ES2219230T3 - PROCEDURE AND DEVICE FOR OBTAINING A PRESSURE OXYGEN PRODUCT BY LOW TEMPERATURE AIR DECOMPOSITION. - Google Patents

Abstract

For producing a pressurized product by low-temperature producing a pressurized product by low-temperature fractionation of air in a rectification system which has a high-pressure column (13) and a low-pressure column (14), a first feed airstream (12) is introduced into the high-pressure column (13), and an oxygen-rich fraction (38) from the low-pressure column (14) is brought (39) to pressure in the liquid state and introduced (41) into a mixing column (16). A second feed airstream (6, 15) is introduced into the lower region of the mixing column (16) and brought into countercurrent contact with the oxygen-rich fraction (41). The mixing column (16) is operated at a pressure (PM1S) which is lower than the operating pressure (pHDS) of the high-pressure column (13). A total airstream (1) which comprises the first and second feed airstreams is compressed (2) to a first pressure (p1) which is lower than the operating pressure (pHDS) of the high-pressure column (13) and is purified (3) at about this first pressure (p2) . The purified total airstream (4) is divided into the first (5) and the second (6) feed airstream. The first feed airstream (5) is further compressed (8) separately from the second feed airstream to a second pressure (P2) which is at least equal to the operating pressure (PHDS) of the high-pressure column (13).

Description

Procedure and device to obtain a pressure oxygen product due to low air decomposition temperature.

The invention concerns a method and a device to obtain a pressurized oxygen product by low temperature air decomposition according to the respective preambles of claims 1 and 9. A method and a device of the aforementioned class are known from the EP document 697576 Al. In the invention the mixing column is operated at a pressure that is lower than the operating pressure of the high-pressure column of the two-column system used to the nitrogen-oxygen separation.

The rectification system of the invention can be built as a two column system, for example as a classic double column system, but also as a system of three or more columns. In addition to the columns for the separation of nitrogen-oxygen, said system may present other devices to obtain other air components, especially noble gases (for example, krypton, xenon and / or argon).

The oxygen-rich fraction, which is used as load for the mixing column, has a concentration of oxygen that is higher than that of air and that, for example, is in 70 to 99.5 mol%, preferably 90 to 98 mol%. Per column mixer means a counter current contact column in which an easily volatile gaseous fraction is sent to I find a hardly volatile liquid.

The process according to the invention is suitable especially for obtaining impure oxygen gas under pressure. As impure oxygen, a mixture with a content of oxygen of 99.5% in moles or less, especially 70 to 99.5% in moles Product pressures are, for example, from 2.2 to 4.9 bars, preferably 2.5 to 4.5 bars. Of course, in case necessary, the pressurized product can be compressed even more in a state gaseous.

In EP 697576 A the air is compressed total up to about the pressure of the high pressure column and the air in the mixing column is then expanded until the operating pressure of said mixing column, performing the expansion of a part of the column air mixer in a way that produces work. In this way, the high pressure of this partial air stream can be used certainly to get cold. However, the procedure known is not energetically favorable in all cases.

A similar process is described in the document EP 1024464 Al not yet published. Here some currents are purified of first and second load air separately from each other.

The invention is based on the problem of indicating a class procedure cited at the beginning and a device corresponding to have an energy consumption especially reduced.

This problem is solved by the fact that a total air flow, comprising at least the first and the second charging air currents, is compressed until a first pressure (P2) that is lower than the operating pressure (P_ {HDS}) of the high pressure column, and is scrubbed under approximately this first pressure (p1), the current of Total purified air is distributed in the first and second charging air streams and the first charging air stream it is additionally compressed separately from the second stream of charge air to a second pressure (p1) which is at least equal to the operating pressure (P_ {HDS}) of the column of high pressure.

Therefore, the total air flow is not compressed at the highest pressure in the system, but at a higher value low. The part or parts of the air that need a pressure relatively high - especially high column air pressure - are additionally deliberately compressed by separated. In this way, you can have enough with the application of energy as small as possible during air compression of load.

