Patent ID: 6202441
Filing Date: 2001-03-20
Classification: F25J,Y10S

Abstract:
A process for separating air by cryogenic distillation comprising the steps offeeding compressed, cooled and 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 or to a top condenser of an argon column, sending at least a portion of the second oxygen enriched stream to the 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 20% argon from the low pressure column,sending the first argon enriched stream to the 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 operates at a pressure at least 0.5 bar lower than the pressure of the low pressure column.