Recovery of krypton and xenon from air separation plants

Claim 1

A METHOD OF RECOVERING A MIXTURE OF KRYPTON AND XENON FROM THE METHANE-CONTAMINATED SUMP VAPOUR PRODUCT OF AN AIR DISTILLATION COLUMN, SAID PRODUCT ALSO CONTAINING OXYGEN, SAID METHOD COMPRISING THE FOLLOWING STEPS: PASSING SAID SUMP VAPOUR PRODUCT UPWARDLY THROUGH A FURTHER DISTILLATION COLUMN PROVIDED WITH A LIQUID REFLUX, IN COUTERCURRENT WITH SAID LIQUID REFLUX, TO THEREBY PREFERENTIALLY EXTRACT FROM SAID VAPOUR PRODUCT KRYPTON AND XENON, CONDENSING SAID VAPOUR PRODUCT AT THE TOP OF SAID FURTHER DISTILLATION COLUMN, RETURNING PART OF SAID VAPOUR PRODUCT TO SAID LIQUID REFLUX, AND REMOVING THE OXYGEN CONTENT FROM SAID CONDENSATE, RETURNING THE REFLUX CONTAINING KRYPTON AND XENON TO SAID SUMP TO PROVIDE A SUMP LIQUID ENRICHED IN KRYPTON AND XENON, WITHDRAWING SAID ENRICHED SUMP LIQUID AND PASSING IT AT AN INCREASED PRESSURE INTO THE TOP OF A FIRST RECTIFYING COLUMN, PERMITTING SAID ENRICHED SUMP LIQUID TO FLOW DOWN SAID FIRST RECTIFYING COLUMN AND THEREBY ENRICHING THE CONCENTRATION OF KRYPTON AND XENON IN SAID LIQUID, REMOVING THE ENRICHED LIQUID FROM THE BOTTOM OF SAID FIRST RECTIFICATION COLUMN, AND INTRODUCING SAID ENRICHED LIQUID AT AN INTERMEDIATE POINT INTO A SECOND RECTIFYING COLUMN, REMOVING VAPOUR FROM THE TOP OF SAID SECOND RECTIFYING COLUMN, AND RETURNING SAID VAPOUR TO THE BOTTOM OF SAID FIRST RECTIFYING COLUMN, RECYCLING UNCONDENSED VAPOUR FROM THE TOP OF SAID FIRST RECTIFYING COLUMN TO THE BOTTOM OF SAID FURTHER DISTILLATION COLUMN, AND REMOVING THE PRODUCT MIXTURE OF KRYPTON AND XENON FROM THE BOTTOM OF SAID SECOND RECTIFYING COLUMN.

Claim 2

A METHOD OF RECOVERING A MIXTURE OF KRYPTON AND XENON FROM THE METHANE-CONTAMINATED SUMP VAPOUR PRODUCT OF AN AIR DISTILLATION COLUMN, SAID PRODUCT ALSO CONTAINING OXYGEN, SAID METHOD COMPRISING THE FOLLOWING STEPS: PASSING SAID SUMP VAPOUR PRODUCT UPWARDLY THROUGH A FURTHER DISTILLATION COLUMN PROVIDED WITH A LIQUID REFLUX, IN COUTERCURRENT WITH SAID LIQUID REFLUX, TO THEREBY PREFERENTIALLY EXTRACT FROM SAID VAPOUR PRODUCT KRYPTON AND XENON, CONDENSING SAID VAPOUR PRODUCT AT THE TOP OF SAID FURTHER DISTILLATION COLUMN, RETURNING PART OF SAID VAPOUR PRODUCT TO SAID LIQUID REFLUX, AND REMOVING THE OXYGEN CONTENT FROM SAID CONDENSATE, RETURNING THE REFLUX CONTAINING KRYPTON AND XENON TO SAID SUMP TO PROVIDE A SUMP LIQUID ENRICHED IN KRYPTON AND XENON, WITHDRAWING SAID ENRICHED SUMP LIQUID AND PASSING IT AT AN INCREASED PRESSURE INTO THE TOP OF A FIRST RECTIFYING COLUMN, PERMITTING SAID ENRICHED SUMP LIQUID TO FLOW DOWN SAID FIRST RECTIFYING COLUMN AND THEREBY ENRICHING THE CONCENTRATION OF KRYPTON AND XENON IN SAID LIQUID, REMOVING THE ENRICHED LIQUID FROM THE BOTTOM OF SAID FIRST RECTIFICATION COLUMN, AND INTRODUCING SAID ENRICHED LIQUID AT AN INTERMEDIATE POINT INTO A SECOND RECTIFYING COLUMN, REMOVING VAPOUR FROM THE TOP OF SAID SECOND RECTIFYING COLUMN, AND RETURNING SAID VAPOUR TO THE BOTTOM OF SAID FIRST RECTIFYING COLUMN, RECYCLING UNCONDENSED VAPOUR FROM THE TOP OF SAID FIRST RECTIFYING COLUMN TO THE BOTTOM OF SAID FURTHER DISTILLATION COLUMN, AND REMOVING THE PRODUCT MIXTURE OF KRYPTON AND XENON FROM THE BOTTOM OF SAID SECOND RECTIFYING COLUMN.