DE102016003383A1 - Method and apparatus for the cryogenic separation of air - Google Patents

Abstract

The method and apparatus are used for cryogenic separation of air. A distillation column system is used with a high-pressure column (2), with a main condenser (3) and a first upper column (4) arranged above the main condenser (3). Above the first upper column (4) sits an argon condenser (5), in addition to the combination of the main condenser (3) and the first upper column, a first secondary column (7, 207). A first stream of liquid nitrogen (26) from the high-pressure column (2) is fed to the top of the first secondary column (7, 207). In the distillation column system, a second upper column (6) is disposed above the argon condenser (5). Liquid raw oxygen (15) from the bottom of the high-pressure column (2) is introduced into the lower region of the second upper column (7, 207). An argon-enriched gas stream (32) is withdrawn from the liquefaction space of the argon condenser (5) and the bottom of the first subsidiary column (7, 207) is in bidirectional flow communication (37, 38, 237, 238) with the lower region of the first upper column ( 4) or with the lower portion of the second upper column (6).

Description

The invention relates to a method according to the preamble of patent claim 1.

The basics of cryogenic decomposition of air in general and the construction of two-pillar plants in particular are in the monograph "Cryogenic technology" by Hausen / Linde (2nd edition, 1985) and in an essay by Latimer in Chemical Engineering Progress (Vol. 63, No. 2, 1967, page 35) described. The heat exchange relationship between the high-pressure column and the low-pressure column of a double column is usually realized by a main condenser in which head gas of the high-pressure column is liquefied against vaporizing bottom liquid of the low-pressure column.

An "argon discharge column" here refers to a separation column for argon-oxygen separation, which is not used for obtaining a pure argon product but for discharging argon of the air to be separated into the high-pressure column and low-pressure column. Its circuit differs only slightly from that of a classical crude argon column, but it contains significantly less theoretical plates, namely less than 40, especially between 15 and 30. Like a crude argon column, the bottom portion of an argon discharge column is connected to an intermediate point of the low pressure column and the argon discharge column becomes cooled by a top condenser, on the evaporation side of which relaxed bottom liquid from the high-pressure column or another cooling liquid is introduced; an argon discharge column has no bottom evaporator.

The term "argon column" here includes argon effluent columns and conventional crude argon columns, as well as intervening forms of argon-oxygen columns.

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 space and an evaporation space, which consist of liquefaction passages or evaporation passages. In the liquefaction space, the condensation (liquefaction) of the first fluid flow is performed, in the evaporation space the evaporation of the second fluid flow. Evaporation and liquefaction space are formed by groups of passages that are in heat exchange relationship with each other.

The main condenser and the argon discharge head condenser are designed in the invention as a condenser-evaporator. In this case, the main capacitor as a single or multi-storey bath evaporator, in particular as a cascade evaporator (for example, as in EP 1287302 B1 = US Pat. No. 6,748,763 B2 described), or be designed as a falling film evaporator. It can be formed by a single heat exchanger block or by a plurality of heat exchanger blocks, which are arranged in a common pressure vessel.

A "main heat exchanger" serves to cool feed air in indirect heat exchange with recycle streams from the distillation column system. It may be formed from a single or multiple parallel and / or serially connected heat exchanger sections, for example one or more plate heat exchanger blocks. Separate heat exchangers which specifically serve to vaporize or pseudo-evaporate a single liquid or supercritical fluid without heating and / or vaporization of another fluid, do not belong to the main heat exchanger.

The relative spatial terms "top", "bottom", "above", "below", "above", "below", "next to", "vertically", "horizontally", etc. refer here to the spatial orientation of the separation columns and apparatus in normal operation. An arrangement of two columns or parts of equipment "one above the other" is understood here that the upper end of the lower of the two parts of the apparatus is in working condition at lower or same geodetic height as the lower end of the upper of the two parts of the apparatus and the projections of the two parts of the apparatus overlap in a horizontal plane. In particular, the two parts of the apparatus are arranged exactly one above the other, that is, the axes of the two columns extend on the same vertical line. "Side by side" two apparatuses stand if their projections do not overlap in a horizontal plane; The two apparatuses are then regularly arranged at least partially at the same height.

