EA024400B1 - Method for producing gaseous compressed oxygen product by low-temperature air separation - Google Patents

Abstract

The invention discloses a method for producing a gaseous compressed oxygen product by low-temperature separation of air in a distillation column system. The use of the invented method is especially beneficial in economical respect due to higher productivity, higher purity of the product, lower operation costs and/or capital expenditures. The method according to the invention comprises the use of a distillation column system (50, 51) comprising a high-pressure column (50) and a low-pressure column (51), a main air compressor, a main heat-exchange system (3), a booster compressor (5), a first turbine (11), and a second turbine (22). The method according to the invention is characterised by that the first turbine (11) drives the booster compressor (5), and the second turbine (22) drives a generator (23), or the second turbine (22) drives the booster compressor (5), and the first turbine (11) drives the generator (23).

Description

The present invention relates to a method according to the restrictive part in claim 1 of the claims.

Methods and devices for low-temperature air separation are known, for example, from the book Low-Temperature Technology, 2nd edition, 1985, chapter 4, p. 281-337.

The distillation column system of the present invention may be a two-column system (for example, as a classic two-column system), or, alternatively, it may be a three-column or multi-column system. In addition to columns for the separation of nitrogen and oxygen, it may include additional devices for the manufacture of high-purity products and / or other air components, in particular, noble gases, for example, for the production of argon and / or for the production of krypton and xenon.

In this process, the liquid stream of compressed oxygen product is evaporated by the coolant, and as a result, it is obtained as gaseous compressed product. This method is also called the term internal compression and serves to produce compressed oxygen. In the case of supercritical pressure, the phase transition actually does not occur and the product flow is then pseudo-evaporating.

The high pressure coolant is liquefied (or pseudo-liquefied if it is at supercritical pressure) (pseudo) by evaporated product flow. Some amount of air is often used as a heat carrier, in this case it is the third air flow and the fourth air flow, both of which branch off from the original supplied compressed air.

Methods of internal compression are known, for example, from the following patent documents:

BU 830805, BU 901542 (= ϋ3

2712738/05 2784572), BU 952908, BU 1103363 (= UZ 3033544), BU 1112997 (= of 3214925), BU 1124529, BU 1117616 (= OZ 3280574),

BU 1226616 (= of 3216206), BU 1229561 (= iZ 3222878), BU 1199293, BU 1187248 (= 03 3371496), BU 1235347, BU 1258882 (=

3426543), BU 1263037 (= 05 3401531), BU 1501722 (= 03 3416323), BU 1501723 (= 03 3500651), BU 253132 {= 05 4279631),

BU 2646690, EP 93448 B1 (= of 4555256) EP 384483 IN 1 (= of 5036672) EP 505812 B1 (= of 5263328) EP 716230 IN 1 BUT of 5644934) EP 842385 B1 (= of 5953937), EP 758733 IN 1 (= of 5845517), EP 895045 B1 (= of 6039885), BU 19803437 A1, EP 949471 B1 (= □ 3 6185960 B1) EP 955509 A1 (= OZ 6196022 IN 1) , EP

1031804 A1 (= OZ 6314755), BU 19909744 A1, EP 1067345 A1 (= of 6336345), EP 1074805 A1 (= 03 6332337), BU 19954593 A1, EP

1134525 A1 (= 05 6477860), BU 10013073 A1, EP 1139046 A1, EP 1146301 A1, EP 1150082 A1, EP 1213552 A1, BU 10115258 A1, EP 1284404 A1 (= 03 2003051504 A1), EP 1308680 A1 (= OS 6621) ), BU 10213212 A1, BU 10213211 A1, EP 1357342 A1 or BU 10238282 A1, BU 10302389 A1, BU 10334559 A1, BU 10334560 A1, BU 10332863 A1, EP 1544559A1, EP 1585926 A1, BU 102005029274 A1,

EP 1666824 A1, EP 1672301 A1, BE 102 005 028 012 A1, MO 2007033838 A1 IO 2007104449 A1, EP 1845324 A1, BE 102 006 032 731 A1, EP 1892490 A1, BE 102 007 014 643 A1, EP 2015012 A2, EP 2015013 A2,

EP 2026024 A1, IO 2009095188 A2 or BU 102008016355A1.

