PROCESS AND APPARATUS FOR THE SEPARATION OF AIR BY CRYOGENIC DISTILLATION

摘要

A process for the separation of air by cryogenic distillation in a distillation system including at least a high pressure column (43) and a low pressure column (45) is disclosed, wherein air is compressed in a main compressor (3), compressed air is cooled in a heat exchange line (41), cooled, compressed and purified air is sent from the heat exchange line (41) to the high pressure column (43), in a first mode of operation, at least 90% of the air compressed in the main compressor (3) is further compressed to a first pressure at least 30 bars higher than the pressure of the high pressure column (43), the air at the first pressure is sent to the heat exchange line (41), cooled and divided in two, one part being liquefied and sent to the distillation system and one part being expanded in at least one turboexpander (29A, 29B) before being sent to the high pressure column (43) and in a second mode of operation, at most 70% of the air compressed in the main compressor (3) is further compressed to a first pressure at least 30 bars higher than the pressure of the high pressure column (43), the air at the first pressure is sent to the heat exchange line (41), cooled and divided in two, one part being liquefied and sent to the distillation system and one part being expanded in at least one turboexpander (29A, 29B) before being sent to the high pressure column and at least 30% of the air compressed in the main compressor (3) is sent at the outlet pressure of the main compressor (3) to the heat exchange line (41), cooled and sent to the high pressure column (43).