the mechanical energy is converted into electrical energy in a generator 8 and brought to a suitable voltage in a transformer 2. Subsequently, the electrical energy in the motors 4 and 6 is converted back into mechanical energy. The air separation in the strict sense 7 (ASU) is formed by a conventional air separation plant, the medium pressure nitrogen (PGAN -

Pressurized Gaseous Nitrogen) under a pressure of, for example, 12 bar. This medium-pressure nitrogen must then be further compressed in a nitrogen gas compressor 5 to a pressure of, for example, 100 bar to

High-pressure nitrogen (HPGAN - High Pressure Gaseous Nitrogen) can be delivered, for example, to support oil production (to EOR - Enhanced Oil Recovery). (The operation of the gas turbine unit 1 is explained in more detail below in FIG. 2).

The invention is based on the object to produce a pressurized nitrogen product under very high pressure in an energetically particularly favorable manner and thereby to use a relatively inexpensive apparatus.

This object is solved by the entirety of the features of claim 1. In the invention, a pressurized nitrogen product is obtained directly by internal compression under a pressure of 15 to 100 bar. If this pressure for the

given application (for example, in the case of oil production - EOR = Enhanced Oil Recovery) sufficient, needs the gaseous pressure nitrogen outside the

Air separation plant not to be densified and the corresponding energy and equipment expense is eliminated. Of course, an external further compression above the internal compression pressure also in the invention is possible; but even then the energy consumption is relatively low and it is sufficient for a relatively small nitrogen gas compressor. The operating pressures of the columns (at the top of each head) are in the invention

- 6 to 12 bar in the high pressure column 202 and

- 3 to 5 bar in the low pressure column 204th

In principle, it is known to operate nitrogen internal compaction in the pressure range of 15 to 100 bar. In an application of this known teaching on the However, according to the method of US Pat. No. 6,141,989, the person skilled in the art would only compress the part of the air which is absolutely necessary for the internal compression to an elevated pressure which is more than 5 bar above the high-pressure column pressure. A compression of the total air to this very high pressure would appear as avoidable waste of energy, because this high pressure for the remaining part of the feed air, not for the

Internal compaction is required, hardly seems to make any sense to use.

In the context of the invention, however, it has surprisingly been found that in this special process, which serves mainly or exclusively for the production of pressurized nitrogen by internal compression, especially during compression of the

Total air to a very high pressure overall results in a particularly energetic process.

In this case, the expenditure on equipment can be kept comparatively low, in that despite the high air pressure only a single externally driven compressor is used, namely the main air compressor. Thus, of course, one-stage turbine-driven compressors (booster) are not excluded, which require no external energy, but is driven so to speak with the energy generated in the main air compressor, which is converted into mechanical energy during the work-relaxing relaxation in the turbine.

Preferably, the "first partial flow", which is expanded to perform work, is formed by the entire remainder of the total air flow, which is not required as a "second partial flow" for internal compression. The "first partial flow" of the air can be before the

cooling work to be cooled below ambient temperature, in particular in the main heat exchanger to an intermediate temperature between the temperatures of the hot and the cold end of the main heat exchanger. It then enters the work-performing expansion in the gaseous state and is finally at least partially introduced in the gaseous state into the distillation column system, in particular into the high-pressure column. The gas portion of the first partial flow forms the rising vapor in the lower part of the high-pressure column. Alternatively to the gaseous introduction into the high pressure column, the

working first relaxed partial stream in a sump evaporator

High pressure column partially or completely liquefied and fed liquid into the high-pressure column; the rising gas in the lower part of the high-pressure column is then formed by the vapor generated in the high pressure column sump evaporator.

Further energy can be saved in the invention by a special

Design of the distillation column system, as described in claim 2. The distillation column system is therefore not operated as a classic Linde double column (that is, the high-pressure column head condenser is not cooled with bottoms of the low-pressure column), but the

High-pressure column head condenser is operated with liquid air only (that is, with a liquid having the same or similar composition as the atmospheric air). The "second part of the feed air" is directly or via a separator (phase separator), which may be arranged in a separate container or installed in the high-pressure column, in the

Evaporating space of the high-pressure column head condenser, without previously participating in the rectification in one of the columns of the distillation column system.

