Apparatus and method for separating air by cryogenic distillation

Abstract

An apparatus for separating air, comprising a double column, means for sending air to the purification unit at a pressure that is no more than 1 bar higher than atmospheric pressure, a pipe for sending a first air flow, the first air flow having been purified in the purification unit, to the heat exchanger at a fourth pressure that is no more than 1 bar higher than the second pressure, a pipe for sending the first purified air flow, which has been cooled in the heat exchanger, to the second column for separation, and a booster compressor, the apparatus not comprising any means for depressurizing the first flow.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a § 371 of International PCT Application PCT / FR2019 / 052934, filed Dec. 5, 2019, which claims the benefit of FR187376, filed Dec. 21, 2018, both of which are herein incorporated by reference in their entireties.FIELD OF THE INVENTION[0002]The present invention relates to an apparatus and to a process for the separation of air by cryogenic distillation.BACKGROUND OF THE INVENTION[0003]In particular, it relates to an air separation apparatus comprising a double column with a first column operating at a first pressure and a second column operating at a second pressure, lower than the first pressure. The top of the first column produces a gas which condenses in a reboiler of the second column.[0004]It is generally an objective of air separation apparatuses to look for the lowest possible energy consumption.[0005]The purification of air is generally carried out at a pressure equal to or greater than that of the first pressur...

AI Technical Summary

Benefits of technology

The invention describes a process using a low expansion ratio, between 1.2 and 3.8, for a cryogenic turbine compared to conventional turbines which have an expansion ratio of 4 to 10. This low expansion ratio results in higher turbine efficiency and lower energy loss.

Problems solved by technology

As the refrigerating capacity of the process according to the prior art is fixed and remains low since the process does not produce a liquid final product, this means that the expansion ratio of the turbine is very low which gives a turbine which is inefficient and in any case not at all standardized, indeed even nonexistent, among suppliers of cryogenic turbines.

This enormously complicates the regulation and makes it necessary to proportion the purification to the lowest pressure which might be had with a refrigerating capacity lower than nominally expected or in a transient phase.

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