Cryogenic distillation method and installation for air separation

Abstract

Separation of air is obtained by vaporization of pressurised liquid in an exchange line of a air separation unit by heat exchange with a compressed gas at a cryogenic temperature. - The process is carried out in an installation comprising a double or triple air separation column operating at a high pressure and with an exchange line, in which - (1) all the air is raised to high pressure, greater by at least 5 bars to the mean pressure, and purified; - (2) part of the air flow is cooled in the exchanger and divided into two fractions; - (3) each fraction is expanded in a turbine; - (4) the inlet pressure of each turbine is greater by 5 bars to the mean pressure; - (5) the exhaust pressure is equal to the mean pressure; - (6) part of the air expanded in one of the turbines is sent to the double or triple column; - (7) a cold compressor, mechanically connected to one of the expansion turbines aspirates air, which has been cooled in the heat exchanger, and exhausts air at a temperature higher than the inlet temperature, the fluid thus compressed being re-introduced in the exchanger in which part condenses; - (8) at least one liquid from the column is vaporized in the heat exchanger. - The turbine not coupled to the cooled compressor is coupled to a compressor followed by a refrigerant, and, optionally, the temperature of aspiration of the cold compressor approximates to the temperature of vaporization of the liquid. - An INDEPENDENT CLAIM is also included for the installation of the process.

Description

technical field [0001] The present invention relates to a method and apparatus for separating air by cryogenic distillation. Background technique [0002] It is known to produce gas from pressurized air by gasification of pressurized liquid by heat exchange with compressed gas above cryogenic temperature in the exchange line of an air separation plant. Devices of this type are known from FR-A-2688052, EP-A-0644388, EP-A-1014020 and patent application FR 03 / 01722. [0003] The thermal efficiency of these known devices is not very high because the heat influx associated with cryogenic compression must be removed. [0004] In addition, in the case of the solution shown in Fig. 7 such as US-A-5475980, the entire turbine connected to the low temperature supercharger is associated with an energy absorption system (oil brake) integrated on the shaft of the machine, and technically Limited to low power levels (around 70kW). [0005] Regardless, this type of approach is indeed eco...

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Problems solved by technology

[0003] These known devices are not very thermally efficient, since the heat inflow associated with cryogenic compression has to be rejected

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