The smallest expenditure on devices is achieved when the first pressure is approximately equal to the pressure of operation of the mixing column. In this case, the air of The mixing column (second load air stream) can be introduced into said mixing column without further variation measures of pressure.

As an alternative to this, the first pressure can be lower than the operating pressure (p_ {Mis}) of the mixer column In this case, the second charging air stream, separately from the first charging air flow, up to a third pressure (p 3) that is at least equal to the operating pressure (p_ {MiS}) of the mixer column

Preferably, the oxygen rich fraction Pressurized in liquid state is heated in exchange for indirect heat with a reheated air stream before Load it in the mixer column. The reheated air stream it is formed, for example, by a part of the cargo air that is found at the pressure of the high pressure column. This is extract, at an intermediate temperature, the heat exchanger main in which charge air is cooled to about dew point, and, without further temperature variation measures, it is put in indirect heat exchange with the liquid rich in oxygen. In this way, the temperature of the liquid that is charged in the mixing column is optimally adapted to the conditions during the exchange of countercurrent materials within said mixer column

In the procedure cold is generated so favorable by expanding a third load air stream in a productive way of working and introducing it in the low column Pressure. In this way, the pressure gradient can be used "natural" between the first pressure or another pressure of the procedure to compensate for insulation losses and eventually Blend a portion of the products.

Preferably, the third air stream of load is recompressed before the labor-producing expansion, especially using the mechanical energy generated during the working production expansion for the operation of the equipment recompression A combination of turbine-booster in which the expansion turbine and the recompressor are mechanically coupled through a tree common.

The third load air stream can be compressed at the first pressure and purified together with the first and the second charging air currents. The following is led directly to the recompression team or is it recompressed even together with the first air stream of load.

As an alternative to the insufflation of the third load air current in the low pressure column, the second Charge air stream can be expanded producing work after additional compression and before feeding to the mixer column The additional compression is then performed up to a second pressure that is clearly higher than the pressure of the mixing column.

The invention also concerns a device according to claim 9.

The invention and others are explained below. details of it in more detailed way making reference to examples of execution represented in the drawings. Show in these:

Figure 1, a procedure and a device with working production expansion of a part of the compressed air at the first pressure,

Figure 2, a modified process with expansion Working producer of one part of the compressed air to the second Pressure,

Figure 3, a procedure with expansion working producer of the mixing column air and

Figure 4, another variant of Figure 1 without turbine air recompression.

In the process represented in Figure 1, it carries load air 1 in a two-stage air compressor 2 with cooling after a first pressure p1 of, by example, 2.7 to 3.7 bars, preferably about 3.2 bars, and said loading air enters this pressure in a purification equipment 3 which is preferably formed by a pair of adsorbers of molecular sieves The total purified air 4 is distributed in three partial currents 5, 6, 7.

The first charge air stream 5 is additionally compressed in a first 8 to a second compressor pressure p2 of, for example, 4.4 to 7.0 bar, preferably around 5.7 bars, and enters a heat exchanger main 10 after a subsequent cooling 9. The first charging air stream exits the heat exchanger main 10 through a pipe 11 at approximately the temperature of the dew point and is fed to a high pressure column 13 to through a pipe 12. The operating pressure P_ {HDS} of the high pressure column 13 is, for example, 4.3 to 6.9 bar, preferably around 5.6 bars. In addition, the system rectification features a low pressure column 14 that is made operate below, for example, 1.3 to 1.7 bars, preferably about 1.5 bars.

The second charging air stream 6 is also driven by the main heat exchanger 10 a approximately the first pressure p_ {less losses of power and pressure losses in the purification equipment) and passes finally to the mixing column through a pipe 15. The power point is immediately above the sump of the mixing column 16.