Out EP 828122 A1 It is known to arrange a high pressure column with main condenser and an argon column with argon condenser on top of each other.

The invention has for its object to adapt such a method to the design of the argon column as Argon-Ausschleussäule and thereby achieve a particularly high capacity of the system and not increase the area requirement of the system or even to reduce.

This object is solved by the features of claim 1.

In particular, in the invention, a second upper column is placed over the argon condenser. The high-pressure column, the first upper column and the second upper column thus form a triple column. Between the columns are the main condenser and the argon condenser.

At least a portion of the crude liquid oxygen from the bottom of the high pressure column is introduced into the lower portion of the second top column. Thus, the second upper column forms the function of the upper part of a low-pressure column for oxygen-nitrogen separation. The "lower region" of the second upper column, into which the crude oxygen is fed, is understood in this application to be the lowest mass transfer region of the second upper column, which extends at most over one third of the height of the second upper column. Preferably, the raw oxygen is fed partly directly into the region below the lowermost mass transfer elements and partly a few trays (for example four to ten theoretical trays) above the second upper column. Somewhat less favorable, but easier, is to feed directly below the bottom mass transfer elements.

From the liquefaction space of the argon condenser an argon-enriched gas stream is withdrawn, which is withdrawn as residual gas, product or intermediate product stream. The sump of the first secondary column is in bidirectional flow communication with the lower portion of the first upper column or with the lower portion of the second upper column. Thus, the first secondary column fulfills the function of the entire length or the upper part of a low-pressure column for oxygen-nitrogen separation.

Overall, a column arrangement results in particularly high capacity with a comparatively low footprint. From the perspective of the transport of the columns to reach a maximum capacity at a limited by a maximum transport height column diameter.

It is also advantageous if a second stream of liquid nitrogen from the high-pressure column is fed to the top of the second upper column. Second upper column and first secondary column thus share the function of the upper part of the low-pressure column in order to optimize the capacity.

In a variant of the invention, the first upper column is designed as an argon column, in particular as an argon discharge column, in that its head is in flow connection with the liquefaction space of the argon condenser. The argon condenser here forms the top condenser of the first upper column.

The sump of the second upper column is preferably in fluid communication with the evaporation space of the argon condenser. The argon condenser thus forms the bottom evaporator of the second upper column.

In another variant, the first secondary column is in its bottom region in bidirectional flow communication with the lower region of the first upper column and it is fed in an intermediate region, a liquid stream from the bottom of the second upper column or from the evaporation space of the argon condenser. Here, the first secondary column also contains the argon section.

Preferably, an intermediate location of the first subsidiary column is also in fluid communication with an intermediate location of the first upper column. Here, argon from the first secondary column is channeled into the upper area of the first upper column.

In one embodiment of the invention, the first secondary column is in its sump region in bidirectional flow communication with the lower region of the second upper column. Here, therefore, these two columns are completely connected in parallel and form the upper part of a low-pressure column.

In this case, a second secondary column may be arranged below the first secondary column, the bottom region of which is in bidirectional flow communication with the lower region of the first upper column. This additional column is then operated approximately parallel with the first upper column. Both columns realize the oxygen part of a low-pressure column for nitrogen-oxygen separation.

The head or an intermediate point of the second secondary column can be in fluid communication with an intermediate point of the first upper column, so that capacity can be shifted back and forth from one column to the other (capacity equalization).

In a further variant of the invention, the head of the second secondary column is in flow connection with the liquefaction space of the argon condenser. Here, therefore, the second secondary column is operated as argon column or argon discharge column.

The first upper column may include a partition wall portion at the top by having an upper mass transfer portion disposed immediately below the argon condenser. In this case, the upper mass transfer section is subdivided in a gas-tight manner into a first mass transfer space and into a second mass transfer space by a vertical, for example, flat partition wall. The first The mass transfer space is at the top in fluid communication with the second upper column and open at the bottom; it forms the argon section of a low-pressure column. The second mass transfer space is sealed gas-tight at the top to the second upper column, is in flow communication with the liquefaction space of the argon condenser and is open at the bottom; it forms the argon column or argon discharge column.

[to claim 13]
The invention also relates to a device for cryogenic separation of air according to claim 13. The device according to the invention may be supplemented by device features which correspond to the characteristics of individual, several or all dependent method claims.