In particular, when this liquid air is the only cooling fluid for the

High-pressure column top condenser, the two columns can be arranged side by side without the need for process pumps to lift liquids. The system becomes more compact and the columns can be largely prefabricated and then transported to the site.

Preferably, the main air compressor has a single drive unit, which is formed in particular by a gas turbine unit, a steam turbine, a gas engine or a diesel engine. This drive unit then represents the sole source of external energy of the whole system, apart from liquid pumps, which consume much less energy than gas compressors, and the power supply for auxiliary equipment such as control and regulation equipment, lighting, etc. This achieves a very extensive simplification of the compressor drive;

Generators, transformers and electric motors for gas compression are unnecessary and therefore can not lead to energy losses. This is especially true when the main air compressor is the only one powered by external energy

Gas compressor used in the process. Moreover, it is favorable if, in the method according to the invention, the second partial flow of the high-pressure total air flow in an expansion turbine

(Liquid turbine) is relaxed in place of the relaxation in a throttle valve and thereby liquefied and then introduced into the distillation column system.

On a bottom evaporator of the low pressure column can be dispensed by steam generated in the evaporation chamber of the high-pressure column head condenser in the bottom region of the low-pressure column is introduced, said steam forms the entire ascending in the lower portion of the low pressure column gas.

In a first embodiment of the invention, a "third partial stream" of the first liquid nitrogen stream is fed as reflux to the low-pressure column, and the internal compression nitrogen stream is formed by a second partial stream of the second liquid nitrogen stream. By the use of

Liquid nitrogen from the high-pressure column overhead condenser as reflux for the low-pressure column, a correspondingly increased proportion of the liquid nitrogen from the low-pressure column top condenser of the internal compression can be supplied. (The term "third sub-stream" here means that in the process a "second sub-stream" of the first liquid nitrogen stream may or may not exist.)

In a second embodiment of the invention, the internal compression nitrogen flow is formed by a second partial stream of the first liquid nitrogen stream (from the high pressure column top condenser) and a second partial stream of the second liquid nitrogen stream (from the low pressure column top condenser), these two partial streams being separate on the

Be brought product pressure. When nitrogen is under two or more

Different product pressures are needed, it is in a modified form

Embodiment also possible to bring the two second streams to different product pressures or partial streams to the required pressures (after pumping) to relax; the various internal compression nitrogen flows under the different pressures are then separated by the

Main heat exchanger led and as pressure nitrogen products among the

won different pressures. In a third embodiment of the invention, the second partial stream of the second liquid nitrogen stream (from the low-pressure column overhead condenser) is first brought to approximately high-pressure column pressure in the liquid state, and then combined with the second partial stream of the first liquid nitrogen stream (from the high-pressure column top condenser). The mixture then forms the internal compression nitrogen stream and is brought together in a further step from the high pressure column pressure to the product pressure.

In the method according to the invention, cold is preferably produced in a single expansion machine, wherein the first partial flow of the high-pressure total air flow is at least partially introduced into the high-pressure column downstream of its work-performing expansion. The expansion machine can be formed for example by an expansion turbine. It may be coupled to a secondary compressor in which the first partial flow of the high-pressure total airflow upstream of its work-performing expansion or the second partial flow of the high-pressure total airflow or the high-pressure total airflow is recompressed to a pressure which is higher than the total air pressure.

Basically, the process of the invention utilizes two condenser evaporators, the high pressure column top condenser and the low pressure column top condenser. In special cases, however, it may be beneficial to use a third condenser-evaporator in the form of a high-pressure column bottom evaporator. There, bottom liquid of the high-pressure column is evaporated in indirect heat exchange with condensing air, which takes the form of a third part of the

High-pressure total air flow is introduced into the liquefaction space of the high-pressure column bottom evaporator. The evaporated bottoms liquid is introduced as ascending gas in the high-pressure column, where it strengthens the

Release effect. The "third part" of the high-pressure total air flow can be formed by the work-performing expanded first partial flow or by a part thereof.

In all variants of the method according to the invention energy can be saved by the second partial flow of air in a turbine-driven

After-compressor are recompressed to a second air pressure, which is higher than the total air pressure. The booster is preferably used by the Powered relaxation machine, in which the first partial flow of air is released to perform work.

It is also advantageous if the second partial flow (52) of the high-pressure total air flow (1 1, 81 1) is expanded in an expansion turbine (instead of the expansion in a throttle valve) and thereby liquefied and then introduced into the distillation column system. This relaxation turbine

(Liquid turbine) is preferably braked by a generator that generates electrical energy.

