Process for the cryogenic distillation of air at elevated pressures which have multiple reboiler/condensers in the low pressure column

摘要

The present invention is a liquid nitrogen reflux means improvement capable of allowing the operation of conventional dual and triple reboiler air separation cycles at elevated pressures. The improvement comprises: (a) heat exchanging a portion of the liquid oxygen bottoms of the second column against a nitrogen vapor stream removed from the higher or lower pressure columns or derived from the gaseous nitrogen product, wherein prior to such heat exchange the pressure of the liquid oxygen bottoms portion or the nitrogen vapor stream or both the pressure of the liquid oxygen bottoms portion and the nitrogen vapor stream is adjusted by an effective amount so that an appropriate temperature difference exists between the liquid oxygen bottoms and the nitrogen vapor stream so that upon heat exchange the nitrogen vapor is totally condensed and the liquid oxygen bottoms portion is at least partially vaporized; (b) utilizing the condensed nitrogen as reflux in at least one of the two distillation columns; and (c) warming the vaporized oxygen to recover refrigeration.