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Intermediate Pressure Column in Air Separation

IP.com Disclosure Number: IPCOM000019394D
Publication Date: 2003-Sep-12
Document File: 4 page(s) / 70K

Publishing Venue

The IP.com Prior Art Database

Abstract

An additional column is introduced to a standard two-column (or three-column in case of argon recovery) air separation unit. This column operates at a pressure between the high pressure and low pressure column pressures and separates low pressure column feed streams: oxygen-rich liquid and/or liquid air into oxygen-enriched liquid and nitrogen-enriched vapor.

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Intermediate Pressure Column in Air Separation

An additional column is introduced to a standard two-column (or three-column in case of argon recovery) air separation unit. This column operates at a pressure between the high pressure and low pressure column pressures and separates low pressure column feed streams: oxygen-rich liquid and/or liquid air into oxygen-enriched liquid and nitrogen-enriched vapor.

Figure 1

The schematic of Figure 1 shows a conventional, double column cycle: pumped liquid oxygen plant with argon, air expansion to low pressure or high pressure column, and high-pressure gaseous nitrogen product taken off the high pressure column.

Figure 2

The schematic of Figure 2 shows one possible implementation of the idea. Liquid feed streams RL and LAIR2 are introduced into an intermediate pressure column. They are separated into RL2, LAIR3, and GAN2 streams. RL2, containing more oxygen than RL, is subsequently vaporized in a sequential manner in intermediate pressure column and sidearm column condensers and then introduced into low pressure column as a gaseous feed. LAIR2, an optional feed to an intermediate pressure column, becomes LAIR3 low pressure column reflux after the flash recovery and/or some separation. GAN2 gaseous product is expanded to Waste to provide additional refrigeration. It can be warmed up against the main expander stream or in the main heat exchanger to increase the amount of work that can be obtained from the expansion. A fraction of the sidearm flow (SDF) is condensed in an intermediate pressure column reboiler to provide boilup for the column; it is then introduced into the sidearm column, preferably at the optimal feed location. Introducing oxygen-enriched vaporized RL2 stream into low pressure column reduces vapor requirement of the column’s rectifying section and improves oxygen and/or argon recovery. It also lowers or eliminates oxygen and/or argon recovery decrease as...