The energy efficiency can in the inventive method by a boost circuit for the high-pressure column (claim 12) or a

Reinforcement circuit for the low-pressure column (claim 13) or by a combination of these two amplification circuits can be further improved

The invention also relates to a device according to claim 14. The device according to the invention can be supplemented by device features which correspond to the features of the dependent method claims. The invention and further details of the invention are explained in more detail below with reference to exemplary embodiments shown schematically in FIGS. 2 to 12. Hereby show:

2 shows the operation of an air separation plant according to the invention with a gas turbine unit as the only drive,

FIGS. 3 to 5 show three embodiments of the distillation column system of a system according to the invention,

Figures 6 and 7 show two embodiments of a cooling and liquefaction unit of a system according to the invention and

Figures 8 and 9 show two embodiments of air pretreatment and cooling and

Liquefaction units of a system according to the invention, Figure 10 shows an embodiment of the method according to the invention in

Overview,

Figure 1 1 and 12 two further embodiments of the invention with

Amplification circuits. In Figure 2, the part of the air separation plant, which is arranged downstream of the main air compressor 9, only schematically shown as a box 10 (ASU). Inside this box hides an air pre-treatment unit, a cooling and liquefaction unit and a distillation column system. These process steps are presented in detail in the following drawings.

In the main air compressor 9, which has multiple stages with intercooling, atmospheric air (AIR) is compressed to a total air pressure higher than 20 bar and in a concrete numerical example is 37.5 bar. The high-pressure total air flow 1 1 (HP-AIR), which exits the main air compressor 9, is introduced into the air separation plant in the strict sense 10. From there will be one

internally compressed pressure nitrogen product stream 12 (ICGAN - Internally Compressed Gaseous Nitrogen) withdrawn under a product pressure which is above 60 bar, for example at about 70 bar. The nitrogen product stream 12 is in the

Application example used to support oil production (to EOR - Enhanced Oil Recovery).

All stages of the main air compressor are driven by a common shaft connected to the shaft of a gas turbine unit 1 comprising a gas turbine compressor 13, a gas turbine combustor 14, a gas turbine expander 15 and, optionally, a steam generator 16 (HRSG - Heat Recovery Steam Generation). In the gas turbine compressor 13, ambient air (amb) is compressed; in the combustion chamber 14 natural gas (NG) is burned with the compressed air. the

Combustion gas from combustion chamber 14 is deprived of heat in the steam generation; the cooled combustion gas is - possibly after cleaning - blown back into the environment (amb).

Figure 3 shows a first embodiment of a distillation column system as used in the invention. The distillation column system has a

High-pressure column 202 with high-pressure column head capacitor 204 and a

Low-pressure column 203 with low-pressure column head capacitor 205 on. Both

Head capacitors are designed as a condenser-evaporator. The operating pressures of the columns (at the top of each head) are in the example

- 6 bar in the high pressure column 202 and - 3.5 bar in the low-pressure column 203.

A "first partial flow" 201 (AIR) of the high-pressure total air flow 1 1 (see FIG. 2) after work-performing expansion in the cooling and liquefaction unit (see FIGS. 6 to 9) is gaseous under the pressure of 6 bar into the lower region of the high-pressure column 202 initiated. A "second partial flow" 206 (JT-AIR = Joule-Thomson Air) of the high-pressure total air flow is taken from the cooling and liquefaction unit at a pressure of 3.5 bar, in a throttle valve 207

High-pressure column pressure is released and introduced via line 208 in a predominantly liquid state into a cup 209, which is arranged within the high-pressure column 202 at an intermediate point. This cup 209 serves as a separator (phase separator).

