Air separation system and method

Patent metadata

Field	Value
Publication number	US-10254040-B2
Application number	US-201715399297-A
Country	US
Kind code	B2
Filing date	Jan 5, 2017
Priority date	Jun 2, 2014
Publication date	Apr 9, 2019
Grant date	Apr 9, 2019

Abstract

A system and method for separating air in an air separation plant is provided. The disclosed systems and methods divert a portion of the compressed, purified air stream to a bypass system configured to selectively produce a higher pressure compressed output stream or a lower pressure compressed output stream. The higher pressure and/or lower pressure compressed output streams are cooled in a main heat exchanger by indirect heat transfer with a plurality of product streams from the air separation plant and then rectified in the distillation column system. A second portion of the compressed, purified air stream is partially cooled in the main heat exchanger and expanding in a turbo-expander to produce power and an exhaust stream which is directed to the distillation column system of the air separation plant where it imparts additional refrigeration generated by the expansion of the compressed air stream in the turbo-expander.

First claim

What is claimed is:

1. An air separation system comprising:
an air intake system comprising a main air compressor, a purification unit connected to the main air compressor, the air intake system configured to produce a stream of compressed, purified air;
a bypass system in flow communication with the air intake system and configured to receive a first portion of the compressed, purified air stream and condition the first portion of the compressed, purified air stream into a compressed output stream; the bypass system comprising a booster compressor circuit having one or more booster compressors, a bypass circuit, and a plurality of control valves to control the flows through the booster compressor circuit and the bypass circuit;
a main heat exchanger in flow communication with the air intake system and the bypass system, the main heat exchanger configured to receive the conditioned compressed output stream from the bypass system and indirectly heat one or more pressurized liquid streams with the compressed output stream;
the main heat exchanger further configured to receive a second portion of the compressed, purified air stream from the air intake system and partially cool the second portion of compressed, purified air to a temperature that is between the temperature of the warm end of the main heat exchanger and a temperature of the cold end of the main heat exchanger;
a distillation column system comprising a higher pressure column and a lower pressure column connected to the main heat exchanger and configured to rectify the cooled, compressed output stream and thereby to produce the one or more pressurized liquid streams;
a turbo-expander in flow communication with the main heat exchanger and configured to receive and expand the partially cooled second portion of the compressed, purified air stream to produce power and an exhaust stream, the turbo-expander further connected to the distillation column system so that the exhaust stream is introduced into the distillation column system to impart refrigeration to the air separation plant; and
a controller operatively coupled to at least the bypass system to control the plurality of control valves to selectively introduce the first portion of the compressed, purified air stream into either the booster compressor circuit and thereby produce a higher pressure compressed output stream or the bypass circuit to produce a lower pressure compressed output stream;
wherein the bypass system is configured to prevent the one or more booster compressors from surge conditions during production of the higher pressure compressed output stream and to maintain a purge stream in the booster compressor circuit during production of the lower pressure compressed output stream;
wherein the controller is further configured to gradually divert some of the further compressed portion of the compressed, purified air from the bypass circuit to the one or more booster compressors in the booster compressor circuit when shifting from production of the compressed output stream at the lower pressure to production of the compressed output stream at the higher pressure; and
wherein the controller is still further configured to gradually divert some of the further compressed portion of the compressed, purified air from the one or more booster compressors in the booster compressor circuit to the bypass circuit when shifting from production of the compressed output stream at the higher pressure to production of the compressed output stream at the lower pressure.

2. The air separation system of claim 1 wherein the plurality of control valves further comprise a recycle control valve operatively associated with the recycle circuit, and wherein the controller is configured to control the recycle control valve to circulating a recycle stream flowing within a recycle circuit from an outlet of the one or more booster compressors in the booster compressor circuit to an inlet of the one or more booster compressors.

3. The air separation of claim 1 wherein the plurality of control valves further comprise a purge control valve operatively associated with a low pressure gas supply conduit, and wherein the controller is configured to control the purge control valve to supply a purge stream of a purified, low pressure gas via the low pressure gas supply conduit to the one or more booster compressors in the booster compressor circuit when the one or more booster compressors in the booster compressor circuit are deactivated.

4. The air separation of claim 1 wherein the exhaust stream is introduced into the higher pressure column of the distillation column system to impart refrigeration to the air separation plant.

5. The air separation system of claim 1 wherein the exhaust stream is introduced into the lower pressure column of the distillation column system to impart refrigeration to the air separation plant.

6. The air separation system of claim 1 wherein the booster compressor circuit is coupled to the warm end of the main heat exchanger such that the higher pressure compressed output stream is directed to the warm end of the main heat exchanger.

7. The air separation system of claim 1 wherein the bypass circuit is coupled to the warm end of the main heat exchanger such that the lower pressure compressed output stream is directed to the warm end of the main heat exchanger.

Assignees

• Rauch Jeremiah J
• Dowd Sophia J
• Warta Andrew M
• Sarigiannis Catherine B
• Zhang Wei
• Praxair Technology Inc

Inventors

• Rauch Jeremiah J
• Dowd Sophia J
• Warta Andrew M
• Sarigiannis Catherine B
• Zhang Wei

Classifications

• F25J3/0409

  of oxygen · CPC title

• F25J3/04218

  Parallel arrangement of the main heat exchange line in cores having different functions, e.g. in low pressure and high pressure cores (F25J3/04503 takes precedence) · CPC title

• F25J3/04024 Primary

  of purified feed air, so-called boosted air · CPC title

• F25J3/04084

  of nitrogen · CPC title

• F25J3/04296

  Claude expansion, i.e. expanded into the main or high pressure column · CPC title