The invention and further details of the invention are explained in more detail below with reference to the drawings schematically illustrated embodiments. Hereby show:

1 A first embodiment of the invention with a long first subsidiary column,

2 a second embodiment with a partition wall section in the first upper column, a short secondary column and a cascade evaporator as argon condenser,

3 and 4 two examples with two side columns,

5 a configuration in which the argon column is realized in the second secondary column and

6 a variant of 1 ,

In the drawings, air compressor, pre-cooling of the air, air cleaning and cooling in the main heat exchanger are not shown.

1 shows how cleaned and cooled feed air 1 from the cold end of the main heat exchanger, not shown, in the gaseous state to the high pressure column 2 is initiated. The high pressure column 2 is part of the distillation column system, along with the main condenser 3 , the first upper pillar 4 , the argon capacitor 5 , the second upper pillar 6 and the (first and only) side column 7 , The two capacitors 2 . 5 are each designed as a condenser-evaporator.

Another feed air stream 8th is in the liquid state of the high pressure column 2 forwarded to an intermediary. At least a part of it will be lead 9 taken immediately again, in a supercooling countercurrent 10 cooled and over the lines 11 and 12 the second upper column 6 or the secondary column 7 fed at a suitable intermediate point.

Liquid crude oxygen 13 from the bottom of the high-pressure column 2 is also in the subcooling countercurrent 10 cooled. The cooled raw oxygen 14 is over the wires 15 and 16 similar to the liquid air on the second upper column 6 and the side column 7 distributed.

Gaseous head nitrogen 17 the high pressure column 2 becomes a first part 18 led to the main heat exchanger (not shown), there warmed and withdrawn as a gaseous pressure nitrogen product. The rest 19 goes into the liquefaction room of the main condenser 3 , A first part 21 of the liquid nitrogen formed there 21 , In this way, the head of the high pressure column 2 over the wires 17 . 19 . 20 . 21 in fluid communication with the liquefaction space of the main condenser 3 , The remaining liquid nitrogen 22 from the main capacitor 3 is overcooled ( 10 ) and via wire 23 withdrawn as liquid nitrogen product (LIN).

At an intermediate point, the high-pressure column 2 becomes liquid impure nitrogen 24 removed and after hypothermia 10 over the wires 25 and 26 the second upper column 6 or the secondary column 7 abandoned at the head.

The main capacitor 3 is designed as a three- to six-storey cascade evaporator and sits directly in the bottom of the first upper column 4 , Its evaporation space is thus with the sump area of the first upper column 4 in fluid communication. The swamp of the first upper column 4 , which in this construction is equal to the evaporation space of the main capacitor 3 is, becomes liquid oxygen 27 taken and over line 28 fed to an internal compression. In this context, it is brought to a higher pressure in a pump, heated in the main heat exchanger and finally recovered as a gaseous pressure oxygen product. Part 62/63 of the liquid oxygen 27 may be overcooled ( 10 ) and as a liquid product (LOX). Alternatively, the oxygen product 27 also evaporated in a secondary condenser or removed directly from the first upper column in gaseous form.

The head of the first upper pillar 4 communicates with the liquefaction space of the argon condenser via the gas line 29 and the fluid line 30 / 31 in fluid communication. The entire liquid produced in the argon condenser 31 is as reflux in the first upper column 4 used. Via wire 32 is uncondensed argon-rich gas with an argon concentration of ... mol% from the liquefaction space of the argon condenser 5 deducted. It is heated either in a separate passage group or together with another residual gas in the main heat exchanger (not shown). If the energy is not to be recovered, it is also possible to directly blow off the cold gas into the atmosphere.

The argon capacitor 5 is formed in this embodiment as a classic single-storey bath evaporator and in the bottom of the second upper column 6 arranged so that it is in fluid communication with this. Liquid sump fraction 35 the second upper column 6 becomes the Nebensäule 7 supplied at an intermediate point. At the head of the second upper column 6 becomes a nitrogen-rich gas 33 deducted and via wire 34 , through the subcooling countercurrent 10 and direction 36 led to the main heat exchanger, not shown.