The gaseous portion from line 208 rises within high pressure column 202; the liquid portion is at least partially removed again and introduced via line 210 and throttle valve 21 1 in the evaporation space of the Hochdrucksäule Kopfkondensators 204, as well as another liquid air stream 221, which is formed by the small amount of liquid generated during the work expansion relaxation. Steam generated in the vaporization space of the high pressure column top condenser 204 is withdrawn via line 212 and fed to the lower portion of the low pressure column 203 as ascending vapor. Gaseous head nitrogen 213 from the high-pressure column 202 is introduced at least to a first part 214 in the liquefaction space of the high-pressure column top condenser 204 and there at least partially, preferably completely or almost completely liquefied. In this case, a "first liquid nitrogen stream" 215 is formed. A first partial flow 216 of the first liquid nitrogen stream 215 is as reflux liquid to the

High pressure column 202 abandoned. Another part (the "third substream") 217 of the first liquid nitrogen stream 215 is cooled in a subcooling countercurrent 218 and fed to the low pressure column 203 after throttling relaxation 219 via line 220. (In the embodiment of Figure 3, there is no "second substream" of the first liquid nitrogen stream 215.)

The oxygen-enriched bottom liquid 222 of the high-pressure column 202 is subcooled in the subcooling countercurrent 218 and introduced via throttling valve 223 and line 224 into the evaporation space of the low-pressure column top condenser 205. Another cooling fluid for the low-pressure column headcapacitor 205 becomes formed by the bottom liquid 225 of the low-pressure column 203, which also in the subcooling countercurrent 218 supercooled, throttled (226) and in the

Evaporation space of the low-pressure column top condenser 205 introduced (227) is. In addition, purge liquid 228 is fed from the high-pressure column top condenser 204 into the evaporation space of the low-pressure column top condenser 205. From the evaporation chamber of the low-pressure column overhead condenser 205, a rinsing liquid is likewise withdrawn (purge) and discarded or compressed to the supercritical pressure and passed through the main heat exchanger. In the liquefaction space of the low-pressure column top condenser 205, at least a first part 231 of the gaseous top nitrogen 230 from the

Low-pressure column 203 at least partially, preferably completely or almost completely liquefied. In this case, a second liquid nitrogen stream 232 is formed. A first partial stream 233 of the second liquid nitrogen stream 232 is introduced onto the low-pressure column 203 as further reflux liquid. A second partial stream 234 is supplied to an internal compression and thereby brought in a pump 235 in the liquid state to a product pressure which is between 20 and 100 bar and in the example is about 70 bar. The supercritical nitrogen (ICLIN - Internally Compressed Liquid Nitrogen) is supplied via line 236 of the refrigeration and nitrogen

Condensing unit supplied.

Steam formed in the low pressure column overhead condenser 205 is withdrawn via line 240, warmed in the subcooling countercurrent 218, and finally fed to the cooling and liquefaction unit as residual gas (WASTE).

About the lines 237 and 238 may be part of the gaseous

Head nitrogen from the high-pressure column 202 and the low-pressure column 203 are obtained directly as a gaseous pressure product (HPGAN - High Pressure Gaseous Nitrogen / MPGAN - Medium Pressure Gaseous Nitrogen), which is naturally still warmed in the cooling and liquefaction unit to about ambient temperature. If desired, a third substream 239 of the second liquid nitrogen stream 232 may also be recovered as liquid nitrogen product (LIN - Liquid Nitrogen). Alternatively to the embodiment of Figure 3 with cup 209 within the

High pressure column 202, a separate separator (phase separator) can be used; the gaseous fraction is then introduced into the high-pressure column, the liquid at least partially into the evaporation space of the high-pressure column top condenser 204th

While only a single internal compression pump 235 is used in FIG. 3, in FIG. 4 the two are used. A first pump 335a brings the second partial stream 334 of the second liquid nitrogen stream 232 as shown in FIG

Low pressure column pressure on the product pressure; however, this electricity includes in

Contrary to Figure 3 not the entire internally compressed product, but only a part. The remainder of the internally compressed nitrogen is formed by a second substream 319 of the first liquid nitrogen stream 215, which is brought to the product pressure by the high pressure column pressure in a second pump 335b. The two

Internal compression nitrogen streams are combined at 337 and together form the supercritical nitrogen (ICLIN) in line 336.

In addition, in Figure 4, a portion 343 of the liquid air from the cup 209 in

Subcooling countercurrent 318 cooled and via line 344 of

Low pressure column 203 fed to an intermediate point.

FIG. 5 differs from FIG. 4 by a third condenser-type evaporator, the high-pressure column bottom evaporator 438. In its evaporation space, the gaseous air 401 (AIR) is completely condensed. The resulting liquid 442 is additionally introduced into the cup 209.

