Process and apparatus for the cryogenic separation of air

摘要

Oxygen-containing gas comprising no more than about 50 mol % oxygen is fed (150) to an auxiliary separation column (40) in a multiple column cryogenic air distillation system comprising at least a higher pressure ("HP") column (10) and a lower pressure ("LP") column (30) for separation into nitrogen-rich overhead vapour and oxygen-rich liquid. Oxygen-rich liquid is fed (154) from the auxiliary column (40) to an intermediate location in the LP column (30). The auxiliary column (40) is refluxed with a liquid stream from or derived from the HP column (10). One advantage of the invention is that the diameter of the upper sections (II, III) of the LP column (30) need no longer be larger than the diameter of the rest of the column system thereby increasing the capacity of the column system (under the constraint of a defined maximum column section diameter).