Abstract: Air separation, in particular apparatus and method for reducing the loss of krypton and xenon during air separation by cryogenic distillation. The invention provides a method of separating air by cryogenic distillation, including forming a first liquid oxygen stream, and a second liquid oxygen stream having a lower concentration of krypton and xenon than said first stream, withdrawing the second stream as product, and subjecting the first stream to further separation to enrich it in krypton and xenon.

Abstract: A gas mixture comprising carbon dioxide, at least one gas having a lower boiling point than carbon dioxide, and at least one gaseous impurity having a higher boiling point than carbon dioxide (the impurity typically being hydrogen sulphide) is purified by a rectification process. The gas mixture (typically with a carbon dioxide partial pressure of 20 atmospheres) is precooled to the dewpoint of the carbon dioxide or below and is then rectified to form a liquid fraction relatively rich in the impurity or impurities and a product gaseous fraction relatively lean in or free from the gaseous impurity or impurities. The liquid fraction may be subjected to a second rectification to yield pure carbon dioxide.