Figures 6 and 7 show two embodiments of a cooling and

Liquefaction unit 50, which may be combined with Figure 2 and each of the distillation column systems of Figures 3 to 6.

In FIG. 6, the total purified high pressure total air flow 81 1 (see FIGS. 8 and 9) under the total air pressure is supplied to the warm end of a main heat exchanger 51, here realized as a single plate heat exchanger block. A first partial flow 56 of the high pressure total air flow 81 1 is removed at a first intermediate temperature from the main heat exchanger and a

Expansion turbine 57 fed, which drives a Nachverdichter 53. The

working air released air 58 is introduced into a separator (phase separator) 59. The largest part of the work-performing expanded first partial flow 58 is introduced in gaseous form via line 201 into the high-pressure column of the distillation column system; the separated liquid 221 is treated as described in FIG.

A second partial flow 52 of the high-pressure total air flow 81 1 is removed again at a second, higher intermediate temperature and in the

turbine-driven booster 53 with aftercooler 54 recompressed to about 50 bar. The recompressed second partial flow 55 is again introduced into the warm end of the main heat exchanger 51, where it is fed to the cold end and pseudo-liquefied there. The supercritical second substream 206 is introduced into the distillation column system in the manner shown in Figs.

The supercritical internal compaction nitrogen 236/336 (ICLIN) flows under the

Product pressure to the cold end of the main heat exchanger 51 too. There it is pseudo-vaporized and warmed to about ambient temperature and finally recovered in gaseous form as internally compressed pressurized nitrogen product 60 (ICGAN). Also, the gaseous streams 237, 238 and 241 from the distillation column system are heated in the main heat exchanger 51 to about ambient temperature. The

warmed nitrogen streams are delivered as products 61/62 (HPGAN / MPGAN). The warmed residual gas stream is partially blown off via line 63 into the environment (amb) and partially as regeneration in the

Cleaning device 802 used for the feed air (see Figures 8 and 9).

In the distillation column systems of FIGS. 3 to 5, high-pressure column 202 and low-pressure column 203 are arranged next to one another. If there is very little floor space available, however, it is also possible with the invention to arrange the columns one above the other like a classic Linde double column. In this case, starting from the bottom, the following pieces of equipment are placed in a line one above the other:

High-pressure column 202 (in the case of FIG. 5 with high-pressure column bottom evaporator 438 installed in the high-pressure column)

High pressure column top condenser 204 - low pressure column 203

Low-pressure column top condenser 205

FIG. 7 differs from the line 765 of FIG. 6. The second partial flow 752 of the high-pressure total air flow is not precooled in the main heat exchanger, but by admixing a small part 765 of the cold first partial flow 756 before entering the turbine 57

FIG. 8 shows, in addition to the cooling and liquefaction unit 50 from FIG. 6, a first embodiment of an air pretreatment unit 799. The compressor stages 804, 806 and 807 and the coolers 805, 808 of the main air compressor 9 are not part of the air pre-treatment unit.

The compressed total air 800 is in a pre-cooler 801 at about

Cooled ambient temperature and then in a cleaning device 802 having molecular sieve adsorber purified. The cleaned and on the

Total air pressure compressed high pressure total air flow 81 1 is introduced into the cooling and liquefaction unit 50. In principle, the air pre-treatment unit 799 can be operated under the total air pressure (see FIG. 10). However, at the high air pressures used here, it is more convenient in most cases to operate the air pretreatment unit as shown in Figure 8 at a lower pressure by placing it between two stages 806 and 807 of the main air compressor. This will be the

Design of molecular sieve adsorber vessels and switching valves easier and the losses when switching the adsorber are lower.

All three stages 804, 806, 807 of the main air compressor 9 of the embodiment are driven by a single shaft, which is connected to the shaft of a

Gas turbine unit, a gas engine or another engine is connected.

Between the first two stages 804, 806 an intercooler 805 is connected, behind the third and last stage an aftercooler 808.

FIG. 9 differs from FIG. 8 in that a part 902 of the supercritical high-pressure air 901 is not conducted via line 206 to the distillation column system, but is relaxed in a throttle valve 903 to an intermediate pressure corresponding to the inlet pressure of the last stage 807 of the main air compressor 9 (plus line losses). It is completely warmed up in the main heat exchanger 51 and then fed to the entry of the last stage 807 of the main air compressor 9. As a result, the amount of high-pressure air used to vaporize internal compression nitrogen is increased. This leads to a reduction of the final pressure of the main air compressor and one can reduce the number of compressor stages (cost advantage).