The secondary pillar 7 stands at its swamp with the swamp of the first upper pillar 4 (or the evaporation space of the main capacitor 5 ) in flow communication. Via wire 37 a part of the flows in the main capacitor 3 formed gas in the secondary column 7 ; Liquid flowing down in the secondary column is sent via line 38 in the first upper column 4 guided. Via wire 39 may be an intermediate liquid or a gas from the minor column 7 in the first upper column 4 be directed. At the top of the side column 7 becomes a nitrogen-rich gas 40 deducted and via wire 34 , through the subcooling countercurrent 10 and direction 36 led to the main heat exchanger, not shown.

The 1 shows a "long" first auxiliary column 7 , in which the entire function of a low-pressure column for nitrogen-oxygen separation is realized, namely the composition of the oxygen product in the sump to a predominantly nitrogen overhead product. The capacity is distributed between the first upper column, the second upper column and the secondary column. The lower section of the low-pressure column function (oxygen section) is realized in the lower two sections of the first upper column, instead of, and additionally in the lower section of the secondary column 7 , The upper section of the low pressure column function (nitrogen section) passes through both the uppermost sections of the second upper column 6 as well as through the three uppermost sections of the minor column 7 realized. In a numerical example are in the second upper column in total 23 theoretical plates arranged in the argon section 11 theoretical plates, in the oxygen section 30 to 35 theoretical plates and in the argon discharge column 25 theoretical floors. In another embodiment, the upper portion of the low pressure column function (nitrogen portion) may pass through the three uppermost portions of the second upper column 6 will be realized.

In 2 By contrast, a "short" first secondary pillar 207 shown that only the upper low-pressure column part twice. Her marsh is above the gas line 237 and the fluid line 238 with the sump area of the second upper column 6 in fluid communication. Immediately below this compound, the second upper column contains a liquid collector 250 , This is related to the special design of the argon capacitor 5 as a two-story cascade evaporator (pocket evaporator). In principle, any type of evaporator can be used here, a cascade evaporator, a reflux evaporator or a forced flow evaporator. The collected liquid is here in the upper bag pair 251 of the argon capacitor 5 initiated and flows from there into its evaporation chamber. The remaining liquid portion runs out of the lower bag pair 252 over and is placed on a liquid distributor, not shown.

The first upper column points in 2 an upper mass transfer section 253 which is disposed immediately below the argon capacitor and formed as a partition wall section. He is through a vertical partition 254 gas-tight in a first mass transfer room 255 and into a second mass transfer room 256 divided. Both mass transfer rooms 255 . 256 are open at the bottom. The first mass transfer room 255 forms the argon section of the low-pressure column. Gas rising from it continues to flow upwards into the second upper column 6 , Its return fluid receives the first mass transfer section 255 from the evaporation space of the argon condenser. The second mass transfer room 256 On the other hand, it is sealed gas-tight at the top towards the second upper column and is in fluid communication with the liquefaction space of the argon condenser. The whole in the argon capacitor 5 generated liquid is the second mass transfer section 256 supplied as reflux liquid; it fulfills the function of an argon column.

In all embodiments, a portion of the crude oxygen may be a few floors above the argon condenser in both columns 6 and 207 be fed.

In the embodiment of 2 can deviate from the graphic representation, another arrangement of the column can be realized. Then the combination of main capacitor 3 , first upper column 4 , Argon capacitor 5 and second upper column 6 on the floor and the high pressure column 2 is located next to it. This alternative spatial arrangement is basically possible in all embodiments of the invention.

3 differs from 2 by an additional second secondary column 307 under the short first side pillar 207 is arranged. She stands at her swamp on the pair of wires 337 / 338 in fluid communication with the sump of the first upper column; on her head is on the lines 339a / 339b another flow connection to the first upper column 4 namely at an intermediate point immediately below the upper mass transfer section 253 , Thus, the mass transfer elements in the second secondary column 307 the lower part of the first upper column 4 connected in parallel and together with this form the oxygen section of the low-pressure column for oxygen-nitrogen separation.

The embodiment of 4 differs from that of the 3 that only part 15 of supercooled crude oxygen 14 is introduced into the second upper column; the rest 16 flows the first secondary column 7 at an intermediate point too. In addition, here is the argon capacitor 5 as in 1 designed as a single-storey bath condenser. The capacitor can be made arbitrary as previously noted.

