Process for low-temperature air fractionation

• US 5,263,328 A
• Filed: 03/25/1992
• Issued: 11/23/1993
• Est. Priority Date: 03/26/1991
• Status: Expired due to Fees

• Current Assignee: Linde AG (Linde Plc)
• Original Assignee: Linde AG (Linde Plc)
• Inventors: Rohde, Wilhelm
• Primary Examiner(s): Capossela, Ronald C.
• Application Number:
  US07/857,140
• Time in Patent Office: 608 Days
• Field of Search: 62/38, 62/39, 62/13, 62/25
• US Class Current: 62/646
• CPC Class Codes: F25J 2215/50 Oxygen or special cases, e.g. isotope-mixtures or low purity O2
• CPC Class Codes: F25J 2240/10 the fluid being air
• CPC Class Codes: F25J 2245/40 the recycled stream being air
• CPC Class Codes: F25J 2270/04 Internal refrigeration with work-producing gas expansion loop
• CPC Class Codes: F25J 3/04018 of main feed air
• CPC Class Codes: F25J 3/04024 of purified feed air, so-called boosted air
• CPC Class Codes: F25J 3/0409 of oxygen
• CPC Class Codes: F25J 3/04103 using solely hydrostatic liquid head
• CPC Class Codes: F25J 3/04115 characterised by the type of prime driver, e.g. hot gas expander
• CPC Class Codes: F25J 3/04157 Afterstage cooling and so-called "pre-cooling" of the feed air upstream the air purification unit and main heat exchange line F25J3/04618 takes precedence
• CPC Class Codes: F25J 3/04193 Division of the main heat exchange line in consecutive sections having different functions
• CPC Class Codes: F25J 3/04303 Lachmann expansion, i.e. expanded into oxygen producing or low pressure column
• CPC Class Codes: F25J 3/04412 in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
• CPC Class Codes: Y10S 62/939 Partial feed stream expansion, air

Abstract

For the low-temperature fractionation of air, especially for the production of medium purity oxygen, the entire feed air (1) is compressed in a first compressor stage (2) and purified by adsorption (4). A first component stream (101) of the air is introduced into the high-pressure stage (7) of a two-stage rectifying column (6). A second component stream is passed to the low-pressure stage (8), and this stream is separated, after adsorption (4), from the remaining feed air, heated against compressed feed air (3), and engine-expanded (13). The thus-produced work is utilized at least in part for the compression (2) of feed air.

Claims

1. A process for the low temperature fractionation of air in a two-stage rectification column (6) having a high pressure stage (7) and a low pressure stage (8), comprising:

compressing raw feed air (1) in a first compressor stage (2) to approximately high-pressure stage pressure;

purifying the compressed raw feed air by adsorption in a purification sage (4) to obtain compressed, purified feed air;

dividing the compressed, purified feed air into a first component stream (101) and a second component stream (102);

heating the second component stream in indirect heat exchange (3, 3'"'"') against the compressed raw feed air or the compressed, purified feed air so as to cool the compressed raw and compressed, purified feed air;

engine-expanding (13, 13'"'"') the heated second component stream so as to cool the second component stream and to provide work for the compression (2,

     16) of a process stream;

conducting the resultant engine-expanded second component stream to the low pressure stage (8); and

conducting the first component stream to a feedpoint in the high pressure stage.

2. A process according to claim 1, wherein work obtained during the engine expansion (13) of the second component stream is utilized for driving the first compressor stage (2).

3. A process according to claim 2, wherein the indirect heating of the second component stream is conducted against compressed raw feed air.

4. A process according to claim 1, wherein a third component stream (103) is branched off downstream of the purification stage (4), recompressed in a second compressor stage (14), then cooled (5), engine-expanded (15), and fed into the low-pressure stage (8), wherein work obtained during the engine expansion (15) of the third component stream is used for the recompression of the third component stream in the second compressor stage (14).

5. A process according to claim 4, wherein work obtained during the engine expansion (13'"'"') of the second component stream is utilized in a third compressor stage (16) for the recompression of the third component stream.

6. A process according to claim 4, wherein a fourth component stream (104) is branched off downstream of the purification stage (4), recompressed in a fourth compressor stage (16), then cooled (5), expanded, and fed into the high-pressure stage (7), wherein work obtained during the engine expansion (13'"'"') of the second component stream is utilized for the recompression of the fourth component stream in the fourth compressor stage (16).

7. A process according to claim 6, wherein the third and fourth component streams are recompressed in a joint third compressor stage (16).

8. A process according to claim 6, wherein the indirect heating of the second component stream is performed against at least one of the recompressed third and fourth component streams.

9. A process according to claim 6, wherein liquid oxygen is withdrawn (9) from the low-pressure stage (8), is pressurized (17), and is then vaporized in indirect heat exchange (5) with the recompressed fourth component stream (104).

10. A process according to claim 9, wherein the fourth component stream (104) is at least partially condensed during indirect heat exchange (5) with evaporating oxygen and resultant stream is then introduced into the high-pressure stage (7) at a point above the feed-point first component stream (101).

11. A process according to claim 4, wherein work produced during the engine expansion (13) of the second component stream is utilized for driving the first compressor stage (2).

12. A process according to claim 11, wherein the indirect heating of the second component stream is conducted against compressed raw feed air downstream of the first compressor stage (2) and upstream of the purification stage (4).

13. A process according to claim 1, wherein said process stream is feed air.

14. A process according to claim 1, wherein the indirect heating of the second component (102) is conducted against the compressed raw feed air.

15. A process according to claim 14, the indirect heating of the second component (102) is conducted against the compressed purified feed air.

16. A process according to claim 15, wherein the indirect heating is conducted against a portion of the compressed purified feed air.

17. A process according to claim 14, wherein the indirect heating is conducted against the entire compressed raw feed air.