Patent ID: 6568210
Filing Date: 2003-05-27
Classification: F25J

Abstract:
A method for obtaining a gaseous product by low temperature fractionation of air in a rectifying system having a high-pressure column and a low-pressure column, said method comprising:a. supplying a first, purified, and cooled stream of air to the high-pressure column; b. passing at least one liquid stream from the high-pressure column into the low-pressure column; c. drawing off a product stream in the liquid state from the low-pressure column and, in the liquid state, bringing the product stream to an elevated pressure; d. evaporating the product stream having an elevated pressure in an indirect heat exchange with a second purified stream of air, thereby at least partly condensing the second purified stream of air; e. work-expanding at least part of the at least partially condensed second stream of air and subsequently passing the second stream of air into the low-pressure column; and f. the pressure of the second stream of air at the outlet of the work-expanding it lower than the operating pressure in the sump of the high-pressure column, wherein the work-expanding of the at least partially condensed second stream of air is carried out in a single step.