In 5 the argon column will not be in the first upper column 4 but in the upper part of the second secondary column 507 , The head of the second side pillar 507 stands over the wires 329 and 331 with the liquefaction space of the argon condenser 5 in fluid communication. The lower part of the second secondary column 507 corresponds to the second secondary column 307 of the 3 and 4 , The first and the second upper column 4 . 6 form a conventional low-pressure column for nitrogen-oxygen separation with the argon condenser 5 as intermediate heating. In the argon capacitor 5 not evaporated liquid 557 flows into the first upper column 4 , Head steam 358 the first upper column 4 is introduced into the second upper column.

6 corresponds largely 1 however, there are three additional gas pipes 659 . 660 . 661 between the first subsidiary pillar 307 and the first and second upper columns, respectively 4 . 6 , As a result, even more flexible capacity between the left and the right column can be moved back and forth and thus maximizes the capacity of the entire system. The main difference of 6 and 1 to the other one is that the complete liquid from the upper part of the Nebensäule (line 15 in 4 , Management 660 from 6 ) is passed to the argon capacitor. This can be the maximum. Reach liquid excess (purge) in the evaporation chamber of the argon condenser and run this as a cascade evaporator or forced-flow evaporator. The embodiments of the 1 to 5 are better suited for the use of a bath condenser as argon condenser.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• EP 1287302 B1 [0006]
• US 6748763 B2 [0006]
• EP 828122 A1 [0009]

Cited non-patent literature

• "Cryogenic technology" by Hausen / Linde (2nd edition, 1985) [0002]
• Latimer in Chemical Engineering Progress (Vol. 63, No. 2, 1967, page 35) [0002]

Claims (13)

