| 摘要 |
In a method for separating air by cryogenic distillation in an installation comprising a double column comprising a medium-pressure column (15) and a low-pressure column (17), the low-pressure column containing a bottom vaporizer (19), an intermediate vaporizer (21) and a top vaporizer (23), compressed air is purified in a purification unit, cooled in an exchange line and sent to the medium-pressure column of the double column, an oxygen-rich fluid is tapped from the low-pressure column, heated and sent to the client, nitrogen tapped from the medium-pressure column is split into at least three parts, a first part of the nitrogen is expanded in a first turbine (47), a second part of the nitrogen is compressed in a cold compressor (51) and sent to the bottom vaporizer, the nitrogen thus condensed being sent to at least one column of the double column, and a third part of the nitrogen is sent to the top vaporizer, without a pressure modifying step downstream of the column from which it is tapped and upstream of the top vaporizer, the nitrogen thus condensed being sent to at least one column of the double column, and a stream of gas is sent to the intermediate vaporizer, this stream consisting of compressed, purified and cooled air. |