The third partial stream 7 is recompressed from about the first pressure p1 in a second recompressor 17 to a third pressure p3 of, for example, 3.8 to 5.6 bars, preferably about 4.7 bars, and then of a subsequent cooling 18, is conducted by the pipe 19 to hot end of the main heat exchanger. Nevertheless, it is cooled only to an intermediate temperature and before from the cold end it is removed again from the heat exchanger main 10 by a 50 pipe and expanded producing work in a turbine 20. The expanded air 21 is blown into the column of low pressure 14. The compressor 17 and the turbine 20 are coupled mechanically directly.

The rectification system is built in Execution examples as a classic double Linde device column with a condenser-evaporator 22 in quality of main condenser. However, the invention can be used. also in rectification systems with other configuration of condenser and / or column.

Liquid 23 enriched in oxygen from the high pressure column drain 13 is cooled in a first counter-current subcooling apparatus 24 and powered, after a throttle 25, to the low pressure column 14 in an intermediate point 26. Nitrogen gas 27 from the head of the high pressure column 13 can be heated in one part 28 in the main heat exchanger 10 and recovered as nitrogen product under pressure 29. The remainder 30 is condensed from substantially complete form in the main capacitor 22. The liquid nitrogen 31 obtained in this way is delivered at least in a part 32 as a return to the high pressure column 13. In case If necessary, another part 33 can be removed as a liquid product. A intermediate liquid 34 (impure nitrogen) of the high column pressure serves, after subcooling 24 and strangulation 35, as a return for the low pressure column. Impure nitrogen gas 36 coming from the head of the low pressure column is heated in heat exchangers 24 and 10 and removed finally by pipe 37. As represented, this nitrogen can be used as a regeneration gas for the debugging equipment 3.

Liquid nitrogen 38 is removed from the sump of the low pressure column, set at a pressure of, for example, 5.7 to 6.5 bars, preferably around 6.1 bars, in one pump 39, heated in a second subcooling apparatus a countercurrent 40 and finally delivered (41) to the head of the mixer column 16. In the second subcooling apparatus a countercurrent 40 especially cools an air stream reheated 42 that is derived from the first air stream of load upstream of the cold end of the heat exchanger principal, specifically at an intermediate temperature that is more lower than the turbine inlet temperature 20. After its cooling through a pipe 43, this air stream is meets again with the first load air stream 11. A through the valve 44 the amount of the current of air flowing through the second subcooling apparatus a countercurrent

Impure gaseous oxygen under pressure 51 is removed of the head of the mixing column 16, heated in the main heat exchanger 10 and recovered as product 52. A sump liquid 45 and a liquid are removed from the mixer column. intermediate liquid 46 and these are fed to a suitable point of the low pressure column 14 through pipes 47 and 48, respectively.

Figure 2 differs from figure 1 solely because the third load air stream 207 is additionally compressed together with the second air stream of load on the first recompressor 108. In this way, a higher inlet pressure in the turbine 20 and therefore It generates colder.

In the variant of figure 3 it is operated the purification equipment at a first pressure p_ {1} 'which is more high than the operating pressure p_ {MiS} of the column mixer. The first pressure p_ {1} 'is here of, for example, 2.7 at 3.7 bars, preferably around 3.2 bars. The second charge air stream 306 expands here upstream of its mixer column feed. There is no third load air flow that is blown into the low column Pressure. The second charge air stream 306 is compressed additionally, downstream of its total air bypass purified, in the second 317 recompressor, which is powered by the turbine 320. The second charge air stream 349 compressed in addition to, for example, 3.8 to 5.6 bars, preferably around 4.7 bars, it is fed to turbine 320 by a 350 pipe and expanded there producing work up approximately the pressure p_ {MiS} of the mixing column.

Similarly to what happens in Figure 3, in the procedure of figure 4 to the debugging equipment 3 is done operate at a particularly low first pressure p_ {11} '' of, for example, 2.7 to 3.7 bar, preferably around 3.2 pubs. As in Figure 1, turbine 420 is requested with a third load air stream 407, 450 which, however, it is not recompressed here, but it expands directly producing work from approximately the first pressure p_ {1} '' to approximately the pressure of the low pressure column. The 418 turbine powered compressor is used here to additionally compress the second charge air stream until the second pressure pe, which is approximately equal to the pressure operating p_ {MiS} of the mixer column.