Process for the cryogenic separation of air in a distillation column system, comprising - a high-pressure column ( 2 ), - a main capacitor ( 3 ), which is designed as a condenser-evaporator and whose liquefaction space with the head of the high-pressure column ( 2 ) is in fluid communication, - above the main capacitor ( 3 ) a first upper column ( 4 ) whose bottom is connected to the evaporation space of the main condenser ( 5 ) is in fluid communication, - above the first upper column ( 4 ) an argon capacitor ( 5 ), which is designed as a condenser-evaporator, - a first secondary column ( 7 . 207 ), in addition to the combination of the main capacitor ( 3 ) and the first upper column, wherein - purified and cooled feed air ( 1 ) in the gaseous state in the high-pressure column ( 2 ), - a first stream ( 15 . 16 ) of crude liquid oxygen ( 14 ) from the bottom of the high-pressure column ( 2 ) is introduced into a column of the distillation column system which is under lower pressure than the high-pressure column ( 2 ), - a first stream of liquid nitrogen ( 26 ) from the high pressure column ( 2 ) on the head of the first subsidiary column ( 7 . 207 ), - from one of the columns of the distillation column system, an oxygen product ( 17 ) is subtracted and - from the head of the first secondary column ( 7 . 207 ) a gaseous nitrogen-rich product ( 40 . 34 . 36 ), characterized in that - in the distillation column system above the argon condenser ( 5 ) a second upper column ( 6 ), - the first stream ( 15 ) crude liquid oxygen from the bottom of the high-pressure column ( 2 ) in the lower area of the second upper column ( 7 . 207 ), - an argon-enriched gas stream from the liquefaction space of the argon condenser ( 5 ) and - the bottom of the first secondary column ( 7 . 207 ) in bidirectional flow connection ( 37 . 38 ; 237 . 238 ) with the lower portion of the first upper column ( 4 ) or with the lower portion of the second upper column ( 6 ) stands. Process according to claim 1, characterized in that a second stream of liquid nitrogen ( 25 ) from the high pressure column ( 2 ) on the head of the second upper column ( 6 ) is abandoned. Method according to claim 1 or 2, characterized in that the first upper column ( 4 ) is formed as an argon column by its head in fluid communication ( 29 . 30 . 31 ) with the liquefaction space of the argon condenser ( 5 ) stands. Method according to one of claims 1 to 3, characterized in that the bottom of the second upper column ( 6 ) with the evaporation space of the argon condenser ( 5 ) is in flow communication. Method according to one of claims 1 to 4, characterized in that the first secondary column ( 7 ) In its bottom region in bidirectional flow connection ( 37 . 38 ) with the lower portion of the first upper column ( 4 ) and you - in a intermediate area a liquid stream ( 35 ) from the bottom of the second upper column ( 6 ) or from the evaporation space of the argon condenser ( 5 ). Method according to one of claims 1 to 5, characterized in that an intermediate point of the first secondary column is in flow communication with an intermediate point of the first upper column. Method according to one of claims 1 to 6, characterized in that the first secondary column ( 207 ) in its bottom region in bidirectional flow connection ( 237 . 238 ) with the lower portion of the second upper column ( 6 ) stands. Method according to one of claim 7, characterized in that below the first secondary column ( 207 ) a second side column ( 307 ) whose bottom region is in bidirectional flow connection ( 337 . 338 ) with the lower portion of the first upper column ( 4 ) stands. A method according to claim 8, characterized in that the head or an intermediate point of the second secondary column ( 6 ) in fluid communication ( 339a . 339b ) with an intermediate point of the first upper column ( 4 ) stands. Method according to one of claims 8 or 9, characterized in that the head of the second secondary column ( 307 ) in fluid communication ( 329 . 331 ) with the liquefaction space of the argon condenser ( 5 ) stands. Method according to one of claims 1 to 10, characterized in that - the first upper column ( 4 ) an upper mass transfer section ( 253 ), which immediately below the argon capacitor ( 5 ), wherein - the upper mass transfer section ( 253 ) by a vertical partition ( 254 ) gas-tight in one first mass transfer room ( 255 ) and into a second mass transfer room ( 256 ), - the first mass transfer space ( 255 ) at the top in fluid communication with the second upper column ( 6 ) and is open at the bottom and - the second mass transfer space ( 256 ) at the top to the second upper column ( 6 ) is closed gas-tight and in flow connection ( 29 . 30 . 31 ) with the liquefaction space of the argon condenser ( 5 ) and is open at the bottom. Method according to one of claims 1 to 11, characterized in that the main capacitor ( 3 ) above the high pressure column ( 2 ) is arranged. Apparatus for cryogenic separation of air with a distillation column system, comprising - a high-pressure column ( 2 ), - a main capacitor ( 3 ), which is designed as a condenser-evaporator and whose liquefaction space with the head of the high-pressure column ( 2 ) is in fluid communication, - above the main capacitor ( 3 ) a first upper column ( 4 ) whose bottom is connected to the evaporation space of the main condenser ( 5 ) is in fluid communication, - above the first upper column ( 4 ) an argon capacitor ( 5 ), which is designed as a condenser-evaporator, - a first secondary column ( 7 . 207 ), in addition to the combination of the combination of the main capacitor ( 3 ) and the first upper column, wherein the device - means for introducing purified and cooled feed air ( 1 ) in the gaseous state in the high-pressure column ( 2 ), - means for introducing a first stream ( 15 . 16 ) of crude liquid oxygen ( 14 ) from the bottom of the high-pressure column ( 2 ) in a column of the distillation column system, which under lower pressure than the high-pressure column ( 2 ), means for applying a first stream of liquid nitrogen ( 26 ) from the high pressure column ( 2 ) on the head of the first subsidiary column ( 7 . 207 ), - means for removing an oxygen product ( 17 ) is withdrawn from one of the columns of the distillation column system, and - means for removing a gaseous nitrogen-rich product ( 40 . 34 . 36 ) from the head of the first subsidiary column ( 7 . 207 ), characterized by - a second upper column ( 6 ) in the distillation column system above the argon condenser ( 5 ), - means for introducing the first stream ( 15 ) crude liquid oxygen from the bottom of the high-pressure column ( 2 ) in the lower area of the second upper column ( 7 . 207 ), - means for withdrawing an argon-enriched gas stream ( 32 ) from the liquefaction space of the argon condenser ( 5 ) and - means for establishing a bidirectional flow connection ( 37 . 38 ; 237 . 238 ) between the bottom of the first secondary column ( 7 . 207 ) and the lower portion of the first upper column ( 4 ) or the lower portion of the second upper column ( 6 ).

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