FIG. 10 shows an embodiment of the method according to the invention in its entirety. Here, the pre-cooler 801 and the

Cleaning device 802 of the air pre-treatment unit 799 under the

Total air pressure operated. The main air compressor 9 has several stages with intercooling and is formed by a single machine. Its shaft is powered by an electric motor, a steam turbine, a gas turbine unit, a

Gas engine or another engine, such as a diesel engine driven.

The cooling and liquefaction unit 50 shown in Fig. 10 corresponds to that of Fig. 6, the distillation column system 1000 to that of Fig. 3. The air pretreatment unit 799 and the main air compressor 9 of Fig. 10 may be used with any of the other cooling and liquefaction units described herein and with each other of the distillation column systems shown in this application are combined. The embodiment of Figure 11 is based on Figure 10. It has a

Fluid turbine 1107 instead of the throttle valve 207 and is also equipped with a boost circuit.

In the liquid turbine 1107, a substantial portion of the pressure energy contained in the second substream 206 may be recovered and converted into electrical energy in a generator 1171 connected to the turbine. This measure contributes noticeably to the favorable energetic balance of the method according to the invention and can also be used in all embodiments described above. Conversely, the embodiments of Figures 1 1 and 12 can also be operated with a throttle valve instead of the liquid turbine. The steam withdrawn from the evaporation space of the high-pressure column top condenser 204 is supplied here only to a part 112 of the low-pressure column 203. The remainder forms a circulation stream 1 172, which in a single-stage

Compressor (booster) 1 173, which is designed as a cold compressor, is compressed from about 3.9 bar to about 6.9 bar. The compressed recycle stream 1 174 is introduced at an intermediate point in the main heat exchanger 51 and cooled there to the cold end. The cooled circulation stream 1 175 is again fed to the high-pressure column 202 at the bottom and intensifies the separation process there. Therefore, the whole thing is called a gain cycle.

The work-performing expansion of the first partial flow 56 of the high-pressure total air flow 11 is carried out in two expansion turbines 57a, 57b connected in parallel. The first turbine 57a drives the hot secondary compressor 53 for the first partial flow 752 as before, the second turbine 57b drives the cold compressor 1 173. The two turbines 57a, 57b in the exemplary embodiment have the same inlet and outlet parameters with respect to pressure and temperature (FIG. at others

Embodiments, the inlet temperatures may also be different). FIG. 12 differs from FIG. 11 in that the boost circuit 1272/1273/1274/1275 does not lead from the evaporation space of the high-pressure column top condenser into the high-pressure column but from the top of the low-pressure column 203 into the liquefaction space of the high-pressure column top condenser 204.

As a result, the conversion at the high-pressure column top condenser 204 is increased and thus the amount of rising gas 212 for the low-pressure column 203, ie the conversion in the low-pressure column.

Similar to FIG. 3 (HPGAN, MPGAN), gaseous nitrogen product can also be withdrawn directly from the top of the high-pressure column 202 and / or the low-pressure column 203 and heated in the main heat exchanger 51 in the methods of FIGS. 11 and 12.

The intensifier circuits shown in FIGS. 11 and 12 can be used with any other of the cooling and liquefaction units described herein as well as with each other of the distillation column systems shown in this application are combined.

Claims

claims

A process for producing pressurized nitrogen by cryogenic separation of air in a distillation column system comprising a high pressure column (202) and a low pressure column (203) and a high pressure column top condenser (204) and a low pressure column top condenser (205), both as

Condenser-evaporator are formed, wherein

- The low pressure column (203) the lowest operating pressure of all columns of the

Having distillation column system,

- compressed air in a main air compressor (9) to a total air pressure and thereby a high-pressure total air flow (1 1, 811) is formed,

- the main air compressor (9) the only one driven by external energy

Gas compressor used in the process

a first partial flow (56) of the high-pressure total air flow (11, 811)

work-performing expansion (57) and introduced into the distillation column system (201),

a second part-stream (52, 55) of the high-pressure total air stream (11, 811) is cooled in a main heat exchanger (51) and at least partially introduced liquid (206, 210) into the distillation column system,

