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Air Separation Method and System for Producing Elevated Pressure Nitrogen Products

IP.com Disclosure Number: IPCOM000237657D
Publication Date: 2014-Jul-01
Document File: 3 page(s) / 30K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method and system for producing gaseous nitrogen products at two different pressures by vaporizing pumped liquid nitrogen from cryogenic distillation of air against condensing air streams in separate heat exchangers. The condensing air stream that is in heat exchange relationship with the vaporizing higher pressure nitrogen product is compressed to a higher pressure than the condensing air stream that is in heat exchange relationship with the vaporizing lower pressure nitrogen product.

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Air Separation Method and System for Producing Elevated Pressure

Nitrogen Products

ABSTRACT

A method and system for producing gaseous nitrogen products at two different pressures by vaporizing pumped liquid nitrogen from cryogenic distillation of air against condensing air streams in separate heat exchangers. The condensing air stream that is in heat exchange relationship with the vaporizing higher pressure nitrogen product is compressed to a higher pressure than the condensing air stream that is in heat exchange relationship with the vaporizing lower pressure nitrogen product.

DESCRIPTION

With reference to Figure 1, an air separation system 100 is illustrated that is designed to produce nitrogen products at two different pressures. A feed air stream 2 is compressed in a main air compressor 4. After removal of the heat of compression in an after-cooler (not shown) the compressed feed air stream is purified within a known adsorptive pre-purification unit 6 to form a compressed and purified air stream 8 that is divided into three portions, namely stream 10, stream 12 and stream 16. Stream 10 is cooled in a first heat exchanger 24 against warming portions of nitrogen rich gas stream 46 and pumped liquid nitrogen stream 68 from a distillation column arrangement 44. This way a first vapor feed stream 36 and a first liquid air stream 38 is derived from stream 10. Stream 12 and stream 14 are further compressed in compressors 16 and 18 to form stream 20 and stream 22, respectively. Stream 20 is at a higher pressure than stream 22. After removal of heat of compression in after-coolers (not shown), stream 20 is fully cooled in a second heat exchanger 26 to form a second liquid air stream 34. Stream 22 after removal of heat compression in an after-cooler (not shown) is partially cooled in the second heat exchanger 26. The refrigeration for cooling of stream 20 and stream 22 in heat exchanger 26 is provided by warming portions of nitrogen rich gas stream 46, pumped liquid nitrogen stream 66 and pumped liquid oxygen stream 56. Both heat exchanger 24 and 26 are preferably of brazed aluminum type. Resulting cooled stream 28 is expanded in an expander 30 to generate refrigeration and form a second vapor feed stream 32.

The first vapor feed stream 36, first liquid air stream 38, second vapor feed stream 32 and second liquid air stream 34 are subjected to cryogenic distillation using a known distillation column arrangement 44 that operates in what is known as a Linde cycle. The distillation column arrangement 44 contains at least two distillation columns. One of the distillation columns operates at a higher pressure than the other and serves to separate nitrogen from the oxygen and thereby to produce a nitrogen-rich vapor column overhead and a crude liquid oxygen column bottoms also known as kettle liquid. This crude liquid oxygen column bottoms is further refined in the lower pressure column to produce a nitrogen-rich vapor column overhead and an...