Patent ID: 7076971
Filing Date: 2006-07-18
Classification: F25J

Abstract:
1. A method of producing, in gaseous form and under high pressure, at least one fluid chosen from oxygen, argon and nitrogen in an air separation unit, in which all the air intended for distillation is compressed in a compressor, the compressed air is purified, at least a first portion of the air is supercharged to a high pressure, the compressed and purified air is sent into a heat exchange line of the installation where it cools, the compressed, purified and cooled air is separated in a system of columns of the unit comprising at least one distillation column, a fluid is withdrawn in the liquid state from one column of the system of columns, the said fluid in the liquid state is brought to the high pressure, it is vaporized by heat exchange with the air and the vaporized liquid at this high pressure is warmed in the heat exchange line of the installation, at least one portion of the supercharged air is expanded in an expansion turbine from the high pressure to a second pressure, the expanded air then being sent into one column of the system of columns, in normal operation the supercharged air being cooled down to the inlet temperature of the turbine in the exchange line upstream of the expansion turbine, wherein, during start-up of the air separation unit at least one portion of the air supercharged to the high pressure is sent upstream of the expansion turbine without passing through the exchange line.