Process to produce a krypton/xenon enriched stream directly from the main air distillation column.

摘要

In a process for the cryogenic distn. of air using high and low pressure columns in a multiple column distn. system, wherein: (a) at least a portion of the air feed is fed to the high pressure column for rectification into a high pressure N2 overhead and a high pressure crude liq. O2 bottoms; (b) at least a portion of the crude liq. O2 bottoms is fed to the low pressure column for rectification into a low pressure N2 overhead and a low pressure liq. O2 bottoms; and (c) at least a portion of the liq. O2 bottoms from (b) is boiled in a sump located at the bottom of the low pressure column; a method to produce a stream enriched in Kr and Xe directly from the low pressure column comprises: (i) withdrawing an O2-enriched vapour stream and an O2-enriched liq. stream from a point at least one equilibrium stage above the sump; (ii) returning the O2-enriched liq. stream to a point between the sump and the low pressure column's initial equilibrium stage; and (iii) withdrawing the Kr/Xe enriched stream from the bottom of the sump. Pref. after step (iii) the process further comprises: (iv) removing any C2+ hydrocarbons and N2O from the Kr/Xe enriched stream in an adsorber; (v) boiling the Kr/Xe enriched stream in a second sump by indirect heat exchange against a condensing process stream (pref. a portion of the high pressure N2 overhead) and the vapour is returned to the low pressure column and a prod. stream further enriched in Kr/Xe is withdrawn from the bottom of the second sump.