Patent ID: 6347534
Filing Date: 2002-02-19
Classification: F25J,Y10S

Abstract:
A process for separating air by cryogenic distillation comprising the steps offeeding compressed, cooled purified air to a high pressure column where it is separated into a first nitrogen enriched stream at the top and a first oxygen enriched stream at the bottom, feeding at least a portion of the first oxygen enriched stream to an intermediate pressure column to yield a second nitrogen enriched stream at the top and a second oxygen enriched stream at the bottom, sending at least a portion of the second nitrogen enriched stream to a low pressure column, sending at least a portion of the second oxygen enriched stream to a low pressure column separating a third oxygen enriched stream at the bottom and a third nitrogen enriched stream at the top of the low pressure column, sending a heating gas to a bottom reboiler of the low pressure column, removing at least a portion of the third oxygen enriched stream at a removal point, removing a first argon enriched stream containing between 3 and 12% argon from the low pressure column, sending the first argon enriched stream to an argon column having a top condenser, recovering a second argon enriched stream, richer in argon than the first argon enriched stream, at the top of the argon column and removing a fourth oxygen enriched stream at the bottom of the argon column wherein the argon column has a bottom reboiler heated by a gas stream, wherein the gas stream contains at least 90% nitrogen, and wherein the gas stream heating the bottom reboiler of the argon column is at least a portion of one of the first, second and third nitrogen enriched steams.