- Gaseous nitrogen head (213) from the high pressure column (202) in the

High-pressure column top condenser (204) is at least partially liquefied and thereby a first liquid nitrogen stream (215) is formed,

a first substream (216) of the first liquid nitrogen stream (215) as

Return fluid is applied to the high pressure column (202),

- Gaseous nitrogen head (230) from the low pressure column (203) in the

Low-pressure column top condenser (205) is at least partially liquefied and thereby a second liquid nitrogen stream (232) is formed,

a first substream (233) of the second liquid nitrogen stream (232) as

Return fluid is applied to the low-pressure column (203),

an internal condensing nitrogen stream, which is formed by a second partial flow (319) of the first liquid nitrogen stream (215) and / or a second partial stream (234, 334) of the second liquid nitrogen flow (232), is brought to a product pressure in the liquid state ( 235, 335a, 335b) which is higher than the operating pressure of the high pressure column (202), the internal condensing nitrogen stream (236, 336) brought to the product pressure is warmed in the main heat exchanger (51) and subsequently withdrawn as gaseous pressure nitrogen product stream (60) under the product pressure,

- At least one oxygen-enriched product gas stream (63, 64) from the

Withdrawn distillation column system and is warmed in the main heat exchanger (51) and

- withdrawing all oxygen-enriched product gas streams (63, 64) in the gaseous state from the distillation column system,

characterized in that

- The outlet pressure of the first partial flow (58) of the high pressure total air flow

(1 1, 81 1) at the work-performing expansion (57) is equal to the operating pressure of the high-pressure column or higher,

- The feed air in the main air compressor (9) to a total air pressure

is compressed, the at least 5 bar above the operating pressure of

High pressure column (202) is located, and

- The interior condensing nitrogen stream (234, 236, 319, 334 336) in liquid

Condition is brought to a product pressure (235, 335a, 335b), which is between 15 and 100 bar.

A method according to claim 1, characterized in that at least a part (210) of the second part (206) of the feed air as cooling fluid in the

Vaporization space of the high-pressure column top condenser (204) is initiated, in particular, the entire cooling fluid (210, 221) for the

High-pressure column head condenser (204) is formed by feed air.

Method according to claim 1 or 2, characterized in that the

Main air compressor (9) has a single drive unit, which is in particular by a gas turbine unit (1), a steam turbine, a gas engine or a diesel engine is formed.

Method according to one of claims 1 to 3, characterized in that at least part of the second partial flow (52, 55) of the high-pressure total air flow (11, 81 1) after its cooling in the main heat exchanger (51) in a liquid turbine is working expanded.

5. The method according to any one of claims 1 to 4, characterized in that in the evaporation space of the high-pressure column top condenser (204) generated steam (212) is introduced into the bottom region of the low-pressure column (203), said steam in particular the entire lower section of the

Low pressure column ascending gas forms.

6. The method according to any one of claims 1 to 5, characterized in that a third partial stream (217) of the first liquid nitrogen stream (215) is fed as reflux to the low-pressure column and the internal compression nitrogen stream is formed by a second partial stream of the second liquid nitrogen stream.

7. The method according to any one of claims 1 to 6, characterized in that the Innenverdichtungsstickstoffstrom (236, 336) by a second partial stream (319) of the first liquid nitrogen stream (215) and a second substream (334) of the second liquid nitrogen stream (232) is formed, these two

Partial streams are brought separately from each other to the product pressure (335a, 335b).

8. The method according to any one of claims 1 to 7, characterized in that the first partial flow (58) of the high pressure total air flow (1 1, 81 1) downstream of its work-performing expansion (57) at least partially in the

High pressure column (202) introduced (201) is.

9. The method according to any one of claims 1 to 8, characterized in that the bottom liquid of the high-pressure column (202) is evaporated in a high-pressure column bottom evaporator (438), which is designed as a condenser-evaporator, wherein in the liquefaction space of the high-pressure column bottom evaporator ( 438) a third part of the high-pressure total air flow (1 1, 81 1) is introduced, which is in particular at least partially formed by at least part of the work-performing relaxed first partial flow (401).