The main heat exchange system serves to cool the source air by indirect heat exchange with return flows from the distillation column system. It may consist of one or more parallel or serially connected heat exchange sections, for example, one or more plate heat exchange units.

A method of the type described above is known from US Pat. No. 5,329,776.

The present invention is to propose a method of the type described above, the use of which is particularly advantageous economically due to increased productivity, improved product purity, reduced operating costs

- 1,04400 and / or lower capital costs.

This task is achieved due to the distinctive features given in claim 1 of the claims.

In principle, in the compressing compressor also either only throttled air (third air flow), or all turbine air (in particular, the first, second and third air flows in total) can be re-compressed to a pressure exceeding the outlet pressure of the main air compressor (first pressure ). In the context of the present invention, however, it is shown that a combination of the following measures results in a particularly favorable quantitative ratio between the turbine flow (first or second air flow, depending on which turbine drives the biasing compressor) and the discharge flow (third air flow) approximately 1: 1,1:

recompressing only the first and third air streams;

no re-compression of the second and fourth air streams;

expansion of the first turbine flow (first air flow) from the second pressure;

expansion of the second turbine flow (second air flow) from the first pressure.

Favorable quantitative ratio with a combination of turbine and injection improves the manufacturability of the corresponding device and ensures a particularly high efficiency of the compressing compressor.

In the pressure values given in the claims, the natural pressure drops are not included. Here, pressure values are considered equal if the pressure difference between the respective positions does not exceed the natural pressure losses in the pipeline, which are caused by pressure drops in pipes, heat exchangers, refrigerators, adsorbers, etc. Similarly, the two streams are then also considered to have the same temperature if their temperatures differ by an amount that corresponds to the temperature difference caused by natural fluctuations or normal insulation losses along the line.

Each turbine is mechanically connected directly to a biasing compressor or to a generator for generating electricity. Here, the term direct mechanical connection means direct connection by an expansion device and a biasing compressor or generator, for example, through a common shaft, and not through a gearbox. Connected devices thus have the same rotational speed. It is considered particularly favorable when the first turbine is connected to a biasing compressor, and the second turbine is designed as a generating turbine.

The first pressure (output pressure from the main air compressor) in the present invention is, for example, from 6 to 30 bar (0.6-3 MPa), preferably from 10 to 25 bar (1-2.5 MPa); the second pressure (the outlet pressure from the compressing compressor) is, for example, from 8 to 50 bar (0.8-5 MPa), preferably from 12 to 40 bar (1.2-4 MPa).

Preferably, the second intermediate temperature (T2) is at least 2 K lower than the first intermediate temperature (T1). For example, the first intermediate temperature (the input temperature of the first turbine) is 115 to 135 K, and the second intermediate temperature (the input temperature of the second turbine) ranges from 110 to 130 K.

In addition to the compressed oxygen product stream, it is also possible to produce nitrogen as a gaseous compressed product, where the liquid nitrogen product stream is removed from the distillation column system, brought to an elevated pressure in a liquid state, evaporated or pseudo-evaporated at this increased pressure in the main heat exchange system, heated to approximately environment, and finally output as a stream of gaseous compressed nitrogen product.

In the context of the present invention, it is considered expedient that the biasing compressor is designed as a cold compressor, in other words, its inlet temperature is lower than 210 K, in particular lower than 170 K, for example lower than 160 K. However, it often turns out to be higher than the first intermediate temperature ( first turbine inlet temperature). For example, the inlet temperature of the compressing compressor ranges from 125 to 160 K.