In all the execution examples the compressor air and the recompressor 8, 108 have been built preferably together as a three stage machine. Expressed from another way, the additional compression of the first air stream of loading is done in the third stage of a machine, whose stages first and second serve for upstream air compression of debugging equipment 3. As an alternative to this, this machine it can also be built with four stages, being arranged in this case the first three stages in front of the team debugging 3.

Claims (9)

1. Procedure for obtaining a product of oxygen at pressure due to decomposition of low temperature air in a rectification system that features a high column pressure (13) and a low pressure column (14), in which a first stream of loading air (12) in the high pressure column (13), ? (39) is put under pressure in state liquid a fraction (38) rich in oxygen from the column low pressure (14) and this fraction is delivered (41) to a column mixer (16), a second stream of loading air (6, 15, 306, 406) in the lower area of the column mixer (16) and puts it in counter current contact with the oxygen rich fraction (41), running the column mixer (16) at a pressure (p_ {MiS}) that is lower than the operating pressure (P_ {HDS}) of the high pressure column (13), and in which ? is extracted from the upper area of the mixer column (16) impure oxygen gas under pressure (51) as head product and this is recovered as oxygen product to pressure (52), characterized because • a total air stream (1), which It contains the first and second charging air currents, it is compressed (2) at a first pressure (p1) that is lower than the operating pressure (p_ {HDS}) of the high column pressure (13), and is purified (3) at approximately this first pressure (p1), air flow is distributed total debugged (4) in the first (5) and the second (6, 306, 406) charging air currents and • (8, 108) is further compressed first load air stream (5) separately from the second charging air flow up to a second pressure (p2) that is at least equal to the operating pressure (P_ {HDS}) of the high pressure column (13). 2. The method according to claim 1, characterized in that the first pressure (p1) is approximately equal to the operating pressure (p_ {MiS}) of the mixing column (16). Method according to claim 1, characterized in that the first pressure is lower than the operating pressure (p_ {MiS}) of the mixing column (16) and that the second load air stream (306, 406) is compressed additionally (317, 417) separately from the first load air stream to a third pressure (p 3) that is at least equal to the operating pressure (p Mi) of the mixer column (16). Method according to one of claims 1 to 3, characterized in that the oxygen-rich fraction put under pressure in the liquid state is heated, before being delivered (41) to the mixing column (16), by indirect heat exchange (40 ) with a reheated air stream (42). 5. Method according to one of claims 1 to 4, characterized in that a third load air stream (7, 50, 207, 407, 450) is produced, producing work (21) and this (21) is introduced into the low pressure column (14). Method according to claim 5, characterized in that the third load air stream (7) is recompressed (7) before the work-producing expansion (20), especially using mechanical energy generated during the work-producing expansion (20) for recompression (17). Method according to one of claims 5 and 6, characterized in that the third load air stream is formed by a part of the total air stream (4) downstream of the purification equipment (3) and is fed (7, 207) to the recompression equipment (17) directly or after a joint additional compression (108) with the first load air stream. Method according to one of claims 1 to 4, characterized in that the second load air stream (306, 349, 350) is expanded (320) producing work before being introduced into the mixing column. 9. Device to obtain a product from oxygen under pressure due to decomposition of low temperature air with a rectification system that features a high pressure column (13) and a low pressure column (14), and with a first loading air line (5, 11, 12) leading to the high pressure column (13), • a liquid pipe (38, 41) for extract an oxygen-rich fraction from the low pressure column (14), which contains means (39) to increase the pressure and that leads to a mixing column (16), a second cargo air line (6, 15) leading to the lower zone of the mixing column (16), • an oxygen product pipe that is connected with the upper zone of the mixing column (16), and • a total air line that extends through an air compressor (2) and a purification device (3) and that is connected downstream with the first and second load air lines, characterized in that a recompressor (8, 108) is arranged in the first cargo air line (5, 11, 12).