10. The method according to any one of claims 1 to 9, characterized in that the second partial flow (52) of the high-pressure total air flow (1, 81 1) in a turbine-driven secondary compressor (53) to a second air pressure

is recompressed, which is higher than the total air pressure. Method according to one of claims 1 to 10, characterized in that at least a part of the second partial flow (52) of the high pressure total air flow (11, 81 1) is expanded in an expansion turbine and thereby liquefied and then introduced into the distillation column system

Method according to one of claims 1 to 1 1, characterized in that

a circulating stream (1172) from the evaporation space of the high-pressure column

Withdrawn top condenser 204, in a cycle compressor (1 173), which is designed in particular as a cold compressor, is compressed,

- The compressed recycle stream (1 174) in the main heat exchanger (51) is cooled and

- The high-pressure column (202) is supplied. 13. The method according to any one of claims 1 to 12, characterized in that

- A circulation stream (1272) withdrawn from the upper region of the low-pressure column 203, in a cycle compressor (1273), in particular as

Cold compressor is formed, is compressed,

- The compressed recycle stream (1274) in the main heat exchanger (51) is cooled and

- Is fed to the high-pressure column top condenser (204).

14. Apparatus for generating pressurized nitrogen by cryogenic separation of air with

a distillation column system comprising a high pressure column and a

Low-pressure column, and a high-pressure column top condenser (204) and a low-pressure column top condenser (205), both of which are designed as a condenser-evaporator, wherein

the low-pressure column (203) has the lowest operating pressure of all the distillation columns of the distillation column system during operation of the plant,

and with

- A main air compressor (9) for generating a high-pressure total air flow

(1 1, 81 1) by compressing feed air to a total air pressure, wherein - the main air compressor (9) represents the only external energy driven gas compressor of the device, - means for work-performing expansion (57) a first partial flow (56) of

High pressure total air flow (1 1, 81 1),

- Means for introducing (201) of the work-performing relaxed first partial flow

(58) into the distillation column system,

a main heat exchanger (51) for cooling a second partial flow (52, 55) of the high-pressure total air flow (11, 81 1),

Means for introducing (206, 210) the cooled second substream at least partially in the liquid state into the distillation column system,

- Means for introducing gaseous nitrogen head (213) from the high-pressure column (202) in the liquefaction space of the high-pressure column top condenser

(204)

- means for removing a first liquid nitrogen stream (215) from the

Liquefaction space of the high pressure column top condenser (204),

- Means for introducing a first partial flow (216) of the first liquid

Nitrogen stream (215) as reflux liquid in the high-pressure column (202),

Means for introducing head nitrogen (230) from the low-pressure column (203) into the liquefaction space of the low-pressure column top condenser (205),

- means for removing a second liquid nitrogen stream (232) from the

Liquefaction space of the low-pressure column top condenser (205),

- Means for introducing a first partial flow (233) of the second liquid

Nitrogen stream (232) as reflux liquid in the low-pressure column (203),

- means for forming an internal compaction nitrogen flow through a second

Partial flow (319) of the first liquid nitrogen stream (215) and / or a second partial stream (234, 334) of the second liquid nitrogen stream (232), - means (235, 335a, 335b) for increasing the pressure of the

Internal condensing nitrogen flow in the liquid state to a product pressure higher than the operating pressure of the high pressure column (202),

- Means for heating the brought to the product pressure

Internal condensing nitrogen stream (236, 336) in the main heat exchanger (51) - means for withdrawing the heated internal condensing nitrogen stream as gaseous pressurized nitrogen product stream (60) under the product pressure;

- Means for withdrawing at least one oxygen-enriched

Product gas stream (63, 64) from the distillation column system,

- means for heating the oxygen-enriched product gas stream (63, 64) in the main heat exchanger (51) and with - means for withdrawing all oxygen-enriched product gas streams (63, 64) in the gaseous state from the distillation column system,

characterized in that

- the outlet of the means for work-relaxing (57) in

Flow connection (58, 201, 442) to the high-pressure column (202),

- The main air compressor (9) on the compression of the feed air to a

Total air pressure is designed, which is at least 5 bar above the operating pressure of the high-pressure column (202), and

the means (235, 335a, 335b) for increasing the pressure of the

Internal condensing nitrogen stream (234, 236, 319, 334 336) in the liquid state are designed to increase the pressure to a product pressure which is between 20 and 100 bar.

15. The device according to claim 14, characterized in that the device has no means for withdrawing a liquid oxygen-enriched product stream from the distillation column system and in particular no pump to bring a liquid oxygen-enriched stream to an elevated pressure.