Further, the present invention and additional features of the present invention will be explained in more detail with reference to the exemplary embodiment shown schematically in the drawing. The distillation column system according to the exemplary embodiment in the first embodiment comprises a high pressure column 50 and a low pressure column 51 as the only distillation columns, as well as a main condenser that is not shown in the drawing and through which the upper part of the high pressure column and the lower part of the low pressure column are in the heat exchange connection. The working pressures (in each case in the upper part) are 5.4 bar (0.54 MPa) in the high-pressure column and 1.3 bar (0.13 MPa) in the low-pressure column.

Atmospheric air is compressed to a first pressure p1 of 12 bar (1.2 MPa) in the main air compressor, which is not shown. The original feed air (1), compressed to the first pressure, then (after pre-cooling and cleaning, which are also not shown) is divided into four air streams, the first air stream 10, the second air stream 20, the third

- 2 024400 air stream 30 and fourth air stream 40. Preferably, these four subdivided streams (besides any possible fractions, such as, for example, air used in pneumatic devices) form all the original air, and no other parts of the air stream exist which enter the separation device.

The first air flow passes through line 2 to the warm end of the main heat exchange system 3 and is first cooled to an intermediate temperature of 136 K. It passes at this intermediate temperature through line 4 to a biasing compressor 5, which is designed as a cold compressor, and re-compressed to a second pressure p2 of 17 bar (1.7 MPa). The recompressed first sub-stream passes through line 6 at a temperature of 156 K back to the main heat exchange system 3. The first sub-stream 10 leaves it at the first intermediate temperature of 119 K and enters the work-producing expansion into the first turbine 11, which actuates the clamped compressor 5 through a common shaft. The first substream 12, which performs the expansion work, finally arrives at a pressure of 5.5 bar (0.55 MPa) in the high-pressure column 50.

The second air flow is cooled in the main heat exchange system 3 to a second intermediate temperature of 115 K. The cooled second sub-stream 21 enters the work-producing expansion into the second turbine 22, which drives the electric generator 23. The second sub-stream 24 that performs the work while expanding passes at a pressure of 5.5 bar (0.55 MPa) through line 7 into the high-pressure column 50.

The third air flow 30 passes along with the first flow through lines 2, 4 and 6 and 20B of the compressing compressor 5, but then passes through the main heat exchange system 3 to the cold end. During this process, it liquefies. After throttling 31 to the pressure of the high pressure column, the throttled third air stream 32 enters the high pressure column 50 through line 7.

The fourth air stream 40 passes through the main heat exchange system 3 from the warm end to the cold end at the first pressure p1. After throttling 41 to the pressure of the high pressure column, the throttled fourth air flow 42 enters the high pressure column 50 through line 7.

The flow 52 of the liquid oxygen product leaves the low pressure column 51 and, in the liquid state, is brought in the oxygen pump 53 to an increased pressure of 28 bar (2.8 MPa). High-pressure oxygen 54 evaporates in the main heat exchange system 3, is heated to approximately ambient temperature, and finally exits through line 55 as a stream of gaseous compressed oxygen product (OOX-1C).

The stream 56 of the liquid nitrogen product is withdrawn from the high-pressure column 50 or from the main condenser and, in the nitrogen pump 57, is brought in a liquid state to an elevated pressure of 28 bar (2.8 MPa). At this increased pressure, it evaporates in the main heat exchange system 3, is heated to approximately ambient temperature and, finally, leaves through line 59 as a stream of gaseous compressed nitrogen product (ΟΑΝ-ΙΟ).

Next, the nitrogen product stream 60 and the nitrogen stream 62 with impurities exit in a gaseous state from the low pressure column 51, are heated in the main heat exchange system 3 to approximately ambient temperature and are used as a low pressure nitrogen product () through line 61 or as regeneration gas through line 63.

In the second embodiment, the distillation column system according to the exemplary embodiment further comprises producing argon; in particular, it contains a column of crude argon and a column of pure argon (both are not shown in the drawing). Liquid pure argon 70 leaves the column of pure argon and is brought in a liquid state in an argon pump 71 to an elevated pressure of 31 bar (3.1 MPa). The high pressure argon 72 evaporates in the main heat exchange system 3, is heated to approximately ambient temperature, and finally exits through line 73 as a stream of gaseous compressed argon product (OAK-1C).

Claims (4)

1. A method of generating a gaseous compressed oxygen product by low temperature separation of air in a distillation column system (50, 51), which comprises a high pressure column (50) and a low pressure column (51) in which all of the feed air is compressed in a main air compressor to form compressed the source air (1) to the first pressure (p1), which is at least 4 bar higher than the working pressure of the high pressure column (50), at least a portion (2, 20, 40) of the compressed source air (1) is cooled in main heat system (3) in indirect heat exchange with at least one return stream (54, 58, 60, 62, 72) from the distillation column system (50, 51) and introduced into the distillation column system (50, 51), the first air stream (2) which is formed from the first part of the compressed source air (1), 2. The method according to claim 1, characterized in that the second intermediate temperature (T2) is at least 2 K lower than the first intermediate temperature (T1). 3. The method according to claim 1 or 2, characterized in that the obtained stream (56) of a liquid nitrogen product is removed from the distillation column of the system (50, 51), brought to a high pressure in a liquid state, evaporated or pseudo-evaporated at this increased pressure in the main the heat exchange system (3) is heated to approximately ambient temperature and finally discharged as a stream (59) of a gaseous compressed nitrogen product. - 3,224,400 compressed to the aforementioned first pressure (p1), introduced into the main heat exchange system (3) and cooled to form a stream (4), which is re-compressed in a booster compressor (5) to form a re-compressed first air stream (6) to a second pressure (p2), which is higher than the first pressure (p1), the re-compressed first air stream (6) is introduced at the second pressure (p2) into the main heat exchange system (3) and there it is cooled to the first intermediate temperature (T1) to form a cooled first air flow (10), cooled the first air stream (10) is directed to the first turbine (11), where it performs work during expansion, at least part (12) of the cooled first air stream (10) that works during expansion, is introduced into the distillation column system (50, 51 ), the second air stream (20), which is formed from the second part of the compressed source air (1), compressed to the first pressure (p1), is introduced into the main heat exchange system (3) and there it is cooled to a second intermediate temperature (T2) to form a cooled second air stream (21), chilled the second second air stream (21) is directed to the second turbine (22), where it performs work during expansion, at least part (24) of the cooled second air stream (21), which works during expansion, is introduced into the distillation column system (50, 51), the third air stream (2), which is formed from the third part of the original compressed air (1), compressed to the first pressure (p1), is introduced into the main heat exchange system (3) and cooled to form a stream (4), which is re-compressed in the booster compressor (5) with the formation of re-compressed about the third air stream (6) to the second pressure (p2), the re-compressed third air stream (6) is introduced at the second pressure (p2) into the main heat exchange system (3), cooled in the main heat exchange system (3) and liquefied or fluidized with the formation of a liquefied or fluidized stream (30, 32, 7), which is then introduced into the distillation column system (50, 51), the fourth air stream (40), which is formed from the fourth part of the compressed source air (1), compressed to the first pressure ( p1), is introduced at the first pressure (p1) into the main heat system (3), cooled in the main heat exchange system (3), liquefied to form a liquefied stream (42), which is then introduced into the distillation column system (50, 51), the resulting stream (52) of liquid oxygen product is removed from the distillation column system (50, 51), brought to a high pressure in a liquid state, evaporated or pseudo-evaporated at this increased pressure in the main heat exchange system (3), heated to approximately ambient temperature and, finally, gaseous compressed oxygen is removed as a stream (55) characterized in that the compression compressor (5) is driven by a first turbine (11) and the generator (23) is driven by a second turbine (22) or the compression compressor (5) is driven by a second turbine (22) and the generator (23) are driven by the first turbine (11). 4. The method according to any one of claims 1 to 3, characterized in that the booster compressor (5) is designed as a cold compressor.